Foiler Design

[CT 249]

Originally Posted by sigurd

Super interesting paper. The drag figures from the hull and tramps makes me wonder why the moths are not doing these things:
1)Lower freeboard

I think they have already been cutting the freeboard down as far as they can, considering that the boat has to get through waves when it's off the foils.
Freeboard has been a hot issue in Moths since Joshua Slocum was in nappies. :-)

2)netting and not fabric tramp

Years ago, they had no tramp; just a space and a hiking strap. IIRC, netting (consisting of a whole lot of small rounded sections that may be extremely high drag) creates more windage than a fabric tramp, and (to the best of my inexpert recollection) it's harder to move around on because it is more flexible.

Again, tramp windage and usability has been something they have been working on since I was a kid.

3)jibing the daggerboard so the hull can point straight into the wind (makes for funny landings at 20kt I guess)
4)International Canoe style seat instead of tramp (with windward heel the lee tramp is the draggiest one I assume)

Not allowed for one.
For another, retaining balance while slamming the seat across is hard enough in a 3' wide Canoe. It would surely be even harder n on a 1' wide hull, or while flying through a gybe or tack. For a start, where do you stand or sit while the seat is being slid across?
5) if the tramp sail is removed as in 2 and 4 then it may start to make sense to make gunwales more rounded.
???

At least some of these have been hot issues for eons, and the subject of much development within the class already.

[Doran Oster]

Hello,

I am new to this forum, so please excuse me if I am asking dumb questions.

I sailed Raves for a few years and where I developed a system for controlling the flaps manually rather than with wands. It was an obvious improvment, both in speed and fun, over wands. All of the top sailors in the class followed suit before the class died out. I still have my Rave rotting away, but I mostly sail an A-Cat now. I am starting a project to add foils to the A-Cat. My current concept is to ditch the T-Foils and wands, and try a scaled-down but self-correcting system like L'hydroper's.

So here is the dumb question: Is there a mathmetical method for describing Tom Speers H105 foil cross-section or another method of importing the cross-section as a curve into Pro/E? Is the H105 section public domain or does Tom license it? And another dumb question, would anybody recommend an alternate crossection?

Doran

[Doug Lord]

Doran, welcome! Dr. Sam did an 18' surface piercer-maybe he would help:
hydrosail@aol.com Also, Tom is a member here and you could PM him.
I'm working now but later on the other computer I can get you the foil sections Steve Killing used on the design for Rocker-the C Class foiler w/fully submerged foils.
Sounds like a great project. By the way ,Tom has some interesting ideas on how a surface piercer could actually benefit from an active control system like a wand....

[Doran Oster]

Hi Doug,

Thanks for the response. I'll contact Tom directly. And thanks in advance for Killing's sections.

I made some drawings of a piercer with flaps, but at this stage, I prefer a passive system. It is hard to arge with l'hydropter. Is l'hydropter's foil design published?

Does anybody use two surface-piercers for rudders rather than one t-foil? I don't want to modify my A-Cat too much for this experiment.

-d

[Karl Wittnebel]

I am confused by the use of these terms. It would seem to me that, in order to generate an upward lift vector, the wake behind a hydrofoil would have to move downward behind the foil, which would make it "downwash", not "upwash" relative to gravity. But perhaps there is an upward component to the wake also...like a boat wake extending out laterally in both directions.

In Moths, the trend is definitely toward longer rudders, which probably has nothing to do with optimal lifting foil position re: mainfoil, but is interesting nonetheless.

Re: netting, some guys sail with it, mostly on the model that it works on the big tris and cats. It looks pretty cool and you can certainly see the foils better in real time.


Quote:
Originally Posted by Karl Wittnebel View Post
Tom where is that tutorial? I looked on his website but didn't find mention of optimizing two foils in relation to each other.
This isn't Matveev's material, but I just ran across NACA-RM-L52L11, which has test data for the waves behind a hydrofoil. This should help you locate the aft foil in the upwash from the forward foil.
__________________

[Doug Lord]

Originally Posted by Doran Oster

Hi Doug,

Thanks for the response. I'll contact Tom directly. And thanks in advance for Killing's sections.

