Model Boat Mayhem
Technical, Techniques, Hints, and Tips => Glue etc. => Topic started by: BeeJay UK on August 04, 2020, 03:54:53 pm
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Advice time folks. What is the best adhesive to glue wood deck supports to the inside of a GRP hull. I am going to glue a 6 x 12mm bearer all round the inside with 10 x 12 across the transom, then glue cross bearers to those with PVA.
I was thinking of using epoxy, but I am open to other ideas. I have epoxy, W/P PVA, CA, impact & resin in stock so one of those options would be handy. But if something way better is recommended then I'll splash out.
Thanks.
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Probably the strongest method would be to use Glassfibre resin to bond the two together. The resin soaks into the timber and bonds to the GRP. If you reinforce the joint with glass mat it should be nearly indestructible.
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Ask Stan he knows a lot about the new glues told me to use STIKALL and I used it to stick Ali square tube to ply wood on my SD14 and it was perfect its one of a new breed of glues will use it on all most all my gluing jobs from now on.
Regards Howard.
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Probably the strongest method would be to use Glassfibre resin to bond the two together. The resin soaks into the timber and bonds to the GRP.
I don't think epoxy or polyester resin bonds to already cured resin. It is a mechanical bond. That said, for model boating purposes, an epoxy adhesive will normally give a very good joint if you ensure that the GRP surface is roughened.
When using epoxy adhesives the general rule that the longer the setting time the stronger the bond so standard Araldite with a 14 hour setting time will give a stronger bond than a 5 minute epoxy. It is horses for courses. If the joint is structural such as wooden deck supports to a GRP hull then use a longer setting time. If you are just sticking on fittings than a quicker setting version is fine.
Colin
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The inside of the GRP hull is very rough anyway, I am not really concerned about the bond to the hull, more concerned about the bond to the wood battens.
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Epoxy will be fine to the wood.
Colin
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I don't think epoxy or polyester resin bonds to already cured resin. It is a mechanical bond. That said, for model boating purposes, an epoxy adhesive will normally give a very good joint if you ensure that the GRP surface is roughened.
When using epoxy adhesives the general rule that the longer the setting time the stronger the bond so standard Araldite with a 14 hour setting time will give a stronger bond than a 5 minute epoxy. It is horses for courses. If the joint is structural such as wooden deck supports to a GRP hull then use a longer setting time. If you are just sticking on fittings than a quicker setting version is fine.
Colin
There is some kind of "fag packet" rule I read often enough on RC Groups forum about not trying to bond using polyester to an epoxy substrate, but epoxy bond on a polyester substrate is fine. Polyester to Polyester and Epoxy to Epoxy is fine.
Personally I've never had any problems epoxying bits to a polyester GRP hull but I've not much experience the other way. Actually these days I tend to use cyanoacrylate and put a fillet of epoxy on after -the GRP breaks before the wood does with the Cyano anyway but you must clean and thoroughly rough-up the GRP first.
"Sticks all", "sticks like s**t" (real name), "no nails" etc, is not new at all -just I think not so many folk use it often because of the way it's sold and the way to apply it.
The inside of the GRP hull is very rough anyway, I am not really concerned about the bond to the hull, more concerned about the bond to the wood battens.
...It will almost certainly still not be too great for bonding to. Rough it up with coarse paper and get rid of the dust first! It only takes a few minutes. And ideally rough-up the surface of the wood also so it's not smooth and has some "hairs" standing".
Rich
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I've always used epoxy to glue wood to polyester grp hulls, never had any problems. I do roughen the surface first though as I feel that cured grp has a very smooth surface so as Rich says it's worth doing for all the time it takes.
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Topic sticky in Paint, finishing and Care by Stavros
P40 - midway down.[size=78%] [/size]
https://www.modelboatmayhem.co.uk/forum/index.php/topic,39337.0.html (https://www.modelboatmayhem.co.uk/forum/index.php/topic,39337.0.html)
Another one I've heard that is good is Stabilit Express
Declan
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There's no need to overcomplicate things. An epoxy glue will do a perfectly adequate job at a reasonable price.
Colin
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Use fibreglass resin along with tissue or one of the new breed of industrial glues used in the building trade. I have used Everbuild Stixall for a while personally I think epoxy is a old glue. Stabalit Express is a good glue but at £30 not for everyone. I have seen timber fixed in GRP hulls with epoxy and after a while the joints failed. Epoxy may be your preferred glue so be it but look at some the newer glues out there you may be surprised.
Stan.
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Using epoxy is not my 'preferred' option, just one of my available options. I have reservations about epoxy concerning longevity, I have known it to 'unstick' in applications other than boats.
Mind you, I think that some of that may well be down to unequal quantities of hardener & adhesive and insufficient mixing.
We do all tend to judge the 50/50 proportions by eye, a notoriously inaccurate method, however few of us have scales accurate enough to do it by weight.
