end plate effect

[kickingbug1]

    i have been thinking of adding a small triangular wing to the bottom of the keel on my cp16 to help with the leehelm. to accomplish this i think i could fabricate 1/4 inch aluminum plate the same shape as the bottom of the keel and affix it with epoxy. on the underside i would drill and tap a number of holes in pairs fore and aft. an aluminum "wing" could be then bolted to the bottom. the number of threaded holes would allow me to experiment with optimum location for the wing and the shape of the wing. the leading and trailing edges of the wing could be shaped for performance or possibly be "foiled" much like a rudder. any thoughts?

[nies]

When I first got my 78' it had lee helm,a book Practical Sailing by Tony Gibbs(82') gave good advice.....to permanently correct "increase the rack of the mast by tipping the mast aft"............while under way keep  captain and crew forward as far as possible and comfortable................I racked the mast aft and sit mid ship and that corrected the lee helm .......nies

[Salty19]

There is a site that you may want to register on and pose your question:

http://www.boatdesign.net/

Some real boat designers are on there, they can probably give you good advice as to feasibility, location, size, shape, etc. 

I would think that a fin would be most beneficial in reducing side-slippage and heeling effect, but I'm not sure...I design computer networks, not boats

I wonder if part of the leehelm issue is the mast rake, and perhaps sail trim?

[NateD]

There was some discussion about this back in December: http://cpyoa.geekworkshosting.com/forum/index.php?topic=5910.0

I don't think it is going to do much to help lee helm. It would only shift your center of lateral resistance when the boat heels. But I guess if you're only feeling it when the boat is heeled, then it might help. As others have said, mast rake and balancing your sails will probably fix the issue. These boats are known more for weather helm than lee helm.

[kickingbug1]

    hopefully i will get to test your ideas before it gets too cold. i thought you raked the mast forward not aft?

[mattman]

Hi, Kickingbug1, when do you experience the lee helm? I notice a tendency for neutral helm in really light air. Weight forward and induced heel tends to help. I also think that the high freeboard and rather soft turn at the waterline provides very little bite forward allowing for the bow to fall off. When I look at the underwater profile it seems the keel is well aft of the cle topside compared to a standard spade where the cle appears more centered. (I know this observation is superfluous, by definition the cle topsides has to be forward for leehelm- and aft for weather helm,and cle below is effected by the trim on the hull and subsequent lift changes which would influence helm balance and underwater cle, now I wonder what the design parameters were for for crew weight and placement??? ). Btw, the cp16 sails very much the same as a tangerine (Renken) 18 I had for a year back in my early days. I never did get that boat to sail particularly well. They seem to have very similar underwater profiles as well as the high freeboard forward. It would be fun to play with a centerboard 16 to see where the best helm is with centerboard position and hull trim. I think that would be quite telling. Is there one that comes to Carlyle or we could travel to find one!! I am sure the two of us can get out and do some comparison sailing and if we got wroundy out there that would increase the data input. Not sure I will get out again this fall on the 16- the band is busy and still a weekend of racing on the Flying Scot, then the dreaded holiday season, but I am scheduled for the Abacos in the spring-woohoo!!.
Happy sailing.

[kickingbug1]

    thanks for the input matt. i might get out today if i can talk her into it. supposed to be west at 10 to 20 which is about perfect (less wave action). the problem that i have is really me not dealing with the boat as it is. i think it could point a lot better than it does. after reading some info about the precision 165 which has a shallow draft kind of wing keel and supposedly points pretty well, i thought the com-pac might be improved. worse case scenario, i end up with a piece of aluminum on the bottom of the keel (the "wing" could be removed. if you can get away to sail give me a call 588 3889. according to the local weatherman we will still see some warm days before winter sets in.

[skip1930]

This small triangle plate is HORIZONTAL? And not vertical right? [Vertical ... how ya get her on a trailer without busting it off?]

O.K. the wing keel was invented to decrease the ship's draft.
More weight down there with less depth.
It has nothing to do with combating lee helm.
That's hull and keel shape hydro engineering.
The sail is lifting device, like a wing on an aeroplane. You stop the lee helm, you stop the lift. You stop the boats progress through the water.
And not a lot of benefit if it's foiled ... that's a selling point for showrooms. [I know we have foiled rudders, they help. I don't see working for a keel. It's not an America's cup boat.]

Just like my rock protecting 6mm marine aluminum 'KEEL BOOT' cut to the shape of the keel and glued on with Marine-Tex, this could be the 'base plate' to attach a small triangle fin.

