Refoaming a 1970 OMC TideRider

[tinman694]

I am new to the forum--but have some past experience with boats (and mainly cars) over the years. Last year, i acquired a 70 model OMC Tiderider. The outer hull is in very good condition---with only 2 minor abrasions. The inside was VERY sad--it sat outside and the floor was rotten---along with soaked foam. I have read several posts regarding the replacement of the stringers and foam--none seem to be what I am looking for.

The question for me is, What foam will be best to replace what I have removed?

Looking at what is available, I see a 4lb. foam available which will be pour in place (Not a big deal). The problem is that the original foaming process used a large metal press to hold approximately 1000 lbs of force on the hull to ensure the foam was correctly placed. As the foam is a structural part of the hull, does anyone have a good feeling of just pouring new foam in its place without some type of pressure device?

The stringers are just laminated up 5/8 plywood---I plan to use well dried treated, then build it up and epoxy it together as a unit before installation.

Any other tips or tricks would be greatly appreciated!

[tuantom]

It seems odd to me that the foam would be structural - it's usually flotation and, if using 4 lb, maybe some deck support. Do you have any pictures?

[PAR]

4 pound foam wouldn't add a particularly significant amount of structural stiffness, to an old chopper gun hull, that was likely overly heavy during lay up.

Tom is probably correct in that the foam was floatation, which would also be typical of the era boat you have.

I wouldn't use treated lumber or plywood with the jury still out on the new treatment chemicals and bond properties with epoxy. Try some of the stuff (foam) available at WWW.FGCI.com which is available in three different densities, including 4 pound.

The foaming press the manufacture used, was to insure the expanding foam didn't distort the hull as it cured, not to force it into every nook and crannies, though it did have that side benefit.

There are many previous threads on this site covering stringer and sole replacement, with several possible avenues of pursuit.

[tinman694]

Seems like the foam was for hull rigidity. OMC manufactured the boats with a cost incentive in mind--so they seemed to use the foam as support for the main part of the deck. From what I can determine, the original spec seems to fit with the 4lb foam (although from what I removed, it was more like 16lb when saturated!) From what I can estimate, the saturated foam added something like 1500 pounds or so to the weight of the boat!

I appreciate the statement that the press was to make sure the deck didn't distort...that is what I was also thinking, but was not sure. Plan still is to make up new stringers with Plywood---most are telling me NOT to use treated, but just good quality plywood and coat it with epoxy---then pour in place 4 lb foam and shave it to dimension (not hard to do at all)

The rest of the repair is just standard glassing and painting up....not too hard at all.

looking forward to having it done in the next 2-3 months or so.... Have the old electric shift outdrive (and a spare) ready to go!

[PAR]

4 pound is the stuff you want, though personally I'd use 2 pound and rely on stringers (1/2" plywood tabbed on edge to the hull shell) to support the sole.

Yep, PT isn't the stuff you want, it's junk wood from hybrid fast growth trees, relatively weak and the new chemicals will eat up normal fasteners. A good grade of exterior or marine grade plywood (preferred) will be the ticket.