73 Tahiti stringer/floor replacement

[gatahiti]

I have recently acquired a 73 tahiti jet boat, about 18-19 footer. I saw one in a grainy picture that looks like it, labeled it a Tahiti Tornado. The PO had begun a floor replacement and stopped. It has three stringers. The center is a treated 2x8 (or 10) that has been attached by strips of fiberglass wrapped over it every two feet. I think I can break the stringger off the hull easily. Needless to say...this must go. The other two stringers need replacing as well. One has been exposed to the weather at the transom end where the fiberglass was broken off during the floor removal. The wood is sort of dry rotted feeling and can be broken apart with bare hands. The other stringer may be ok...but has holes from the screws which attached the deck all along its length. It also has a seperated scarf joint. The boat has been in the rain for an undetermined amount of time so i figure its probably shot. The two engine stringers are fully encapsulated and solid, no hollow sounds when tapped and I can not deflect these or find anything bad about them. The transom is solid, but transoms are not very substantial on these boats at any rate.

My original plan was to use pressure treated wood for stringers and pressure treated plywood for the floor. I have since ditched this after reading through multiple threads here. My current plan is to use nontreated wood and very good exterior grade plywood for the floors. I have done a fair bit of fiberglass work but only with polyester and with automobiles.

Now for my questions. When i get to replacing the outside 2x4 stringers, should i shoot for a one piece stringer or scarf joint two pieces together? Would a 1x4 lap board on each side of the scarf joint be required or would a simple joint suffice?

My plan has so far been to bond the stringers to the hull and weight clamp it. Then encapsulate it using vacuum bagging with a layer or two of cloth. Is this the appropriate method or should i do both all in one shot? I havent completely decided if i will use one or two layers of cloth, by using vacuum bagging I am thinking two since the laminate will be thinner than if i rolled it out by hand. Should I use polyester for all of this (since the hull is polyester)? Or should I bond the stringer to the hull with polyester then do the encapsulation with epoxy?

The center stringer comes back to a bulkhead that is in front of the engine stringers. This piece is visibly rotten. What I intend to do is create my new center stringer and bulkhead and attach these with stainless screws to each other with a little gusset on each side. Then I plan on glassing two drains (one on each side of the center stringer) into which a standard transom plug will fit. I suspect there may come a time when I need to wash out the engine area and would like to plug these holes to prevent water from getting inside the front of the boat. The rear seat will sit somewhere in this area so I plan to install a couple of inspection covers right in front of the bulkhead under the seat, or possibly sinking my battery boxes under the seat, although I would like to put them closer to the transom due to the weight. Back to the stringer. I plan to install the bulkhead and center stringer as a unit in the same fashion as the two outside stringers, encapsulating these as well.

My floor plan is to cut my 3/4 inch playwood to shape, then cover the underside with a layer of fiberglass mat and resin and vacuum bag it. If i am using epoxy on the stringers shoudl i also use epoxy here since i will be bonding/screwing the floor to the stringers. I plan to install the floor after covering the bottomside/edges and screw it to the stringers to clamp it down and locate everything with screws. Should I then remove these screws after the resin bonding the floor to the stringers has dried and before laying the cloth/mat on the deck? They will serve no purpose, and leaving fasteners under fiberglass in this fashion goes against what i have learned. (repairing corvettes with popriveted on fenders and flairs which are crudely glassed over by someone who doesnt realise the strength is in the fiber, not in a half inch of resin and plastic body filler......need i say more?) The next to the last step in my half formulated plan is to cover the floor with mat and cloth and vacuum bag this down. The prep and spray everything in site with a nice gray gelcoat. Am i seriously misguided in this thing? or have i overthought this? Will polyester resin be fine for all of it? or should i really consider epoxy? I dont know if i can use it as described. I have never worked with it before. You can see the stringers/bulkhead in the pics. I have some removal finishing to do.

The broken scarf joint is in the lower left of this picture.

Thanks for reading my post

Eli

[gatahiti]

Well I suppose i will just proceed with the polyester since no one has any insight on the use of epoxy in this application.....I dont want to try something new and have it fail horribly on me. Although I am worried about the polyester not sticking as well...

[sleekcrafter]

Epoxy resins work well, but they are very exspensive, I like MAS and West Systems for structure work, and repair work. Prep for the resins to bite should be done with 40 grit on the hull. Clean is also key, vaccum a all debris and wipe down, prior to applying resin. Douglas Fur is what I used for my stringers, and 5/8 plywood resin coated on the bottom, with two layers of glass mat on the top, joining the floor to the sides.

