Planning to use lauan

I'm plannin to use lauan for my first self designed small skiff. If it doesn't go well I'll call it an experiment. Does anyone know what I can expect, or any tips for planing an 8 to 1 bevel for scarfing, with the nominally 1/4 stuff. Is that big middle ply going to be workable with a hand plane?

 

Avoiding Scarfing, with good strength

Take a look at: http://www.boatdesign.net/wiki/MaterialsForBoatbuilding#BONDING_FIBERGLASS_TO_PLYWOOD
and Dave Parnell's methods for joining plywood panels.

Make sure you put up a photo when it's in the water!

 

You might consider going with a better plywood grade, as 3 ply lauan is very weak, especially in the long dimension.
Considering the predominant cross-grain inner ply, you might want to go with backer blocks rather than scarfs.

Alan

 

Yep, Alan beat me to it. 1/4" lauan can only be a short term experiment at best, particularly if the outer layers are little more then paper thin. If you embalm it in goo and cloth, you can make it work, but you'll need to basically make a 'glass boat with a lauan core (the 'glass bears the loads, with the plywood acting as a form).

 

Guessing PAR responded to my earlier, later edited reply. The gist of it was that the luan described has paper thin outer veneers and one giant inner ply.
As such, unlike most plywood, its strength is greatest along the 4 ft dimension. You can, as PAR said, embalm the ply in lots of epoxy and glass, but to do so would be false economy. So much work and so much epoxy all to protect an inferior plywood core makes no sense. It would have been better to start with a quality exterior or marine plywood having more balanced strength characteristics and let the plywood supply the strength.

A.

 

Agreed Alan, though I suggested the option, it's not a particularly economical one, in weight, effort or money.

 

luan plywoood

I've built three boats using Luan ply. They were all sort of experimental so long life wasn't a big concern. The plywood was saturated with Minwax wood hardener before painting and we got about 8 years life out of the boats. It seemed like a good trade off for what we were doing. the first boat became the plug for the mold that I am working with now, and another boat is awaiting some modifications to the bottom. I wouldn't want to do these things with a boat built of 1st quality materials. I'd love to know what that Minwax wood hardner is and be able to get it in bulk.

 

It's impossible (from here) to know what a boat will be used for. No doubt your experimentation wasn't to do with longevity or strength. Paint alone is, I agree, appropriate. Cheap, like the plywood.
Can I ask, what kind of boats you were working with?

A.

 

should have said more about the motive

I want to find the right design for a very specific use. I never designed before, have built a redmond bluegill and cmd dingy. Used exterior ply from lowes ( I know I know, a no no).
What I want is a boat to fish from in local creek, secondarily, river. Flat water. My needs are, in order I think;

1.Rides in bed of F150.

2.I can move it myself up and down 50 ft bluffs.

3.Stable enough to stand up and cast fly rod in.

4.Cheap at first, I may build it two or three times to tweak the design, then I'll get the expensive wood. So, any thoughts? I guess I should be in the design section now. Oar power by the way, but just maybe can add sail someday. It's okay to laugh. Square bows leave me cold at present, also.

 

Sounds like you are talking about a 10 ft skiff with about a four foot beam, and weight of no more than 75 lbs.
This means lightweight construction, either 1/4" ply or strip built (and ply is the natural choice for a skiff with conically developed sections).
Here's a tip you oughta follow up on, and you'll see why. Tom Hill designs some real great looking (and performing) wide-lapstrake dinghys. These are really light. They use plywood strakes and no frames, I believe. The laps essentially create stringers sectionally, one for every lap. The result is a structure so stiff it needs no additional support structure. Designing your boat around that method will allow the use of cheap ply and will yield an ultra-light (40 lb!) hull. Your low-grade plywood boat will not be very strong, but will allow you to exerience the method and advantages of low weight. when ready, your eventual boat will be both strong and light.
You'll have to google Tom Hill + glued lapstrake or something to see the boats.

Alan

 

http://www.angelfire.com/ego/lewisboatworks/html/Fishbuild18_a.htm

10 ft long with 54" beam, 1/4" ply, 15 hp cap with 24 mph from a 10 hp motor.

http://www.angelfire.com/ego/lewisboatworks/html/fishbuildnav_a.htm

Here is the complete build... This sounds similar to what you are after. To reduce weight...do not build the boxes, but use plank seats.

Steve
PS: And YES...it is made of Luan. It is still in one piece although showing some wear and tear ( It has come off and landed on the hwy at 60+ Twice...). It fits inside a full sized pickup on top of the wheel wells and is maneuverable by one reasonably strong male.

 

It has been a year and a half since the last post to this thread so I probably should not respond here but it FITS. FYI - Luan. Lowes is selling a substitute for Luan under layment that is made in China. The label on each sheet says
"Samling" 5.2mm Hardwood Plywood , Exterior (12549). It is priced at $ 10.78 per 4' x 8' sheet. It is three equal thickness laminations with two paper thin skins. Smoothe, tight grain and feels stiff. I boiled two 3" x 3" samples for one hour. No delamination but a small area thickened approx .020. The area dimension was about 1/2" x 3/4".Lowes personnel said they have been selling it for a year. Can anyone shed more light on this material?

Bill

 

Built it.

Without having seem this tread, I built this exact boat. The boat weight in around 75lbs. Used it fix seawalls and was very strong. I would carry 12 bags of concrete it it. Could be lift by two men and carried in my truck. Used fiberglass over luan then epoxyed the whole thing. Made mistake in not epoxying inside well, moisture got into luan eventually weaken it and made it heavier. I reinforced it with 2x4 on outside and used it for another 6 months. It got to a point that it was so heavy and weak. Luan was all gone only fiberglass/epoxy shell remained. I sunk it and gave a fine ceremony, at the end I made money with this boat and used it for 2 years. It cost $400 to make, a surprise.. Fiberglass and epoxy is not cheap anymore.

Next time, I will build fiberglass over foam.

 

Samling?

To popperstop: This sounds exactly like what I used. Was about 3/16 mystery wood (looked a little like birch) and was called 1/4 luaan. Seemed a little flimsy but after building with Tom Hill Lapstrake method plenty stiff enough. So far has held up fine, I do not baby the boat either. What I like about the wood is the smooth surface has not showed any surface checking. One plank edge has delaminated over approx 5". I'll repair that in half an hour or so. I used premium polyester construction adhesive from lowes, which has held up better than epoxy in my experience. So I don't know much about this wood but I would use it again. The 3/16 as opposed to 1/4 is lighter and seems strong enough for this 10"6" rowboat.

 

lauan

yes it is, sharpen your blockplane & move across the ply scarf at all angles around 45 degrees, the glue in the ply wiil hammer the plane edge so sharpen every hour, you can also glue sand paper to 18 mm ply x 100 mm x 300 mm pads, various grades, say 120 to 40, think of sand paper as a shaper,get a strait edge & check the scarf diagonally, dry run all cramps, plastic covered pads & cramping cleats, blow all clean with an air gun.