16' Fiberglass Tri-hull Rebuild

[SAT_Bob]

Re: 16' Fiberglass Tri-hull Rebuild

Okay, that makes sense. Do I use the Cabosil for the filler?

 

[SAT_Bob]

Re: 16' Fiberglass Tri-hull Rebuild

Well I made a little more progress over the weekend. My son was home for the weekend and helped me with one of the holes we cut with the circular saw during the initial demolition. :facepalm: In looking at the cut more I noticed that there was about 5 inches right in the middle where the cut didn't go all the way though the hull so I'm repairing 2 holes about 2 feet long each instead of one long 5 foot hole.
Anyway, here are a few pics of the work showing what I started with and the finished layup. I'm happy with it and it seems plenty strong. I only made the repair on the inside for now and will probably tackle the bottom once I flip the boat at some point. I used 1.5oz CSM for the first 2 layers, 1708 for the 3rd and 1.5oz CSM for the 4th, with each layer about 1.5 inches larger than the one before. Also, the black marks in the photo on the bottom right are where I marked the glass with a sharpie before cutting it out.



First time for any fiberglass work for either of us and it was fairly straight forward. I've been reading everyone's posts on this forum and you guys really helped me out. As so many have said before, I couldn't have gotten this far without you.

 

[Woodonglass]

Re: 16' Fiberglass Tri-hull Rebuild

From the looks of it, no bubbles or wrinkles, I'd give you an A+ on your first Glass Layup job!!!

 

[SAT_Bob]

Re: 16' Fiberglass Tri-hull Rebuild

Thanks WOG! Yeah, it wasn't as bad as I thought it would be and I'm glad to have the first glass job behind me. Just hope I don't get over confident for the next one.

 

[SAT_Bob]

Re: 16' Fiberglass Tri-hull Rebuild

Greetings. I hope everyone is doing well! It's been awhile but I've been working on the boat as time permits - and it hasn't "permited" as much as I'd hoped. I've been following along with what everyone else has been doing and it's really be great to see some awesome progress by you good folks.

I've been grinding away at mine and am getting close to begin going in the other direction. Looking forward to beginning to put her back together.

I was taking out about 5" of the two outside stringers closed to the transom so I can grind that area to get ready for the new transom. I thought they were going to be 2x4 laying on their sides enclosed in fiberglass but they're actually some type of foam. The only foam in the original boat by the way.

Here's a picture looking down on the pieces I cut out. They are sitting on the bottom of the hull.



Here's an older picture from before I got it all cleaned out looking from the bow that shows the two side stringers:



Can I just use 2x4 boards and cover them with fiberglass? I figure it will be stronger than the foam.
If not, what type of foam do I need to get to replace these stringers with?

As mentioned, this was the only foam on the boat and I want to foam when I put her back together. What type of foam can I use below deck? Can I just use the foam sheets from Home Depot or Lowes? Is there a guide so I know how much to use?

As always, you're help is really appreciated.

Thanks...Bob

 

[Auger01]

Re: 16' Fiberglass Tri-hull Rebuild

If the stringers are foam core there is really no reason to replace them. Foam doesn't rot. You might just be able to remove about 12" of the stringers nesr the transom to get the new transom in and then just replace the small sections that were removed.

 

[Georgesalmon]

Re: 16' Fiberglass Tri-hull Rebuild

Its probably a polyurethane foam board. the foam is not there for strength its just a form to create a hat section for the glass to lay over. The strength/stiffness is in the shape of the glass going up, over, and down. Pretty common years ago. Back in the 60's and early 70's we used lots of stuff to do that from 1/2 sections of cardboard carpet tubes to large diameter rope. Its all there just to stiffen the flat panels of the hull without adding a lot of weight.

 

[SAT_Bob]

Re: 16' Fiberglass Tri-hull Rebuild

Thanks for the replies and information Auger01 and Georgesalmon. I'll just remove enough to get to the transom and then build it back.

 

[Woodonglass]

Re: 16' Fiberglass Tri-hull Rebuild

Yup, I'd recommend using the blue or pink foam from Lowe's to use as a form when you go back. I'd use some CSM as a first layer, then some Heavy Woven Roving, then 2-3 layers of 1708 and you should be good to go.

 

[SAT_Bob]

Re: 16' Fiberglass Tri-hull Rebuild

Okay, I got some time this weekend to clean up the garage a bit and finish the repair to the bottom of the hull where we cut through. This time my glass work wasn't nearly as good as the first time. Too much time between tries and too much confidence. Actually, it was too much resin! I tried using the bubble buster roller on it and that helped some but there are still quite a few spots where there's air bubbles. At least that's what I think.

Here's an image with three shots of the finished product.



