Foiler Design

Doug Halsey's foiler

Here's the thread, Doran: http://www.boatdesign.net/forums/mu...ng-hydrofoil-trimaran-without-amas-23293.html

 

Very cool.

 

I agree with Doran Oster. Yes, zooming in on Halsey's foiler one can see the freely moving airborne water droplets, a phenomenon typical of high Reynolds number flows. And the intricate non-spherical shapes of the droplets show that the Weber number is high.
Regards,
Booster

 

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Doran, with your experience with manual altitude control on a Rave I'm curious if you think the same think would be an advantage on a bi-foiler like a Moth for racing? Assuming the skipper was willing to practice, do you think altitude control using something like a twist grip on the tiller to control the main foil flap could be doable and faster than the wand?

 

Hi Doug,

The hand controls and subsequent automatic incidence control made the Rave much faster than the production boat with wands. Modified boats came out of the water faster, stayed on foils longer, and pointed higher. They made the Rave a lot more fun.

Raves are peculiar. The skipper sits in a chair looking forward. The hand controls were usually three levers that you straddled. The middle lever controlled the rudder and the other two controlled the front flaps. Since you are stuck in a seat, you cannot use your weight for controlling heel. You set the weather flap for negative lift instead.

I have never sailed a Moth on foils, but I understand that the rudder flap is controlled by the skipper and the single front foil flap is controlled by a wand. The skipper shifts his weight to counteract the heeling moment and to control the plane of the foils. You will have to ask a Moth skipper if there is time for adjusting the front flap. I don’t know.

I am a little too big for a Moth. Actually, I’m a little too big for an A-Cat. I would like to build a foil boat with enough sail so that my weight is not a factor. I don’t see bigger boats on two foils. My experience with the Rave has taught me enough about T-foils for now, so now I am interested in surface piercing foils. I would like to work with someone who understands fluid dynamics better than me. I like Tom Speer’s idea for forming a team effort.

-Doran

 

Thanks Doran. Most Moth skippers I've talked to think that there is already too much to do. I tried it on the first version of my boat a few years ago and ,other than a poor installation by me(with slack in the cable) it seemed to work well. I didn't really spend enough time to properly evaluate it, though.
I'm working on version 2 now-we'll see.

 

There is a description of our hand controls at www.doranoster.com.
-d

 

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Wow! Thanks a million,Doran...
Are you pretty much sold on doing a surface piercer next?
One thing I did for my new boat was to calculate what range of all up weight I wanted ideally for my 240lb(going on 220) for max performance singlehanded but with the capability of taking one other person for performance daysailing and I came up with a number of candidate cat hulls and then went looking. I found a very slightly damaged Hobie Miracle(19.5' as purchased; 21' as modified) hull which meets my requirements almost perfectly. It is being modified a lot-deck, bow, foil locations, extra reinforcement but was $300 and will save a lot on starting from scratch. Just an idea....
PS-I used the total weight of the boat(incl crew) as the displacement for one hull after looking at photos of the boat flying a hull. Since a couple of experimental variations of the new boat will have weight close to this weight and have to carry it at less speed than the Miracle flying a hull before foiling, the mods include changing the forefoot and bow and creating a rudder trunk faired into the hull making it appear to be double ended. Without this transom mod there would be a lot of transom drag in a couple of the experimental versions. This way the hull works well from the lightest version to the heaviest version.

 

Doug,

How are things going on your build? Why don't you blog it on blogspot.com - they'll give you a free site and it is dead easy to use. It is a useful tool to both give you motivation as people following the blog are interested and it also serves to quiet down the critics because they see progress.

It is fun to do and will serve those that want to follow you as a roadmap.

Cheers,

--
Bill

 

Not going well at all, Bill. I have www.monofoiler.com and will update that site with details down the line. What is the cost of a blog like that?
I'm certainly not interested in doing something to "quiet down the critics" nor do I want anyone following me "as a roadmap"-my work is too experimental and I wouldn't want someone going off the road and hitting a tree-like I do from time to time.

 

I pay $112 a year to my hosting service and if I put a simple set of Google ads on the site, then it will pay for itself. As it is, $112 is one very nice dinner out with my wife and she'd rather I post my work for the next year. We can stay home, make a bitchin' pizza from scratch and watch an old Bogart movie.

Everybody is interested in quieting the critics. Critics, Doug, are but the flip-side of adulation. If none of this is important to you, then why spend any time on the Web Fora at all?

 

Hi Doug,

I would like to see your design drawings or models if they are not propriatary. I have purchased Designfoil and can import its foil cross-sections into Pro/E. DF is disigned for air flow, but it provides a way to modify the Reynolds number. I expect it will provide the basic coefficients for hydrofoils at sailing speeds. I hope to play with it this weekend.

Pro/E can extrude foils with complex profiles and ever-changing crosssections. It can predict the weight of the foils but I don't have the chops or software to predict how much load these designs will support or how to optimize the design. How do the big kids do it? Is there a service for hire?

-d

 

Generally, blogs are free. The little one I'm maintaining for the build of my son's boat hasn't cost a cent.

