Fiberglass hull rebuild

hello all, I am currently in the progress of builing a 19’ Tunnel Vee center console flats boat. I purchased the hull for what the Yamaha 115 commercial two stroke was worth and I figured it would need some repairs.

To get to the point the boat was very poorly build, stringers rotted due to exposure, tabing delaminated and keyslot transom rotted. I have the hull stripped and ready to go back together, I would consider myself a novice and have some experience with epoxy but great with wood working.

I have the hull all ground down cleaned and ready. Materials on hand are,
1/2” AB Marine ply
3/4” AB Marine ply
6” 1708 tape
1708 cloth
Marine Epoxy (slow hardener)

The hull was originally designed with a three stringer system and laminated hull stiffeners
It was said that the builder probably used the laminated hull stiffeners to compensate for a thin layup, currently I have all the stringers out and stiffeners removed and there is little flex at all with the exception of the tunnel area.

I am looking for recommendations as I would like to do it right. Thanks for your input and I look forward to learning as I go.

Pic of prior to grinding out ridges and delaminated tabing today.

 

I admire your gumption. Had it been me, I’d probably have walked away from it after removing that deck. No doubt you can rebuild this with enough time, effort, glass, and epoxy, but you need to ask yourself what you’ll have at the end of it. The remaining hull that you’re working with appears to be heavy (not in a good way) and manufactured with cheap polyester resin and chopped glass.

You might think about cutting your losses and just building one from scratch. This is a simple hull and definitely could be built by someone like yourself with general woodworking skills. There are a lot of good plywood epoxy designs you can purchase, and even get the plywood in a precut kit that you then assembly and finish. Bateau and Glen-L are two reputable sources - there are others as well.

 

Deering, thanks for the recs, however at this point I am in so deep and this is a project for my boys. We already built one of the kit boats together

SK14 from Bateau.

The hull is layered Matt and roven I’m not sure on the laminated schedule but it was built by Glen French who owned Explorer Boats before Dargel bought them out.. I spoke to the company that supplied Glen with materials and he said the actual hulls were good. I would like to figure out how to make it right. Thanks

 

It’s always a good idea to first cradle the hull carefully so it retains its shape as you remove its structural members.
If the hull is moving when you get in the boat to work, you may need to tip it up on its sides so you don’t have to put your weight on it to work, or it will be impossible to tab in structural pieces.
Grind everything smooth, clean and relatively flat, anything that’s not solid laminate gets sanded down to solid substrate.
The ribs/stiffeners likely could have stayed, they looked to be hollow tubes, but now you need to grind them flush to the hull, removing old tabbing.
Build a plywood grid of stringers and bulkheads carefully fitted to the hull, so that the interior is all boxed in for max strength.
As an aside, I recently helped with a similar job where the entire grid was built from sections of rectangular fiberglass ductwork that was salvaged from some industrial application. it was surprisingly easy, as the ductwork was thin, and each “box” could be fitted individually before being fastened in. End result was a very strong eggcrate, the only wood was battens along the top to fasten down the floor to.

 

See answer and question above. Thanks so much I really appreciate your input.

 

From What I can see in your picture, the old configuration had only one bulkhead in the bow.
The engineering people on this forum would crunch numbers to determine spacing and strength needed, but my seat of the pants approach would be to place two, one just ahead and one behind the console, and partial ones wherever you need to compartment the floor for gas tanks and storage.
Lots of flat area there, the stiffeners will need to be replaced, or the bottom will flex.
They can be foam or hollow, thin wall PVC sliced in half is easy to use and glass over, even cardboard will work!
Stick them down with hot glue.
The stringers must definitely be tied to the transom, possibly even reinforced to help transfer the motors thrust to the hull without flexing the transom.
Have you investigated the integrity of the transom?

 

The boat originally had a box frame in the stern as the transom, it is a keyslot. It consisted of three layers of 3/4 ply one of which ran P-S and was taped into the sides of the hull. It was all saturated and was removed

Original layout, plan was to put back as original but extend the deck forward. Here is a mock up of what I was thinking,

 

Tunnel: The only real soft spot in the hull is the tunnel section, to start I thought I would smooth out the outside corners and fillet the inside corners tape and add one layer of 1708 wet on wet to give a little more bulk and stiffness.

