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plywood choices

#21
Guys I apprciate all the info. All this info is for my 3rd one I'm fixing to start. Still finishing the 2nd flat bottom. The 3rd will be a UJ Piroge. I have found a place I can get 16' rough cut ceder, pine, or cypress. I would like to plane it down to 1/8" or so and build the Piroge out of 2" strips and no epoxy. In my mind the wood would be simi smooth but would age and look "cool". If I can't do it in strips I would just plane it down to 1/8" and use a 10" strip for each side and either a plywood bottom or glue 10" strips together. I wouldn't have to scarf for length which would cut down on seams. Does my idea sound feasable? And would I use "glue" to seal the bottom to the sides?
 

seedtick

Well-Known Member
Jul 22, 2006
1,142
4
Denham Springs, LA
#23
don't think 1/8" thick solid wood only of any species is strong enough for for a boat. Especially if you want it to "weather" 'cause it'll likely stress crack as it weathers and goes through wet and dry cycles.

An old boat builder told me that a 12" wide cypress board will move about 1/2" going from dry to soaking wet. Old cypress boats were built and kept in the water so they never dried out and never leaked. Our challenge today is to build a cypress boat that is tight when it's dry and to keep the wood dry so it doesn't move. That's why you'd paint, varnish or epoxy - to keep water away from the wood

Folks I know that have boats that are mostly on the dry and look old and weathered coat the outside and let the inside weather. No coating on the inside lets it weather and turn gray and the coating on the outside keeps the wood from soaking up water when it's being used.
 

seedtick

Well-Known Member
Jul 22, 2006
1,142
4
Denham Springs, LA
#26
1/8 plywood is way stronger than 1/8 plank

other folks here have lots of experience building with 1/8" plywood and epoxy/glass

not sure that translates directly to 1/8" plank and epoxy/glass

I believe that folks that build strip canoes, etc. use 3/16 or 1/4 thick strips then encapsulate with epoxy/glass. Haven't heard of anyone using 1/8 strips

you might be plowing new ground here
 
#28
I know that a 12' 1x4 pine board weighs 7lbs. So if I plane cypress down to 1/4" strips and use 10" sides and the weight is close to that of pine. I should be able to build a 14' pirogue for under 30lbs? Does that sound right?
 

seedtick

Well-Known Member
Jul 22, 2006
1,142
4
Denham Springs, LA
#29
a quick check of a few internet sites show density of cypress to be .4 to .5
compared with water

a cubic foot of cypress would weigh between 25 and 31 pounds

a cubic foot is 12 board feet

therefore a board foot of cypress would weigh between about 2 and 2.6 pounds.

one board foot at 1" thick is one square foot, so a board foot at 1/4" would be 4 square feet

don't know the details of your design but a 12' pirogue needs about 40 square feet for sides and bottom

40 square feet at 1/4" thick is about 10 board feet, which means 20 to 26 pounds just for the wood for sides and bottom. Time you add seats, trim, glass and epoxy you'll be over 30lb.
 

Kayak Jack

Well-Known Member
Aug 26, 2003
13,040
74
81
Okemos / East Lansing Michigan
#30
1Fast68, another consideration here than may have slipped past you is that the sides are NOT a square plank. The longitudinal edges are curved.

If you make a 10" side from one piece of wood with square corners, it's going to have to start out wider than a finished 10".

If you already knew this, then I'll quietly go back to my glass of scotch. (In fact, I think I'll do that no matter what you knew or didn't.)
 

oldsparkey

Well-Known Member
Aug 25, 2003
9,877
37
75
Central , Florida
www.southernpaddler.com
#34
Kayak Jack said:
OK, I thought it had some rocker in the bottom. Sorry 'bout that.
It does have rocker in it about 2 inches. The end pieces and the ribs cause the rocker by the angle that is on the outside of them. Not only the angle from the boat the angle that the outside of the ribs is trimmed/cut at. :D

Fasting the side panels at one end is no problem and doing one side at the other end is sort of fun :roll: but that last one is a sucker when doing it yourself.

Chuck.
 

jimsong

Well-Known Member
May 24, 2008
247
1
lakside village, texas
#35
Yeah, I didn't consider how difficult that second end of a pirogue would be!
the first went so well, I went ahead and epoxied that last stem joint, started my the four screws, and casually reached for the side. I mean how difficult can it be to bend a ten inch piece of quarter inch ply, sixteen feet long?
The stem and the side were nowhere near one another, when the side with the stem already attached slid off the saw horse and the fight was on!
I wrestled the assembly all over the yard, epoxied my screw gun, hair, clothing, and saw horses. I ripped off the last pair of latex gloves I will ever wear on a build, finally pinning it against an elm tree, jamming a short 1X10 amidships, and succeeded in getting the screws driven home.
Speak of your learning experiance!
I will have some help on the next one, or rig some way of immobilizing that second end. I might consider polyurethane glue instead of the epoxy,And pneumatic "T" nails insted of the drywall screws.
Pirogues must learn; I will win EVERY time! (Given enough time.)
 
Likes: FrankAS

seedtick

Well-Known Member
Jul 22, 2006
1,142
4
Denham Springs, LA
#36
next time make a couple of jigs out of scraps to bend the sides around as you close up the end

if you don't have clamps, bring the two ends together with rope or ratchet straps

i bend in 3/4" planks this way, so 1/4" ply is doable
 

keith

Well-Known Member
#40
the thing i picked up was to plane down a bd to 1/4". that glass stuff has a place, its just not my thing. but i take a board and plane it down to 1 inch or 7/8, (3/4 store bought) and table saw 1/4 strips then the bead thing. have a nice day, later keith