fiberglass layup schedule

[WillyC]

Alright guys, I'm looking for a little advice for laying up the inner skin of my transom. I'm looking for some info. on what type and weight of fiberglass cloth to purchase. Also how many layers would be required. I have a 1976 20' cc. I removed the splash well and boxes/seats at the transom and have the transom area ground down for the rebuild. I purchased a sheet of 1 1/2 inch coosa board (not in yet) that I will use for the core and will be working with epoxy (not sure either West System or Raka epoxy). I read the west system basic fiberglassing manual and still need a little more advice. Thanks -Will

[pogden]

Will,

I'm about in the same boat as you 78 MA [img]/images/graemlins/grin.gif[/img]
Just finished removing my old transom and grinding whats left of the old wood off(almost). Was considering using a different core than wood where did you order your foam?
I'm using 18 and 24 oz WR with RAKA epoxy. I was going to lay up a few layers of the glass on the old inner hull to build it up and then use three sheets of 1/2 inch foam sandwiched between layers of glass. at 0, 45 and 90 degree planes to one another. I'm sure others have did it other ways, hope that helps.

Pat [img]/images/graemlins/smile.gif[/img]

[Ed]

Will-

While roven woven may work in this instance, I would use the following layup schedule because it offers (in my opinion) better adhesion.

2 layers of 1.5 oz mat
1 layer of 1.5inch Coosa
1 layer of 1.5 oz mat
1 layer of 1808 biaxial
1 layer of 1.5 oz mat
1 layer of 1808 biaxial
1 layer of 1.5 oz mat ( this layer is optional....it seals off the last layer of 1808 and prevents any strands from fraying, etc.)

The important thing is to make sure that each layer of laminate is progressively longer and taller and overlaps the previous piece. This will assure that each laminate is bonded to the hull versus having all layers bonded to the first laminate.

Hope this makes sense.

Ed

[pogden]

Ed,
I have 3/4 oz mat, would that be sufficent in the lay up?
I had heard that it is good to use mat in between WR, but was also told that epoxy doesn't penetrate mat very well.
?? [img]/images/graemlins/confused.gif[/img]

[WillyC]

Ed and Pat,
Many thanks. Thats exactly what I'm looking for.

Pat,
I contacted the manufactor of Coosa and spoke with a company rep. They gave me the name and number of the closest distributor which for me was in New Orleans. The following link is their web address. I went with the blue water 26 because it is their strongest grade (density of 26 lbs per square foot). No rot and 30% lighter than plywood. It is expensive but not that much more than two sheets of 3/4 inch marine ply. They emailed me some spec sheets of some of their products. I will forward them to you if you are interested. Thanks again -Will

http://www.coosacomposites.com/

[rockdoc]

Ed, (and others)

What are the pros and cons of doing an "inside job" versus an "outside job" on a transom replacement? In other words, cutting the outer skin (ouch) or the inner skin of the boat? I imagine an inside replacement is preferable, and easier if the floors and stringers are getting work also.....And, in your layup schedule recommendation, which are the inner and outer laminations? I'm assuming the 2 layers of 1.5 oz mat are inside, just thought I'd ask to make sure.

Thanks!

Steve

[rockdoc]

Ed,

One more question:

are your layup recommendations to Will for the thickness of an entire transom, or just in addition to the glass that's still there (the outer shell in his case).

Thanks again!

Steve

[EBEACH]

Will,

Be careful with the thickness of your core material, I used (2) 3/4" ply on my 20 Sceptre, and it was too thick to get the splash well back in. The original specification on the core was 1 3/8 marine ply. I figured another 1/8 won’t make a difference. Wrong!

I’m using it again on my 23 and it will fit, but not by much.

Jim

[warthog5]

West System's 5 to1 epoxy is what I would NOT use in doing this job. Your going to need a epoxy that has a longer pot life.
Even with a longer pot life you will be rushing.
A 2 to1 like Raka or System 3 or FGCI's 2 to1.

[WillyC]

Jim,
How did you remedy your thickness problem on the 20 footer?
As I recall when removing the splashwell and boxes/seats there was room inbetween the transom and backs of the seats but the top of the splash well was butted against the transom. This is making me a little nervous. Maybe I should have ordered the 1 3/8 inch coosa board.

Ed,
Do you think it would be ok to layup the two layers of mat and then secure the core with the glue and screw (thru bolt) method. Let that cure and then finish the rest of your layup schedule all in one shot. Thanks -Will