69 Woodson Tri-hull with 68 Johnson 55hp

[JASinIL2006]

For grinding, I would probably grind just enough to get to good, clean glass. I don’t see the advantage in removing more material than you need to.

For OSB (assuming you mean OSB and not waferboard), what is the advantage? OSB takes on more damage when edges/holes get wet than does plywood, and it’s main strength advantage is in shear. When used in flooring, you generally need to use thicker sheets of OSB than plywood (3/4” vs. 5/8”) which means more weight. I don’t have anything against OSB, I just don’t think this is the best material for this application.

 

[Redtruck12]

I don’t understand why you would even consider OSB.
no easier to work with and cost difference will be minimal.
if you rebuild it properly and glass it properly (not like the factory “slap together”) you should be able to keep things dry for a long time. Cutting corners to save what???
exterior grade plywood is my vote.

as for grinding, I agree, get it down to clean somewhat flat glass that you’re new glass can bond to but no need to go deeper.

 

[gm280]

Okay...I am not an extremely well edge-you-ma-kated person, and I didn't sleep in a Holiday Inn last night either, but with all the project threads I've read on these forums, I can't once remember even one person rebuilding with OSB...not one!

Exterior grade plywoods are always used. Why, you may ask? Because the glues used to make exterior grade plywoods are just that, exterior glues that will stay together in a lot of questionable situations. However, being this is YOUR project, all we can do is give our opinions against OSB and you do what you wish. That IS how these forums work.

You post a question, we give you our opinions and YOU decide from there.

As for grinding, it looks like you done a great grinding job to me, especially the transom. That looks really good. No, don't continue grinding if you have a clean surface that the new fiberglass will adhere to. No need for that.

I will say one more thing, built this like you want it to be around for years. Don't cut corners now. You have already done the hard dirty, crappy, smelly, work and no need to take the short cuts for any reason. But then again, that is only my opinion...

 

[Hab]

I guess let me put your minds at ease for now, im not concerned about cost at this point. i have an alterior motive, and possibly a test subject. I built a small utility trailer a few years ago. The Admiral and I haul ouselves and 3 kids to Michigan every summer from Tulsa. Us, the kids and enough junk to camp (Cabin camping anyway) out for a week takes a ton of space, so I constructed this small trailer to give us some extra carrying capacity behind the minvan. I skinned it with OSB, and am wanting to reskin it with glassed over 3/8"OSB once the original 11/32" finally gives up and falls apart. Its survived some pretty good monsoons uncovered,allthough i do keep it tarped for most of the year. 1st 2000 mile trip was 2016, this year will be its 4th.

The trailer is in pieces right now, im re-working the suspension that the Admiral tested to failure last summer....Dont ask.
the draw bar and fenders were once a Tee-Nee trailer, that was bastardized before i got, i just bastardized it more for my purposes, so dont crucify me for it.

 

[Hab]

Ran across a good read this weekend "The Elements of Boat Strength" by Dave Gerr. He makes an attempt to simplify a very complex engineering problem (building a safe boat) and makes layup schedule recommendations with easyish to figure methods.

 

[Hab]

Few more hours tonight...... Man this hull is pock marked as bad as the moon with holes and junk. I guess im going to give in and call it FD on the grind for the hull. I think im better off patching this junk rather than cleaning to the gel. Other than that got a transom template mocked up. I guess i got to decide on materials now, and go get me some resin.

 

[Hab]

Allright, Im at the point of putting in an initial order for resin and fiber. Anyone have an opinion on finishing procedures. I have read about wax and PVA, and seen the boatworks guy use gelcoat to finish layups. Just wondering whats possible to finish these layups that are done in stages.

 

[sphelps]

Just do your lay ups and let it cure ...Sand , fair , then paint or gell coat afterwards if you want .

 

[Timr71]

Looking good. Just read your whole thread. following along now. Good luck.

