Fiberglass thickness.

[PatinIdaho]

Sorry, it might be long but details matter.
When my boat was built, the bilge structure was done with a chopper gun outside of the hull, using no fabric at all and i assume poly resin. No wood parts had rounded corners and the fiberglass was not in full contact with the wood as can be seen in the pics.
The wood parts were not glued together and steel staples were used to connect them.
The structure was then glued in using i don't know what.
It looks like they were using fiberglass thickness for strength, about 1/4 in or more.

Im trying to keep as much of the original fiberglass structure in place as possible.

To get back to the original thickness, what would be the best way to do it?
Round all corners and use csm to 1/4 thickness, then tab it with 3 or 4 layers of 1708/csm fabric over it all.
Or, a few layers of 1708/csm fabric over it all tabbing back onto the original structure with progressively larger layers.
If this is better, how many layers? Would this end up being stronger and lighter?

PS. I'm using Vinylester resin.

 

[tpenfield]

It looks like you are trying to preserve the outer fiberglass layer of the engine mount stringers. If I were going this, I'd mix up some putty (aka peanut butter) with the VE resin and some filler and apply it generously to the curved areas on the inside (purple areas). Then coat the wood core pieces with lots of VE and install them, which sould have some of the putty oozing out of various areas.
.

 

[PatinIdaho]

No. Im not trying to keep that at all. That pic was to show what was.
When i cut them out they will pretty much be down to what the arrow is pointing at.

 

[tpenfield]

So, what is your question? rounding corners? building back what was there?

I would use 1708 more so than CSM . . . Each layer of 1708 will yield 0.045" thickness. Getting 1/4" thickness is 6 layers of 1708. CSM has very little strength.

When you lay up the 1708, soak the underside of it with resin (i.e. the CSM side) as it will force air out of the cloth as you lay it up onto the framing.

 

[PatinIdaho]

I guess im not explaining very well, but you did answer my question.
I'll build it back with 1708.
Thanks!

 

[PatinIdaho]

Next question.
On the lower half of the transom skin you can see where it turns a different color.
Tapping on it, it sounds solid. I can't really dig into it with a sharp edge. I can sand it away but i need to get into it maybe .050.
Maybe resin starved?
Grind it away?
Has anyone seen this before?
Dealing with Aircraft composites is so much more straightforward! Not so confined either.

 

[tpenfield]

If you had a wet transom (wood) and mostly in the lower section, it would explain the dis-coloring. If it is solid and clean from any bits of the wood core, then you are fine as is. Proceed with the re-build.

 

[PatinIdaho]

I was leaning in that direction but wanted to ask. Thanks!
Still have some work to do on the transom, but i think ill spend today cleaning up some of the hull.
So far, sanding is by far the worst part of this job and im doing more than just the hull.
Also redoing the swim deck. Between the skin and wood, there is a 1/4 inch of some kind of putty that has to be sanded out before i can fix the cracks and holes.
I weighed it before starting and it was 85 pounds of water dripping out rotten wood. Want to see what it weighs after repair.
Bought 2 sheets of 3/4 ACX yesterday, not realising i needed a 3rd for the swim deck.

 

[MikeSchinlaub]

Transom looks pretty normal to me. If you would see any white or bright pink spots, that would indicate lack of resin or an air pocket and should be ground out. It can also look pink once it's getting thin, so just stop if you start hitting gel.

The stringer structure was bedded in with resin putty. You'll want to do that again when you rebuild it. Same with the transom and swim platform.

You don't really have to build the glass back that thick. They just piled it onat the factory. I like to fill any deep low spots with csm before bedding wood in, then 2 csm and 1 roving is plenty.

It's important to keep the roving in as big of a piece as you can manage though. It's strength comes from being long continuous strands. Same with the 1708. Make sure to stagger any seams too.