Glue - Light Ply to Foam

[Nigel Heather]

Building a battery tray for my Max Flight Ruckus which involves gluing some light ply to the foam - I have UHU POR and two part epoxy - would one be more suitable than the other?

[Ron Gray]

Out of the two I would use POR. However my first choice would be Gorilla Glue Brown.

[Tom Gaskin 1]

POR or Gorilla Glue - if no voids to fill I use the GG clear - it's non-foaming, and I used it to build my foam Hanky-Planky.

 

Tom

[Nigel Heather]

10 minutes ago, Ron Gray said:

Out of the two I would use POR. However my first choice would be Gorilla Glue Brown.

I have some Gorilla glue to, bought for DIY rather than modelling, it is brown but not sure it is the specific one you mean.  It is quite runny and expands when it cures - is that the one you mean.

[leccyflyer]

Given the choice of glues that you mentioned, I'd ask how easily you could restrain the lite ply against the expansion of the Gorilla glue and whether you want the job to be done quite quickly. You won't want the lite ply being pushed away from the foam as the Gorilla glue expands, so if it's tricky to ensure that, for the expansion period, then I'd go for the UHU Por used as a contact adhesive.

[Ron Gray]

52 minutes ago, Nigel Heather said:

I have some Gorilla glue to, bought for DIY rather than modelling, it is brown but not sure it is the specific one you mean.  It is quite runny and expands when it cures - is that the one you mean.

Yes, that’s the one. As Leccy says above, it will expand/foam when setting so plonk a weight on the ply to keep it in place.

[Engine Doctor]

The expanding power of Gorilla glue and similar should not be under estimated. When it first came on the market I used it to laminate some balsa . I applied a very thin coat to the laminations and weighted it down with two dry lead acid batteries to keep it flat. While it was setting i carried on working on the job in hand and suddenly there was a large crash behind me as the expanding glue had raised the batteries enough to slide off the bench ! 

Brilliant glue for foam to most materials as it creeps into the foam ceĺls and surfaces. 

Also found that if mixed well with a tiny ammount of water it will expand even more to fill and strengthen any weak box sections with very little weight penalty.

Some makes seem to foam more than others . Falcon Aviations version was excellent and set very quickly followed by Axminster Tools offering. The current Gorilla does seem to take a little longer to set these days possibly for a better shelf life ?

[GrumpyGnome]

Eek!

 

When I use GG on foam, I tend to prick holes in the surface to allow the glue to penetrate further - suppose it also gives the glue somewhere to expand

into.

[Nigel Heather]

Thanks for all the advice.

 

I need to glue light ply plates inside the foam fuselage.  The position is important as they have slots that a ply floor for the battery to slide into.  Using gorilla glue sounds a bit risky as it would be difficult to hold the plates securely in position whilst the glue cures.  So going to go with UHU POR.

 

Cheers,

 

Nigel

[Eric Robson]

Nigel.Don't use the Uhu as a contact adhesive unless you can garrantee getting the position right first time,

For a job like that I usually coat the ply, put it in position, making sure it can't move and leave it overnight.

 

Edited April 25 by Eric Robson

[leccyflyer]

Agree with Eric here, now that you have described the criticality in positioning and how difficult it could be getting the positioning correct, If you can clamp it in place, having got it into position then use the UHU Por conventionally, leaving it to set overnight, The perfect adhesive for this job for me would be my old friend Super Phatic, give the liteply a coating, get it into position, clamp it in place and leave it overnight.

[Nigel Heather]

53 minutes ago, Eric Robson said:

Nigel.Don't use the Uhu as a contact adhesive unless you can garrantee getting the position right first time,

For a job like that I usually coat the ply, put it in position, making sure it can't move and leave it overnight.

 

Thanks for the advice - I never realised that you could use UHU POR as a contact adhesive - have always just used as a traditional glue.

[Ron Gray]

If you don’t want the contact adhesion that POR gives you and you are worried about Gorilla Glue brown expanding then use Gorilla Glue clear (as Tom suggested above). It will give you the strongest joint.

