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On DeckMovable Ballast

Printed From: Yachts and Yachting Online
Category: Dinghy classes
Forum Name: Dinghy development
Forum Discription: The latest moves in the dinghy market
Printed Date: 13 Aug 22 at 9:23pm
Software Version: Web Wiz Forums 9.665y -

Topic: On DeckMovable Ballast
Posted By: Doug Lord
Subject: On DeckMovable Ballast
Date Posted: 16 Sep 05 at 8:51pm
I've been tossing this around for a while: what about a 16-17' fairly high performance dinghy designed so that the skipper sits down in it like a mini 12 but with a difference: the majority of ballast would be in a"wing" between 6 and 10' long and would slide side to side either by electric power or by the crew using a "bicycle winch":leg power moves the weight(weight about 170-200 pounds). The whole wing would move side to side along with a weight sliding on it so the CG of the movable weight could get up to 8' or so from the CL of the boat.The wing would be supported by "Trapeze" wires. The wing and the crew seat would be somehow tied together so that the crew could slide aft as necessary and/or the boat would be equipped with a rudder t-foil.
There would be a deep daggerboard(retractble) with some weight on it- and the ends of the wing would contain buoyancy pods to help prevent a permanent capsize.The hull would be fairly narrow and the wing would pivot for trailering or stowage.It would have a spinnaker...
These are pictures of an rc model with such a system on it:
"" -

"" -

The concept is to allow high performance without the physical requirements of most dinghies in order to open up the thrill of performance dinghy sailing to people that for whatever reason don't want to or physically can't hike or use a trapeze.
I'd really like to hear comments...
Edited to try to determine why the url's here are "live" and the one on my last post is not...

Posted By: Isis
Date Posted: 16 Sep 05 at 9:53pm
Its a nice idea opening the high performance realm to those who, for whatever reason, just arent agile enough to sail the available boats but for the same reason that they cant sail them at the moment I dont think it would be sucsesfull. High performance boats are very dynamic boats to sail. Thier design means they have very little static stability and you are constantly moving about responding to the boats movement. Whilst the principle obvoisly works on a small scale i dont think you would get enough  responce from the balast to make it sucsessfull in the 'real world'


Posted By: ssailor
Date Posted: 17 Sep 05 at 9:14pm
true, not only that, the idea of a high performance boat is that its your weight keeping it flat therefore they dont weigh much, so i feel it wud be good but not quite a skiff!

Any one in need of quality carbon fibre work (tillers etc) at decent prices!

Int 14 Gbr 1244 'Nucking Futs'

The New Port rule!!.

Posted By: *GM*
Date Posted: 18 Sep 05 at 12:15am

Hmmm, the SA discussion was quite amusing.... - 6731d34c7d88be63fd538&showtopic=23407


What's it rate...........

Posted By: Stefan Lloyd
Date Posted: 18 Sep 05 at 8:34am

What happens when you capsize with the ballast on the "down" side (which is going to happen sooner or later)? OK, so you have flotation, so the boat doesn't actually sink, but how do you right it?

You actually need quite a lot of flotation to generate 170-200kg. It would be bulky.

Electric power and dinghies in salt water - sure - that will work for about 5 minutes.

Isis's point about the need for righting moment to be dynamic is also a very good one.



Posted By: Doug Lord
Date Posted: 18 Sep 05 at 2:55pm
This idea won't produce a skiff necessarily -just a high powered dinghy.
In the states the Martin 16 uses electrical components for handicapped assistance very successfully-not to mention all the ocean racers using electric winches or electric based canting keel systems(Schock 40); there have been tremendous advances in making that stuff work extremely well in a harsh environment.
The initial concept includes a weighted daggerboard -the boat would be self righting . In a worse case scenario with the wing fully extended: if the wind quit there is more buoyancy in the wing+ buoyancy pod then there is weight; If the boat was capsized it would right itself. At least when sailed in it's "safest" mode. It could, theoretically, be sailed without the keel weight and still be rightable by an able bodied person.
Whether the ballast is moved electrically or manually it is possible to design a system that moves the weight from max extension to center in one second-faster than a normal "crew" could move.91kg. of ballast with a CG at 2.43m from the CL at max extension is a lot of RM. Further, the ballast is adjustable, is never late, does exactly what you want done when you want it done and, most importantly, MOVES FAST.. A "robocrew" that makes this a potentially exciting singlehander.

Posted By: Stefan Lloyd
Date Posted: 18 Sep 05 at 3:16pm

Hm....have you had much actual experience with boat electrics or keelboats?

Electrics fail all the time, even on bigger boats, let alone something as wet as you are proposing.

Anyone who has sailed high performance keelboats for very long has had the experience of them not self-righting, even without the benefit of moveable ballast on the wrong side pinning the boat down.

Posted By: Doug Lord
Date Posted: 18 Sep 05 at 3:45pm
Don't focus too much on the electric option-the standard design would be manual-even though the electric system(with manual backup) could be made to work very reliably.
"Movable ballast on the wrong side pinning the boat down" . If you reread the previous post you'll notice the part about more buoyancy in the wing than weight.
But no matter how well designed there are conditions that will be too much for this boat-or any boat. Since the concept works on model boats the next step is to-sometime- build one and test it- the fun potential is there as well as the high performance potential with or without a keel.
I'm interested in seeing what Bethwaite comes up with in his "LAS"-lead assisted skiff- which, as I understand it, is being looked at for the 2008 Paralympic's.

