for making wood fins , whats the point in using marine ply?..its all covered with fiberglass in the end and no water touches the wood. so why not just use any kind of wood you want to use…?
everybody is allways marine ply this and that…i just dont see why what kind of wood you use matters…
am i right or am i right.
nah your wrong 
marine(or any ply for that matter) ply has lots of layers which makes them easy to foil
you can see the lines and graduations are smooth
i use aircraft grade ply its 6mm thick and has 12 laminations
so i can get a really even foil
That’s the shit…
What’s up Paul
greg
heya greg
been pumping here for two weeks
overhead and clean
just got another order from a dude who saw the last one
very stoked
but really you can use any wood you want
even cardboard for that matter
or rice cakes
or cabin bread
or laminate some money in there
or some girly pics
Hi -
As is often the case around here, a simple question led me to do a little research.
Your run of the mill construction grade ply often has voids somewhere in the mid laminates. Those might be exposed as you foil the fins. Your marine grade ply generally has fewer voids and is laminated with water proof glue. Once glassed, the glue shouldn’t make that much difference but voids might be kind of funky. Aircraft grade is the best and is graded for structural applications that demand the best wood and the best glue. All plywoods have different grading scales that separate the best from the just OK.
Check this link and become a plywood expert like Herb Spitzer. He makes his own when he laminates his taco skateboard decks in a custom plywood press.
Hi -
As is often the case around here, a simple question led me to do a little research.
Your run of the mill construction grade ply often has voids somewhere in the mid laminates. Those might be exposed as you foil the fins. Your marine grade ply generally has fewer voids and is laminated with water proof glue. Once glassed, the glue shouldn’t make that much difference but voids might be kind of funky. Aircraft grade is the best and is graded for structural applications that demand the best wood and the best glue. All plywoods have different grading scales that separate the best from the just OK.
Check this link and become a plywood expert like Herb Spitzer. He makes his own when he laminates his taco skateboard decks in a custom plywood press.
John - that’s 100% correct. Paul may be correct in that the marine plywood he gets may have more veneer layers than plywood used in his area for general construction, but the spec difference is in the allowable voids. I think that you are probably spot on about the advantages of fewer voids when it comes to fin building as well. Boatbuilders that I correspond with seem to agree that the quality of marine ply in the US has gotten considerably worse over time while the price has skyrocketed (there has been some suspicion that at least some manufacturers are just labeling ordinary exterior ply as “marine” and jacking up the price accordingly), and many of them have recently been substituting a product named MDO (for Medium Density Overlay) plywood. MDO was originally marketed for use in outdoor signs, so it obviously has to be ultra stable in wet conditions. It has a layer of plastic or some other material that will easily accept paint (the Overlay) on one side (occasionally on both sides), and typically that overlay is primed at the factory. Unfortunately the price of MDO seems to have gone into orbit as well. I need a 60"x18"x1/2" piece of weatherproof wood for a non-marine project, and the local sign company quoted me at $65, or nearly $9 sq ft. That means that I will be headed in a different materials direction for my project, OTOH you could make quite a few fins from that $65 piece. What difficulties would be presented by the overlay and primer in fin construction would need to be determined by experimentation.
-Samiam
All plywoods have different grading scales that separate the best from the just OK.
In the U.S. I’ve watched basic Birch ply go from fairly good last July to what gives the impression as being rough, almost still-drying crap. This is basic DIY-store purchase stock. You can see the change just in the splintering on the edges of their cuts before shipping. I’ve been told there are several reasons, including scarcity of materials as parts of the U.S. rebuild after natural disasters of recent years; also increased RV and boat building, regular home building, and home remodeling. And this past wek I read that California has outlawed formaldahyde use in plywood for health/safety reasons…who knows what that will do to the equation.
