Mixing glue

Posted by Paul

Mixing glue is probably the one job that will remain consistent from start of the boat until it is finished. So getting it right is fairly important because if you get it wrong the first time you will most likely be doing it wrong for the whole boat, and that could be diabolical. I am not trying to scare you because it is not a hard thing to master. Instruction manuals will tell you how to mix the glue but there is nothing like seeing it done for yourself so if you can visit someone building a boat and can get some hands on experience then do so because it is much better than anything you will read.

I have included some photos of what the resin/hardener and the resin/hardener/microspheres looks like before and after mixing but again it will be much better to mix some yourself. After a while you will get to feel how well mixed it should be, and how thick it should be when you are adding the powders.

The resin and hardener come in drums to which you can attach pumps that automatically deliver a 5:1 mix of resin to hardener with just one pump on each. You will use so much resin/hardener that you get 44 gallon drums of the stuff! There is a special wall mount pump that inserts into the larger (44 gallon) drums and will pump out both at once with one pump directly from the big drums. You can decant to the smaller containers but on some of the larger “wet out” jobs you will soon get sick of pumping from the small pumps.

At the moment though the jobs are small so the we use “takeaway” size tubs to mix into and mix with plastic spatulas. It is recommended that you scrape the sides of the tub as the hardener can stick to the sides, you cant see it but I take their word for it and constantly scrape around the sides, otherwise it is just a matter of mixing like you would whisk an egg. The resin/hardener starts off with milky streaks and will mix to an almost clear state with some bubbles in it.

The mix method for the resin/hardener/microspheres is the same but you add the powder to the mix after you have thoroughly mixed the resin/hardener. It is recommended that you can always add more powder to the resin/hardener until you get the consistency you need but if it becomes too thick it is not recommended that you should add more resin/hardener, so add a little power at a time. Another good reason to only add a little powder is that it is extremely light and will blow away into the air with just the gentlest whisk. This will be familiar to anyone that has made a cake. The idea is to “fold” the powder under the liquid until it is all wet then you can mix more vigorously. A couple of minutes of hand mixing should suffice, and don’t forget to scrape the sides of the tub frequently. Another tip is that you will get some lumps of powder, try to squash as much out against the side or bottom of the tub as you can but you will never get them all before the mix starts to go off so don’t get to hung up on getting it super smooth, you can remove more with the brush when you apply it and you can just leave them in the tub or remove them somewhere else such as on a wiping cloth.

For gluing panels together, you have to add a powder called 403 microfibre blend (other powders are added for different jobs such as fairing or filleting) the thickness required is about the consistency of clag. So keep adding powder until the mix is still fluid but not runny. I am finding that using a cooking measure as a scoop is handy and I find that 2 pumps of each and a level (not heaped) 1/4 cup of powder is about the right mix. This ratio holds for larger mixes, so 4 pumps of each would be 1/2 level cup (2 x 1/4 cup or using a 1/2 cup measure, its the same!!) and so on, but I am yet to make a mix of more than 4 pumps. I don’t pour it all in at once for reasons mentioned but also so that I can still judge it by feel.

One final tip, always wear gloves and a face mask, as you want to avoid the fumes and the powder. You will no doubt get glue on things it was not intended to be on, like mobile phones! But at least with gloves on, you can remove them before answering it!

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