Posted By: CurlyBen
Date Posted: 18 Sep 05 at 4:06pm
Another problem with the electric option is the weight - batteries are very heavy and I can't see how else you'd power it. You could make them part of the ballast, but then you've got the risk of electric cables being snagged when the thing moves. Also, I think model boats tend to be sailed on small ponds with little in the way of waves- I'm not certain on this but the pics I've seen suggest that - so simply scaling up may not work. Finally, even if the weight can move fast enough, I doubt you could control it accurately enough to be able to keep the boat flat in gusts/waves.

Posted By: Stefan Lloyd
Date Posted: 18 Sep 05 at 5:03pm

Originally posted by Doug Lord

If you reread the previous post you'll notice the part about more buoyancy in the wing than weight.

And if you reread my first post, I said that enough buoyancy to counteract 200kg of ballast is going to be bulky. 

Posted By: Doug Lord
Date Posted: 18 Sep 05 at 7:12pm
Proposed "wing" ballast is 75-91kg. And variable...

Posted By: Stefan Lloyd
Date Posted: 19 Sep 05 at 6:51am
My mistake - I forgot you quaint Americans still use Imperial units. Doesn't change the point though: 90kg of buoyancy will be bulky.

Posted By: a_stevo
Date Posted: 19 Sep 05 at 7:28am
why not just go all out and make it a tri? its going that way. you'll end up with a move powerful safer simpler and lighter boat

Posted By: guytoon
Date Posted: 19 Sep 05 at 9:08am
Martin and Be0thwaite already worked together on this kind of boat : -  (sorry guys it's in french)

Cherub 2692 "NBS"

Posted By: Black no sugar
Date Posted: 19 Sep 05 at 9:43am

That's Europe for you, guytoon! I don't mind links in French... Surprisingly easy to understand Wink
For all incurable Anglophones, the link provided in guytoon's message on the French forum is in English! So stop the panic attack now, drop the paper bag and click on this link: - rt


Posted By: Stefan Lloyd
Date Posted: 19 Sep 05 at 9:52am

Originally posted by guytoon

Martin and Be0thwaite already worked together on this kind of boat

Doesn't really sound the same. If I have understood the first post in the thread, Doug is talking about something a bit IC-like, but with ballast on the plank rather than the helm. 

Posted By: guytoon
Date Posted: 19 Sep 05 at 10:14am
Here is another approach from bethwaite.

Cherub 2692 "NBS"

Posted By: Doug Lord
Date Posted: 19 Sep 05 at 1:03pm
Looking forward to seeing more on Bethwaites"LAS" but the "Martin 29er" is nothing like I propose. Stefan is right: the weight slides on a curved wing shaped appendage moving the ballast 2.43 m to weather(the whole wing moves as well). More or less equivalent to a single heavy crew on a trap standing on one meter wide wings attached at the deck edge of a 1.3m wide boat. Loads of RM!
Enough RM that ,according to Bethwaites formula the boat would theoretically be able to plane upwind.
I don't see a small high powered multi being safer than this boat! Maybe faster but this boat will be self righting-at least when configured in it's "safe mode".
I built a 14' tri a while back that you sat down inside and the sensation of being so low-with your head real close to the water is amazing-that will certainly add to the experience of sailing this boat.
Keeping the power manageable and the ballast easily under control is a challenge but I think it is feasible.

Posted By: redback
Date Posted: 20 Sep 05 at 10:05pm
You know there is a sports boat with a swing keel.  It was at the Boat Show but I can't find an ad in Y&Y and I can't remember its name.

Posted By: Isis
Date Posted: 20 Sep 05 at 10:25pm
Ive just read the Sailing Anarchy thread... obvouisly got a lot of respect on there Doug


Posted By: Iain C
Date Posted: 20 Sep 05 at 10:39pm

Originally posted by redback

You know there is a sports boat with a swing keel.  It was at the Boat Show but I can't find an ad in Y&Y and I can't remember its name.


It's the Backmann 21...and I want one!!


RS700 GBR922 "Wirespeed"
Fireball GBR14474 "Eleven Parsecs"
Enterprise GBR21970
Bavaria 32 GBR4755L "Adastra"

Posted By: Doug Lord
Date Posted: 20 Sep 05 at 10:42pm
ISIS, believe me "respect" is a two way street-some individuals that replied to that thread have reasonable ideas ; others start out and finish up with personal attacks with no rational response at all-so be it.
RB- Bethwaite is introduceing a 26 footer with a 60(!) canting keel with a wingshaped bulb for lateral resistance.(And mini's ,and a company in Spain ripping off CBTF ect)
But on my proposed 17 footer the RM achievable is FAR in excess of that achievable with a canting keel with the same weight.

Posted By: Isis
Date Posted: 20 Sep 05 at 11:20pm
Fair play.
Can I ask how much experiance you have sailing high performance boats/skiffs?