Stringers:
Plan was to build new stringers by laminating two layers of 1/2” and have offset joints, the original stringers were 3/4. The original stringer layout was one center(keel) one P side and one S side. The keel stringerwould run bow to stern and the other two would run from the bow bulkhead to the stern. From my knowledge on layup, bed stringers in thickened epoxy, fillet, tape 3 layers offset then glass the entire stringer up and over. That’s about as far as my thought process has made it and I am completely open for suggestions.

 

Most small boats like this had no engineering done prior selling them to the public, so if the first ones failed in some way they just added more CSM. What you described for the rebuild will most likely far exceed what was there, and what's needed.

 

Lol that definitely showed in how it was built. Thanks for the input. I figured anything would definitely be an improvement, just didn’t want to overbuild by to much.

 

The top of the stringers can be set at the correct level for the deck, they can be set high and cut back to the correct level, or they can be set low and another piece of lumber scabbed onto the side that brings them to the correct level.
You have to round the edges to get glass to wrap around with no air bubbles, so if you round the top of 1" thick ply stringers (1/4" round over is minimum, 3/8" is better) that doesn't leave much area for contact with the deck and ply edge doesn't work too well for fasteners anyway.
The best is to have the ply at the correct level with some lumber (1x2 or 2x2) scabbed on which gives you more bearing surface for glueing or embedding and actual lumber for fastening.
It's somewhat important to not overbuild things and make the boat too heavy.
When glassing the stringers it is easiest to do the sides separately and then cover the top with a third piece that overlaps on the sides.
Use throw away rollers for spreading the resin and a bubble buster roller for consolidating it all.
For bubble busters to work properly it is important to keep the fins clean and open and spinning freely on the axle. Also keep the fins smooth so they don't snag the glass fibers. Typically after several cleanings resin builds up in the fins and the axles clog so they don't roll smoothly. If you buy aluminum b busters, when they get clogged up, you can take a propane torch and set the whole thing on fire to burn out the resin and take the roller off of the axle and ream out the hole with a drill so it spins freely again. A little bit of wd40 doesn't hurt anything also.
You can also use body putty spreaders for consolidation, they are not as easy but might be more practical.

 

Great information and thanks so much, I was planning on using battens for sure. Will definitely get a buster for sure. On stringer height I left a 2” ridge when I cut the deck out around the hull so I would have a reference line as well as keeping some stiffness until framing was completed. Hoping to get started tonight. Got her all cleaned and ready.

 

Use this roller. My favorite thus far by far.

Keep it in a half gallon of acetone in a five gallon pail with lid then blast it with air.

https://www.amazon.com/Fiberglass-Laminating-Roller-Bubble-Aluminum/dp/B007VQS102/ref=mp_s_a_1_2?ie=UTF8&qid=1544651953&sr=8-2&pi=AC_SX236_SY340_QL65&keywords=bubble+buster+roller+1/2"&dpPl=1&dpID=41KHZcl3WRL&ref=plSrch&th=1&psc=1


I keep a 3" and 4" flat trowel in acetone as well.

Acetone will solve certain handles; the melamine? type seem fine. Plastic no.

I use both the consolidater and the squeegee. The squeegee will help move resin if you have a shortage. It is left to dry no acetone.

Great advice from the others; only adjunct here.

 

Thanks Fallguy, I purchased a 6”,4” and a 3”. Got the transom boxes, Tunnel fillet and taped tonight. Will glass the tunnel tomorrow and post up some pics. I forgot how much fun 1708 is na, not to bad as long as you get a good fillets down. I taped the Tunnel inside and outside corners with two offset tabs and one on transom corners just to clean it up for adding core and tabbing. One thing is for sure the print through of the roving will sure mess with you, it looks like bubbles everywhere . Thanks again for the information it really helps.

 

Thinking ahead on the stringer battens, would it be safe to router a cove (rounded radius) down the center of say a 1x3 and glue on top of stringers with thickened epoxy for the battens. Or would it be a week joint?