16' Fiberglass Tri-hull Rebuild

[SAT_Bob]

Re: 16' Fiberglass Tri-hull Rebuild

I placed my order with U.S. Composits yesterday and should get it mid next week. Now to finish up the demo.

 

[SAT_Bob]

Re: 16' Fiberglass Tri-hull Rebuild

Okay, so how do I go about removing the stringers. I know I can use an oscillating saw to cut out the exiting fiberglass, remove the stringer and then grind away at what's left, but how do I get to them? Can I just stand in the empty hull? The boat's on stands as you can see in the pictures above but it's basically resting on 5 points. I don't want to go through it -- or the project would be over.
Can I lay a piece of plywood across the hull to distribute my weight? Also, my weight would be on one side of the boat or the other when I remove the center stringer. I'm not exactly a lightweight at 220lbs. Anyway, what is typically done to remove and grind out the stringers on a 15' boat. Ideas and suggestions would be appreciated. Pictures would be awesome.

 

[SAT_Bob]

Re: 16' Fiberglass Tri-hull Rebuild

Anyone?
Maybe a dumb question since I don't have 6' arms and that would be the only way I'd be able to do the work without getting into the hull but I just want to make sure I'm going about it the right way. I have the stands but that doesn't provide much other than the 5 contact points. Would it be best to build a cradle instead of the stands? Anyway, I just want to make sure I'm going about this the right way and don't jack something up. Thanks in advance for the help.

 

[jbcurt00]

Re: 16' Fiberglass Tri-hull Rebuild

Build a support cradle, once you remove the stringers (the backbone of the boat) you don't want to distort the hull in any way. Just supported by the jacks, it might, whether you get in it or not.

You'll need to be IN the hull to remove the stringers

You'll need to take LOTS of measurements before you gut it to make sure you're putting it back together the way it was before (hull shape)

angle grinder, saw-zall, multi-tool can all be used to cut thru the glass to remove the stringers.

Once removed, use a sanding disc or flap wheel on an angle grinder to grind down any remaining glass edges from the previous stringers

Any areas adjacent to the stringers that will get new glass & resin during put back need to be hit w/ the flap wheel or sanding disc to expose fresh glass. This ensures your new work bonds to the existing as best as possible

Should be helpful:
"Fabricating Decks, Stringers, and Transoms"

 

[SAT_Bob]

Re: 16' Fiberglass Tri-hull Rebuild

Thanks jbcurt00, I'll look around for ideas for the cradle.

 

[SAT_Bob]

Re: 16' Fiberglass Tri-hull Rebuild

Actually, I guess I'll fix the hole in the transom and bottom before moving to the cradle. I think that'll be easiest.

 

[sphelps]

Re: 16' Fiberglass Tri-hull Rebuild

Hi SAT_Bob ! Gunna tag along if it's ok .. I am restoring a tri hull very similar to yours with my son in law . Just installed the transom and moving on to grinding the rest of the hull for the stringers. You are on the right track but a good cradle is a must . Just thinking with the length of the slice in the hull you may want to install at least one layer of csm from underneath ,after proper grinding and prep , before you patch the inside . I think then place a bunk directly under the cut just so things stay in it's proper shape. I may be off base so hopefully some more experienced members will chime in .
Good luck ! SP...

 

[SAT_Bob]

Re: 16' Fiberglass Tri-hull Rebuild

I appreciate you following along SP. Just point me in the right direction if you notice me going astray. I'm fairly handy but this is the first time I've tackled anything like this and it's pretty daunting.
Yeah, I was thinking along the same lines as you are on the slice on the bottom. Grinding a bevel on both the top and bottom and doing a layer of CSM, 1708, CSM, CSM on both sides. That's basically what the guy in the video I watched earlier did. Here's the link if you haven't seen it, it's pretty good. Fiberglass Boat Repair~ There's A Hole In My Boat Part 1 - YouTube.
After looking at some other posts and thinking about it I think the best approach: The first 4 steps will strengthen the hull for the rest of the restore.

1. fix both holes (transom and bottom)
2. cut out about 6" or so of the two side stringers and grind down what's left of the tabbing to make room for the transom.
3. fabricate the new transom
4. install the new transom.
5. build the cradle
6. proceed with the stringer replacement...

Anyway that's what I'm thinking today...

 

[sphelps]

Re: 16' Fiberglass Tri-hull Rebuild

You might want to build the cradle before you replace the transom . The reasoning is you want the hull sitting as close to it's original shape as possible before ya start sticking things together . Our Glassmaster had a pretty bad twist in the hull that I had to straighten out .
Flat and level . It's just a thought .. :joyous:

 

[SAT_Bob]

Re: 16' Fiberglass Tri-hull Rebuild

Good point. I don't want to deal with any twists.

 

[mercurymang]

Re: 16' Fiberglass Tri-hull Rebuild

Tagging along as well. I'm about to get started on my winter project and have a very similar hull. I'm curious. When you cut your hull with the saw, how far would you say you had your blade extended?

 

[Woodonglass]

Re: 16' Fiberglass Tri-hull Rebuild

Before you get to far into moving her around, I'd suggest you do the following. This may sound a bit "Radical" but since the cut is so long I believe this is the best method for the repair.