Please take a look and let me know what you think. I'm not worried about the cosmetic appearance of this particular patch since it's going to be covered by the floor. One other piece of information, I'm going to be adding the same layup on the bottom of the hull since I beveled both sides to make sure it is strong enough. On the bottom there'll be 1 layer of CSM, a layer of 1708 and then 2 layers of CSM. Now for my questions regarding this patch:

• Do I need to grind it all off and start over?
• Do I need to grind off just the bad parts and put another layer of 1708?
• What about just covering what's there with an additional layer of 1708?
• Can I just leave it as is? Like I said I'm not worried about appearances here but I am worried about strength and the integrity of the hull.

Now for my next question, this one about the transom. Do you think I have enough ground off, particularly around the bottom drain hole and on the sides in the corners. I just don't want to take off too much and wind up going through the bottom. I've already had enough fun with that! :facepalm: This shows the full transom skin and then two shots around the drain hole, one from inside and one outside the hull.



This is a shot of one of the corners looking from inside the hull.



If I have to grind some of the resin away from the drain hole or in the corners what do you recommend? Maybe a Dremel? If so, what bit?

Thanks again for everyone's help. It's certainly appreciated.

 

[Woodonglass]

Re: 16' Fiberglass Tri-hull Rebuild

Soooo on the patch, give us some actual details on how you did the step by step lay up.

 

[SAT_Bob]

Re: 16' Fiberglass Tri-hull Rebuild

Sure. I'm using 435 Standard Polyester Layup Resin and mixing it at 1%.

First layer was 1.5 oz CSM and let that set up. That was on Thursday and then I wasn't able to get back to it until Sunday. Not the original plan but it seemed okay when I went back to it on Sunday.

On Sunday I was able to get back to the project. Since it had been a few days i hit it with the grinder just a bit to open it up so there wouldn't be any issue with the new layers bonding.
I put some resin over the area and set down the 1708.
Added some additional resin on top and worked that in with the chip brush.
Then put two layers of CSM and added more resin on top with the chip brush.
I went over everything with the bubble buster to spread out the resin and make sure it was saturated.

I think it was adding the additional resin over the final two layers of CSM that got me into trouble. I probably should have worked in what was there and it would have been enough. But I'll leave the diagnosis to the experts.

 

[Woodonglass]

Re: 16' Fiberglass Tri-hull Rebuild

First, no need to hit it with the grinder. Since 435 has no wax in it you have a long time between lay ups. A wipe down with Acetone was all that was needed. Your assessment is SPOT ON. Probably to much resin. We tend to use to much IMO. Also I use a shortnap roller when working on flat surfaces. Seems to work better. Also we seem to OverWork it some times. Once it's down, flat and clear...It's done.

 

[SAT_Bob]

Re: 16' Fiberglass Tri-hull Rebuild

So do you think it's okay as is?

 

[SAT_Bob]

Re: 16' Fiberglass Tri-hull Rebuild

Hey Wood, so just to verify, do you think this section is okay as is?

Also, can you take a look at the second question when you have a chance? It's on post #50. I want to make sure I have enough ground off on the transom, especially along the bottom and in the corners. Let me know if you need some more pictures or something isn't clear.

 

[Woodonglass]

Re: 16' Fiberglass Tri-hull Rebuild

Sorry for not getting back sooner. ON the inside patch, I'd use a dremel and grind out any bubbles and patch em with small pieces of CSM dabbe in with a chip brush. You're just looking for water proofing. You're plenty strong enuf on the patch. When you get to the outside, all you need to do is grind and feather about 3 - 4" all around and then use CSM, 1708, CSM, CSM in progressively larger pieces. I'd actually make a patch on the bench on wax paper and carry it to the hull and apply it in one shot and use a bondo spreader to smooth it out. That method works really well. You can leave the waxy paper on until it starts to tack up and then peel it off. Have a acetone soaked rag handy to wipe off the resin runs.

 

[SAT_Bob]

Re: 16' Fiberglass Tri-hull Rebuild

Thanks. I'll have a go of it with the Dremel and then apply the patches of CMS. Good idea on the outside, making the patch on the bench first. I'll try it out when I start on the outside of the hull.

 

[SAT_Bob]

When I cut out the new transom how much space do I need to leave on the sides and bottom for the PB to ooze out? Is 1/8" to 1/4" about right?

 

[Woodonglass]

1/4" should be just about perfect!

 

[Rickmerrill]

Hi Bob, I'm enjoying watching your restoration and would like to follow along. I too have a couple of holes in the hull. One through the bottom (sawsall) and one through the transom (grinder)! My second favorite website, after iboats of course, is boatworks.com. He's done some good videos (see the ones on structural repair of FG) I like them a little better than Tap Plastics. He runs a one man shop in Wisconsin and isin's selling anything - he's just starting to get advertisers but you can skip them. He's kinda like WOG with a video camera and a pony tail! Most everything he says agrees 100% with with you see here. I have no affiliation, he just explains things well and I learn best by watching.