Glass or not?

[jhunt4679]

Should I glass the main bulkhead to the sides of the hull or leave a gap for flex? What I took out had about a 1" gap but I know the last one who did this butchered the rebuild and it was only attached at the floor with 2 angle brackets. By the way this is just a template I have to re-engineer the whole thing. 21' 1988 Galaxy

 

[ondarvr]

Normally they are glassed in completely, you don't need a 1" gap, you just need to make sure the plywood doesn't touch the hull side, 1/8" is as good as an inch.

 

[jhunt4679]

Thank you ondarvr! I just wasn't sure about tying it into the hull. I do have one question though about the plywood being against the hull. If you are using thickened resin (thickener & 1/4 chop) to bed-in (attach) anything how is that different than the plywood with routered edges touching the hull? I have seen the same statement throughout these forums but the resin is way harder than the plywood when cured. I can see where square edges could be a problem but if they are rounded would it be a problem? I'm just asking.

 

[ondarvr]

Putty does have some flex, plywood on edge is very stiff, and when you point load the hull on a 1/2" wide surface the area around the plywood flexes and the area in contact with the plywood can't move at the same rate.

The putty fills the gap, plus when used as a fillet spreads the load out even further, then flexes at a rated much closer to that of the fiberglass laminate. This makes it less likely to cause cracking.

Some people use putty, other use a flexible adhesive, some use foam, others use nothing, it doesn't make that much of a difference in how you create the gap, or its size, the goal is to just keep the plywood from contacting the hull.

 

[jhunt4679]

Thank you for the explanation, it makes sense!

 

[jhunt4679]

I bedded all my stringers, around my transom and deck with thickened resin with fillets. I'm about 22 gallons of resin into this already!

 

[Ned L]

Yes, bulkheads need to be tied to the hull. Flush to the hull is not a problem, it is just easier to leave some 'slop room'. ......... Hmmm,... If you are really concerned about the edge of the plywood causing some point loading along the hull then the way to address that would be with heavier (and tapered thickness) tabbing. Whether it is plywood against the hull or thickened resin/epoxy against the hull the end result of 'hardness' is the same.

Remember, more resin is not better. You want to use only enough to wet out the cloth, it is the glue, not the strength member. Vacuum bagging uses the least resin and makes the strongest lightest result.