Gluing Aluminium

Hi,

Background

I'm into radio controlled yachts which require a sail winch servo. One type is called a Drum Winch which requires a cord to be looped around a drum on the servo and a pulley at 30cm or more distance. The pulley is sprung to keep the cord under tension. Most modellers fix the two components into the yacht which works well but created challenges if you need to take them out for repair or change. (A deck will be glued in place restricting access).

I've made some drum winches using aluminium square tube to hold the pulley at the required distance from the servo. I also make a bracket for the servo out of aluminium and bolt the two together. This unit can be easily pulled out through a small opening.

Gluing the Aluminium instead of bolting it.

Without booring you with details, the unit can be more effective if built up from 3 or 4 pieces of aluminium. These are quite small and bolting them all together is less than optimal. So on my current build I'm going to glue them. I see on YouTube that this requires careful stages:

1. Clean any oil or grease off the surfaces. Degreaser and/or washing up liquid.

2. Rough the surfaces with 180/240 grit paper.

3. Clean again.

4. Glue and clamp

My questions

Has anyone glued aluminium and if so, what glues are most effective.

Any tips on the process?

Thanks

Stuart

Gluing aluminium is well proven. Most Aston Martins and JLR models are held together this way with two pack epoxy, and occasionally a rivet at the end of a linear run to guard against peeling, which I believe is the most common failure mode.

I use polyurathane adhesive sealant to attach aluminium plates to cover holes in electrical cabinets at work & have also used it to mount plastic parts to painted aluminium and GRP surfaces. Many motorhomes and caravans are glued together with this stuff - it grips very well (getting a glued part off is a real battle ! ) & doesn't cure totally hard, having a small amount of flexibility.

I think the stuff I am using at present is a Henkel product, but Sika also do an extensive range + there are other manufacturers . Only downside is that the tubes "go off" after opening however you try to seal them.

Nigel B.

Thorough preparation is the key to success [sorry for the dreadful pun]

Aside from the high-end car manufacturers ... look for information from the Aircraft repair people.

I had a very useful discussion with the man at British Airways [but that was about 35 years ago]

MichaelG.

.

Warning ... this is 302 pages:

https://www.sto.nato.int/publications/AGARD/AGARD-CP-550/AGARDCP550.pdf

But it downloads very quickly, and is searchable  ... Enjoy !!

Edited By Michael Gilligan on 30/03/2021 16:50:30

Can you not have two units but set at the correct distance with fittings in the hull at the correct distance from each other or is it a case of only one access point which would mean extracting both pieces through a single access point.

Dutch former aircraft company Fokker introduced and succesfully applied adhesive bonding of aluminium structures.

Cleaning and surface preparation prior to bonding was essential.

Adhesive bonding was not the cause of their bankrupt 😉.

Have a look at the recent thread on JBWeld, that will do the trick. If you want to sound out your use Ramon has been known to participate in sailing RC yachts too so will have a good understanding of the likely loads.

Use scotch weld 2216, it will bond aluminium without any issues. It's also good for areas where vibrations are involved as it is slightly flexible, it is also unaffected by fuel (kerosene) We use it at work on aircraft composite to aluminium repairs, and in fuel tanks etc. I have used it to fix DRO brackets to my lathe and mill instead of drilling, it's as good as bolted. No major preparation required, just wipe the surfaces clean with acetone and you're done.

The bond would be even better if you could shot blast the areas of the joint and then degrease them.

Good to hear how to bond DRO brackets to the lathe in stead of bolting! I do not like to drill holes in original parts of a “vintage” lathe.

I think chemical or mechanical cleaning will be a better pretreatment than degreasing with an organic liquid.

Loctite 480 is a rubber-reinforced, quick-cure adhesive ('super-glue' ) with good shock resistance and peel strength. It's also good in humid environments. It works exceptionally well, even on very smooth (not abraded or scuffed-up) surfaces. I've been very pleased - amazed even - with results. I don't know how it would stand up to contact with petro-chemicals or other solvents we use in the workshop. I think it's also known as 'Black Max'.

Edited By Kiwi Bloke on 30/03/2021 20:57:42

I don't think I ever came across mechanical preparation before bonding on the repair manuals. Probably because the aluminium sheet is clad, and abrading it will effect it's corrosion resistance. Wiping with MEK or acetone is always recommended. Acetone is more readily available tho. Of course one could try different ways as mentioned above and get good results.

