Laminated coaming question

[Bcone1381]

Is the idea of using 1/8 Russian Birch Plywood for a laminated coaming built in accoradance with the assembly manual pg.66 A godd or bad idea? My Lumber supplier also sells a product they call Bending Plywood. Would that be a better product to use?

[Kudzu]

You can use plywood, I have done it. But bending plywood is not easy so you have to use thin stock and I didn't like the end results. It was too flexible.

 

I just finished a plywood coaming with the screws coming in from the bottom and I like the way it looks a lot. It wasn't as hard as I though it would be either.

[Action Tiger]

I would second Jeff. The Kudzu style of plywood coaming intrigues me.

Rumor is Santa is getting me some Firefly plans. Maybe I'll try the plywood coaming...

[Bcone1381]

I envisioned wrapping the coaming mold 4 times with the 1/8" stock to build up a 1/2 inch thickness. Would that be too fleixble? I have one make of oak with those demensions on my wifes Ravenswood and its plenty sturdy.

[woodman]

I was going to try laminating 1/8'' BB.  instead of using the maple one of these days....It would be plenty strong......I was thinking of laminating an extra tall ring that could be cut into a swooping look ...

 

[Kudzu]

I used 3mm or 4mm Okume it flexed a lot. BB might be stronger??  Just have to try it and see.

[HenrikeM]

Another example, seems as if almost everyone here has its own solution: I tried to use only leftover (ply)wood stripes from my stich&glue kayak, so I laminated stripes of 4mm okoume / 1inch wide/ for my coaming and with a rope at the outside using epoxy. Then I filled the gap between the wood and the rope with dark brown epoxy (not shown in the picture). It's strong enough I think.

[Action Tiger]

I have built a lot of curvy things with plywood: boats, theatrical set pieces, skateboard ramps (including one complete bowl), what I think is art...

You can do a lot with it, if you don't know you can't. Yes, can't. One thing you can't do with plywood is bend it on two planes. Unless you don't know that.

I'm tired of gluing things, so I prefer steaming one thick piece, but if I were laminating I would still use real wood, I think.

When you cut plywood into little strips and then edge load it, part of your material gives no strength, due to the alternating orientation of the plies. Real wood will have uniform stiffness, in theory. Although, in a lam like this, the glue is most of the strength anyway, I suppose. What do I know?

I say do it and let us know.

Man, am I helpful, or what?

[Action Tiger]

Henrike, you posted while I was typing.

Das ist sehr schön!

[HenrikeM]

I thought your post was a direct reply, and how fast someone could type (not me, using an incredible small smartphone)

Yes the two planes thing... there is so much epoxy between the stripes and especially the rope that it doesn't flex much.

[Bcone1381]

Gentlemen,

This information helps me a great deal, and I appreciate the wisdom you all bring.

For Woodman:

This is a profile shot of the coaming on my wife's Ravenswood.

It's made of oak and was flat. I then set the coaming onto the kayak frame and wrapped a ratchet strap around it and cranked up the tension to get the flex I was looking for. I suppose it sat there a week or so. It was removed to cover the frame, and I think the tension of the fabric may help it keep that shape.

[Hirilonde]

When you cut plywood into little strips and then edge load it, part of your material gives no strength, due to the alternating orientation of the plies. Real wood will have uniform stiffness...............

Yup

 

The other thing is that some people are confusing strength with rigidity.  If a combing bends too much, most likely during entry and exit, even though it is strong enough, damage to the skin, stitching and/or paint can occur.

[woodman]

Action Tiger, did you use to skate? I did, built ramps also,, When you said bowl as in a skateboard bowl? 

[Action Tiger]

Henrike: I type on a little phone, too. And I'm 1.9 meters tall with size 50 shoes and hands to match. I type slowly on this thing.

Woodman: I still skate. With my sons, now. And, yes sir, skateboard bowl. Two, actually. One had a spine transfer to another half pipe. The first one we planked by ripping ply and Masonite into strips. The second we used geometry and cut fitted wedge pieces.

Y'know a boat ain't nothing but an inside out ramp.

Out here we have a resurgence of skateparks, though, so ramp building for cash is dead, and there's a good skatepark right down the road from our new house, so we don't have a ramp. For now...

Sorry for the derailment.

[Action Tiger]

I lost my beard in a trimming accident. But, there I am, two weeks ago.

Now, back to coamings. Really.

[woodman]

I was skating back around 1978 at 25 yrs. old back when the boards got wider..I built a portable 1/4 ramp to set up in a warehouse to skate up onto the block wall, or set it up against my old 69 Ford van an roll out on top, then I built a second half and created a half pipe....It was portable..just unbolted and stuck in the van....I'm 61 now so forget it, some of my 50 yr. old budies still skate......Pic. of me with a pony tail back in the day......

.I still have 2 boards..

Looks like we hijacked this post!

[Action Tiger]

Oops, sorry for the jack.

One more bid for a thicker steamed coaming. It's easier to cut one thicker piece than several smaller pieces. The only glue is in the scarf, which is easy to cut/plane by hand. I think the steaming changes the wood, too. I think it sort of allows the cell walls to ease into the new shape as if they grew that way.

Plus, when people see no glue lines, they will trip out. You think a fabric boat confuses people, try explaining steam bent wood.

All you need is a kettle, but I found a nice industrial steam iron that is plenty wet for these little sticks...

Also, it is so amazing to bend a piece of wood into a circle with your (gloved) hands, and just have it stay that way when it cools.

I am easily amused.