[GrumpyGnome]

Yup, either GG clear; or GG Brown used sparingly, and fix it in position (which I think you'll need to do with Por as well) while the glue sets.

[Nigel Heather]

Out of curiosity, anyone know the science behind contact adhesive.

 

For example I watched a guide on how to use POR to glue a foam former to a foam fuselage side.  The suggestion was to apply POR to the edge of the former, offer it up to the fuselage side and then immediately separate the two parts.  I guess this was to allow POR to be precisely applied to the fuselage.  Then after 10 minutes of drying, offer up the two parts for the final fixing.

 

So what is the science?  Why is letting the glue dry before joining more superior than just leaving the parts together in the first place and letting the glue cure with them in-situ?

 

I always imagined that you used contact adhesive when you wanted an instant bond - for example if you were applying foam sheet over a curved turtle deck and you want the foam to conform to the curve and stay put without having to use tape and pins to hold it down.

 

Cheers,

 

Nigel

[John Lee]

John Brisrow of Delux Materials went into the science of adhesives on a BMFA In the Air Tonight presentation about a year ago. I can’t remember if he covered your exact query but you should find it of interest.

 

 

[Ron Gray]

IMO the main advantage of contact adhesive is that there is no, or very little, need for pinning / clamping. A few years ago I applied POR to 2 surfaces slid them together to make sure that I had an even coating them pulled them apart and promptly forgot about them for about a day! I contacted (no pun intended) someone at UHU to ask them if this would be a problem and the reply was no, but make sure that they are perfectly aligned as you won't get any wriggle room. They were right!

[leccyflyer]

I use UHU Por as a contact adhesive probably 80% of the time that I use it at all, but you're right Ron, no wiggle room at all. It's also excellent on that mode for attaching self-adhesive Velcro to balsa, foam or ply, where the self-adhesive heeds a primed surface to work properly.

[Nigel Heather]

I experimented today.  Stuck two pieces of light ply to a scrap piece of foam, one using the contact method and one using the traditional glue method.

 

As you said the one with the contact method adhered instantly with no wiggle room and was solid from the moment that the two parts made contact.  The one using the  traditional method could be slid around for quite a while, and took a lot longer for the glue to cure, I'd say a couple of hours at least, but once it had cured it was as solid as the contact method.

 

So in my finding, the contact method is a lot quicker and allows you to conform the parts to any curves without any pinning, but the grab is instant and does allow any wriggle room.  The traditional glue method, allows repositioning, takes much longer to cure and would need pinning to conform to any non-flat shape, but once cured seems just as secure.  Guessing the longer cure time is because glue is open to the air.

[Ron Gray]

A lot depends upon how ‘dry’ the POR is before bringing the pieces together. If it’s touch dry then it’s an instant bond with no wiggle room, if it’s slightly tacky then it’s still a bond but you can move the parts a little bit. The real test, for me, was when I used to use Velcro to position batteries in my models. I stuck it on using POR but found that the strongest bond which kept the battery Velcro in place was formed when I let the POR completely dry before bringing together. I stopped using velcro a couple of years ago and use ‘anti-slip’ material instead.

Edited April 27 by Ron Gray

[leccyflyer]

Yep, my method for attaching Velcro to airframes is that I put a squirt of UHU Por on the relevant bit of the aeroplane, smear it out into a thin layer using a lolly ice stick then go and do something else whilst that dries completely, before bringing the Velcro and dry UHU Por back together again and it's stuck tight. I still use Velcro, mostly as seat belts in those models where I'm not using wooden retainers, built from those same lolly ice stick, ply scraps and occasionally nylon wing bolts.

[Nigel Heather]

Good tip for velcro.  I have a roll of self-adhesive velcro, must be a few years old and I notice that over time in storage the backing paper has detached and the adhesive dried up.  So POR will save the expense of replacing.

 

BTW, I will use velcro for the battery but this is building a little platform for the battery because in the Rukus the space is limited and ESC, RX and Battery are all expected to occupy the same area.  Strangely, the manual which covers assembly in minute detail totally skips over how you are supposed to arrange the battery ESC and RX.

Edited April 27 by Nigel Heather