Weight estimation for wood coatings

[hashtag_laeuft]

Hi ..

thanks for the explanation @Rumars .

The hull thickness, fiberglass coating, framing, etc. are driven by the overall design. What works for one may not for another. Maybe you could get a book with simple formulas for designing boats, like Gerr's.

Thats true. But the question was not about scantling.

 

[gonzo]

The laminate over plywood is part of the scantlings.

 

[philSweet]

Well, it is about scantlings in a way. We need very much to know what plywood you are using (species, thickness, number of veneers, and rating (BS 1088 etc.) Bruynzeel Mahogany AAA with 1 mm veneers is a totally different animal than Merrit A/B marine fir with maybe five veneers for 12mm stuff. The coating system for the latter needs to be more than twice as extensive as that of the former. Assuming this isn't all clear brightwork and the surface veneers are decent, you need to sand and prime before putting a veil of glass down only if a cloth snags when you pull it over the surface. That will be true for any softwoods. So yes, seal, sand and fill both sides of the panels on the flat. Use laminating epoxy uncut, 100% solids. Warm the bare panels for several hours in the sun, then transfer to a cooler area for coating. That eliminates bubbles and helps seal the end grain and reduces the chance of bubbles later.

For a plyboat of that size, I would want at least ten oz/sqyd worth of woven glass over an okume ply hull and deck to handle scuffs, bangs, and dock rash. For fir, I'd want a bit more. You might as well just go with light biax stitchmat over fir - but it drinks gallons of epoxy.

 

[hashtag_laeuft]

Hi @philSweet ... thanks for the constructive reply and information.
The hull is constructed as multi-buckling frame (is it called like that?), composed from a bottom plate, lower chine, upper chine and a side plate.
I'm not yet done with the scantlings, but I guess it will turn out to be 12 mm for bottom and lower chine and 10 for upper chine and side plate. According to the manufacturer, the boards are manufactured in accordance with Lloyds Register BS 1088:2018 - Marine Plywood - and EN 314-1993, Bonding Class 3 Exterior (AW 100). The 12 mm boards have 7 veneer layers and the 10 mm boards have 5 layers.