I made some drawings of a piercer with flaps, but at this stage, I prefer a passive system. It is hard to arge with l'hydropter. Is l'hydropter's foil design published?

Does anybody use two surface-piercers for rudders rather than one t-foil? I don't want to modify my A-Cat too much for this experiment.

-d

--------------------------
Doran, here is the foil section(Selig 3010) and data from it:

[Doran Oster]

Thanks, Doug!

[Doug Lord]

Originally Posted by Doran Oster

Hi Doug,

Thanks for the response. I'll contact Tom directly. And thanks in advance for Killing's sections.

I made some drawings of a piercer with flaps, but at this stage, I prefer a passive system. It is hard to arge with l'hydropter. Is l'hydropter's foil design published?

Does anybody use two surface-piercers for rudders rather than one t-foil? I don't want to modify my A-Cat too much for this experiment.

-d

===========================
Doran, here is a picture of Dave Carlsons foiling A Cat. The biggest problem I see is the narrow beam-Hydroptere is 59' LOA and 80' wide! Looking forward to hearing more as you go forward!

[Doran Oster]

The A-Cat is only intended as an inexpensive test bed for the foil design. If the concept works, a custom hull could be justified. On the other hand, an A-Cat with piercing foils should be more stable than the bike design of a moth, I suppose.

I found several software programs at the NACA site that provides the foil shapes and analysis that I was looking for.

Does anyone know if heliocopter blades have a uniform foil shape, or is there an adjustment in the foil shape to compensate for the blade twist?

The Rave default incidence angle was set at about 3 degrees. What are moths doing?

-d

-d

[Doug Lord]

Originally Posted by Doran Oster

The A-Cat is only intended as an inexpensive test bed for the foil design. If the concept works, a custom hull could be justified. On the other hand, an A-Cat with piercing foils should be more stable than the bike design of a moth, I suppose.

I found several software programs at the NACA site that provides the foil shapes and analysis that I was looking for.

Does anyone know if heliocopter blades have a uniform foil shape, or is there an adjustment in the foil shape to compensate for the blade twist?

The Rave default incidence angle was set at about 3 degrees. What are moths doing?

-d

-d

======================
Doran, I'd sure think an oversquare trimaran platform would be the best foiler platform-Sp or fully submerged for lightness, RM etc..But I see what you're trying to accomplish as well.
Helicopter blades have washout-they're twisted. Have you seen the new carbon foils Dr. Sam is offering?
http://sites.google.com/site/hydrosail/HydroSail-Home

Dr. Sam told me the Rave was +2.5 degrees on the mainfoils and 0 degrees on the rudder(relative to the static wl)-both foils symetric; the early Moths were about 1.5 degrees on the mainfoil and 0 degrees on the rudder foil(both asymetric 63412 sections), if I remember correctly. On a few boats now the angle of incidence of both foils is independently adjustable on the water(as it is on my new-and old boat). My boats use a symetric rudder foil and an asymetric main foil and there are some Moths like that as well.

[bistros]

Originally Posted by Doran Oster

The A-Cat is only intended as an inexpensive test bed for the foil design. If the concept works, a custom hull could be justified. On the other hand, an A-Cat with piercing foils should be more stable than the bike design of a moth, I suppose.

I found several software programs at the NACA site that provides the foil shapes and analysis that I was looking for.

Does anyone know if heliocopter blades have a uniform foil shape, or is there an adjustment in the foil shape to compensate for the blade twist?

The Rave default incidence angle was set at about 3 degrees. What are moths doing?

-d

-d

Doran:

I have never designed a successful foiler. I can not produce a single picture of one of my designs foiling - even while tow-testing under power. I can not produce a single picture of me foiling. I am not an aerodynamicist, a hydrodynamicist or a qualified naval architect.

I have now established that I am just as qualified a foiling sailboat designer as the most prolific posting foiling "expert" on the forum.

I guess I could compensate for my lack of achievement and success by posting lots of pictures of other people's designs foiling, but that just seems a little disingenuous to me. I'd rather you judge my post with clear knowledge of my qualifications, so you can value it appropriately.

