Converting Plywood Design to Composite Panels

[James Mills]

If an ambitious builder wanted to take an existing plywood design and build it in composite panels, what R & D tests on the composite panels would he perform to closely match the performance (sans the weight) of the plywood in the design.??????

I've gotten pretty good at making panels on the mold table. I really like the polypro' honeycomb by Plascore and Nidacore. My thinking is make panels without core, shape them into the hull you want. Vacuum bag the core material, vacuum bag the skins on the other side of core into place. I've had it with fairing and sanding. I've been obsessing about ways to do this.

Then again, buy the Tig unit, Pulse on Pulse Mig, Plasma Cutter, ... make it out of tried and true 5000 series aluminum and be done with it.

What does the collective wisdom of the group think??

Thanks,
James

[KnottyBuoyz]

You should really talk to Ausiwik (Steve Marshall) and have a look at his web site. http://marshalldesign.blogspot.com He posts here so hopefully he'll chime in on your thread.

We're discussing the same options with Jacques Mertens for a 28' trawler project which was designed for S&G Ply. Trying to decide if it's worth the extra money to go with foam instead of ply.

[fastwave]

Also the new antrim40 yacht has been built out of flat composite panels. Just launched. Worth checking out

[Ausiwik]

Gentlemen< How could I resist ?? especially when baited by Le Provocateur & Raconteur.
What your proposing can work really well however but I would try to include the core and laminate on the table first
You would only glass the out side (table side of your panels) I have tested and used a product very similar to Nida core and whilst heaver than Diviny cell core (or similar ) it had excellent adhesion to the glass laminates and with only a single side laminate in place will bend to form more easily than a pvc core. (provided that laminate is not real thick and curve is not to tight !!

On the down side all of my panels were done using infusion.
Unfortunately, because of the structure of the honeycomb core (Nida core ) I dont think this (infusion) is possible.

That situation may have changed with the increased use of infusion I would think they wont be left behind.
(interestingly I was around in Seattle Washington when Nida first came on the scene 1990 I think Iwas attending one of the early semposiums on resin infusion.
The Nida core rep showed me (with brochure) how they used Nida core for road fill such as bridge abutments and up to many feet thick!!!.

Any how there are ways to use it in big panels and still vacuum bag it down to you laminate for a good bond without going for a secondary bond using some sort of bog.
Cost is certainly a very big advantage as I paid less than 1/3 the amount I paid for similar Diviny cell core here in Australia (not Austria as George would say)
Laminate size, is I think one for conjecture.
A design for ply may not have been built for any scanteling rule to begin with so using it as a basis may not be the best procedure
Possibley (and this is the cheapest )you could find a similar
composite boat and asscess what its scantalings are or employ a navel architect to do the job for you, but just copying what works might well be the way
As Le Provocateur & Raconteur suggested check my site You'll see panels pulled around into shape there also look at Kelsell web site hes a leader in flat panel work. Hope thats a help
Steve Marshall

[KnottyBuoyz]

Originally Posted by Ausiwik

Gentlemen< How could I resist ?? especially when baited by Le Provocateur & Raconteur.

I enjoy volunteering other people to do work for me! I didn't think you'd mind Steve!

Have you splashed your trailerable trawler yet?

Rick

[James Mills]

Steve,
Thanks for your reply. I've looked at your web site before. It is inspiring.

I made a hard top for my motorboat using Plascore laminating one side with the core and bending it to shape, laminating the other side. The problem I ran into is a hard edge where the core seams are. Nida core only comes in 4' x 8' M/L sheets I think. Plascore comes up to 50' x 5' sheets I think -- but I haven't priced the big sheets --- expensive I would think. Also, I'm deadly afraid of print thru - something I've experienced with the Plascore and thin laminates. I've seen beautiful expensive custom boats built with foam plank and expoxy and after a few years, you could see the foam planks thru the outer skin. A heart ache I would prefer to avoid. Too avoid print thru is one of my thoughts for laminating the outer skin seperate from the core bond. Thinking using more glass and resin rather than bog to bond the core to the skin -- additional strength than just bog.

I'm surprised to hear the foam weighs less than the Nida core. I would think for an equal weight part the Nida Core would out perform the foam.

I'm off to the IBEX show in Miami in Oct. Fascinating show. Hope to get a little more insight into what I'm trying to do.

Thanks again.

James

[Ausiwik]

Good morning
Rick I have not as yet complete the the Trailer Trawler I have none the interior but have done an injury which has almost bought me to a halt (over last 3months ) an operation is pending and will be back into it on recovery
(try building a boat with one arm it sucks)
I have sidetracked and developed a means for triming core panels which I hope to start marketing or dispose of gainfully (its a little ripper!!)
HI James I just posted a long winded blurb in another section on what just spoke of ( creating hard top). With the print through thing the things that have become apparent are polyester and vinyl ester are more likely to show it than epoxy (lower shrinkage )
I did a few panels with I plascore which were quite successfully and showed no print through at all.
I first put down medium thick gel coat (on my release coted table) and allowed full day cure I then followed this with 1 layer of 3/4 oz chopped strand mat and allowed full days cure on this. I followed with 600 gm DB Stitched cloth I lightly roll coated the the 8x4 core with resin and placed the core into the still wet laminate (I have infusion cyt that allows long gel times ) I then lowered a sheet of 1/2" mdf onto this and bagged that down it worked fine and gave a excellent bond .
As an extra to this process I layed the identical gel coat / chopped strand bit on to a release coated sheet of polyester ply (3/16 with a very shiny polyester coat used to line some bathrooms )
And followed with the same laminate as on the table While every thing was wet. That is, all the table laminate and core i rolled a light coat on the upper face of core very carefully and with help flipped over the extra sheet of shiny ply and its laminates and lowered onto the core, lowered the mdf onto the whole stack and vac bagged with not to much pressure.
The whole sandwich came out beaut with double gel coat faces
I used this same double face set up with infusion process which worked well except for some print through on grooved side of my divinicell core.
hope I got this in order and that it makes sense !!
Steve Marshall

[longliner45]

hey I have a question ,,and Im not being facitious,,but why modify the prints to use a composite? is not the tensil strength of plywood stronger and more easaly repaired?,,,I have seen balsa cored hulls that have minor damage ,,but costly to repair ,, or is it too difficult to get good marine ply these days ,,,longliner

[James Mills]

longliner45,
Looking for a broader market for selling the boat than a wooden boat would offer. Not my prejudice so much as the buying public. Also, I think a higher performance boat can be had with light weight cored composites. Also again, with long composite panels, no need for scarfing and the panel should bend into a very fair shape. After my last project, I've decided I hate fairing and sanding.
James

[KnottyBuoyz]

Originally Posted by Ausiwik

Good morning
Rick I have not as yet complete the the Trailer Trawler I have none the interior but have done an injury which has almost bought me to a halt (over last 3months ) an operation is pending and will be back into it on recovery
(try building a boat with one arm it sucks)

Sorry to hear that Steve. Take care. Keep us posted if it's not too hard to type one handed!

[Ausiwik]

Thanks Rick
Steve Marshall