Anyone doing this? I know some of the SUP manufacturers are bagging ply over 1 lb foam and the boards are very light and can literally be smacked repeatedly with a hammer without as much as a scuff.
Kirk
I found that 1/8"ply over <1lb foam was too heavy, and I only did one side. The other was 1/8" balsa. I only used the ply on the bottom because the top has too many compound curves. Boards I made with just balsa were considerably lighter. It is very strong, but I just finished a balsa compsand with a 1/8" skin and just for the heck of it, I gave it a few hard hits with a closed fist and didn’t get any pressures. Any other board would have had a small pressure at minimum if not a bad one.
The skin has 4oz glass under the wood and 4oz over it.
Hitting a board with a hammer will leave a scuff mark, maybe no damage, but a small scratch or scuff from the metal if it has a gloss finish. Hitting it with any part of your body won’t leave any marks on the board, maybe a bruise on your body.
Hi, I have purchased materials to build a flat water paddleboard for my wife. It will be vacuum baged 12.5 feet long, 4" thick home depot eps foam core with 2.7 mm home depot ply skins and 4 oz glass.
My original plan was to glass both sides of the plywood to make a true sandwich structure. The home depot ply looks like very thin luan veneer with some kind of crappy much thicker veneer on the inside.
I am thinking of skipping the inner glass on the bottom to save weight but I’m not so sure because of the low quality of the wood and I imagine my wife will be hitting things and/or dragging the board over logs and oyster beds. If she can drag it. I would like to keep the weight less than 30 lbs but we’ll see.
I am not planning any compound curves on this project. The top and bottom skins will be the same dimensions but offset by 6-12". The sides will then be twisted so that that the tail will be thin, the rear section of the rails will angle out towards the bottom, the middle section will be vertical and the forward section will angle in to a sharp v in the nose.
As far as compound bends in plywood go I have a bit of experience with that. I once built a tortured plywood kayak design (Chris Kulzicki’s “yare”) whick had very much compound curving in the hull. I was so curved it didn’t look anything like a typical plywood boat.
I also used to build and sometimes sell some vacuum laminated plywood kiteboards which had about 2" rocker and a 1/4" concave in the bottom.
You have to be careful how much compound bending you try to put into plywood as it can only take so much. I made some foam core kiteboards with balsa or other veneer on the deck and bottom and one time I had problems when my friend wanted me to use a cretian type of veneer on the deck. This was sort of a “veneer-backed veneer” like 2-ply plywood and it did not conform to the stronger compound curves where the deck curved into the rail.
The kiteboards were done over high density foam although a few early experiments were done over xps foam. With very ligh eps you have to consider that even if the wood can potentially make the curves, the stress of forcing the curve might crush the foam underneath.
There is no chance of wrapping rails with plywood, but it is possible to put in some deck dome and/or bottom curves and then build out the rails with some other material such as foam or balsa.
The nice thing about a vacuum bag is you can test everthing dry to make sure it works before you add any epoxy.
Trent
Current Hobie wave SUP’s (< 8 foot) are fairly thick plywood over 1 lb EPS with D-cell rails. Very strong (I wouldn’t give it the hammer test though), but the construction is way too heavy for regular SUP’s and they paddle like a submarine vs. a same length non-plywood type. Can’t have much bottom contours with this construction either.
If you set a small dia router bit @ .5mm depth and run a series of strategic slots in the compound curve areas of the plywood panels, it will take to the curve far better…the slots will fill with epoxy under vacuum ,and form shallow ribs to hold the shape…considering youve done a few , you should know what I mean…got a nice flat table to work on ?
Hi, I got my wife’s eps/plywood sup built. It is 12’8" x 31" x 4" .
It is a little on the heavy side; it weighs just over 35 lbs but it’s built like a tank with 4oz / 2.7mm ply/ 4oz full sandwich construction on deck, bottom and rails.
Also a veneered tail block, two cotton fabric inlays on the deck plus screw inserts and hardware for center handle, nose handle and deck tie- downs. I still have to install the home-made gortex vent.
I let her try it out prior to the final epoxy fill coat and it has enough volume so that we can probably use it as a tandem paddleboard on flat water.
I probably could have saved a fair amount of weight by only using inner glass on on the deck standing area but as I mentioned earlier I expect this thing to be abused and I want it to last.
trent
It is but I’m spitting chips that for years I laboured unduly as the product I needed was there all along… Just down the road. Only a search away. didn’t have the I/net then. D’er.
So trent , I wanna see some pictures !!! The 35 lb. sounds about right for all the stuff you put on it. With a 2.5 oz glass job and no inlays,hardware ,handles and stuff it would have come it at about 28 lbs.
I’m lucky I’ve got a veneer supplier close by. I can get up to 4 meter lenths of plantaion Cedar radially cut [12ft] X 300mm [1ft] up to 500mm wide @ 3.2mm thick [1/8th] … because of the way it’s cut it naturaly wants to curl. This is what u need to source in your local. Forget plywood … they stick it together will formaldihide. Don’t want to be sanding that shite. I’d rather sand my own chemicals ! ;)
Plywood is workable sure but there are better alternative. Search under veneer. Google is your friend.
Cheers.
You can get Aircraft ply at thicknesses even below 1mm!
quanta that stuff sounds awsome .
I found the extra thin ply to be extra expensive too.
1/8" poplar over xps. I run some 1/16" deep grouves on the underside of the ply around the nose area to help with the compound curve. If you don’t glass them they weight the same as a pu board with a med heavy glass job.
This one is now about 2 years old and has been left on the roof of a car in the sun many times and no delams.
Hi Wood Ogre, here are some pictures. I hope you will not be disappointed as for sure I am not the craftsman you are.
I decided to use the 3.7oz glass because it was cheaper than the 2.5 oz but looking back that was probably a stupid decision. I could have had close to half less weight from the glass and another close to hallf less less weight from the resin.
Then again you can feel the board flexing in chop from the motorboat wakes so maybe the glass schedule I chose is barely enough.
Like I said before no compound curves in this one because it was supposed to be a quick and dirty build, It probably would look a little nicer if I a least thinned it out in the tail but then again its nice to have all the volume back there because you can walk all over the deck.
trent
