aeroskiff 16

Hey Doug;
Just happened on to your aeroskiff 16 gallery shots by accident (clicked on a picture next to your name.)It is very similar to some ideas I have been playing around with but it looks like you have actually built the damn thing--Have you actually sailed it?I was wondering about how much breeze you would have to have for the designed weight sailor to sit on the wing with out capsizing to windward? I may try to build a slightly beamier version (I weigh 250) next summer.Does it have the SCP ratio to plane upwind--Looks like it would--Very cool looking craft.

---Saw

 

Hey, Saw the 16 was finished, sailed and foiled. It sailed very well as a "seahugger" but didn't meet my expectations as a foiler. The times it did foil were fairly hairy experiences but it never crashed or capsized(with me on it). My sailmaker managed to capsize the thing. The altitude control system was a manual system that didn't work too well-though well enough that I'm convinced it could be the fastest way to sail a monofoiler. I originally had two designs before building the boat-one was a skinny main hull with a rack like system-thats the one I should have built. On this boat the bow caused problems trying to get to take off speed in the short chop of the intercoastal-it was a bad design for a foiler. But with a modified bow(fine entry) I think it would work well. In addition, the cross arms were installed too low where they came off the boat and with even a slight roll they hit the water causing lots of drag. I made several mistakes but I finally got the thing to foil-very poorly- before I donated the hull to Calema sailing school. Tinho and I made a trade last year and I got the hull back in return for a 19' skinny hull I was working on. I'm modifying the bow and deck of the boat to serve as a prototype for the Trapwing movable ballast boat(see the "Design Challenge...." thread in this forum.http://www.boatdesign.net/forums/sailboats/design-challenge-trapwing-deck-ballast-12-22-a-29610.html
While I made several mistakes with the boat and the foil control system didn't work too well initially, there were some innovations that worked real well:
1) square top jib-a first as far as I know. The jib was attached to the rig by a short "gaff" that allowed the camber to be adjusted at the head. The attachment point of the gaff was adjustable and allowed the jib luff to twist to windward, in effect, giving the whole rig a bit of twist. Both main and jib had excellent gust response. The masthead rig seemed to work real well, as I thought it would, from model tests.
2) the foils were 100% retractable-and the first to do that on any monohull foiler. The boat was trailered with the foils retracted and didn't have to be walked out to deep water as a Moth does.
3) the foils used an experimental partial span flap that worked well on the F3 model where it was first tested and seemed to work well on this boat. It was hard to make any concrete judgement about that due to the very little time the boat was foiled.
4) the main foil and rudder foil had an adjustable angle of incidence system that was a first as far as I know on a monohull foiler. The main foil system wasn't installed until just before I donated the hull but it was instantly clear that it made a major difference in ease of set up and tuning the foils.
5) I went with the wider hull to eliminate having to use "buoyancy pods" as I had designed for version 2-they would have helped on this boat as well and I believe they are critical for any "Peoples Foiler" wannabe for off the foils stability and ease of handling.
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This boat was quite a learning experience for me and will again sail(and foil) in its experimental "Trapwing" prototype mode-with a modified bow and LOA increased to a bit over 18'. A modified foiler version will have sliding bench seats, buoyancy pods, manual AND wand altitude control, the same rig, raised cross arms, a modified and extended bow and the same foils.The boat will be used from now on as an experimental platform.......

 

Thanks,Doug for taking the time to respond-
Im probably going to design my version as a "sea-hugger"-without foils- I'm thinking in terms of something like a scow-canoe about 50 inches wide and 16 ft long,narrower than a standard scow,but built low and light like a canoe,with hiking wings similar to what you have on the aeroskiff(I'll have to think about the wave dragging problem) and either fully decked over like your design or maybe with just a small footwell.I would hope to build from plywood and still keep it very light,maybe laser weight,but certainly less than fireball weight(175lbs).My main concern is,that it needs to have enough static stability that I'll be able to board the damn thing (thats going to be its name--The Damn Thing 1)without capsizing at the dock.Once I get some wind in the sails,I hope to be able to sit out on the wings,fast and stable.

 

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I'd go with a narrow, fine entry UNLESS you specifically design it to sail like a scow-heeled. My boat was designed to sail flat and I simply had brain fade with that bow-big mistake but at least I tried. The boat is light but very strong so the mods to the bow won't add too much weight for the experiments I want to do.

 

<removed>

He's really talking about an International Canoe type boat with racks instead of a sliding seat. The 16/30 canoe project from Woodenboat this past year is just about right, but there is a learning curve to make it stay upright at the beginning.

--
CutOnce

 

re:aeroskiff

hey,Doug;
I take your point about the scow type bow-I was considering that shape purely for stability concerns.It seems to me a pointy bowed boat (all other things being equal) would have to be either wider or longer to have the same stability as the scow shape.

---Saw

 

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Don't get me wrong-I like the scow shape-I raced on board an e-scow-its a blast! You're right about the greater initial stability but the scow has to be designed to sail at an angle of heel.
Have you seen the "mini" designed sort of like a scow? It seems a bit ugly but it is apparently quite fast. Heres a picture-I'll try to find the article about it...
Excellent video of the boat sailing against another Mini: http://www.voilesetvoiliers.com/cou...video-voile-mini-650-magnum-david-raison-scow

 

Thanks for the video,Doug.
looks interesting.Have you seen the classic video of the old rainbow scow? Hard chine instead of all rounded and smooth,but seems to be a real performer in its day.My boatbuilding skills run more toward that type.I'm thinking similar that type,but much shallower,decked over,and lighter,yet longer.I dont know if the flat bottom/ample flare was "designed" to be sailed heeled or if that just happens as a result of being able to carry a rather large sail area for its weight due to the inherent stability of the scow form but in any event it seemed to work.