In the academic world it is really important to publish your work - succeed or fail. The same thing holds true for non-educational endeavors, but sadly the nonsense legal fiction concept of "intellectual property" raises it's idiotic head and causes progress to slow, companies to fail and lawyers to get rich.

As you are talking about ground breaking and experimental work, publishing can bring positive constructive criticism and contribution from people all around the world. The quality and diversity of the skills necessary to get all the details right on a project of this scale is huge. Problem solving becomes easy when there are many sets of eyes looking for causes.

Saving the people that follow you from duplicating mistakes you have made and solved allows them to concentrate on improving the state of the art, not relearning lessons already past. This is why, good or bad, publishing is important.

The world would not be where it is today without open collaborative knowledge sharing through publication. It is entirely possible to be open and accept outside input without sacrificing commercial potential.

--
Bill

 

==================
Doran, all I have now are some very rough sketches of two of the versions of the new boat and two rigs and the full size plans that I'm working with.
They(not the full size plans) are in my gallery on boatdesign. My original set of foils was based on the 63412 section and made by John Ilett in Australia about 9years ago. The main foil was 63412 asymetrical and the rudder foil was 50% of the mainfoil area and symetrical. They'll be used on the new boat. The two things that are different about them are:
1) Because of discussions with Dr. Sam about flap lockup due to foil flex I tried a small partial span flap(pix in gallery)-which worked very well on the 9% t/c foils on the F3 model-and seemed ok on the 16. Tom Speer thinks that may cause xtra drag compared to a full span flap. Dr. Sam had problems on the Rave with the flap locking under load when the foil bent but the Rave loads are much higher than on my bifoiler. I'm going to extend the flap length(span) a bit though since I want to try a 30% flap.
2) One of the things I want to experiment with down the line is intentionally jumping the boat and achieving safe,reliable re-entry each time(similar to a Rush foilboard-but not as high(!)). To facillitate that I designed the foil with dihedral tips that I think will help re-entry. A secondary reason ,initially, was to use the foil tips in combination with a manual main foil flap control( with minimum flap area) for altitude control assistance when manually flying. The idea was that the tips would come out first making it harder to unintentionally jump. That's a ten year old idea....
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Some interesting tid bits: the mainfoil loading on my new boat with two people on board should be about 150lb/per sq.ft.(light version). A Moth and the 26' Mirabaud bi-foiler mainfoils are both around 160lb per sq.ft..
Have you see John Howes foils? He has designed a foil that does not require an altitude control system when used on a bifoiler. He might be open to you using the section for experimental purposes.
See the pix below including my mainfoil with the very small partial span flap and the Tomohawk that uses Howes foil and the Howes foil itself:

 

Howes foil

Doran, here is a post by Jon Howes from the Tomahawk thread discussing his new foil:
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"I don't want to get in the way of a good fight, but often point out, when enthusiasms start to get in the way, that the art of engineering is being wrong with grace, learning from it and moving on. The Tomahawk foil is an application of a foil section I developed for another, rather extreme application that may (note "may", not "will") remove much of the difficulty of foiling for the average bloke/blokess with the potential for high speeds in the right conditions/points of sailing.

When fully sorted, it may even be quick upwind, however, if too slow to surface run then it will always be slower than a conventional foil. Surface running can occur upwind but obviuously the power needs to be present to get it into surface running mode in the first place. What it has already proved (on the sailboard) is that when fully established at the surface it is very quick. How this compares to a conventional foil, or even a well sailed conventional board, only comparative testing will show although I am fairly confident in the board application that it is faster than the conventional approach.

As for the amount of vertical surface below the foil, yes, this is small but it only needs to work without assistance from the bit above when the boat is sailing fast and it seems to be sufficient for in these conditions. We are currently performing some final optimisations (losing the tee foil on the rudder and using a surface runner here as well, for example, which gets rid of the twist grip. Weight shift can then be used to squash the rudder foil down at low speeds, at higher speeds both foils then surface run).

I think the boat is likely to be slower around a course than a current Moth but much easier to sail/simpler. The board, from Linton's comments, can be pretty terrifying. Since I am not (yet) a board sailor I have to take his word on this. In case it got missed when posted elsewhere, here is the email I got from him after first flights on the board:

"Sam and I both sailed

Oh my word!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

That was the scariest bit of fun I have ever had.

Damn it felt as though it was quick or as quick as I want to go!

Apart from some side slippage issues and fin stall (which can happen on normal windsurfing) the board was really close to being very good.

Jon I reckon I will soon have all the information you will need to properly design this.

Buzzing

Linton

We will talk"


My sailing experience: self taught at age four in a modified Royal Air Force dinghy that used to be carried in a Lancaster (apparently), moved on to an Oppy, sail number 285 which makes me feel ancient, thence to Moths, both the British kind and the foreign version of inferior manufacture (Empire moment there, sorry), various charter experiences getting all the while heavier and more traditional, current boat, five tons of decaying rainforest built in 1936 and anything else I can scrounge a ride on.

Jon.
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www.howes-macnaghten.com
www.isentropic.co.uk
www.monofoil.com
www.tomahawkfoils.com "