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That was horrid, but the worst of the grinding is done. Its time to pickup some materials. I broke through from grinding in a few spots, and there is a few holes from previous owner(s). What type of mat, or cloth should i patch down over these small spots before laying something over the whole bottom? Some chop strand under the patch maybe?



After dealing with the holes I was thinking this for materials/layup:

For the wood 1/2 balsa core, 1/2" Merttini marine ply from Peacock Lumber for the stringers, floor, and transom.

Epoxy for the resin, but i dont know really much about choosing one. Im not afraid to try a house brand thats proven over west system stuff. I grab some thickener stuff and maybe something to make it thinner for saturation needs. And possibly a tint for the top coat.

Im going with the wieghts instead of vacum bagging.

1.5 oz stitch mat for first layer on the lightly sanded with 80 grit original bottom surface.

Balsa down on thickend epoxy.

Some sort of bi-axial cloth over the core with 45/45 4" wide tape for the tabbing/joining.

Stringers on the bottom with core in between since thats how it was made originally. What thin cloth should i use when laminating the stringers and floor before installing?

I will be joining the stringers with knees just past the bottom bottom bolts (15" off pad) of the inside of the transom. I was going to cut a window on the inside transom glass to tab the stringers directly to the new transom wood. I want to avoid cutting out the splash well, so Im planning on cutting the outer skin off leaving 1" perimeter like on the hydrostream website. Cut and fit 3 layers of 1/2 ply, re apply outer skin and fare the seam back in. Maybe a lite cloth over it all when im done.

Some of my questions about mixing, blush, sanding, thickening additives, etc will be answered by the supplier(s), but is the lay up and material choice ok? Id rather take advise from here then a sales person.

Ive read about all i can read and its time to just do it. I have a decent understanding of the workmanship details like radiuses, rolling speed, setup times , planning, etc. But, its trully my first time at a glassing project this big.

You obviously have the knowledge of what it takes to complete your project - but you are basically asking should you buy a Chevy or Ford or Dodge. There is no correct answer. It is your own preference what structural materials and resin to use. The only thing I can caution from reading your questions is do not use epoxy resin with chopped fiberglass mat if you select epoxy as your resin choice.

Noah's has a very good inventory of the marine plywood, balsa and composite sheet material - so they can give you good advice for wood versus composite. They have a decent selection of fibreglass materials. Composite Canada has an excellent selection of fibreglass materials - but do not inventory any wood materials and have limited composite sheet material. Both companies offer very good professional advice on the different products they carry.

Good luck with your decision and keep us posted with your progress.

Thanks dougw for the noah's idea. Ill check them out. Peacock lumber is very close to my house, but ive never heard of that specific type of marine ply(Merttini). Its $138 for a 4x8x15mm sheet. I need about one and a half sheets for all of it. I was flirting with the idea of a composite transom if i could get half sheets for the same price as a 4x8 wood sheet. Price would be a wash due too the waste.

Yes, I remeber now about the binding agents in chop mats not being compatible with epoxy.

So, some sort of stitched mat maybe for the first layer on the bottom. For the hole repairs i guess just a little bit of lose strand fiber material and resin. Then a small piece of fabric over it. I figure adding a bit of build up to those spots of break through/grind out of holes for repair may help level it out for the core to sit better.

Any and all advice is apprecited. Every little bit helps.

this is much lighter than wood.
https://www.plascore.com/markets/marine/

I have it down on 3 points now working on the transom. I now understand the suggestion to let the bottom "hang". The pad hook is about 1/8" now compared to over the roughly 1/4", or more it had. There is one spot on the running suface beside the pad with a slight, positive bulge when i put a long stright edge on it. Its maybe 1/16 at the most.

I have to get the transom done before i put the stringers in. I cut a window on the inner transom skin to attach the stringer knees directly to the transom wood.

Im contemplating calling a shop to price out what vacuum bagging down the core would cost vs. buying the materials and tools myself. Im most likley never/seldom to use the vacuum equipment ever again. I like the idea of a stronger, safer, lighter boat.

One downside to farming it out is that after testing with putting wieght(s) on the pad area the hook, and bottom straighten out very close to perfect. With vac bagging there is no significant weight pushing down well curing.
I figure if i can get the bottom straight(er) while curing the core i would be saving myself time on the blue print, less filler, etc.

I will wieght down the stringers well glueing them in, and that may bring it back close so no wieght vac bagging would be more feasable.

Just trying to make a plan without any real experience. I have all the materials for doing the transom, stringers, and a full surface 2 oz. cloth skim ready to go. I have the final rock race of the season up in parrysound this weekend then i can really put more into this build. The timing should be good for low humidity, and still exceptable curing temps.

Im back at it. Transom is 3 layers of 1088 ply .375+.375+.5 inch with 6 oz. between the two inside sandwiches. The plys are angle cut, and the first two are horizontal, and last is a three cut vertical. It all jams in tight under the outer edges. It takes a mallet to get the last layer in. The knees on the inside Im adding to the stringers will back brace all the cuts. All the cuts land between the bolt pattern of the motor.



I drilled out the bolt hole areas, and splashwell drain to fill full of thickend epoxy for water and crush resistance.







I clamped it out the best i could, and put some screws threw where i couldnt clamp that easy. In hindsight I wish I made a large plate and backed it with wax paper. It turned out decently flat, and way better then the bulging from rotting wood of the past. It will need a bit of fairing out, and I may add a 2 oz skin, or something. It squeezed in a bit lower then the outside parimeter, so i gots room for more material when smoothing it out.

Got the wood all worked out, and starting the bigger part of the job.

Nice work.
I also thought about vac bagging (a number of transom projects lined up).
Have an HVAC Hornet vac pump, priced out all the goodies required to get set up properly and thought, hmm, this could get expensive. Decided to pass for now. 1st job is just a little thing so doing it the old skool way will be easiest. Will re-visit vac bagging for next 2.
Keep up with the posts

Two layers of glass in the bottom all gooed in and had to stop. I wanted to get the stringers bedded, but I was already extra late for work. Everything to do with resin/glass has taken 3x the amount of work I initially planned on. Yeah, Tomcat this stuff is getting expensive. The only things i stepped up from the cheapest proper material is epoxy and the biaxle cloth. Im at $1200 for all the glass, epoxy, wood, tools, and consumables.



A layer of continuous 2 oz 0-90, and a layer of 12 oz 45/45 over it is done. I wanted to build up and smooth out the skin under the core and stringer to go in next.

Good call on the epoxy. Bet your lungs & nose will thank you.
I'm using up my last Poly resin on my little Zodiac Rib transom job, from then on it's epoxy.
Was cutting & grinding last weekend in that heat, nasty.