Really? A 1/4 inch plate. Drill and tap a multiplicity of holes into a glued on plate? The tapped holes need to be blind holes otherwise ...
... I think when the screws hit the fiberglass under the keel they will pop the glued on plate off.

Your not going to drill through the plate and into the keel's fiberglass-cement-and pig iron and keep it water tight. Not possible.

I certainly would not drill-tap-and screw on a small triangle plate to a 1/4" plate, fearing it will bust off sometime.
Pick the location and Weld the son-of-a-gun on to the base plate before the base plate is glued on. [Don't want to destroy the fiberglass under the plate with welding heat.]

You asked. Just my two cents. skip.

[Craig]

Agree w/Skip! A lot of negatives with little gain. My initial concern was also the strength/integrity issues Skip addresses. The fewer the holes in your boat, the better! Correct your lee helm issues with rig tuning  and weight distribution(you may want to experiment with some ballast). Raking the mast aft is the correction for lee helm. I firmly subscribe in the KISS approach!

[mattman]

Kinkingbug1, it is fun to improve ourselves and out boats. That is why I sail, I never stop learning. Taking lessons learned from one boat to another is a joy. After flying the spinnaker all season on the scot-I sure look at the luff of the jib on the yflyer differently...Thanks for your number, will give a call as the schedule opens. 

[Citroen/Dave]

1.) Ops.  Check the owners manual.

2.) Some time ago I proposed adding a little depth to the keel in the shape of a hydrofoil. (See "Taking the brakes off" and that thread in C16.)  The goal was to stop the drag caused by the blunt cut off of the keel.  I noticed that the top of cunning tower of modern submarines, viewed from the side, were shaped like half the tower in cross section.  Subs certainly do not need turbulence and drag while trying to remain undetectable.  I though that a "keel bra" would allow the C16 to go faster, sooner, until hull speed was achieved, and give my boat a little more protection from the rocks.  Now, I am content not having to raise the side boards of the trailer to accommodate such experimentation.

3.) This idea followed after seeing that most planes at Ragan Airport are now sporting winglets to reduce drag.  I don't like the idea of winglets for the C16 keel. If I am heeling that much and slipping sideways, I don't want additional downwards lift like a racing boat to counter the heeling. My C16 is old and I don't want to exceed the stress limits designed into the standing rigging.

My three cents worth,
Dave

[Glenn Basore]

I had experienced Lee Helm on my small Hunter 170 and with the help of an experienced sailor with the same boat and a shroud gauge, we Tuned the shrouds to what he had on his boat. My boat was now the same as his and was a dream to sail, no more Lee Helm.

My point here is, I would start with the shroud lines (all of them) using the shroud gauge, its the only way to see what amount of tension you have on them . hopefully equal !  also, the gauge will call out specif numbers for thickness of your shroud lines , I think I was at less than 10 %.

If you can find another boat like yours that sails well, without lee helm, you could check his shrouds.

The only thing I would think the wing keel would help with would pointing into the wind better.

Glenn

[nies]

All rigging books state aft and it worked for me , since a few others think forward maybe there's something making your boat special.................i would recommend starting on shore with the boat level and tune stays to the same tension and the mast exactly vertical, go for a sail , if still lee helm rack the mast aft, if it gets worst then rack forward ..........one way or the other your problem should be solved.......nies

[kickingbug1]

    i asked for it and i got it-----

[skip1930]

"Aeroplanes 'are now sporting winglets to reduce drag'."

Well almost. When Burt Rutan was well-known as a designer of experimental planes. And Jeana Yeager held nine world flight records as a pilot. Winglets were invented and experimented with to assist in flying non-stop around the world. Unfortunately, one winglet was ground of on the tarmac in take off and the other fell off in air. No matter. Dick Rutan and Jeana Yeager finished the epic flight.

The installation of winglets reduce turbulent vortex's. Thus enhance lift and that allows for shorter wings and shorter wings have less surface area and that is where a reduction in drag occurs.

So why are we in a frenzy to add surface area to what is under water? ... it's bad enough when surface area is added to what is above water.

All this fin talk is horizontal and not vertical. Although a short vertical fin may help her point higher ... it also makes a change in direction more difficult.

Marine Architects are always juggling and cyphering for the best compromise. And that's all boats are. Compromises.

The civil war era racing sail boat, the schooner AMERICA, had severely canted masts and won handsomely over it's competition. After the war she was found sunk in a backwater with no masts at all. When she was refloated and re-rigged her two masts were vertical.

skip.