It’s like wine, I suppose…twice the price gets you three times the experience…
yes of course i realise that any ply will give you the lines to make an even foil…
but anyway…the actual question…yeah that makes sense about “why marine ply”, higher stardards so i wouldnt run into ugly voids beteween any layers… but from the sound of it, the high grade stuff is getting rare these days…
ok i got it now…
where are you at Onion?
there’s a really great wood store here
that has all kinds of high quality ply.
i bought a quarter sheet of 9ply 1/2" apple.
i think i paid like $30
Apple is great ply…MAKE SURE IT’S EXTERIOR !!!(waterproof glue).
Now days, I make whatever ply I want.I made a racing deck for the world’s champ last month. No wood in it at all, just Formica shells w/ hi-density foam core and 125lbs burst wt. brown paper in it.
And thanks John for the props.Now back to the foam and glass pit…Herb
oh man, i don’t remember if it was exterior or not.
i didn’t think to ask 'cuz i was making keels with it
and i figured that they would be glassed over and sealed.
will they be okay?
Yes Chris,
They will be fine,just make sure that they stay sealed in resin/glass.Repair any damage that exposes the wood as soon as possible.
Even ext. glued ply will delam if exposed to water for a metered length of time.Just the int.glued stuff will delam much faster…like really,really fast.
Most or all Apple ply is ext.glued…it’s a high end ply , usually maple and birch or maple and ash.
Did you buy a 4x8 ft. sheet at 5/8" thick 7ply ?
If it’s yes,I’ll bet you paid good $ for it.
You can get some cheaper birch or luan(mohog), like home depot stuff in 1/8 " and glue it up with either ext./or int. glue .You’ll probably come out alot cheaper in costs.
Apple is generally a AA OR AB Grade…usually never less than a AC grade.
You made a good choice.Herb
im on the east coast, theres plenty of boat building and what not going on in the area, sure i can find some quality marine ply if i actually look around…
anyway just to get an idea of what i can do with the stuff, i dug through dads scraps off different types of plywood… most were pretty thick, about 1/2"-3/4"…but hes got all the wood working tools, so i cut a few strips of ply that looked promising… then fed them though his planer untill i found a surface and thickness i was happy with…
i did run across some nasty spots, but might have found some decent parts of the wood for fins… i bassically found an area where if single foil , the flat will look good, then ill just have to see what i hit while foiling…
id put some pics , but at this point its just strips of wood with a nice grain pattern on the flat… not extremely intresting, but might be once its the finished product…
hes got alot of solid wood that would work well, but i need some lines to go from i think… ive made a few sets of glass fins and found the layers of glass really help to even out the foil of both fins, so i dont want to mess with solid wood just yet… well, i could it wouldnt hurt, just might be a waste of time…
reminds me i need to go look at the stips now to see if i can fit my templates on the clean areas. and take out the damn trash…ugggg.
it’s 2’ x 4’ x 1/2".
it’s nine ply.
i got it from http://www.macbeath.com/.
they have a store near me.
me and my fiance spent about 2 hours just cruising.
there are some really amazing woods in there.
it smells really good too.
it’s my new favorite store!
oh, and if anyone clicks that link,
you might wanna make sure your volume is down…
scares the crap outta me every time!
well, i still havent had a chance to foil those fins yet, but i get the feeling i might run across some bad spots … but who knows…
anyway, i was at lowes today picking up some around the house stuff… and looked around at their selection of wood… nothing there that really looks like much use, or any better than that wood i allready have…
so what sort of store should i be looking in to find marine ply? some sort specialty wood store? i dont recall ever seeing any wood at the boating supply stores but i wasnt looking at the time…
ok i will work on the 2 sets i have drawn out sometime soon, ill see what happens and possibly post some pics if they turn out good, or maybe even if the turn out bad. so then people will know “why marine ply”…
Hi onion,
I suggest re-reading Herb’s post. It doesn’t need to be marine ply. Any nice cabinet grade ply will work. I’ve used the lower end baltic birch from Home Cheepo with pretty good results. Mostly I just go through the scrap pile at my buddies cabinet shop. He’s got the good stuff. Mike
I found some at a lumber yard. Should have small panels for sale.
Any plywood supplier has scrapes…ask…the worst it can get is they say no.Herb
How’s your foot, Herb?
g