Question for Marine People

[Virgs Sew n Sew]

I'm working on a boat for a customer.  Almost done and it looks fabulous (pictures once new carpet is installed and last two seat backs are in place.  Question pertains to these pieces.  They need to be slightly bowed.  Ron (customer) has done all the carpentry on this project.  He is very much a taskmaster and has put several coats of polyeurothane (sp?) on the wood to protect it from the elements.  On these last 2 pieces, Ron soaked them in water until they were soft enough to form.  He dried them and they had kept their shape.  He told me once he applied the polyeurthane he could literally watch then straighten out.

Do y'all have any suggestions as to how Ron can proceed to obtain his desired goal of slightly bowed seat backs?  Any input would be greatly appreciated.  My intent is to print this thread and give it to Ron so that he can carry on.  Of course, if he asks me any further questions, I'll report back to the board to get more information for him.

Thanks in advance!

Virginia

[SteveA]

He may be better off using wiggle wood or a glue bent lamination.
SA

[Grebo]

PVC foam board, heat to shape & no need to paint. Ask June C, she's the queen of boards. :-)

Suzi

[Darren Henry]

I'm with Suzi on the PVC being the better choice. I used to get mine from my friends who had a sign shop when they were ordering theirs for sign blanks. It was called Intacell. Small pieces I heated with the heat gun to mold and the larger ones (where I couldn't keep a large enough area hot long enough) I put in the BBQ.[No oven in my shop, that big].

If he's determined to use plywood; here is what I have done with fair success (mostly on 3-D signage, but works on seats and backs etc..). Picture a roll top desk as you read this :

Make table or skill saw cuts at right angles to bend 1/2 to 3/4 of the way through the wood on the inside of the curve. The distance between them depends on the radius of the bend. The tighter the bend the more relieve cuts required. I generally practice on a piece of cut off to find the minimum depth/number for the bend. Fill the saw cuts with quality wood glue and mold/clamp in place. Finally glue and staple a layer of what Y'all call herculite etc.. making sure to staple to all the "full thickness strips". If the project allows I like to screw the molded piece to  3/4" plywood cut to the same radius. Picture a fence where the 1X4's are attached to the 2X4's on their flat top and bottom.

[SteveA]

Darren
PVC foam board ?   I think the wood has to show that's why he's putting poly on it. 

SA

[Virgs Sew n Sew]

The wood doesn't show (or at least hasn't on any of the pieces I've done thus far).  The only wood that shows gets bolted to the boat.  He just doesn't want wood rot which he found in all of the existing pieces when he stripped the boat to start working on it.

The PVC sounds good to him so far.  How much would he expect to pay for a 26x52 inch piece (just an approximation at this point)?

Thanks again!

Virginia

[brmax]

Not long ago 1/16 and thicker marine mahogany plywood was used in race boats and boating of all kinds, in many of these areas the wood was built in a fiberglass lay up for all kinds of structures.
There is total marine types but a local luan which has had both sides a mahogany but a cheaper center will work in this above water layup easy, imo. The gel and woven glass would be available at a marine or auto supply.
I don't know anything really lower cost unless he uses angle cutting instead of curves and some hardwood bracing on a foam side of sorts, to hold what he tried before, but if looks are in the mix?
To finalize my opinion with hp being more extensive than upholstery, I might get more horsepower information and ideas on support

[Darren Henry]

How much would he expect to pay for a 26x52 inch piece (just an approximation at this point)?

I have no idea what prices are like in Nebraska and haven't used any since I moved here to Brandon 5 years ago. I recall it being not much more than pressure treated plywood once you factor in that it stronger than plywood . [You use 1/8" less thickness. i.e. 1/2" intacell has the strength and rigidity of 5/8 ply etc...]

I would call a couple of local sign companies, especially where you are only needing a part sheet. I keep coming back to the sign industry because I'm guessing Grand Island is alot like Kenora---a couple of hours away from "the big smoke" and a long way from the ocean where upholstery/boat supply companies carry Starboard etc...I know here on the prairies, none of my usual suppliers offer it.

[JuneC]

Is the curved bit supported behind?  Or is it free standing - like a seat back with no fiberglass or frame behind.  If it's supported, PVC board is great.  I've bent quite a few feet over the years, with a not-too-crazy heat gun.  Trick is to get it hot enough to bend without melting it.  It's really pretty easy to work with.  But, if it's not supported, it may not have the structural strength.  I've only ever used 1/2".  Thicker than that I think it would be really hard to get it hot enough to bend without an oven (the outside skin would melt before the interior got warm enough to bend). 

To do it with wood, I think you'd have to either do the bent laminate thing (think - make your own plywood), or score the inner plys with a table saw so it'll bend inwards (would require a shaped frame to hold the wood) or buy the plywood already bent.  Somewhere in my list of favorites is a supplier who sells already curved wood and ply. 

Personally, I'd stay far far away from wood.  I don't care how much finish you put on it, water WILL get in and rot the stuff in a year or two unless it's teak.  I LOVE my plastics - acrylic, coosa, PVC, starboard, whatever.

A piece of PVC board that size should cost less than $50.  A full sheet is around $80 (4 x 8) but buying smaller pieces is more expensive per square foot.  Check your local Home Depot or Lowes for smaller pieces.  Some stores carry it - as well as King Starlight (the light version of Starboard). 

June

[Mike]

I hate the weight of starboard, I repaired a folding cooler seat this week when lifting I thought the foa was full of water but it was dry had to weight 60 lbs

[Darren Henry]

I haven't seen Starboard up here, but that Intacell I mentioned is lighter than pressure treated plywood.