Posted By: Doug Lord
Date Posted: 20 Sep 05 at 11:37pm
I have 45 years sailing and racing experience in a multitude of boats from mono's to multi's. I haven't
sailed a "production" skiff but have many hours sailing my "aeroSKIFF" a 16 foot experimental hydrofoil that is all carbon and weighs 200 pounds; it is a singlehander(that can be doublehanded) with 182 sq. ft of upwind sail(see:

for two year old pictures). I designed and built it and dozens of other boats over the years. Still under development with plenty of problems to sort out-lots of fun though.
I've had a lifelong passion for sailing and design-hence this 17 footer concept; I think based on my experience and the performance of models using the system I describe that there is potential for on-deck movable ballast. Sure there are problems but when you consider the potential of a sit down single hander that could plane to windward it may be worth experimenting with.
Does anyone know why the url in this post is not "live"? On my first post it worked well;this doesn't and I can't see why....

Posted By: Stefan Lloyd
Date Posted: 21 Sep 05 at 8:18am

Originally posted by Isis

Ive just read the Sailing Anarchy thread... obvouisly got a lot of respect on there Doug

SA is truly horrible. I know some people here also post there and once in a while there is something of interest, but the overall atmosphere is so aggressive and there are so many people who evidently haven't a clue about what they are discussing, that personally, I doubt I'd ever bother posting there.

Incidentally there has been at least one abusive post on this thread that Mark has removed. My main concern about Doug starting to post here is that some of his SA antagonists will move in too. I've seen similar happen on other boards. 


Posted By: redback
Date Posted: 27 Sep 05 at 7:53pm

I spoke the Backman 21 builder at the Southampton show.  It looks like a great boat for a blast.  Sadly the demonstator did not have the swing keel working, I'm looking forward to seeing it in the flesh and with its keel working!  I'm keeping my eyes and ears open for a trial sail.  I have tried a SB3 (which is a bit bigger) but the Backman should be faster which will make it quite an exciting boat.  Its altogether a more high tech machine, apart from the keel it has a carbon mast, hightech sails and epoxy hull.  Keep an eye on this one, I reckon its going to figure. -

Posted By: Stefan Lloyd
Date Posted: 28 Sep 05 at 9:06am
Interesting concept but I wonder what happens if you get knocked down with the keel on the wrong side. Small keelboats do experience knock-downs to both windward and leeward. 

Posted By: Doug Lord
Date Posted: 28 Sep 05 at 11:34pm
You know, I hear stuff like that all the time about canting keels and it could be asked about a new movable ballast system such as I propose above. But if the systems are designed right, built well and sailed competently most situations that come up will be able to be recovered from and dealt with in shortorder.
People sometimes forget that similar questions/ problems can happen on any high performance dinghy or high performance keel boat. What happens if you have four guys standing on racks hanging from trapezes and the wind quits or a "hand of God" gust slams them?
;what happens if the bulb falls off a fin keel or a dinghy pitchpoles? You can ALWAYS pick a negative scenario and they WILL happen; you can only hope that the design of the systems involved and the seamanship of the people involved are up to it....

Posted By: Stefan Lloyd
Date Posted: 29 Sep 05 at 6:34am

With respect Doug, your sailing CV doesn't seem to include much keelboat sailing. Mine does. I've watched five crew swim away from a sinking keelboat identical to mine following a knock-down to windward. These things happen and they can have serious consequences. Keelboat racing does not normally have safety boat cover.

Four guys hanging off the trapeze no longer exercise a righting moment once tea-bagged, while the keel of a knocked-down keelboat is exercising maximum righting moment. If that moment is in the wrong direction, "How do you get out get out of that" is an eminently pertinent question to ask; preferably before it happens for real. 


Posted By: aardvark_issues
Date Posted: 29 Sep 05 at 9:33am
Originally posted by Doug Lord

if the systems are designed right, built well and sailed competently

You can never account for Muppets going sailing... I've seen very bad sailors, trying to sail boats well above their station and getting stung pretty badly.

Posted By: Doug Lord
Date Posted: 29 Sep 05 at 2:17pm
Stefan, I'm afraid it sounds like you use a "what if" question regarding the Backman 21 as a sort of indictment when, if you assume that the boat is designed and built right, the answer is simple: move the keel! That very thing happened to Pyewacket(or Glory?) in Antigua last year and the solution? They moved the keel. Not trying to be wise guy I'm just trying to point out that whether it is a canting keel or on-deck movable ballast system the boat SHOULD be designed to deal with the situations you describe.And as you point out any keelboat is subject to a knockdown. So if the boat is designed well , built right and sailed intelligently there should be no problem. But as you know there are always conditions that can get the best of any boat...
   I feel that while questions such as yours SHOULD be asked of every boat they should not be used as an indictment; a presumption of unsuitability unless you are familiar enough with the boat to know that it is NOT designed well or built right...
As to my concept of on deck movable ballast it allows for MUCH more RM than a normal canting keel while at the same time providing buoyancy greater than the weight in the wing and -in"safe mode" with a deep ballasted daggerboard is self righting. As I visualize this idea it could conceivably be sailed w/o the ballased board by an able bodied sailor and righted like any other dinghy-though even w/o the weighted board the thing would be almost self righting.
   The extreme situations you mentioned MUST be taken into account in the design of this boat or it won't work....
And just for the record most of my early, early racing was in a 20' gaff headed keelboat....

