windlass installation... 28 te...

[tomcat rio]

backing plate material...i got a section of oak stair at home depot. seems to be just the thing to use as a backing plate. about 3/4' thick...not sure it needs to be painted as it will be under the bow sprit. i'll probably put some kind of gunk in the bolt holes. stainless washers, of course.
the windlass itself is a horizon h 700.

[DougSea]

I'd hit it with some kind of sealant. It's bound to get damp if not actually wet. Easy to do before it's bolted in.

[Mariner]

Yeah, you definitely want to paint or seal it in some way. I'd imagine it actually gets rather damp in there, which would cause most soft woods to rot.

[JackK]

I would be worried about rot and compression with a wood backing plate. If the wood compresses over time, the bolts will become loose. The bolts then can move around and stress the deck during usage.

Mine is backed with an aluminum plate. I'm not sure how thick but I would guess 1/4 - 1/2" thick.

I remember discussing this with the dealer prior to installation. He also said something about clearing out any coring in the area of thru holes and filling with epoxy (5200 I think). Again this is to prevent compression over time.
____________________
2003 28 TE Dogonit

[tomcat rio]

seems to me they used to make whole boats out of oak, so it should be okay to use it as a backing plate. i guess i'll paint it.
as the photos show, water does collect in the space between the bowsprit and the anchor locker





...

...
http://farm1.static.flickr.com/186/3968 ... eb5134.jpg


http://farm1.static.flickr.com/186/3968 ... eb5134.jpg

[Mariner]

Oak is ok if you seal and protect it. The oak that is grown today does not have the same density and natural oils that was found in old growth stuff around the turn of the century. Mahogany, teak, or Ipe would be better, but come at a significantly higher price due to their cosmetic appeal.

Painted steel or aluminum would be a step better, and of course, stainless steel would be best.

It all depends on how long you want it to last, and how much you want to spend.

I can't see the pictures as photobucket is blocked at my office, but I can tell you, in a general sense, what I would do.

First off, I would rough up the area with a grinder and use 3M 5200 to glue in a piece of 3/4" marine plywood. Then, I would coat the exposed side of the plywood with more 5200, feathering out the edges (it would be good if the plywood had been beveled before installation. I would then build up a roughly 3/8" thick layer of new fiberglass, applying it directly to the still wet 5200 and rolling out any air bubbles. Then, after drilling the bolt holes for the windlass, I would push the bolts through for a test fit and use the largest stainless steel washers I could possibly fit on the other side. I would coat the back side of them with 5200 and position them with the test fit, but then remove the bolts leaving the washers in position and wait for the 5200 to cure. After that was done, I'd coat the bolt shafts with 3M 4800 (like 5200, but not as permanent) and install the bolts and nuts.

If a person really wanted to, they could custom build and drill a stainless backing plate, but it wouldn't be strictly necessary. The purpose of the washers is to prevent the bolts from pulling through. The purpose of the marine plywood is to spread the load evenly across teh fiberglass deck. The purpose of the extra layer of fiberglass is to seal in and protect the plywood, as well as prevent stress cracks from forming in the gel coat at the edges of the plywood. Phenolic board (Star-board) could be substituted for the marine plywood, but is very expensive and not necessary if proper care is taken to seal everyything up.

Using plywood or starboard for the coring material is peferred over steel becuase it will better conform to the imperfect surface of the fiberglass and the new fiberglass is less likely to delaminate from it. Also, it will flex with the fiberglass, preventing stress fractures.

My design might be overkill. But, that's how I'd do it, presuming I had the time and money.

[Mariner]

I should revise that. The overlaying fiberglass could probably be much thinner for most of the span, but thicker around the edges of the board. Like 3/16" for the flat surface, but 3/8" at around the edges. Perhaps build it up to 1/4" around the bolt holes. That saves you material and time and speeds the curing process.

[tomcat rio]

as you posted, i think sealant/ moisture protection is the most important part of the project....
after this i'm just going to give priority to waxing/ polishing replacing old hatch trim and a little fiber glass work. the glass edges of the swim platform need some attention.
i also have to replace the sound proofing in the engine cover.


...http://farm1.static.flickr.com/172/3968 ... .jpg[/img]