Take a 1x4 and tape off one side with clear packing tape. Get under the boat and use deck screws to screw the 1x4 to the hull so it covers the cut with the packing tape on the hull. Yes, I said screw into the hull. I'd recommend 4 screws down each side of the board. These screw hole will be easily repaired later. They are Nothing compared to other glass issues you'll soon be dealing with. After the board has been installed, get inside and grind and feather out the cut as described in the video. I'd recommend applying a layer of PB and then two layers of CSM, a layer of 1708 and a final layer of CSM, Each 1 1/2" larger than the previous. When cured, removed the backer board from the outside, tape over the screw holes, then get back inside and fill the screw holes with pb. You can do the outside hull repairs after all the inside repairs are done. Once that cut is repaired then and only then would I consider moving her to a bunk style cradle which is what she needs.


Any whoooooo that's how this

would do it!!

 

[sphelps]

Re: 16' Fiberglass Tri-hull Rebuild

That is a very good plan Woody ! With the size of the slash it could get real funky on ya real fast . You would just have to work around screws sticking up on the inside but should be no problem .

 

[Auger01]

Re: 16' Fiberglass Tri-hull Rebuild

I would do minimum two layers of 1708 over the entire transom to repair those tears in the transom.

 

[SAT_Bob]

Re: 16' Fiberglass Tri-hull Rebuild

Tagging along as well. I'm about to get started on my winter project and have a very similar hull. I'm curious. When you cut your hull with the saw, how far would you say you had your blade extended?

Hi mercurymang, we actually had the saw depth set to 1/2" which was the thickness of the deck. The problem was the bottom of the deck was rotted pretty bad on the port side so we were too deep when it "mushed" down. :facepalm: Just be really careful and check a lot that you're not too deep. Error on the side of caution and cut shallow first and then go back if you need to.

 

[SAT_Bob]

Re: 16' Fiberglass Tri-hull Rebuild

Before you get to far into moving her around, I'd suggest you do the following. This may sound a bit "Radical" but since the cut is so long I believe this is the best method for the repair.

Take a 1x4 and tape off one side with clear packing tape. Get under the boat and use deck screws to screw the 1x4 to the hull so it covers the cut with the packing tape on the hull. Yes, I said screw into the hull. I'd recommend 4 screws down each side of the board. These screw hole will be easily repaired later. They are Nothing compared to other glass issues you'll soon be dealing with. After the board has been installed, get inside and grind and feather out the cut as described in the video. I'd recommend applying a layer of PB and then two layers of CSM, a layer of 1708 and a final layer of CSM, Each 1 1/2" larger than the previous. When cured, removed the backer board from the outside, tape over the screw holes, then get back inside and fill the screw holes with pb. You can do the outside hull repairs after all the inside repairs are done. Once that cut is repaired then and only then would I consider moving her to a bunk style cradle which is what she needs.


Any whoooooo that's how this

would do it!!

Thanks for the suggestion Woodonglass. I think that's a good idea and a good way to keep everything lined up and straight. One question about the screws, though. You mention using deck screws. Will they hold onto the fiberglass if I screw them in from the bottom? What about screwing them from inside the hull down into the 1x4? Possibly using pan head screws with washers so they don't pull through the hull? Maybe I'm not following along completely.

Also, when I'm finished and have the screw holes left, are you saying to just fill them with PB and that's it? Would I need to grind them out and use the CSM and 1708 layers to patch?

Thanks again for the help, it's definitely appreciated.

 

[SAT_Bob]

Re: 16' Fiberglass Tri-hull Rebuild

I would do minimum two layers of 1708 over the entire transom to repair those tears in the transom.

Good thought Auger01. I'd really like to beef up the transom so I don't wind up with the same issue again. I was thinking of repairing basically the same way I do the bottom. Cutting out the section that's torn, grinding down and building back with two layers of CSM, a layer of 1708 and a final layer of CSM each progressively bigger. Then probably going over the entire transom with a layer of 1708.

 

[Woodonglass]

Re: 16' Fiberglass Tri-hull Rebuild

The screws will have adequate "Bite" to Hold the board as a backer and keep the hull aligned until the glass sets up. It'll only take 45 mins. Yes Tape over the holes on the outside and then fill with PB from the inside. The repairs to the screw holes will be done on the outside and will not require CSM. Only Filler.

 

[SAT_Bob]

Re: 16' Fiberglass Tri-hull Rebuild

Okay, thanks. I'll give it a whirl. Kinda nervous about drilling holes in the boat but what the heck, I already have a slice a mile long. :redface-new: Like you mentioned, the screw holes will be the least of my problems.
One more question though just to make sure I'm clear. You said the repairs to the screw holes will be done on the outside with filler. If I tape the outside and fill with PB from the inside, how will I do the repairs from the outside? Sorry if I'm being dense.

 

[jbcurt00]

Re: 16' Fiberglass Tri-hull Rebuild

The PB filling the screw holes from the inside is the BACKER for the final 'repair' from the outside: filling & fairing the last little bit of a divit at each screw hole w/ fine, very thin consistency filler.