Posted By: Stefan Lloyd
Date Posted: 29 Sep 05 at 2:43pm

I wrote:"Interesting concept but I wonder what happens if you get knocked down with the keel on the wrong side."

That's a question, not an indictment.

And sorry but the resemblance between a 20' gaff headed keelboat and something like the Backman seems a bit tenuous. I've owned and skippered sportsboats, helped run a class association and rewrite the class safety requirements, and I have some idea what they are like and what can go wrong.

The boat identical to mine which I witnessed sink from close quarters shouldn't have sank but it did. Saying something "should" be OK isn't really all that comforting.

Posted By: CurlyBen
Date Posted: 01 Oct 05 at 7:12pm
Another thing to think about is that you're trying to make a high performance dinghy/skiff - they work on the basis of combining very low hull weight and large sail area with a decent righting moment. The RS800 weighs about 10 stone, and presumably your ballast would be a similar weight. Add one crewman and either you're trying to single hand a 800 or double up in a 700 (Not sure if that's clear but I'm thinking of sail area to weight ratio), if you keep the sail area the same. You could increase the sail area, but then you'd be increasing sheet loads, and if this might be targeted at disabled sailors you could end up finding yourself needing winches, and suddenly you're building a sportsboat. This target market would also mean you wouldn't be able to use leg power to move or control the ballast. Just a thought.

Posted By: Phat Bouy
Date Posted: 01 Oct 05 at 9:37pm
Dear Lord, you made the night too long for this bouy.

Call me an old fart but if this boat is designed/made for disabled sailors and is superb at self-righting, what happens if it capsizes and the afore-mentioned disabled falls out but know one notices (it does happen) and the boat rights itself and sails on unattended?

Please do not give me a long list of "ifs", " buts" and "ands" - get the boat built and demonstrate it to the world. Enough of all this talk, if you are so ssure of your design then it's time for action!

Posted By: Doug Lord
Date Posted: 01 Oct 05 at 10:06pm
Sorry old boy but it's not time to build yet. Good to know that Bethwaite and Bulloch are using ON DECK MOVABLE BALLAST on their Pterodactyl concept boat(about 65').
I would think that the likelyhood of the crew falling out of this boat would be much less than the crew falling out of a 2.4 meter which ,to my knowledge, has never happened.
I guess the model will have to serve as proof of concept for now-and believe me it 'twern't inexpensive to build and test:

Posted By: Doug Lord
Date Posted: 01 Oct 05 at 10:17pm
Heres the article on Pteradactyl(on deck movable ballast + buoyancy pods): -

Posted By: Doug Lord
Date Posted: 01 Oct 05 at 10:28pm
And here is the url to the Bethwaite LAS(Lead Assisted Skiff):
Bethwaite Design // Latest News // NEW - UD 18 Skiff sailing for Sailors with disabilities,02,2-0--new---ud-18-skiff-sai ling-for-sailors-with-disabilities.html

Posted By: Isis
Date Posted: 01 Oct 05 at 11:57pm
The 'pteradactyl' may make use of movable deck balast, but it also features several able bodied crew, probibly most of them on wires, its close enough to 5 times as big as your 'concept' and weighs 2 tonnes!!!

Not comparable to a skiff by anyones standards


Posted By: Doug Lord
Date Posted: 02 Oct 05 at 12:45am
The only(!) thing(s) Pteradactyl and the 17 have in common are on deck movable ballast, buoyancy pods and a ballasted appendage in the water. Interesting any way you look at it.
I've not learned how Bethwaite utilizes the ballast on his LAS but I have learned that apparently Herreshoff had a small boat using a brass ingot or so as on deck movable ballast; I was told it was one of his favorite boats.
The more I look into it the more I like the concept and not just for disabled sailors.
The boat seems like it could be configured from a high performance dinghy with numbers similar to a 505/FD to even more powerful. Since the ballast in the wing is adjustable and the ballasted board is removable there may be more than one level of performance/excitement achievable with the same basic hull+wing.

Posted By: Stefan Lloyd
Date Posted: 02 Oct 05 at 8:17am

Originally posted by Doug Lord

Sorry old boy but it's not time to build yet. (snip)I guess the model will have to serve as proof of concept for now-and believe me it 'twern't inexpensive to build and test:

So, I surmise that all this posting on every sailing board in the known universe is about getting positive responses you can show to people who might give you the money to develop it. Good luck!

Deck moveable ballast is a fascinating and promising concept. Signed, A UK Sailor.

Hope that helps.

Posted By: Doug Lord
Date Posted: 02 Oct 05 at 1:39pm
No Stefan, I don't intend to build it commercially-if it gets built it will be for me personally-- at least to start with.
But thanks for your sincere best wishes!
What I'm looking for is every comment possible to help think out the "character" of the boat that uses this system: the degree to which it should be powered up or not etc. Among many useless posts there have been quite a few gems that have helped with the conceptualization of the final version of the boat.

Posted By: Skiffe
Date Posted: 03 Oct 05 at 12:31pm
Originally posted by Stefan Lloyd

Originally posted by Isis

Ive just read the Sailing Anarchy thread... obvouisly got a lot of respect on there Doug

Incidentally there has been at least one abusive post on this thread that Mark has removed. My main concern about Doug starting to post here is that some of his SA antagonists will move in too. I've seen similar happen on other boards. 