Foiling is a performance sailing niche with a wide range of possibilities, and defining a project needs to have a good idea about goals:

1. Is sustained speed on one favorable point of sail the goal
2. Is maximizing time on foils across all points of sail the goal?
3. Is just foiling at all the goal?
4. Is foiling without hiking/trapezing/moving ballast the goal?
5. Is user-friendly, easy and simple foiling the goal?
6. Is foiling at low cost the goal?
7. Is this the first affordable/basic learning step in a much larger "plan" for the future?

There is a world of difference between boats like the Rave and Hobie trilfoiler, the International Moth and large scale foilers like Hydroptere.

If question number 7 above is on the mark, your A-cat idea is a great place to start. It's fast, it is light, and it won't require a huge amount of money to get in the game and take a swing. My recent thoughts about a potential project like yours were aimed at "Yes" to questions number 3 and 6 above, I thought a very light, simple catamaran may be a great place to start.

Perhaps a more in-depth discussion of your design brief and resources may help the "real" experts who follow this forum develop some useful criticism and direction.

Cheers,


--
Bill

[Doran Oster]

Hi Bill,

I posted a reply but it didn't seem to stick. I'll try again.

If you are interested in criteria #3 and #6, then you should buy my Rave.

I am mostly interested in criterion #2.

-d

[bistros]

Originally Posted by Doran Oster

Hi Bill,

I posted a reply but it didn't seem to stick. I'll try again.

If you are interested in criteria #3 and #6, then you should buy my Rave.

I am mostly interested in criterion #2.

-d

You've chosen the most challenging and expensive route. You should take a look at Sam Schnieder's blog, sr-71monofoilerproject.blogspot.com/. Sam has taken the "take no prisoners, high quality" approach to his development. Sam's also very design tool literate and is a second generation designer - his Dad is a naval architect and builder as well.

Your project will demand very light weight, exotic materials, advanced build techniques and solid research and design. If I were in your shoes, I'd consider setting milestones for small incremental mini-projects instead of trying to design the perfect foiler out of the gate. Using your A-Cat as a testbed is well suited to the approach. First things first, getting the foils sorted is number one. One of our major supporters of Canadian high performance sailing is Fred Eaton. "Fredo" is the man behind Canada's win of the C Class Challenge cup, taking the former "Little America's Cup" from Steve Clark and winning the world championship. Fredo hired Steve Killing to design his C Class cats - with full co-operation and assistance from Steve Clark. Fredo built two - Alpha (the winning cat) and Off Yer Rocker (exactly the same hulls & rig, but with foils). Trials proved Alpha faster around the cans, but Off Yer Rocker did show lots of potential and foiled quite successfully. Performance cats are a tough platform - they are so fast normally, that foils do not cause the same level of performance increase that they show on monohulls like the Moth. Fred also was the motivation behind Paul Beiker's B5 I-14 world champion design - Fredo owns the molds & tooling at Object 2 Skiffworks in Toronto.

I'm not interested in a "buy" option, as there was a stunning Windrider Rave for sale locally last year. Basically unused, and reasonable. I just don't have as much interest in foiling as I do in proving to myself that I can build a foiler. For some people the destination is the reward, for me it is the journey.

I like building things and solving problems. Shop time is therapy time for me. I actually like sanding mindlessly for days. It is actually such a departure from my real world development work in terms of visible accomplishment that I find it truly fun. I can't indulge my habits on a grand scale financially (I'm a suburban husband and father with a full time job and mortgage), so I tend to break my projects down into small incremental mini-projects that teach me a lot.

I'm an engineer by trade, and grew up the son of a master craftsman, so that may explain why building is more important than doing.

Best of luck in your project.

--
Bill

[Doug Lord]

Doran, your manual control system for the Rave was very inspirational to me-thanks! I'll sure be interested in hearing how your project progresses. Have you seen Doug Halseys foiler? He posted some pix under the Multihulls thread of the boat sailing w/o amas. I'll find it if you're interested.

[Doran Oster]

Does anybody know how high l'hydroptere can point?

Hi Bill,

Thanks for the references. If you are serious about designing foilers, you will learn a lot from sailing one. It's better than reading a book.

Hi Doug, Yes, I would love to see Doug Halsey's boat. He was the National Moth champion for several years. Maybe the best sailor I ever knew. He is an aeronautical engineer, too. It's a hard combination to beat.

-d