Replace 3/8" plywood "core" with 1/4" G10?

[Cool Beans]

Cockpit sole is getting a bit springy. . .brown water drips when it rains hard. . .thinking a recore is in order this summer

Though, it isn't coring like I would imagine. It is 1/4" thick fiberglass sole, and the 3/8" plywood is glassed to the underside with 2-3 layers of fiberglass. I want to avoid going in from the top. I "recored" 2 areas of the side decks from inside. It wasn't bad. I was thinking the same thing for the bottom of the sole. . .but with 1/4" G10. Cost is a bit more, but on paper the labor and time involved is much less. No fiber glassing except some tape on the edges to keep them from peeling. No potting the fasteners holes. . .no worries about water ingress EVER

Thoughts? Is 1/4" not stiff enough?

Thanks!

 

[jibes138]

Why not use two sheets bonded together for 1/2 inch? Or you could add a sheet of 1/4 plywood to make a 1/2 sandwich. You could coat the plywood all over with epoxy to seal it up. It should a lot easier then trying to wet out fiberglass cloth upside down.

 

[catsailor]

1/4-inch is certainly as strong and stiff as 3/8-inch ply.

I would look a the edges and how they relate to the corners. Should they taper to avoid a hard spot, or would they be fitted at a good stiff spot? Tapering can reduce the tendency to peal; works with G10 but would not be durable with ply.

Lots of thickened epoxy. Lots of surface prep (no old ply remnants). Surface must be flat.

Makes sense to me. I have done very similar repairs, years ago. Yes, the labor was less and the repairs were very satisfactory. Two were OB transoms and they have seen a LOT of vibration.

 

[rardiH36]

If not already considered, a small item which I learned only after re-coring my cockpit sole:

If possible make the new floor with a slight upward convex curve. Water will then run nicely into the scupper drains and not puddle around the pedestal base.

I re-did my new floor flat. Result:- With the weight of the pedestal and the small squeezing together of the top and bottom FRP skins by the pedestal base securing bolts, I get a 1/16" or so deep puddle around my pedestal base always when it rains. Everything in the core is now very sealed with epoxy and caulk so future rot is not a concern. But would be nice not to have the puddle.

 

[Jumpstart]

Pics of pro job done on my cockpit sole. Plywood is 3/4" thick. Balsa Core in forward areas, plywood in back. Keystone glass area is about 1-1/4" think. Only penetrations are in the keystone solid glass area. The whole sole is extremely solid. I doubt that it will ever need repair again. Boat is a 1985 C&C 29.

 

[Cool Beans]

At the edges I was going to put a 1/2" taper along the edge and lay 2 layers of 3" tape over the joint. Should be easy, cockpit is only 6 feet long and 2 feet wide. . .

Hopefully there are no compression issues with the resultant 1/2" thick solid FRP sole when I'm done

Rardi, I wonder if it wouldn't be wise to put a raised base under the pedestal out of some 1/4" G10? Or even a sealed piece of plywood? That way all water flows down and away from the thru bolts? Wouldn't be hard, just need to make sure you have the extra bolt length.

Thanks for the pics Wed, though I do hope to avoid going in from the top

Any other thoughts on this planned adventure?

 

[jibes138]

My O'Day has a raised platform for the pedestal mount. I think that is a really good idea and you should do it..

 

[rardiH36]

....Rardi, I wonder if it wouldn't be wise to put a raised base under the pedestal out of some 1/4" G10? Or even a sealed piece of plywood? That way all water flows down and away from the thru bolts? Wouldn't be hard, just need to make sure you have the extra bolt length...

....Any other thoughts on this planned adventure?

Cool Beans:

Sure; raising the pedestal foundation a bit is another way. But still give thought that the new sole surface is not depressed concave in any spot. Pain in the neck to dab away puddles from the floor .... even after a night of just heavy dew.

As to other thoughts, here is a post of mine from 2009. Probably not your means of repair, but maybe something might resonate!

http://forums.hunter.sailboatowners.com/showthread.php?p=642721&highlight=sole

 

[Steve Dion]

You may want to take a look at a Hunter 37C. They had a raised pedestal mount in their cockpit.

 

[Jumpstart]

The g10 idea might work and I like the idea of the G10 in the area of penetrations. I'm wondering if it would create a hard spot?

 

[Cool Beans]

Raised platform added to list of repairs for the cockpit sole

Hopefully any hard spot issues would be negated with an entire floor of solid FRP

 

[tommays]

Really heavy and costly and no stiffer or better than balsa

I did not feel and difference in the high stress areas i used it in

 

[Cool Beans]

Sorry, forgot about this post. . .

Thanks for the pictures, helluva project man. G10 is heavy, and costly but time saved is what I'm after. . .and being rot PROOF There are 20 bolts that penetrate the floor that hold all the steering gear down. Plus the inspection cover over the pendant and another over the transmission. . .and gas fill. . .and the big hole for the steering cables and shifter. . .That's a lot of fastener potting to do in a cramped space

Ah well, just waiting for it to warm up now

 

[RichH]

Cockpit sole is getting a bit springy. . .brown water drips when it rains hard. . .thinking a recore is in order this summer

Though, it isn't coring like I would imagine. It is 1/4" thick fiberglass sole, and the 3/8" plywood is glassed to the underside with 2-3 layers of fiberglass. I want to avoid going in from the top. I "recored" 2 areas of the side decks from inside. It wasn't bad. I was thinking the same thing for the bottom of the sole. . .but with 1/4" G10. Cost is a bit more, but on paper the labor and time involved is much less. No fiber glassing except some tape on the edges to keep them from peeling. No potting the fasteners holes. . .no worries about water ingress EVER

Thoughts? Is 1/4" not stiff enough?

Thanks!

Stiffness is dependent on thickness (geometric 'moment of inertia' to the 'third power') ... not 'strength' of the materials.

It really takes no more work to apply the proper 'thickness' for the total layup or finished dimension of the FRG + coring. This is a 'box beam' construction and 'stiffness' is a result of 'thickness'.