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Author Topic: Best glue for strong metal-to-plastic/wood/GRP joins?  (Read 20894 times)

Edward Pinniger

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Best glue for strong metal-to-plastic/wood/GRP joins?
« on: June 30, 2010, 02:41:13 PM »

What type of glue (preferably one readily available at hardware stores etc.) is the best choice for gluing wood to metal (or plastic/GRP to metal) where structural strength and durability are needed? For example, attaching metal eyebolts + gooseneck fittings to the wooden spars of a yacht, or gluing metal prop shafts + rudder tubes to a hull.

Currently I use two-part epoxy for this type of job, the problem I've found with this glue is that unless you get exactly the right ratio of hardener to glue, it will either set slowly or not at all. I've also found it very hard to apply neatly even when using a toothpick or metal pin to apply the glue.

I've heard that polyurethane glues are a good alternative to epoxy - what's the best readily available brand? I know some people have recommended Gorilla Glue but have also heard that it takes a long time to set and is rather "rubbery".
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Circlip

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Bunkerbarge

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Re: Best glue for strong metal-to-plastic/wood/GRP joins?
« Reply #2 on: June 30, 2010, 04:53:42 PM »

I use the two part epoxy such as Araldite but for small fittings such as the ones you describe I will use the rapid type, which should be set in about five to ten munites.  It's a simple 1-1 ratio and I've never had mix problems.

For more structural applications I might use the slow setting variety though, which is best left overnight for full strength.  For small fittings however that require strength, such as in rigging, I may well use a mechanical device, such as a threaded rod with a nut on the back, and then cover the whole thing in epoxy.  If you need it neater you can recess the nut and then screw the threaded rod on from the other side.

I've never been a great fan of cyano glues but they do have certain specific uses and may well be suitable with metal and a non absorbent material.  The trouble with wood is that the wood soaks up the glue before it has chance to set and weakens the joint.  It works a lot better on varnished or painted wood but I prefer a glue that does soak into the wood grain wherever possible.  I've also used waterproof Resin-W glue (PVA) for fittings to wood as it does give a very good grip.
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Colin Bishop

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Re: Best glue for strong metal-to-plastic/wood/GRP joins?
« Reply #3 on: June 30, 2010, 04:56:54 PM »

This table from the Deluxe Materials website is very useful.

http://www.deluxematerials.com/download/Quick%20Ref%20Glue%20Guide.pdf

Colin
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derekwarner

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Re: Best glue for strong metal-to-plastic/wood/GRP joins?
« Reply #4 on: June 30, 2010, 09:55:10 PM »

Edward says....... "I've also found it very hard to apply neatly even when using a toothpick or metal pin to apply the glue"  %%... Edward...one method is to shroud the area or component with an o-ring

This allows you to paste the area [within the o-ring] to be glued.....the o-ring can be used as a wiper surface to smooth out the epoxy & when cured just cut the o-ring away - result is one scaled to size epoxy disk  :-)) ...Derek
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triumphjon

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Re: Best glue for strong metal-to-plastic/wood/GRP joins?
« Reply #5 on: June 30, 2010, 09:58:06 PM »

ive been useing  gorrilla glue from my local hardware store , 100% waterproof ! bonds anything .
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787Eng

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Re: Best glue for strong metal-to-plastic/wood/GRP joins?
« Reply #6 on: July 01, 2010, 11:56:54 AM »

If you are after the BEST general purpose glue then look no further that Loctite Hysol 9462....Its outstanding stuff and I will not use anything but...
I was first introduced to the stuff when I used to fly turbine powered RC jets....lots of stresses when a model is flying around at 200mph and landing a 30lb + model %%

Used to glue CF to wood, fibre glass to wood, plastic to metal and all the combinations....

Its not cheep but if you want the best and a glue that sticks like s**t to a blanket then this IS the stuff....

And one other thing it stays where you put it, so wont run all over the place and with a wet finger can be very nicely molded while wet....

Here is just one link to start with...http://alshobbies.com/shop/search.php?Desc=Loctite+Hysol+%239

Mark
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Edward Pinniger

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Re: Best glue for strong metal-to-plastic/wood/GRP joins?
« Reply #7 on: July 03, 2010, 11:39:26 AM »

Thanks to all for the advice + suggestions. I've tried out Gorilla Glue as suggested, and found that (as I'd heard before) the glue expands and foams up a lot when it sets - wiping off the foam before the glue sets is a good idea, but even so the joints end up quite messy and I ended up having to use a sharp knife to remove the glue blobs once it had set. It also remains quite rubbery and spongy when fully set.
However, it does "grip" incredibly well - as I found out when I glued a couple of eyebolts in the wrong holes and had to remove them! - and its rubberiness when set should make it very effective for gluing things like mast/sail fittings on sailing models, which are subject to a lot of stress from different directions when the model is on the water (which might eventually weaken and break if a more rigid, brittle glue is used). I've now used it for all of the mast/spar fittings on my 1800s schooner (Bounty conversion).

I don't know how effective it would be for things like prop shafts and rudder tubes, though, as its foamy, spongy consistency when set probably isn't very watertight. I think I'll stick with (pun intended) epoxy for this type of job for now!

I always use superglue/CA (usually the thick "gel" type) for detail work when gluing dissimilar materials together, but I find it's often too brittle for working parts, and also tends to degrade and become more brittle with exposure to water.

I'll definitely also give the Loctite Hysol a try... it's certainly pricey, but not actually much more expensive than good quality 2-part epoxy.

Also thanks to derekwarner for the suggestion of using an O ring or washer to get a neater joint when using epoxy - will definitely try this in future.
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Subculture

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Re: Best glue for strong metal-to-plastic/wood/GRP joins?
« Reply #8 on: July 04, 2010, 10:44:43 AM »

I like to use acrylic based glues which are sold under brand names like Deluxe materials Fusion, Devcon Plastic Welder or Stabilit Express. These glues really seem to latch onto plastics, to the extent that they're stronger than the surrounding material.

Edward Pinniger

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Re: Best glue for strong metal-to-plastic/wood/GRP joins?
« Reply #9 on: July 24, 2010, 12:19:03 PM »

One further question, has anyone had any experience with  "Titebond" polyurethane glue? Does it have the same annoying "foaming" qualities as Gorilla Glue? (the description "offers excellent sandability" suggests not, but I'd like to know for certain). It certainly seems a lot cheaper.
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rockets

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Re: Best glue for strong metal-to-plastic/wood/GRP joins?
« Reply #10 on: July 31, 2010, 05:10:54 PM »

Loctite Hysol is a very good product, we use it in the aerospace industry. If you are going to use it then be warned, if its the same stuff used in industry wear gloves and be in a well ventilated place. The activator contains nasty stuff that will do nasty things to you.

Rockets.
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tt1

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Re: Best glue for strong metal-to-plastic/wood/GRP joins?
« Reply #11 on: August 01, 2010, 01:14:54 AM »

Haven't used it myself Edward but a fellow modeller informs me that it does foam as per Gorilla Glue.

       Regards, Tony.
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