End Plate Effect for Keel?

[MacGyver]

Could use a thickened epoxy like West System and 404.
That would be cheaper than marine tex......and could still be removed.
Since the plate would be aluminum..... heat applied to the plate would affect the epoxy and cause it to.break down.

Mac

[Pacman]

Mac,

That is a great idea.

I might try an experiment first to see how much heat is required to remove an aluminum plate from fibergalss. (Don't want to harm the boat if I decide to remove the plate from the keel)

Thanks,

Dave

[MacGyver]

One other suggestion is use 40 grit to rough the aluminum plate.
And I would just maybe go around the plate edge where it meets the keel, not gluing the center up. This way it is less to try to remove if issue occurs....

Mac

[Pacman]

Mac,

That is another very good idea.

It it ever did come loose, that would not be a serious problem and, if I did decide to remove it that will make it much easier to do with bonding on the perimiter only.

This is a great community!  Lots of creative thought here.

Thanks, again.

Dave

[skip1930]

Once a flat, glued 6 mm marine aluminium KEEL PLATE, saw cut to size and deburred is adhered to the pristine clean fiberglass of the keel with NO overhang there would never be any reason to want to remove said item. It's not like it's going to fall off. And the only purpose is to give a durable surface to glide over rocks that typically are harder then fiberglass and it's top coat of gel coat. It does nothing to enhance or detract from the sailing qualities of the hull or the rig.

As the design of a CP-19 [Bob Johnson] or CP-16 [Clark Mills] goes, they are still a 'barge' that sails best when stood up, with a relative slow calculated hull speed mostly due to a short waterline when compared to it's width and this combination gives the CP-19, more than the CP-16, all the comfort and stability, shallow draft and room down below. A great boat. I would not want to mess with Mr. Johnson or Mr. Mills's design. The shape, the length, the width, the draft, the quarter wave, the rudder square [foiled or not] foot, the sail square foot has all been taken into account and the appropriate messaging of these numbers has been refined as best as they can.

But for those who must muddle, muddle away.  " a simple flat aluminum plate wont help. " True the plate is only for armor plate. Not water dynamics. I figure the ship's designer took all that swirly and eddy's stuff into account already. That's why they have the sheep skin and I don't.

skip.

[gabi]

http://www.sponbergyachtdesign.com/Keel%20and%20Rudder%20Design.pdf



around page 6 the end plate issue is covered,
in summary the end plate can reduce overall drag if is an efficient foil itself,  otherwise it will increase it,

so although a good idea, a simple flat aluminum plate wont help, 

[NateD]

This is a bit off-topic, but how about an end-plate for your jib too?

http://www.pressure-drop.us/forums/content.php?3167-Radical-18-Rotating-Mast-Debutes-In-Sydney

[Salty19]

I have not adjusted the angle of the mast forward to move the center of effort forward as others have done.

Instead, I made a new rotating mast base that locates the base forward so the mast can remain vertical but with the center of effort moved forward to releive the excessive weather helm of the stock set up.

Also, because the mast rotates, the surface of the mast now acts as part of the airfoil, thereby increasing the effective sail area a bit and further moving the center of effort forward.

The rotating mast modification has been a great success.

Also, I have three rudders: one stock blade, one that is a NACA 12 foil shape, and a third that is still flat but with 2" added to the leading edge to balance the helm.

To my surprise, the balanced rudder seems to be the best of the three.

My next effort will be to fair the balanced rudder to the NACA 12 foil shape in hope of further improvement.

The experiment continues.

ps  I don't know how to post photos here but, if another more computer literate member would be willing, I could e-mail them for posting.

That's right, I forgot you had the swanky rotating mast!  Very nice.   Even with the rotating mast, do insure it's stepped slightly forward, not straight up.  That makes a huge difference in balance. Some experimentation here could pay dividends.  The naca shape should maintain or improve balance, and certainly will reduce a lot of drag. That one mod made our old 16 sail like an entirely different boat.  And with new sails...  That forward leading edge is huge in terms of balancing the helm, no doubt.

BTW, I wasn't trying to crush anyone's dream of modifying the keel, just pointing out what easier mods can be done to improve performance, and to talk to a marine engineer about specifics (shape, location, construction method) during the critical design stage. 

[deisher6]

Hey Pac Man:

What a thread.

I am curious it seems like this thread is talking about either about: raking the mast forward or moving the mast step forward?
I have mine raked slightly forward and it does reduce wether helm.  As expected by moving the center of effort forward.

Have some sailors moved the step forward...If so to what effect?

regards charlie

[Pacman]

Charlie,

I found that, with the stock mast base, I had to rake my mast forward quite a bit to get rid of the excessive weather helm.  It did work but it looked wrong.  The forward tilt of the rig was quite noticable when viewed from the side.

There isn't much sail area in the upper part of the rig so it takes several inches of forward rake to move the center of effort forward a significant amount.

My home made rotating mast base has relocated the base of the mast forward about 1.25 inches on the cabin top.  With my mast vertical, the center of effort of the sail alone is at least 1.25 inches forward.

In addition, by allowing the mast to rotate, the side of the mast becomes part of the airfoil.  

This effectively adds additional "sail" area to the rig and that added sail area is on the forward edge so the rotating mast moves the center of effort of the rig further forward than would be the case if I had simply relocated a non-rotating mast base forward by the same amount.

Hope this helps.

Dave

[Pacman]

If have not mastered the art of posting photos but I could take some photos and send then to you by e-mail if that would help. 

[deisher6]

Thanks Dave. 
I got dismasted the first time out..if I would have known when I fixed the mast step I would have moved it forward.  However I have 5200'd in place so will just go with the forward rake.  You are right it does look a little awkward.

regards charlie

[Pacman]

Charlie,

Others have posted that Debond will remove 5200 so that might be an option if you are interested.

I used wood scrap I had in the shop so I only spent a total of about $10.00 on materials to make my mast step so it is not expensive.

If you might be interested, I could send you a piece of Ipe wood to make the base.  You would have to buy four screws, a bolt, a nut, and three washers.

Also, if you don't have a drill press and taps and dies, I could drill the Ipe wood for the mounting screws and tap threads for the mounting peg (a sawed off and rounded stainless bolt).  I used my stock mast base as a drilling jig so the holes would line up.

Might be a fun winter project.

If you wanted to go back to the stock set-up it would be easy to do that because you don't have to alter the boat in any way.  It is a "bolt-on" set up.

Regards,
Dave

[deisher6]

Hey Dave:
I have been thinking about moving my mast forward.  If it moved less than two inches, seems that it could be done with the original step. 

Did you move the support post inside, although from another thread that post might not be truly necessary!

If you email me pictures of your rotating, displaced, mast step, I will be glad to post them.

deisher6@midrivers.com

regards charlie

[skip1930]

Q? If the mast is raked fwd, and presumably lifts the back of the boom up [keeping that 90 elbo],
does that drive the bow deeper into the water with a good blow?

skip.