I bonded a test bracket to the lathe bed to sample it's strength before the DRO install, I had to knock it off with a hammer to get it off. I hate drilling into machinery and apart from that, I find that bonding allows for better more precise positioning.

To add another option, toughened acrylic adhesives such as loctite F246 or 330 work well and are easy to use. You put an activator on one surface and the "glue" on the other. Some manouvering to adjust is possible for several seconds but it set up to holding strength quickly enough to hand hold it. Note the activator may be sold separately.

Agree with most of the above. In addition if you are using an epoxy based adhesive ,it would be good to clamp the joint whilst the adhesive is curing, and leave in a warm dry place for the recommended cure time. In general long cure adhesives have better properties than slow cure.

cheers

Bill

Thanks everyone. As always a wealth of information is available here!

Specifically; Derek, the boat design dictates how many openings we have, I'm building a 'near scale' model pilot cutter copied from a 1903 original, it only has one entry point.

JasonB, I have seen the JBWeld posts and have ordered some. But I see many alternatives here worth trying if JB Weld is not up to the task. I will come back with my findings.

One restriction I face - in not using a flexible sealant as the boat will eventually sail on salt water so the aluminium must be painted, also requiring careful preparation and etch priming which I suspect would not work well over a flexible joint.

Thanks to all

Stuarty

To prevent corrosion and enable better adhesive efficiency, consider anodising all the aluminium parts before gluing. It makes a world of difference.

cheers

Bill

Hello Stuart

I build RC yachts and race IOM yachts. Mine tend to be built for performance rather than scale so are likely to be more stressed than yours. I frequently glue aluminium bits together and only ever use the slow cure Spanish version of Araldite which is always to hand. I have never found it necessary to buy special products or use special processes for the very small usage. I have two types of Loctite that get quite a lot of use on assemblies and fastenings. The important things to do are:

Consider the gluing area. Aim to make it as large as possible within the design constraints.

Try to design the fitting to avoid peel forces.

Clean and lightly abrade: Here I do a first clean with acetone turning the cloth at each pass to avoid re-depositing grease or dirt. Acetone is a fast solvent so it is quite easy to just move contaminates around if you are not careful. Then I rough the surface by pulling across a Permagrit block and then a final single, one direction wipe with a clean cloth and acetone. I have already mixed the glue and as soon as the acetone has evaporated which is seconds only, on goes the glue. This seals the surfaces and reduces the time available for the aluminium to oxidise. I use plain and pre-anodised sections with equal good effect.

Very occasionally I may pin or rivet a joint as belt and braces using thin brass rod and peening over the ends.

I too sail on the sea but don't worry too much about corrosion even with dissimilar metals. The boats are only out for a few hours at a time and in-between get a good rinse with fresh water. The rest of the time they are in the house.

I also use brass mainly for decorative reasons and of course that can be soldered. Would that be an option for you particularly if you are not too bothered about weight.

One day I am going to try the techniques for soldering aluminium hoping that will enable me to refine my designs. My obsession is keeping the weight out of the hull and rig so I can put it in the keel.

Tim R

I've used arldite 2 part epoxy to glue aluminium endcaps into aluminium tubes many times. The joint is very strong. In fact the chances of pulling them apart is almost none existent.

Any reason why you don’t use technoweld or similar?

Tim,

You're right that near scale has far lower stresses than racing IOM. But largely I enjoy the build as much as if not more than sailing.

Design of the internals is an important part of my build - no one else ever sees them but I like them to be 'right' by my mind. I have designed the components to offer large gluing surfaces and I do intend painting for protection - but if I'm honest more for my own satisfaction in a neat finish

Boat building aside this is an interesting exploration of joining metals. I see a few advantages particularly when joining different metals as the layer of epoxy - albeit thin - should inhibit galvanic corrosion.

It also has advantages over bolting; aluminium bolts seem to be premium priced and steel or brass run the risk of that dreaded galvanic corrosion! Finally, it is neater than bolting if small components are involved and particularly tubes where the bolt could obstruct the cord that runs up the centre.

Keeping weight out of the hull also appeals to me - you are chasing speed, I'm chasing a low centre of gravity to improve stability under sail. With aluminium the block components can be milled to allow thick areas for adhesion, but thin elsewhere. Careful design retains rigidity but reduces weight.

Now to welding - an interesting idea for the future....

Stuart