 

[Hab]

Work, family, summer chores, and the rain, oh god the rain, are slowing me down more than i would like. Not much to report this week. Ive revised my glass and resin order for the 30th time and I'm still second guessing myself. Ive started to work on the temporary shelter for glassing, built 1 of 2 cheap gantry's that will hopefully later be used to help raise and rotate the hull. I feel confident that as soon as i erect this structure, the rains will cease and the temps will soar.
I bought a sheet of exposure 1 ply to construct my transom. Probably a poor decision, but I'm guessing it'll be 15 years before i regret it if i can figure out the glassing, less if I cant. I'm not sure marine or exterior ply was around when the boat was built, but i do know the sheets were simply nailed together, bondoed or zolatoned (deviled) to the hull and glassed over. Im starting to wonder if the additional ventilation allowed by, lets say imperfect manufacturing, was the reason the wood can last longer in some boats than others.
I also started working on my motor, since it requires less overall roll-out to mess with. started that thread today over in the motor section. Thought id start off with something easy like reverse-engineering the 1969 amplifier/CDI box.

 

[Hab]

The rain let up for a few hours saturday, so i finished my multiuse gantry's. Managed to get the transom cut up and glued together today between storms, and worked on my amplifier circuit some. I guess ill have to concentrate on forming my stringers over the next 2 weeks, then ill be fully ready for resin and cloth. The gantry's and a tarp will serve as sun and rain shelter for the few weeks ill be running fiberglass over the transom and stringers. Were going on vacation in 2 weeks, so i wont start glass work till we get back.

 

[mickyryan]

you rockin looks like a fun rebuild, i like tri hulls esp for fishing

 

[Woodonglass]

If you want to use OSB for your stringers, you can but...IMHO you would need to apply 3-4 layers of 1708 and resin to ensure proper strength. OSB is water resistant and pretty strong for flat work. On edge...Not so much. The fiberglass carries most of the stress for stringers but it needs to be a lot thicker if you're going to use non structural components for the interior mold. Minimum glass requires the interior substrate to be able to carry more of the load. 1/4" thick walls of glass would be minimum for OSB stringers. But I AM just an Old Dumb Okie soooo you need to consider that!!!
Now if you want to make OSB I-Beam type stringers then that would be a viable method but kinda difficult to glass.

 

[Hab]

Thanks for the encouragement guys, I'm kind-o stuck on this one. I want to completely disregard the strength of wood, at some point it will get wet and at some point in time i will no longer be able to count on the strength of the wood. At the same time I don't want the shredded wet mess to swell so bad it impacts the fiberglass either. For that reason I guess ill just use standard ply (I think OSB is slightly more dense = more material to swell up or absorb water). Plus Ive never done glass before and if the factory couldn't do it right, well here's hoping i can splash enough resin around to keep it together a few years. My local supply doesn't have 1708, just 24 oz roving. so ill be warping my junk with the heavy stuff.

 

[sphelps]

Make sure you have csm on hand for the roving .. You must put csm down before woven wet on wet ... That’s with poly resin ...

 

[Woodonglass]

Good Luck doing your stringers with 24oz woven roving. That stuff is NOT user friendly. If you've never used it then it will NOT be a pleasant experiences. It does not want to conform to much of anything angular. There's tricks to doing it but for the Novice, it's a real hard process.

 

[AShipShow]

You could also do hollow stringers... use wood or foam as a form and lay up at least 3 or 4 layers of 1708 (or woven roving). Once they are cured, pop them off the mold and trim them to fit the boat and tab them in like you would wooden stringers

 

[Woodonglass]

Also WR uses a LOT of resin. Almost double what 1708 uses. You can order 1708 pretty inexpensive.

 

[Hab]

You could also do hollow stringers... use wood or foam as a form and lay up at least 3 or 4 layers of 1708 (or woven roving). Once they are cured, pop them off the mold and trim them to fit the boat and tab them in like you would wooden stringers

Hmmmmm, im all for experimentation, but for this go around im looking to get the back together as quickly as i can. Albeit im gonna foul it up in places.

Thanks for the suggestions and tips. Ill order less roving and see how it goes on the transom. If its a nightmare like ive been warned, ill report back and order the easy stuff. Ill probably waste plenty of gallons of resin just figuring it out.

 

[Hab]

Looking for some insight into a couple items. Ive read so many re-builds im starting to get lost in the details.

1. When running cloth or csm for the stringers, do you try to run the cloth and CSM the full length say 12' or do you put it in in 50" sections. say were tabbing each side and capping separate. Seems like working with a full length section would be a huge PITA.
2. Foam, Ive seen lots of guys foam the entire hull of their boat (under the deck). Most seem to work out ok, and i don't plan to swamp another boat, but this post has me rethinking the idea. https://forums.iboats.com/forum/boa...repair/463430-putting-foam-in-your-boat/page2 especially post 23.