[gatahiti]

is it worthwhile to go to the epoxy? I am very comfortable working with polyester. Will the west system stick to the polyester?

I found this link, are the west system product recommendations a good rule of thumb?

http://www.hydrostream.org/ArticleArchives/Floor.htm

Would it be horrible to put the stringers in with epoxy then polyester the deck to save money? or is it worth doing all in epoxy to have it done right.

Thanks for the reply,
Eli

[sleekcrafter]

You can epoxy over polyester but not vise versa, but there is no reason you can't do the top of the floor in polyester. I prefer the flexiblity of epoxy resin, and would use it for the stringer and subfloor work. I did a 23 Sleekcraft complete stringers and floors, talk about a rock solid boat, wish I have done that the day I got it. Used it for 10 years after, and still was doing well when I sold it. Remember to prep the surface before each application for maximum bite on your surface. The complete project for me was 5 gallons on West Systems but worth every penny to me I also did major hull and transom modifications to the boat as wellI glassed in the pump opening, and made a 8 degree transition to the transom. A few years later I cut out the entire dash/intrument panel, and added a linear throttle, and quadrant.





This one is a big photo so be patient notice the transom transition for the new pump

[Racemore]

All this Epoxy crap makes everybody think you can't fix a boat without it.It's BS,overkill and to much money.A Vinyl-ester resin is probably the most used by performance boat builders these days.Still a poly boat can be fixed with poly resin.I thing you have to remember that fiberglass flexes.If you mix the types up you can create failure down the river.My suggestion is to use a like product.I would opt for a laminating resin than a general purpose resin.if you don't care what you spend use Vinyl-ester.It has better adhesion and is more flexible.You can make it rocket science but do your self a favor. and make sure it is clean and sanded and cleaned again.Roll the air out of the repair.Gelcoat the repaired area if expose to light and water and it will be fine.

Nice looking rig Sleek,shoulda kept it.Thats alot of work.

[gatahiti]

that is an awesome looking rig! I hope mine one day can be half as tidy. I am seriously just teeter tottering back and forth now. The poly would be alot cheaper but the epoxy is alot more flexible. I know I can fix it using poly, had planned to originally. But i see jamestown distributors has a west system starter kit on sale right now. I think I am gonna give this epoxy thing a whirl

[gatahiti]

wow...has it REALLY been 3 years?

Since this thread I have gotten married, and bought a house. Wife has said "you ought to fix that boat so we can go to the lake...". So i have hauled it out and cleaned it off and I am back at it. Been collecting Olds parts for three years as well

Has anyone built stringers out of laminated plywood? I am having a hard time finding decent material. I am back pondering whether flotation foam will do any good (I am unsure if I can put enough under there to prevent it from sinking) or if i should use a core under the deck.

[GIL_CV21]

head down to the local lumber yard (not Lowes or home depot ) and go through the stacks of kiln dried Doug fir for your stringer material .

[XstreamVking]

I will add my 2cts in here for the heck of it..... Use vinylester resin, make all the stringers and engine blocks out of a good marine or exterior ply 3/4" with few voids in it. Stack it to get the required thickness. Matt in between the pcs. Glass over structural parts with 1708 biaxial glass. Maybe 2 layers? For the floor use some good ply, 1/2" thick and glass the underside with some light wt matt. Over the floor use some 1.5 oz matt on the main part and put some 1708 biax on the seams where it joins the hull and cover this with matt also. Gell is great for the floor. Transom is just replace what was there, cover with some 1708, and matt. Just another way to do it. Old glass is sometimes a biotch to bond to, so grind well and clean. Wherever you glass, coat the old surface with some resin first to get a better bond.... Glass the hull to the deck, and it will be stronger than new....

[gatahiti]

im leaning toward the plywood stringers due to the fact that i feel like i can build a much stronger stringer than a single piece of wood. Should I take care to orient the plywood any particular way?

I will also check the local yards for the fir to see what is locally available. I am really torn still.

I still wish I could give it positive flotation in the bow in case of sinkage.

[GIL_CV21]

you can use ply to make stringers it will work fine but its a lot of work making them where as getting a nice clear 2x10x16 piece of Doug Fir will be plenty strong enough for stringers , its what a lot of boat builders used back in the day .