Mylar Centerboard Gasket

[dndrich]

SCAMPers:

Can't believe I am getting to this point, but the boat is flipped and I am working on the hull. I plan to use the 3 inch mylar gasket material from APS, and cut a slot down the middle with cuts also on the edges to let the mylar open fully. It apparently has dacron on one side. I plan to stick it in place with perhaps 3M 4100, and then put in 1/4 inch 316 stainless screws to help hold it. The screws are fairly flat and will be a bit proud, but I ain't racing, so it should be fine. The question is, do I just screw them through while the 4100 is curing? I don't want water intrusion into my beautiful hull wood. Or, should I drill slightly, and put some 4100 on the screws, and then drive them in? Thoughts? Also, do I need to fashion a wedge at the leading edge to reduce turbulence from the flap sides of the gasket? I will have enough material to cut a wedge for the leading edge.

[dndrich]

Hmm, nobody has an opinion on this?

[PAR]

In all honesty, most boats of this general configuration don't need, nor will benefit from a slot gasket. The usual choices are rubber, dacron (sail material) and assorted flexible plastics, like PVC, etc.

Two flaps, one overlapping the other is the typical mount and the most anal of racers will rabbet these pieces into the planking for a flush surface. These most anal I mention, will also wet sand their hulls before each race with 2,000 grit, before a fine polish and wax job, in hopes these efforts will offer a 1/20th of a knot advantage over their competition.

[dndrich]

My understanding from other SCAMPers is that the centerboard gasket really helps with preventing mud and rocks from jamming the board. That has been my experience too with other dinghys. It also reduced to great degree any splash in the cap area. I am not interested in saving seconds while sailing. Since I have the boat turned over right now and am working on the hull, installing the gasket will be easy. But, I still need to know the answer to my original question!

[Dave Robertson]

We install c'brd gaskets on all Gig Harbor Scamps as standard equipment. We find that the gasket serves several functions... 1) it reduces turbulence at a key point of the centerboard 2) it very beneficial at preventing small rocks, etc from jamming the board when the boat settles on its keelsons when beaching or at low tide.

We use the same type of mylar scrim backed material and fasten it to the hull with 3m VRB tape. On a wood hull we would also use VRB (presuming cured, sanded epoxy hull prior to sanding ) with a few screws anchoring the corners.

[dndrich]

Do you mean VHB tape? I can't find VRB tape. Also, with the screws, how would you seal them from water leaking into the wood?

[Dave Robertson]

Hmm, maybe I didnt answer your question. 3m4200 is designed primarily for components that are intended to be temporary or at least be somewhat removble. 3m 5200 is for permanent installtion so that is what I would use. Predrill your screw holes and drive the screws through the wet caulking. She aint gonna leak! And btw if you really need to remove something bedded with 5200, just warm it with a hair dryer and slide a knife or sharp putty knife through the seam. I would also use a wedge overlay at the keading edge 'just in case'.

[dndrich]

OK, I could use 5200, but the tape idea sounds nice too. If I drive screws in also, how would I seal them when using tape only?

[Dave Robertson]

I think you will reduce the potential for long term issues by using 5200 on your wood boat. The tapes are supposed to be 'self sealing' but..... 5200 will bond the mylar and assure the screws are bedded securely.

[dndrich]

OK, that is what I will do.