1984 2001 rebuild. Pete, go away.

Randy_in_Ohio wrote: I'm not even an engineer and I think I would be hesitant to use a material created from recycled grocery bags and saw dust in a boat's structural system.

I suppose if it worked, some big outfit like Bayliner would use it,think of the money they could save with the amount of boats they crank out.

Composite stringer thread


Yes, the glass "shell" around the stringer will give the boat the necessary rigidity, you don't actually need anything inside the stringer... however, the caveat is that you need to know how thick the fiberglass shell around whatever core you use needs to be to make up for the lost strenght of the original wood stringer core.   If I could difinitively determine the loads that the boat would see, and how in my garage I could acheive the strength necessary to with stand normal loads and safety factor, I would use glass around foam as seen in the post 93 boats. Since you are a boarder and are probably going to attempt balast at some point, you need to consider what effect the extra balast weight has on the hull/stringer system too... in effect, the hip bone connected to the leg bone... etc.
      

why do seacast at all? Would it be too difficult to do a foam filled fiberglass stringer? I suppose the seacast could be simpler and less risky as it is a proven method. But if you were good with the glass I would say save your money on the seacast and go fiberglass.

ok so your last post may have answered my question. need something to screw into, disregard prior post.

Maximal691 wrote: Dreaming, yes I will beef up the glass on it, I just really want the trex in there as a solid piece to screw the decking into.

Trex doesn't hold a screw all that well.   I like you're thinking with wanting to screw down the floor, but more to hold it while the glue dries as opposed to being the permanant fastening solution...   Since the floor acts as an interlocking piece with all the rest of the structure, it takes quite a bit of the transfer load when the hull flexes.    Bedding the floor to the stringer will help with load transfer.   If the floor moves at all, a good deal of the transfer will be lost while the floor is pre-loading.

I don't know the forces on the hull from the water, or from the engine so I don't know those calculations. I have put some thought into the expansion though, and this is what I have come up with. The coefficient of linear thermal expansion of douglas fir is 2.7x10^-6, which is in the boat originally. Epoxy resin is 31x10^-6. Trex is made of roughly 50/50 wood and polyethylene. Polyethylene has a thermal coefficient of 111, and 60 x10^-6 for high density, which are both used in trex. So, they average out to 85.5. Average that with the wood in the trex, 85.5 + 2.7 = 88.2/2 = 44.1. So I know its a very rough number, but lets say the trex has a thermal coefficient of 44.1x10^-6. I don't know the length of the secondaries, but lets go with 12 feet, and the temperature change is from 10 degrees to 100 degrees, the epoxy will expand 0.033" and the trex will expand 0.047". Thats a difference of 0.014", or about 5.5 human hairs over 12 feet. Is this math complete b.s., or will it work? I'm not an engineer, so if this kind of thing is your baby please chime in. I do think the trex holds screws pretty well, not as well as a pressure treated 2x, but enough to keep 5/8" ply down. As long as the stringers are solid, the floor will not have very much upward force on it. Sorry if none of this post makes sense, its been a long day.

max, why are you going this route? im just curious

Maximal691 wrote: I don't know the forces on the hull from the water, or from the engine so I don't know those calculations. I have put some thought into the expansion though, and this is what I have come up with. The coefficient of linear thermal expansion of douglas fir is 2.7x10^-6, which is in the boat originally. Epoxy resin is 31x10^-6. Trex is made of roughly 50/50 wood and polyethylene. Polyethylene has a thermal coefficient of 111, and 60 x10^-6 for high density, which are both used in trex. So, they average out to 85.5. Average that with the wood in the trex, 85.5 + 2.7 = 88.2/2 = 44.1. So I know its a very rough number, but lets say the trex has a thermal coefficient of 44.1x10^-6. I don't know the length of the secondaries, but lets go with 12 feet, and the temperature change is from 10 degrees to 100 degrees, the epoxy will expand 0.033" and the trex will expand 0.047". Thats a difference of 0.014", or about 5.5 human hairs over 12 feet. Is this math complete b.s., or will it work? I'm not an engineer, so if this kind of thing is your baby please chime in. I do think the trex holds screws pretty well, not as well as a pressure treated 2x, but enough to keep 5/8" ply down. As long as the stringers are solid, the floor will not have very much upward force on it. Sorry if none of this post makes sense, its been a long day.

I think it makes perfect sense

Eric, this route is just something that I've been brainstorming the past few months. Brian, the gel is in great shape and the upholstery is flawless, which is a shame since it's that hideous red/burgundy color and I would like white. And yes, it is paint on the hull bottom. Trbenj, I'll glue and screw the floor. Im sure I'll put more thought into the coosa after I meet up with Joe.

Maximal691 wrote: Brian, the gel is in great shape and the upholstery is flawless, which is a shame since it's that hideous red/burgundy color and I would like white.

If its flawless and original you may be able to carefully remove and get a few hundred bucks. I am sure there is someone on here with an 84 that needs upholstery.

i am more curious as why it was painted...salt water?

definetely a salt water boat..you can see the sacrifical anode in the rudder....

MinaquaWI wrote: How about liquid nails Subfloor and Deck adhesive to glue your flooring to your stringers? It has a 450psi sheer strength after 28 days of cure. Engineers?

Nick,
If you are doing a epoxy system, keep it all equal and use the same. You've been over looking at the "home improvement" places too much!! BTW, look up how hydroscopic liquid nails is!

MinaquaWI wrote: On another note, I had a 1985 Malibu Skier and the floor was glassed to the hull (topside only) and was stapled to the stringers. I thought that was an interesting and subpar method.

What do you expect from MB?    

Met up with Joe, he's going to test the epoxy on the trex. It was cool to see his boat, totally inspirational.

I have the time right now, just no money. Paying your way through college is tough without taking loans out. To the people who noticed it was at one point it was a salt water boat, this doesn't bother mensince it's getting a new power plant. If it was a big boat with two v8's that i didn't plan on replacing I would be more concerned. One of the ideas that Joe and I came up with while talking shop, is using a sheet of coosa for the decking where the driver and observer seat are mounted, so there are no spots for screw holes to rot the decking. This is good because I can save money by doing the decking where nothing is screwed, with ply, and only have to buy 1 sheet of coosa. To those who haven't seen it, Joe gave me some scraps and this stuff is pretty awesome. To the guys in the capital district, if you want to see it first hand let me know. Also last night Joe and I were talking about the weight of the trex, and I think I'm going to use azek for the ribs for weight concerns. For those who don't what it is, it's a popular trim for houses made out of PVC. You cn get it in nominal board sizes as well as 4x8 sheets. With the sheet sizes you could cut out bulk heads or something else of that nature. I thought of it as a floor option too, because it could be a maint free floor, without carpet (you can get it in white, but might be slippery) but I'm almost positive it wouldn't hold seat bases in, and the supports underneath it would have be around 11" because it's not that ridgid. Pete, i have full intentions of using epoxy and not liquid nails.