Building with Foam Cure - lessons learned

Hi everyone -

For those that have read other articles here, you know that I have been using Foam Tac glue by Beacon adhesives http://www.beaconadhesives.com/all/hardware/foam-tac/ for over a year now. It is a good product, but quite expensive. The Beacon website lists it at $11.99 USD, although most vendors sell it for around $9.99 for a 2 oz bottle. I have found this allows me to build 2-2.5 planes depending on my usage.

Recently Stephan wrote an article on our blog about a product available at Hobby King called Foam Cure http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=40936

After reading about Stephan's experiences and the low cost, $1 an oz versus $5 an oz, I had to give it a try on my most recent build. I did build this plane with some Foam Tac, but the main usage was Foam Cure. So I just wanted to pass along some lessons learned and feedback from using Foam Cure on this build.

I found Foam Cure easier to use than Foam Tac when trying to lay a bead down between two pieces.  It’s viscosity and make up allowed for a much smoother, more uniform bead.  Foam Tac because of it's elasticity does not always form a smooth bead, especially if the glue has been around awhile.

I found Foam Cure stayed relatively flexible during the first 24 hrs after application, then after 48 hrs became quite stiff, almost like epoxy which is good and bad depending on the application, but now that I am armed with a little experience using Foam Cure, it is an easy work around.  What I learned for hinges and where being used to reinforce the back of a score line along with drywall tape is to let it set up for a couple hours, then work the hinges several times just to sort of “crack” that seam along the hinge or the scoreline.  Once I did that, the hinge stayed flexible while the rest of the glue hardened almost like epoxy.  

This is how I learned this lesson. I used Foam Cure and some strips of drywall tape to reinforce the score lines on the inside of my nacelles and didn’t flex the hinge for a few days and when I did, it was difficult to “crack” the hinge and some of the drywall tape lifted up at the ends of the scoreline, so in future as I said, I will let it set up for a couple hours, then work the hinge several times and life should be good.  Because it is so much cheaper than Foam Tac, I wasn’t worried about “scrimping” on the amount of glue I put on my hinges and other applications, so I confident my hinges are well attached.  Of course only some punishment at the field will prove that theory.  

It is interesting that the Hobby King website says this FOAM-CURE™ does not, however, cure flexible enough to act as a hinge for aircraft control surfaces.  If I was using the glue alone to try and make a hinge, then I would have to agree, it would dry too stiff to be used as a good hinge on it's own. I think in this situation because I am using the drywall tape as the hinge and just attaching it with Foam Cure, it will work just fine.  As I said, from my experiences, as long as I crack the seam a couple hours after applying it to a hinge is stays flexible enough to make very good hinges.

I found because it does not melt the foam like Foam Tac does, that if I needed to lay a bit extra in a spot to hold something, or fill a small gap, I wasn't worried about it deteriorating the foam.  What I have found with Foam Tac is if too much gets put in one spot, it will melt and weaken the foam, turning it almost to a crystalline consistency.  

Once dry, I found Foam Cure is essentially the same weight as Foam Tac, as long as I don't apply it too heavily. This plane I just built is identical to another prototype plane Stephan and I are working on that I just completed using all Foam Tac and the difference between the two is only 3 grams (the second plane with Foam Cure being the heavier one). In my view, 3 grams can be attributed to me getting a little "glue happy" more than anything, I think the glues weigh about the same when dry.

When it comes time to finish and sand the plane, it can be carved/sliced easily with a nice sharp razor blade and then sanded whereas Foam Tac cannot be cut cleanly and in fact will grab the knife blade and I have found myself pulling glue out of the seam where I have put it, even a few days after application.  There is a bit of resistance when initially sanding Foam Cure, but with time and patience, it can be sanded down just like filler, so any excess glue can be easily removed when finishing the plane.  With Foam Tac it “pills” up, cannot be sanded and can get ripped out of the seam if sanded too hard.

If you are going to sand Foam Cure, I would recommend letting it dry for the minimum recommended 12 hours or even longer just to ensure you get the finish you want.

I did find the fumes from Foam Cure a little stronger than with Foam Tac, so when applying a lot of it like when making hinges, it helped to have the window open for a little ventilation.

So overall, I am very happy with the Foam Cure thus far, more to follow as it gets put through it’s paces at the field to determine long term durability.  I will still do a couple builds with Foam Tac and Foam Cure together until my supply of Foam Tac is used up. As long as the plane holds up well at the field, I will be switching to Foam Cure exclusively for it’s ease of use, availability from Hobby King and most of all it’s price, approx $1 per oz of Foam Cure compared to $5 per oz of Foam Tac.

More to follow as I put it through it's paces at the field.

EDIT: Since writing this first article, I have written two more articles which you might find useful if you are considering using Foam Cure glue.

http://migsrus.blogspot.ca/2015/02/building-with-foam-cure-more-lessons.html

http://www.migsrus.com/blog/initial-foam-cure-durability-results

The durability results post is on our new website, you can post questions and comments there without needing a google account.

Cheers,

Scott