I'm the poster of the  "abuisve" post. You can see for yourselves who came here first. However when the ONE thread is started by the some person on THREE forums using the same words well.... as for further coments about Doug I'll keep them to SA

12footers. The Only Way to FLY

Remember Professionals built the titanic, Amateurs built the ark.

Posted By: Doug Lord
Date Posted: 26 Oct 05 at 10:06pm
There is no way that I can see a small boat where the single crew sits inside like a 2.4 Meter having more power and speed than if the crew can move ballast either electrically or manually.And the least force would be required to move the ballast horizontally-as well as less draft and much more RM than with a canting keel. My original idea was to move the ballast inside a "Wing" that also moved to weather leaving nothing on the lee side of the boat at max extension.
But after seeing Langman's new maxi skiff I'm thinking a better design would be a fixed wing(removable for trailering/stowage); this means that for the same RM the wing on this version would be twice as long as the original concept but with buoyancy pods the "capsizability" of the boat would be much less. The appearance would be more like Bethwaites and Langmans boats(only much,much smaller) with the pods designed only for emergency backup not for sailing on(or with).
If the wing is fixed there would be less need for a ballasted daggerboard-it could probably be done away with and the boat would be 20kg or so lighter.
Any brilliant thoughts on this would, of course, be greatly appreciated.

Posted By: a_stevo
Date Posted: 27 Oct 05 at 6:37am
i just dont see any potential advantages of this over a tri. Do you really need this thing to be self righting?

Posted By: Isis
Date Posted: 27 Oct 05 at 12:30pm
As you've probibily noticed by now, im not at all convinced.
You obviously are though. If youre that sure it will be a sucsess: build the damn thing!! proove us wrong!!
Untill then I cant see you getting much other than negative comments from both here and SA


Posted By: Doug Lord
Date Posted: 27 Oct 05 at 5:33pm
Isis, perhaps you noticed or would notice if you read and understood my previous post that I was suggesting a major change in how the wing ballast system would work as compared to the original post. I would have thought that it was clear that there is no settled design yet and that I was asking for a reasoned opinion on the change to the system. Your mantra of "build it" is fairly useless at this point since the very nature of the beast is still undecided. I asked for comments relative to the change I proposed; it is no where near the DESIGN stage yet much less building!
Astevo- There are substantial differences between this and a tri: 1) the buoyancy pods on this thing are not used to develop righting moment.2) the weight of the wing+ ballast would be lighter than the ama's and cross arms of a square tri capable of flying the main hull. 3) While in the new proposal the wing does not slide across the boat-just the ballast does-the wing is still mounted pivotably(and adjustably) so that the boat can heel up to around 20 with the wing still level.4) The hull of this boat would be designed as a planing hull.
Just like in the Bethwaite and Langman Maxi Skiff's there is some simalarity between this concept and a tri . But the most important consideration, in my opinion ,is the fact that the tri REQUIRES the use of the buoyancy of the ama to sail normaly and this concept DOES NOT. Major Difference! This boat would be lighter than a square(high powered ) tri and it would be easier to trailer and store. It would have much less likelyhood of a pitchpole though w/o the ballast(see my previous post) in the daggerboard it would be difficult to recover from one-like a tri.
The thing that I'm trying to work on is whether or not the fixed(side to side) wing would be better than the sliding wing.....
edit: Forgot your question about self righting. For me personally it is essential that it can be singlehandedly rightable-not necessarily "self-righting".If it was to ever develop into a production version marketed to disabled sailors I would think it would have to be 100% self-righting.

Posted By: Isis
Date Posted: 27 Oct 05 at 5:59pm
Isis, perhaps you noticed or would notice if you read and understood my previous post that I was suggesting a major change in how the wing ballast system would work as compared to the original post. I would have thought that it was clear that there is no settled design yet and that I was asking for a reasoned opinion on the change to the system. Your mantra of "build it" is fairly useless at this point since the very nature of the beast is still undecided. I asked for comments relative to the change I proposed; it is no where near the DESIGN stage yet much less building!

Doug: I read and, I believe, understood your previous post and although you were sugesting a major change in the mechanics of the project, the underlying principle remains the same and it is this underlying principle that people are having trouble accepting. So you are not ready to enter the design stage, but as yet you seem to have been met by nothing but criticism of the concept and untill people believe the concept they are unlikely to put forward constructive comments on the actual mechanics of the final design" class="p -" class="p -


Posted By: Doug Lord
Date Posted: 27 Oct 05 at 6:07pm
In point of fact I've gotten several really good suggestions and comments.
   The change I proposed changes the concept substantially from the original idea but both versions are still on the table.
I'm curious about exactly what about the concept, as you understand it, that you object to; can you be very specific?

Posted By: CurlyBen
Date Posted: 27 Oct 05 at 6:35pm
I've made a few other comments earlier in this thread (which I still feel you haven't addressed tbh, most obviosuly that the power to weight ratio will have to remain similar to a skiff and you're near doubling the weight of the thing) but I'll see if you'll listen to this one.. why put solid ballast in the thing? Why not use water and a pump, as that way you can keep the weight of ballast at its optimum level, and it will be lighter to drag up and down slipways, as well as the possibility of having some kind of drain that would enable the boat to be righted without the ballast making any kind of effect.