 

What about an International Fireball? Many have been built from plywood, hard chines, scow front and able to scale up to two people? There's nothing preventing you from implementing a B-14/Moth style seating rack instead of the trapeze.

You'd get a guaranteed performer and there would not be any question about build-ability. The smallish jib of the Fireball is also a good candidate for implementing a self-tacking system as well.

From a comfort point of view, shallow-to-no cockpit boats are extremely uncomfortable, as any hiking activity puts your feet high and forces you to use a huge amount of core muscles in comparison to a deep cockpit boat. The Devoti D-One actually raises it's hiking racks far above the sides of the boat to address this. There is a huge compromise in comfort made to accommodate self bailing cockpits - I've build a self bailing, rear draining boat and my comments are from experience. This is why even the Laser has it's tiny footwell - improved comfort (although Lasers certainly aren't comfortable boats due to the hard edges of the deck).

Highly raised seating racks are awkward looking and may raise balance issues due to the high placement of the crew weight. I always had wondered how much of a problem it would have been on Mr. Lord's aeroSKIFF if it had ever been really sailed/foiled in any serious unstable wind. The problem with dinghies is that you are constantly and quickly moving to deal with lulls and gusts - and moving "up and out" OR "in and down" constantly is a lot more work than just moving on one level.

--
CutOnce

 

The hulls being discussed are not even close to the same thing for comparison when one applies common sense to the design process.

Doug's failed Aeroskiff was supposed to be a foiler and as such, had virtually no connection to the sailing styles one would see with a scow. Scows achieve their speeds by either planing on their broad flat under surfaces, or being heeled up on edge, where they enjoyed very narrow hulls in the water and experienced speeds one typically associates with multihulls.

A foiler hull, no matter the shape, would have long ago left the limits of water contact when the boat got to planing speeds and it should never be seen sailing on its ear, such as one sees commonly in scow techniques. (the high speed windward heel technique known as Veal Heel, notwithstanding)

This whole thing is a red herring when it comes to analyzing the benefits of one hull form over another as it would apply to foil equipped craft and specifically to the now long defunct, aeroskiff.

Now, as to the French, bluff-bowed, scow-esque interpretation of the accepted Mini 6.5 form... In the video, you notice that the boat is never out in sea states which would seriously limit its sailing potential. Always, these guys depict the boat tooling along in relatively calm seas, weight well aft and the bluff bow held clear of the water. There's a reason for that.

Watch any bluff-bowed vessel as it moves through a more dynamic sea state and you will see that it suffers enormously compared to boats with bows that cleave, rather than bludgeon the oncoming waves. Wave induced drag at the point of the bow where it presents the most efficient form will favor those boats that can cleanly part the water, allow it to flow along the hull form and then cleanly return that water to its normal state.

A bluff-bowed design in a typical, oceanic sea state will present a very wide, very draggy form to the waves, slowing the progress of the hull as it seeks to be driven onward. When it is clear of the surface, it looks great, but when it is immersed, it suffers a huge penalty. In flat waters, such as those shown in the video, this design appears to excel. When it is taken out into the open ocean, where mini 6.50 sailing takes place, I bet that it will get banged around and go through stuttering steps as it plows and bolts, rather than cuts, smoothly, through oncoming conditions.

I'm not sold on the design of this French Mini and I'm very much not sold on the design of the hull used by Doug to fashion what was a non-functional foiling boat. Both of them represent too much thinking and not enough of the practice of simply getting it done in a pragmatic design sense.

 

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No, I haven't. One thing about the aeroSKIFF 16 hull:
it was primarily designed as a foiler with the wide hull there to make "see-hugging" less of a balancing act than the Moth. The bow was a problem for foiling in lighter air when there was any chop but I overcame that by foiling the thing in flat water just to sort out the problem with the control system.
A side benefit of the carbon/foam sandwich construction and its light weight was that when the boat was experimented with at the sailing school it would plane with about 60 sq.ft in 10 knots(without the foils). She was built with carbon,corecell and vinylester resin and was 128lb-without the racks.
The next use of the hull will take advantage of its planing ability using "foil assist" as well as its proven ability to foil with the original foils and rig. Lots more sailing/ foiling left for this boat-with a modified bow!
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Here is an article by Elaine Bunting on Raison's scow mini: http://www.yachtingworld.com/blogs/elaine-bunting/453787/pocket-rocket

 

fireball mod

hey Cutonce;
I think the fireball would be a great point of reference for the type of boat I am contemplating.I even mentioned it my remarks to Doug "maybe laser weight,certainly less than fireball weight at 175 lbs".I believe something similar to a shallow, decked fireball would fit my requirements.I would probably have to reduce the sail area slightly since hiking racks are less efficient than the trapeeze for getting weight to windward and also because my boat would be conceived primarily as a singlehander--not a two man boat.

 

Photos of this process?

Is there a time frame for this exciting scenario, or is it something along the lines of the mythological aeroskiff?

 

aeroSKIFF to Fire Arrow

Update on aeroSKIFF hull and foils: The hull is now stored at my sailmakers home and the original plans have changed again. Should the funding become available the hull will have a new bow added and will become the Fire Arrow trimaran.The mainfoil and rudder foil will be used on the trimaran as shown below. A large test model has been built using a modified version of this hull and in it's first full foiling test of July 24th, 2014 did very well.
The test model thread: http://www.boatdesign.net/forums/mu...f-righting-trimaran-test-model-36058-140.html

Pictures--main hull is a modified version of the aeroSKIFF hull:

click for best view--

 

Quoted as reference for another thread