Sea Sled madness. It’s in my brain.

So what is this glass sheathing consisting of, what resin, what glass etc ?

 

Thanks John.

 

Well, that's what I've been asking for advice about. Gerr's Elements of Boat Strength gives 39oz outside, ⅝ planking on 5 bulkheads, 26oz inside. Glass and epoxy. But no suggestions as to specific layup composition. Not even mention of his assumptions. For example I might achieved those weights with woven roving. If I work instead in biax, the resulting panel would be much stiffer. At twice the cost. Gerr suggested 5 bulkheads, but I have 6, or 7 if the ram counts.

Cost, unfortunately, is a large factor for me. Work is slowing right now.

 

You need to decide what resin first I'd say.

I gotta get to fairing.

1200 db is my favorite glass to work with, but 3 layers is quite a challenge to do all wet. You might need to work wet on green and do the tunnel first.

Part of any glass plan requires thinking through the glassing so you don't glass yourself into the center!

 

Epoxy for sure. I think the others won't stay on strip plank. Silvertip from system 3.

Just looked up db1200. Son of a crap! American prices are lower than Canadian. I'm in the wrong country.

I'll ask you lots, Fallguy, if you have the time. Your experience is detailed and current.

 

Fairing at least won't trouble me. I'm a professional drywall finisher. Master of the hawk and trowel.

 

Noah's Marine in Toronto is where I sourced all my glass. Best prices US/Can I found.

I don't profess any expertise, but I really like working with db1200 because it is rather easy to wetout. That said, for your seasled, I might like some 90 fibers...but then again not to trade away the 1200.

The sucky part about db1200 is three layers is a lot of work and overlap planning. I think there is a 36 oz triax Noah's has. That would be a bear to wetout...and it might not lay in nicely like biax would. Two layers of db1700 would get you to 34 oz bottom.

I think, based solely on your 36/24 guidelines, I'd go two layers db1700 bottom and two layers db 1200 bilge. If you plan to beach her; you need to add more to the keel with some 1708 tapes. I'd do them after instead of before.

Can you post your Gerr inputs; the 36 ounce bottom seems awful heavy. I have 44 oz on my foam bottom, bit hull is super narrow at about 2'.

Another possibility would be triaxial. Noahs has a 21-24 oz, depending upon their sourcing. That stuff is 0,45,45 with all layers same weight. You could also use that in the bilge. It does wetout harder, but it can be done in a single go. The finish is not as nice (0 strand is always out). But its a bilge. It might not lay down as nice either.

Final recommendation from me is db1700 x2 bottom
db1200 x2 bilge

Possibly could go db1700 and db1200 bottom. That would reduce your weight and epoxy use some. If you setup some scaffold; you might be able to glass it in a single go.

about db glass, you really want it in a cardboard rolloff tube, it is real snaky and I use sharpie markers to remind me how long it is even along with overlaps and instructions like this goes first.

I always wetout the substrate. You really need to prewet as well or the wood might suck you dry. Roll the entire boat with 2 oz per yard. Wait 30 minutes. Reroll with 40% of glass weight using a 7-9" paint roller. For you 7" won't walk as bad on all that radius. Then roll the marked glass off the tube. Reference lines tell you if you need to pull it a bit or relieve pull pressure. I mark every 3 feet and all my running lines and overlaps. It helps avoid (what did I do here!!!).

Also, if the bottom is impossible to do in a single go; you can glass wet on green. So you glass the bottom db1200 day one and come back and do the db1700 day two. Silvertip has a 72 hour primary bonding window. That said; you will need to spot sand any rough crap from day one.

Also, make sure to prefair any steps between planks or you'll be injecting epoxy later which is a pita.

Sorry if any of this is patronizing. I don't have a gauge for your wisdom.

 

You also might want to know drywall tools are horrible for fairing. They belly too much. We only use concrete trowels for anything over 6".

 

Just so you know, db glass lays down super nice over keels and you have two of them. So you'll need to plan you layout carefully. It might work out to use a narrow 38" glass and a wider 50" glass best. The 50 goes on first, say as db 1200, then a 38" db1700 over each keel; then you fill in all the rest. You don't want to run the db up and only have say 6" off the keel or it will probably misbehave a bit.

If you work it over a couple days, I also usually lay some thixo over the prior overlaps to avoid air entrainment. Treat it like a buttjoint infill. Use epoxy and cabosil 1:2.1 before your preroll.

Air on the bottom is your enemy and you must not allow any. Hydraulic erosion happens easily with voids.

Also, 2" minimum overlaps.

 

How about woven roving laid at a 45° angle to centerline? Certainly won't trap any air. Second layer 90° to first.

 

Fairing epoxy with additives mixed like mayonnaise seems like it would be comparable to drywall mud mixed for second coat filling, in stiffness. I take it, its stiffer than that?

 

Well roving is not as strong pound for pound, so no.

 

I wish I knew what Dave Gerr had in mind. Maybe the weights quoted are for roving, and less biax is fine. Well, if my bottom flexes too much, I'll tab in some floors under the sole.

 

yeah, it is just a bit stiffer

some of the commercial fairing compounds are smoother/nicer, but they have super fast cure times and are quite costly. I really like quikfair for the end job. But not the start...too $$$$ and too fast. We mix 3 oz batches maximum. If you are infilling batches of say 16 oz epoxy; the qf is not the right stuff; imo

Here, you can see fills with epoxy, sil32 and aerosil. About 1-1.5-.5 or so. This area was db1700 with a center wide overlap and took about 36 oz epoxy on two lifts. The last lift will be lot less. I ran two directions, first round for and aft; then 14" trowel sideways. This pic is after first pass. Plenty gets sanded off..not as good as you. One issue with my fairing mix is it is a bit pockey. QF is not.

 

Almost certainly true.

you won't flex with two db1700 on the bottom unless you are planning 60 knots