ACK! skin bendy tips?

[kinto]

i'm stuck...

i've worked with wood since.. well, since the pinewood derby i guess... but i'm having SO much trouble...

the design/ structure is going fine, but i can't seem to skin this thing...

as a teen my friends & i built a few skateboard ramps and we always drenched the ply with a hose to get the bend, but those were like 12 foot tall so it was a more subtle curve...

what i bought from blue box (in one shot, trying to plan ahead) is 5mm ply that *seemed* bendy at the store, but i've now cracked 2 pieces...

any recommendations? i'm hoping to get it camp-able by october and at a total loss for ideas right now...

thanks in advance for any advice

kent

[Shug]

Not sure how this'd work on ply, but when we were fitting gunnels to the boat, they would crack when curved round the hull, so they were steamed, and curved as far as we dared and clamped. Then, next day, hot water, bend a bit more and clamp. Repeat until finished.

[bobhenry]

Where the curve is a tight radius you may have to make relief cuts part way thru the inside layer. You are trying to compress the inside layers and stretch the outer layer. It doesn't seem to like that. Perhaps 2 layers of 1/8 material instead of thicker material. I have soaked the plywood panels in hot water in a large kiddy pool covered with black visqueen plastic sheeting on a bright sunny day for several hours and had good results. Hot towels or flannel sheets soaked with hot water and slowly trained into form worked for me on a small dog house teardrop. Over a period of 6-8 hours I took heavy ratchet straps and tightened and soaked and tightened and soaked and yes it got old by the time I was done but it worked well also.

I am currently working with FRP ( the pebble faced bathroom plastic panels) and it is truely wonderful to use as an exterior skin.

[doug hodder]

As Bob suggests...do 2 layers maybe. I've done some fairly tight bends, like 12" R. using 2 layers of baltic birch 1/8" thick. In the past, I've used the big box store luan 1/4" and it was absolute crap! If possible, check for country of origin. Avoid Chinese stuff, poor quality filler layers in ply is what causes it to fail and the Chinese have turned that into an art.

You would probably end up fighting trying to get baltic birch in 1/4" do do a bend as it's engineered to lay flat.

Regular ply will bend if soaked down, you just need to support it when you do the bend on it, like pull it into place using some ropes and backer boards so that it does the bend equally. It may be tough to do it strictly by hand. Others experiences may vary. Doug

[kinto]

thanks all

@shug... yeah, my girlfriend mentioned maybe trying steam using a clothes iron or such but i'm not sure how to work that and don't have one... note the wrinkles!

@bob... trouble is the 5mm i bought was the thinnest material they have aside from masonite, paneling, etc... i *have* been eyeballing the FRP after reading about it on here, but am not sure i wanna open that can of worms... i'm pretty good at finishing/ disguising mistakes (and screws!) using wood, but clueless when it comes to plastic. oh, also i'm building this entire thing using basically a jigsaw, drill, tape measure & pencil... no circular or table saw so i don't have the means to kerf...

@doug... i'm trying to do the inside bend first, so it's a bit more daunting & difficult to clamp. i'll probably buy some ratcheting cargo straps for the outside bend so hopefully that will go better. i'm actually now thinking i might cut the inside ply into thin horizontal strips then go crazy with wood filler on the interior (it's gonna be painted, not stained) & fill the top (~inner wall) gaps with silicone before the insulation.

thanks again for the responses... overcoming stumbling blocks is half the fun of building!

kent

[CliffinGA]

Kinto look for smaller lumber yards that carry specialty woods for cabinets etc. as they usually carry decent 1/8" luan for thats reasonable for cabinet makers and such.

Cliff

[bobhenry]

thanks all

i'm pretty good at finishing/ disguising mistakes (and screws!) using wood, but clueless when it comes to plastic. kent

No filling no disguising just place them in an orderly row and embelish them with washers, plastic rosettes or even some hex nuts like I did here.





here is my lexan roof TD with the rosettes to hold down the sheeting




and here is a close up !

With plastic paint ( Krylon fusion) you could color to match or contrast !

[S. Heisley]

I have just a couple more tools that you do. You can do a pretty good job of kerfing with a ruler and a box cutter.

I bought both good 1/8" luan from a cabinet maker and some big box store 1/8" luan (5mm?). The big box store stuff curled easier than the better quality.

My first curve (front wall) of good quality luan was a "bleepety bleep" bad one. It wouldn't stand for much advance curling and kept breaking loose from its restraints.

The second curve (a smaller but more curled one) of cheaper big box stuff went better. For that one, I just kept tightening the curl a bit more every 4 to 6 hours until I got it to the shape I wanted. It obeyed and didn't break its restraints. It took a couple days of patience and I was done.

Good luck on yours!

[len19070]

I always cover my trailers with Aluminum and sometimes the roof with EPDM rubber roof.

So what I use for sheathing really doesn't matter.

That said Anything that gets wet will Rot, so the exterior covering is what's really Important.

I use 1/8" Masonite. Ya can almost tie it in a not....$7-8 bucks a sheet too.

A lot of people shy away from 1/8" material but as long as it is curved it takes on new dynamics. i.e. a curved piece is far more rigid than a flat piece. Flat will flex. Curved won't.

Look at the compound bend on the front of this Scotty. 4 different directions in 4' the long way!





This roof is only 1X3's on the flat, "CURVED" with 1/8" Masonite on the outside and 1/8" paneling on the inside (factory did that, not me). 76" wide and the roof will support my 220lbs.


Happy Trails

Len

[dh]

A nice steamy bathroom might help the ply take a bend as well...

[Sam I am]

I used two layers of 1/8" Baltic birch on my tear. It literally falls around the curves with no effort required to bend it! Great stuff! One layer would have been stiff enough, but I wanted some protection from flying stones when towing, and things like falling acorns, etc. when camped. I recommend it highly.

[kinto]

this is the stuff i've been trying to bend...


since i already have quite a few sheets of it i'm really wanting to make it work rather than returning it and getting masonite or whatever instead.

@sharon... i sent you a pm regarding kerfing with a utility knife so thanks in advance for any insight as that's my next plan of attack.

also big thanks to everybody for your tips & advice... i really appreciate all the input because i wanna get this thing done & go camping!

kent