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Yankee #204's New High Density Polyetheylene (HDPE) Centerboard  

July 9, 2012. Scot Ioset has been restoring Prodigal, Yankee #204 and one of his projects is a new centerboard. Here are edited comments consolidated from his posts on the Forum http://dolphin24.org/forum/forum_posts.asp?TID=156 and some of the pictures from his Photobucket file - http://s1134.photobucket.com/albums/m606/hamdental/Yankee%20Dolphin%2024%20Prodigal/ - where additional pictures can be found. Scot and Jonnie Walker (Yankee #227) had an exchange on their centerboard projects on Forum - a fuller flavor of the process, and the results, are there, and are very informative.

Let's start with this picture -

This required some attention

Topic: Replacing a centerboard
Posted: 07 Sep 2011 at 10:46pm (edited)
Are there companies that fabricate a Dolphin CB? Just a proposal from day dreaming if I were to make it myself: What if you had a 1/4" plate of steel torch cut to the proper dimensions, drill multiple 1/4" holes with throughout, say every 2" and sandblast. This would allow for wood ribs to be epoxied not only onto the steel but have epoxy and SS screws through the holes to hold all ribs tightly in place. Shape the foil with planing and sanding, then 3-4 multiple sheets of 6 oz fiberglass cloth epoxied into place. Fair it and finish with an enamel like Awlgrip. Would that work?

Posted: 16 Sep 2011 at 1:06pm
In that there appears to be variations in the CB design by Yankee, I think I might create a plywood prototype of the design used by #227 to see if we can get a good fit. Cutting the plywood would take all of 30 minutes. I have a hose in place of the tube from the centerboard housing that attaches to the fiberglass "pipe" about six inches above the CB housing. I need to take a scope (an auto mechanic friend of mine has one) down that pipe to look around within the housing to see the condition of the pin, housing, etc. It takes images with a camera as well. I will report back with my findings.

Posted: 25 Sep 2011 at 7:17am (edited)
I am researching a little on foil design and have decided to use a NACA 006 design which puts maximum thickness (just over 1" 30% back of the leading edge (5 1/4") .

Posted: 26 Sep 2011 at 2:57am (edited)
My centerboard slot was about 1 1/2 wide at the bottom as I recall and it didn't seem to have a taper but the sides were definitely not parallel (if that makes any sense) - I'd make a full width test panel and make sure it fit up into in the slot first.

Posted: 26 Sep 2011 at 7:31pm (edited)
I have researched materials that would be stable, shapeable, zero water absorption and strong. Talking about manna from heaven...today a contractor friend of mine and I were discussing the restoration of #204. He has a 4' x 5' slab of high density polyetheylene (HDPE) that is 1 inch thick. There is enough to make two, maybe even three centerboards. This is the material that is used in public restrooms between bathroom stalls. He has been trying to find a use for it and he is giving it to me free. Plus we can use his shop planers, grinders, sanders and shapers to form it to the desired shape. The only thing wrong is that the HDPE is.....pink! (It was used supposed to be used in a casino's ladies room). It should weigh in around 75 lbs when finished and has no buoyancy. What's your opinion guys?

Posted: 05 Oct 2011 at 1:34pm
We are going to experiment on a small piece to shape it with shaving and sanding, then use a heavy duty heat gun to seal the outer surface back to the smoothest finish possible. I doubt paint will stick to HDPE, but if paint doesn't stick, marine growth probably can't do it either. I can always dive under the boat out in the lake with the board down and scrub it with a sponge a few times each season. I will be moving the boat onto its new trailer at the end of the month, so with that lift I hope to have a 1" thick plywood prototype to slip up into the CB well to check fit. I will have the winter to make the CB and install it in the Spring.

Posted: 18 May 2012 at 12:33am (edited)
I will send Ron pictures of the new centerboard that we have created from high density polyethylene. It is non-buoyant, slick as glass, and will not absorb water like a fiberglass board. We have enough HDPE to make at least two other boards. Weight is a little light, 40 lbs, but I don't think it is going to matter. The CB is all about ability to point, therefore the symmetrical foil should maximize this ability. I have loads of pictures to share, just too busy finishing the restoration to upload them. I hope to be in the water on our first voyage on Memorial Day weekend.

Posted: 28 May 2012 at 7:42am
The centerboard is finished, but yet to be installed. The re-installation of all the hardware has taken longer than expected, primarily due to a rotten chain plate that is now better than new, and we are on hold until tonight waiting for the Interdeck to fully dry/cure on the deck grip areas. Tonight I want to uncover the pivot bolt of its fiberglass encasement and back it out. I had a good conversation with one of the tech reps at Jamestown Distributors in Bristol, RI that gave me the best method for attaching the pinion to the centerboard. I will share that with all when the photos are completed.

Posted: 07 Jul 2012 at 11:05pm
Well the centerboard has been installed and I have been out twice with #204 in brisk winds of 12-15 knots. The upwind speed and the improved pointing were immediately apparent. The HDPE board is a little light and I am finding ways to add weight to it without weakening the board. The hydrofoil design appears to really help the pointing characteristics. My friend and helper on this project came up with an ingenious way of mounting the pinion wire into the trailing edge of the centerboard using a slot with an inset clevis pin and split ring that does not protrude from the surface of the board. Check it out on my Photobucket link (see above) I am anxious to report back how the HDPE holds up.

Cutting out the blank - pink?

The blank

A foil shaped centerboard

inset pennant pin!!
new, and old CB pin

Stay tuned


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