Of course when we are mixing resin or filler it is even more difficult to be accurate in small quantities. A pea of hardener to a golf ball of filler is only a good guide if you are mixing that much, if you only want a pea of filler it's a bit harder.
As others have said, slow cure epoxies do seem to be stronger than the rapid ones. I do wonder whether that could partially be down to us sub-concsiously rushing the mixing with rapid as we worry about it 'going off' before we assemble everything. Just maybe.
It's certainly a more complex subject than some would imagine. Thank you to everyone for your comments.
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A lot of the complaints about epoxy seem to relate to the cheap pound store versions. (same with Cyano) If you stick(!) with the more reputable brands you are unlikely to have any problems. I've never found squeezing out eaual proportions from a tube or bottle to be a problem but obviously if you are using larger quantities it is a different matter but then you would probably be using epoxy to cover or laminate which is different from using it as an adhesive.
At the moment I use Zap 15 minute epoxy for most purposes as it has a good combination of setting time and strength and seems pretty tolerant when it comes to mixing.
But each to his own.
Colin
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Hi I have used Stablit express and it is a gap filler and very good. However it needs mixing and you have 15 minutes! I was building Libera Ocean a Graupner kit which is about a metre long. It is a strange build as you build everything on an upside down deck, then you stick the hull on! That is the glue goes all around the edges in a narrow trough where the hull meets up.
They recommend Stablit Express for this task and I looked at it and thought this will take time so I had a rehearsal without the glue including clamping etc.
Then I did it with the glue mix it really is a race against time it was successful but without the rehearsal I would not have finished before the glue had gone hard.
If I was doing it again I would use clear bathroom sealant, it would have done the job just as well, lots of surface area, bit controversial but works for me.
Roy
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So Colin says......"I've never found squeezing out eaual proportions from a tube or bottle to be a problem"
Absolutely agree Colin where the mix is 1:1..........however I am sure many modelers have made a 1:20 or 1 :50 mix a little too slow in setting....... or gone off <*< before the glue is positioned correctly
I think this is why our friends at Bunnings sell ''extra" 40gm tubes of Polyester hardened to assist when you have run out of hardener for that 500gm tin of 1:50 mix :o
Derek
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I quite agree Derek, you do have to be very careful if not using 1:1 mixes, one reason why I normally use them!
Of course another rather different alternative is purely mechanical fixings. You only have to follow the posts on this forum to see that we have many, many, people (including myself) who are experts at screwing things up... {-)
Colin
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Apologies to Bunnings......."our friends at Bunnings sell ''extra" 40gm tubes of Polyester hardened" .....
Naturally their 40gm tubes of Polyester hardener is/are yet to be hardened %% ...that is our job to set off & create the exothermic reaction :-))
Derek
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You can slow down the reaction of two part adhesives by refrigerating them before use.
Stabilit Express is a modified acrylic type adhesive, there are numerous other brands and formulations of this type of adhesive readily available.
It has a very long shelf life.
Unbranded MA quite cheap on ebay etc. e.g.
https://www.ebay.co.uk/itm/2x-AB-Modified-Acrylic-Adhesive-Glue-Shoe-Goo-Repair-Tube-Strong-Leather-Rubber/273290663406?hash=item3fa16495ee:g:Ha0AAOSw02Fcd4vS (https://www.ebay.co.uk/itm/2x-AB-Modified-Acrylic-Adhesive-Glue-Shoe-Goo-Repair-Tube-Strong-Leather-Rubber/273290663406?hash=item3fa16495ee:g:Ha0AAOSw02Fcd4vS)
It'll stick pretty much anything, but has a pungent odour and working time is lower than most epoxies. I liek JBweld professional for epoxy. Unlike Araldite, it dries nice and hard and can be worked with files and sanded smooth, so is also an effective filler. Very strong, but more brittle than modified acrylic.
Epoxy will always provide a stronger mechanical bond to GRP than polyester resin.
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You can slow down the reaction of two part adhesives by refrigerating them before use.
Stabilit Express is a modified acrylic type adhesive, there are numerous other brands and formulations of this type of adhesive readily available.
It has a very long shelf life.
Unbranded MA quite cheap on ebay etc. e.g.
https://www.ebay.co.uk/itm/2x-AB-Modified-Acrylic-Adhesive-Glue-Shoe-Goo-Repair-Tube-Strong-Leather-Rubber/273290663406?hash=item3fa16495ee:g:Ha0AAOSw02Fcd4vS (https://www.ebay.co.uk/itm/2x-AB-Modified-Acrylic-Adhesive-Glue-Shoe-Goo-Repair-Tube-Strong-Leather-Rubber/273290663406?hash=item3fa16495ee:g:Ha0AAOSw02Fcd4vS)
It'll stick pretty much anything, but has a pungent odour and working time is lower than most epoxies. I like JBweld professional for epoxy. Unlike Araldite, it dries nice and hard and can be worked with files and sanded smooth, so is also an effective filler. Very strong, but more brittle than modified acrylic.
Epoxy will always provide a stronger mechanical bond to GRP than polyester resin.
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