Posted By: Doug Lord
Date Posted: 27 Oct 05 at 6:57pm
The main reason for not using water is the fact that for the same weight it takes up almost 11 times as much space as lead. And you'd have to use lead in a ballasted daggerboard to make it self righting.
That being said: because this thing has buoyancy pods that have buoyancy equal to the weight of the lead that has been proposed to slide sideways there IS room at the end of the wing. If a pump could be found that was light enough and that could move water from one pod to the other in three-four seconds max then it might be a good idea. Defintely worth looking into. Thanks for the idea....

Posted By: CurlyBen
Date Posted: 27 Oct 05 at 7:06pm
I hadn't thought of it in terms of space, but the pod would have to displace the same amount of water as the lead weighed (or close to it) so I don't think it would take up any more room. Also you wouldn't need to make the daggerboard ballasted, if you designed it so that in the event of capsize you could pivot the arm down and pumped water into it then it would self right that way. Also the pump needn't pump from one pod to the other, you could have a one way dump valve to release the water from one pod whilst simulteanously pumping water into the other. Probably simpler that way.. you could also put a hydroelectric generator in if you were feeling fancy, propelled by the outgoing water. I still think weight is going to be a majot issue, in terms of batteries if nothing else..

Posted By: jpbuzz591
Date Posted: 27 Oct 05 at 7:10pm

But if it is going to be "skiff style" surely having to dump and pump up water will increase the drag by the hull and will compramise speed, or am i just plain wrong here?


Jp Indoe
Contender 518
Chew Valley Sailing club

Posted By: Doug Lord
Date Posted: 27 Oct 05 at 7:23pm
At this point I think moving lead from side to side would require less power and most importantly less time. But I'm going to think about the water idea a lot more-it has some terrific advantages.
The water would probably work better on a laterally fixed wing but you couldn't count on it for a self righting system w/o a whole lot of complication as best as I can tell now.Also, since the design conception of the dynamic positioning of the pods(where they are when sailing) requires the wing to be curved you would definitely have to pump water from side to side or dump one side and pump from the center to the other pod.My gut feeling is that moving the lead will be simpler though I'm not positive about it.
Since this thing needs manual backup to any electric system the lead seems a lot easier to move by hand at good speed as compared to moving 200 pounds of water by hand.In fact a bicycle or hand crank lead moving system would be as fast as the electric version of the same system-water would be slow by hand-I think.
But, again, I'm going to look at it a lot closer and see what comes up....

Posted By: CurlyBen
Date Posted: 27 Oct 05 at 8:49pm
Here's an idea - as you're going to be filling the same volume everytime rather than trying to pump water exactly, why not use something along the lines of a piston - i.e. the piston retracts and so forces water in by vacuum, rather than having to pump it in. Could conceivably be done by hydraulics (avoiding electrics at all), probably easier, quicker, and more accurate to control, should require less effort. Work done is going to be the same to shift 200lbs of lead as it is to shift the same of water, provided the efficiency is the same, which is the harder bit. As for self righting, I may be wrong but I think the big racing tris (as in the 60 odd foot ones!) use a system to pump water to the top hull to right when they capsize.
JP - dumping water won't add drag as soon as the water has left contact with the boat, as it can't apply any force to the boat. The pickup system could, and as water is added the hull will ride lower in the water (maybe hydrofoils will be needed? this things sounding complex!) but as this is only going to happen when you're overpowered it's probably not going to be too big an issue.

Posted By: jpbuzz591
Date Posted: 27 Oct 05 at 8:58pm

yeah suppose ben, personally i'm with most of the guys on the forum and think that maybe doug you are trying to bite off more than you can chew and like isis would like to see some action rather than just talk about it


Jp Indoe
Contender 518
Chew Valley Sailing club

Posted By: 49erGBR735HSC
Date Posted: 27 Oct 05 at 9:17pm
I hope this project works for you Doug but there are a lot of contradicting criterias in your design. For a boat to be fast, it has to be light and dynamic as stated by a few people before. Looking at your RC designs, the equipment you are using on the deck is going to create a lot of drag. Most High performance skiffs are kept as simple as possible to allow for crews to concentrate on sailing the boat as quickly as possible. Reaction times have to be quick too and I don't think its the best idea relying on mechanical equipment to enable a boat to sail effectively and the more complicated that it is, the more prone it will be to failure. If the boat has weight balancing it in a width respective, what sort of method will be implied to balance the boat in a longitudal direction? All high performance boats need continuous adjustments in fore and aft trim to be sailed effectively, if we didn't concentrate on trim on our boat, we'd be stuffed. Using a skiff design with low buoyancy at the front might not be the best option......

Dennis Watson 49er GBR735 -
Helensburgh S.C - Boat Insurance from Noble Marine

Posted By: CurlyBen
Date Posted: 27 Oct 05 at 10:15pm
I think there's still plenty of problems - the ability to react quickly's still going to be hard, and I had a few other points I can't remember now - but I think that water ballast is more feasible than fixed weight ballast. I think it could be quite interesting, but I'm not sure it's really going to work on a small boat. 20 or 30ft and with 3 or 4 crew and it might be very interesting...

