Thread: Laminating plywood, epoxy or something else?

Epoxy will work fine. Don't know how you are going to clamp it together, but one of the advantages of epoxy is its gap filling properties.

I use Titebond PU glue for veneering and laminating, and it is clamped in a vacuum press. Because I am confident about the clamping, PU works very well. It has a 20-30 minute open time and a 60 minute clamp time, so the job is out of the press quickly.

However, if you are not very sure all surfaces will be clamped firmly together, don't use PU. Use epoxy. If there are small gaps PU will fill them with foam, but this foam has no strength.

Epoxy is best for wood, it'll go with plywood as well. It will also bond plywood together. When laminating the plywood, whatever resin you use, I always roll some resin on first, let it cure some, then laminate. This makes a much better bond to the plywood.

Epoxy is the best option, I doubt the epoxy would craze as it is more tough than brittle.

Regards
Keith

Hmmm, sounds like I’m on the right track with epoxy. Thank you all for the reassurance.

Matt

Have a look at the BoteCote Epoxy "Clear System" with the AquaCote polyurethane top coats. Its a similar concept and competitor to System Three, WEST, Everdure etc. but Australian based. They have a sample pack "Aquacote Clear Trial Kit" which includes both products and is ideal for small projects such as yours.

Aquacote Top Coat : Boatcraft Pacific, the home of wooden boat building. (the website may be clunky but their products are good.)

The BoteCote epoxy system is designed for marine applications and can be used as a structural adhesive (with glue filler), and in laminating, sheathing, coating, fairing, casting (limited) applications and as an impregnation / saturation resin to protect wood with the use of their proprietary "thinner" TPA. Crystal clear - i.e. water clear finish.

I have been using it for a while to finish small (600 mm dia) burl slices for coffee table tops. My latest is a red gum burl filled with BoteCote epoxy and ground Gabon Ebony "filler" - saved from a pepper mill project. It certainly does what the manufacturers claim it will do, has very low volatiles, and plenty of working time for coating / fairing applications.

As a structural adhesive my only reservation is that its cure time is long, relative to other structural epoxy adhesives, so if it is used in applications without the use of additional mechanical fasteners (screws etc) it would be wise to allow very generous clamp times to cure.

We always used urea formaldehyde for big laminations but it seems hard to get now. Epoxy is good but don’t make it too thick, I use a small 4” disposable roller for spreading it.

Plus one for Botecote: it specifically mentions a degree of flexibility in their sales blurb, to accomodate wooden boat flexing in sailing- Not the cheapest, but a good, Australian product that people trust their lives to...

+2 for Bote Cote. They have a few diff products, Epox_E-Glue being another one of them. It’s about the consistency of Vaseline and easy to mix and apply. It’s thixotropic so it doesn’t drip every where.
I mostly use their normal epoxy with the different thickeners and TPRDA to thin it. I have a warm-box for resin (gets cold here) which makes it a bit more runny. Have used it for years BoatBuilding
Sorry can’t advise on flex but can’t you make your lam a bit stiffer?

Some interesting suggestions here for me to follow up, thank you all.

The boatcote name rings bells, I think I have seen their products at the local chandlery.

I should be able to reduce the flex by adding laminations as suggested, but I’d also like it to appear reasonably lightweight, hence I’m resigned to a bit of flex from time to time. I won’t be heart-broken if it takes a couple of tries to get right, but I was keen to avoid any known problems such as would have been indicated if everyone here said “don’t do it with epoxy, it will craze like anything!”.

So far nobody is saying that, quite the opposite, so away I go. (Once the weather warms a bit, I don’t have space to create a warm environment for this job so I’ll have to wait on the weather.)

Thank you all, again. Matt

Something to think about def weather, epoxy doesn’t like temps below about 10C. Better o’night at least 15. Can you take your glue up inside to the heat?
Also I did an experimental layup with carbon fibre tape ( from Boatcraft Pacific) - 3 layers of 200gr came out about 1 to 1.5 mm thick and def stiffer than just normal glass. Lots of people use it for stiffening things.

Originally Posted by AndrewPatrol

Lots of people use it for stiffening things.

Where can I get some?

Carbon Fibre Reinforcement for Composites

here ya go.

You may need to get their f’glass cutting scissors too. I have some - so I don’t know if it can be cut with normal scissors.

Take note of what they say about peel-ply.

Good Morning Matt

Boat builders call this technique "cold molding" and a very high proportion of custom racing yachts built in the 1970s thorugh 1990s were so built; it is tough. If you want a very detailed yet very practical explanation, the standard text is still probably:

• Gougeon Brothers, "The Gougeon Brothers on Boat Construction; wood and WEST system materials," (Pendall Printing, Michigan, 1979, 320 pages). Probably available in your local library or possibly online.

Your biggest difficulty will be in squeezing the veneers together without leaving gaps and without leaving flat spots in way of any clamps. I have used two methods successfully:

1. Make a pair of MDF forms and clamp the veneers between them, or
2. Vacuum veneer either around the form or freehand.

For vacuuming, I use a simple vacuum food press - under $100 from Myer or $300 from a hospitality supplier - the quality of the latter makes it a far better buy. The process is quite simple:

• Cut a length of vacuum bag about 200mm longer than your veneer and seal one end,
• Glue and assemble the laminates and put them in the bag,
• Ensure the laminates are all accurately aligned, put bag end into machine and vacuum,
• Bend to required radius, either freehand or on form, and secure overnight,
• Next morning, admire your work!

PS: Unless you have a very high strength requirement and carbon fibre or any form of glass cloth is an unnecessary complication, and visual distraction.

Originally Posted by GraemeCook

Good Morning Matt

Your biggest difficulty will be in squeezing the veneers together without leaving gaps and without leaving flat spots in way of any clamps. I have used two methods successfully:

1. Make a pair of MDF forms and clamp the veneers between them, or
2. Vacuum veneer either around the form or freehand.

PS: Unless you have a very high strength requirement and carbon fibre or any form of glass cloth is an unnecessary complication, and visual distraction.

Another way you can squeeze the veneers together if, like Matt's, they aren't too wide, is to use a couple of ratchet tie-down straps - the wide ones. The can be pulled up really tight and push the veneers together. I've also done small jobs using clamps, but you do need a lot of clamps to avoid flat spots.

Definitely agree about not needing any cloth.