builders question?
 

how many layers of fiberglass do i need between the plys of wood and on inside and outside of the core itself ? and what type. roven or mat? thanks im using 2 3/4 peices of marine ply. also i am planing on installing a bracket incase that makes a diffrence.

None? if gluing two pieces of ply together, use peanut butter and stick them togther. If the question is lay up schedule then I like 4 layers of 1708 biax. read uo there are alot of people who have done transome replacement on here. I am using strick's boat rebuild as a guide

if gluing two pieces of ply together, use peanut butter and stick them togther.

ok thanks

As some of the others have suggested, you can look around here and find several transom rebuilds. But some restorations are better than others. You are safe if you follow just about anything strick has done. He's got plenty of experience and his boats are done right.

You should also consider reading up on the subject. I highly recommend Elements of Boat Strength by Dave Gerr

http://www.amazon.com/The-Elements-B...7213548&sr=1-1

His chapter on fiberglass explains the different types of resins and glass fabrics and other reinforcements available today and makes it a little easier to make intelligent choices. I think you'll find his book is money well spent.

All that being said, your inner and outer laminates should match the original layup. That would be about 3/16" to 1/4" thick. You can use alternating layers of 1.5 oz mat and 24 oz. roving, or you can use the newer, stronger biaxial stitchmat fabrics. Four or five layers of 1808 should do the trick. Gerr's book will tell you how many layers it takes to get the laminate thickness you need.

You can glue your plywood together with resin thickened with cabosil to the consistency of peanut butter. I like to use a notched trowel to apply it. On something that large, I'd use a 1/4" notched trowel.

Dave

Thanks Dave, i was looking at stricks build and he's very informative, i will look into the book as you suggested as well, thanks again. just want to know i can do the job correctly and one time.

Exactly. You wouldn't tear down the engine on one of those big Cats without reading the manual. Gerr's book is as close as I've found to a manual for fiberglass boat construction. If nothing else, it will help you recognize which restorations are done right and which are questionable.
Dave

Ditto on Gerr's book. It will give you tremendous confidence in your work.

Its a nice feeling.

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This kind of info is what cuts the chafe from the stalk.

A long time ago a boat builder who was in the industry for many years told me that the industry standard for the outer transom skin was if I remember right 3/8" and the inner skin was 1/4". Then Hermco once said that they should be equal....so I have still been a little confused about that. On my 1969 20sf the inner skin had only one layer of woven roving on it and it lasted over 30 years!

Generally one layer of 1708 will net you 1/16" thick laminate.

strick

5/16 on the 21

Attachment 1940