Posted By: Doug Lord
Date Posted: 27 Oct 05 at 11:08pm
There are many modern high performance boats that require mechanical systems to allow them to work properly. I can't see any reason why sliding ballast horizontally wouldn't work assuming it was designed to be a reliable system. And the mechanics-either electrically or human powered are extremely simple-don't see any problem there at all. It's been done on models; Bethwaite's planning on doing it on a large ocean racer. Even if you did it electrically it would require much less power to move a given amount of weight horizontlly as opposed to moving a short lever attached to a long canting keel. Not only that but moving the weight quickly side to side could be done manually with no electric power at all.
I sure don't see the drag you were referring to especially on a 17-18 footer where the weight is enclosed in an aerodynamically shaped wing-it would be far less than a crew on trapeze!
As to moving the weight fore and aft: I think I mentioned earlier that the wing and crew seat would be able to move fore an aft to some degree and the boat would most definitely use a rudder t-foil.In fact experimenting with a retractable forward lifting hydrofoil for partial lift w/o an altitude control system is part of the agenda down the line with this boat.Pitch control should be precise and more than adequate just with the t-foil rudder and fore and aft weight movement.
   I mentioned earlier about the speed the weight could move-either manually or electrically and it would be faster than a crew.
I just got thru doing some research on the water idea brought up earlier and water would simply not be able to be moved fast enough.It would require a 480 gallon per minute pump(!) to have enough speed to move the water as quickly as lead can be moved and you would be just plain out of luck if you lost electrical power because there is no hand pump that could do the job remotely quick enough.
The question I'm most interested in exploring/solving is whether or not the fixed wing system(side to side-same as Bethwaite/Langman) would be
superior to the original idea where the wing itself along with the ballast moved as well.Like an IC sliding seat. The original rc test moved both the rack and the weight so that there was nothing to leeward at maximum RM. The Bethwaite/ Langman systems are fixed racks with buoyancy pods. The fixed version would seem to be safer from a capsize perspective (for a disabled sailor) but presents a problem in a pitchpole in that it would not recover w/o the active effort of the crew . So either version requires a ballasted daggerboard for the ultimate in safety which would be required if sailed by a disabled crew. And there is no other boat currently being built anywhere that I know of that would offer the combination of self righting safety and high power to carry sail as is represented by this boat(at least in this size range that the crew sits down inside).Not even the new Bethwaite LAS(Lead Assisted Skiff) offers the power to weght ratio this boat potentialy does combined with a selfrighting capability.
   I apprecate everybody's comments and thoughts on the concept; it is a work in progress and I sure don't have all the answers yet but I'm working on it. Please take the time to look seriously at the ideas here and let me know what you think-especially as regards the two different wing systems...

Posted By: 49erGBR735HSC
Date Posted: 28 Oct 05 at 6:24pm

I think keeping the boat as simple as possible is the best idea. Have a look at modern day skiffs and see how simple the deck layouts are, for example the 49er, the new rules 18s (Murray design), 29er, Musto Performance Skiff, etc. I don't think any heavy boat can be described as a true skiff. My personal opinion is that the balasted boats are going to be an equivalent to small sport-boats, which is not a bad thing. The foils idea seems good, but a lot of development on the foils alone will need to be carried out. Is there no way of designing a skiff which relies on an active crew but can have a fixed position for the helm, maybe a happy compramise. There are a few disabled sailors who are sailing cats successfully just now, maybe this idea should be promoted more as well as developing balast reliant boats. 

Dennis Watson 49er GBR735 -
Helensburgh S.C - Boat Insurance from Noble Marine

Posted By: Granite
Date Posted: 28 Oct 05 at 6:58pm
Why not just go for a multi hull Tonns of stability and speed with out the complexity and vast expence that that brings?

If it doesn't break it's too heavy; if it does it wasn't built right

Posted By: 49erGBR735HSC
Date Posted: 28 Oct 05 at 7:15pm
I remember reading in Y&Y about a sailor who was paralysed from the waist down sailing High Performance cats, think he could have been racing a Tornado then a single handed cat. Why not explore this idea more instead of trying to design radical boats. Why try and solve a problem the hard way when there are easier routes around it. Plus I don't think any of the mono-hull heavy skiffs will ever match a cat in the performance stakes or even get close. Has anyone actually consulted the sailors who would be interested in sailing the proposed classes and actually considered what they want? It's okay having a good idea but in practise it's success when developed is whether it will appeal to other people.

Dennis Watson 49er GBR735 -
Helensburgh S.C - Boat Insurance from Noble Marine

Posted By: Doug Lord
Date Posted: 28 Oct 05 at 9:15pm
Dennis, I don't look at this as doing it the hard way. In fact when this is worked out it will be relatively simple and pretty fast. The only singlehander's(mono's) in a range close to this boat that you sit inside are
fixed keel. Bethwaites "LAS" is doublehanded.I have seen one small heavy "conventional" tri but this thing would be much lighter and probably faster.
I'm a great believer in what foils can add to a boat like this(and/or Bethwaite and Langmans Maxi Skiffs for that matter). Partial lift or full flying foils have a lot of promise. And when you factor in results like the 11' Moth foiler beating A class cats in a series of races and being 15% faster than a 49er you are talking about a coming revolution in dinghy(and keelboat!) performance. But thats another story.
For the time being I think that there might be a market for a boat that the skipper sits down inside to sail like a 2.4 Meter but that is three or four times as fast. I've talked to one disabled sailor that used to sail planing dinghies before he got hurt and he said that he would like to experience the thrill of planing again.(sails a big boat and a 2.4 now) I hope to help him do that even if I just build one boat.
But I think the concept has merit for able bodied sailors as well-maybe older people who just don't want to hike or run across the boat every time they tack or gybe.. The more ablebodied sailors would not need the ballasted daggerboard and that puts the numbers in the category of planing to windward!
Still plenty of problems to solve but it may well be worth it...    

Posted By: 49erGBR735HSC
Date Posted: 28 Oct 05 at 9:33pm
There was actually an International 14 that was developed to allow sailors with limited movement to sail High Performance boats. Deck modifications were carried out, out-riggers added and I think it used Hurricane 5.9 sails with a 14 kite. Can't remember all the details but I'm sure other people on the site will. The boat is in production but can't remember the name of it, think its a Mantra but can't be sure. The concept that you are working on seems to be developing quite well and it will be interesting to see it on the water. Have you thought of contacting RYA Sailability for some feedback on your project?

Dennis Watson 49er GBR735 -
Helensburgh S.C - Boat Insurance from Noble Marine

Posted By: Doug Lord
Date Posted: 28 Oct 05 at 9:49pm
I'd really like to know more about that 14! Post it or e-mail me at : if you find a url for it.
Probably a little early to contact any organizations about this concept. That probably calls for a nearly worked out prototype that they could help optimize but which answers most of the questions that have been brought up here.
Look back a bit when you can and see if you can come up with any pros or cons between the two wing systems...

Posted By: Chris 249
Date Posted: 30 Oct 05 at 11:20am
"And when you factor in results like the 11' Moth foiler beating A class cats in a series of races and being 15% faster than a 49er you are talking about a coming revolution in dinghy(and keelboat!) performance. But thats another story."

Really? What series of races was that? There are hints it may have been at Black Rock but there's nothing on the website I can find. Can you please provide us with more information? Which As are we talking about?

And are you talking about Colin Newman's analysis of Simon Payne's performance at Abersoch Dinghy Week (if I have my regatta right) when you say the Moth is 15% faster than a 49er?

If so, shouldn't you (in the name of truth) say that SOME analysis of ONE regatta said that in THOSE CONDITIONS one of the world's best Moths was faster than the 49ers that raced?

Shouldn't you also perhaps include other information ie Colin's analysis of foiler performance in non-foiling conditions, the Brass Monkey performance etc?

Incredible boats, amazing performers in  the right conditions, spectacular and breathtaking. But are they REALLY 15% faster than 49ers?

Posted By: Doug Lord
Date Posted: 30 Oct 05 at 10:50pm
Chris, the truth is that the Moth is the most advanced singlehanded dinghy in existence.The racing against the A class cats was done over five or 6 races with Rohan sailing against a good A class fleet and the story is on his website. The "15% faster than a 49'er" was (IIRC-ha!) a direct quote of Simon Payne.
I finally found out about the Brass Monkey-Rohan sailing a 5 year old converti-boat and a newcomer to foiling sailing the other Moth-both had breakdowns. There are many more instances of the Moth showing it's speed against cats, 49'er's and I14's then there are "Brass Monkey" type cases.
The fact is that monofoiling as a sailing discipline is new and not-by any stretch of the imagination-a mature technology. In fact. monofoiling technology is in it's infancy and even without any record of competition against other boats is an awesome, incredible, revolutionary development whose potential has not even begun to be realized.
Chris, as an experienced IC and other sailor what is your reaction to the subject of this thread?

Posted By: Chris 249
Date Posted: 31 Oct 05 at 7:00am
Yep, the Moth is the most advanced dinghy/skiff.
Yep, it's gone very, very fast.
Yep, there's more to come.
But is it REALLY 15% faster than a 49er if you look at the broad range of conditions? Simon's comments were about one regatta, I think you'll find.
I could go into detail about the Brass Monkey etc (the fact that the foilers were struggling to keep with Cherubs etc despite being sailed by the world champ and (IIRC) the 29er worlds runner-up, etc). I know it didn't give a balanced view of the incredible performance of these wonderful boats, but neither does your account of their speed.

I was not meaning to attack the foilers, but merely to comment on the hype.

Re the sliding ballast concept. It requires fairly fast work on the seat but (more importantly) fast and fairly powerful work on the mainsheet and makes tacking difficult. Most sailors get totally intimidated by Canoes. Put the average FD/Laser sailor in one and they capsize repeatedly. And while I love Canoes, they still go only about as fast as a Hobie 14.

Given the problems and balancing them with the thrill and speed, I think a disabled sailor is much better off in something like a Windrider tri.

Posted By: Hector
Date Posted: 31 Oct 05 at 2:38pm
And I thought I was barking!

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