Adhesives

Greg Lockhart

Member
Joined
Oct 31, 2003
Messages
162
Location
West Virginia / USA
Total Flight Time
125
My SparrowHawk kit came with Magnabond 6155 adhesive that is used in several applications. Unfortunately 6155 has a short shelf life and at my slow build pace it expires before I can use it. Is there any other adhesives that would work as well but have a longer shelf life... or at least cost less? Aircraft Spruce offers several different structural adhesives but I am not familiar with any of them.
Thanks,
Greg
 
Greg, it depends on the application. If you tell me what they called the Magnabond to be used on, I could give some advice of whats best to replace it with. Aircraft Spruce is about 3/4 a mile from me, so I'm very familiar with their products.

Dennis
 
Dennis, the main application is bonding the rudder / horizontal stabilizer parts together (aluminum, fiberglass, wood). I'll want something at least as strong as the Magnabond.
Greg
 
OK, they sell a great bonding adhesive made by PTM&W Industries called ES6279 adhesive system. Page 33 in the Spruce book. P/N 02-30006 and P/N 02-30007. You can also find out more about it at <http://www.ptm-w.com> .

It's great for bonding fiberglass. It has some rubber in it, so it's not brittle. But to bond aluminum using anything, you need to prepare the aluminum first with Alumiprep No. 33, P/N 09-01621, and then treat the aluminum with Alodine No. 1201 P/N 09-01625 and let it dry, do not rinse.

After that, bond it and it will never fail.

Good luck.
 
Why does the Magnabond have a short shelf life? What is it? Involved in the manufacture of Paints, Adhesives and Fillers, I can tell you we have shelve lives on all our products too. Mostly they are ultra conservative and the true life is often double or even infinite in reality for some products. Of course some products really do have a short shelf life so need to know what it is.
 
I'm using an epoxy gel-coat today that's 2 years expired, but it still works just fine.

I'm not a chemical engineer to answer that question, so I never question them when it comes to something I'll put into an aircraft.

Many adhesives I keep in the refrigerator, like locktites and so on, and they last forever.
 
Generally speaking - if it's epoxy it will have a long or maybe even infinite shelf life so long as you dont leave the lid loose or store at too high a temperature. There are some moisture curing epoxies that if you take the lid off and damp air gets into the hardner then it will start to deteriorate. Urethanes are moisture sensitive so once opened have limited shelf life. Unsaturated esters such as vinyl esters will self polymerise with time and heat so usually have realatively short shelf life. Acrylics and acrylates will depend upon how they're cured and formulated. Unfortunately it's complex but if you look at the MSDS you should get a good idea of what it is. Again, generally shelf lives are conservative, keep cool but don't freeze and extend the life.
 
I think the Magnabond label says 6 months. Mine is more than 2 years out of date. I've used some recently for some minor fasteners and it worked fine but I don't want to take any chances when I build my tail. Also forgot to mention that the Magnabond mix ratio is a pain... 100:35 by "weight". I'd like to find something that's easier to mix.. like 50:50 by volume.
Thanks,
Greg
 
I think the Magnabond label says 6 months. Mine is more than 2 years out of date. I've used some recently for some minor fasteners and it worked fine but I don't want to take any chances when I build my tail. Also forgot to mention that the Magnabond mix ratio is a pain... 100:35 by "weight". I'd like to find something that's easier to mix.. like 50:50 by volume.
Thanks,
Greg

Greg, can't argue with the better safe than sorry story. The mix ratio you indicate means it's almost beyond doubt an epoxy, it also means that the shelf life is likely more as a claim inhibitor rather than factual and in reality the shelf life is probably way beyond the two years you had it already. Yes the 100:35 is a pain, my company does that too not thinking about how other than mixing the total of A:B you measure this. It results in dubious mix ratios and improper cures. But then so does 50:50 as people often don't measure accurately - a dob of this and a dob of that!!Better safe than sorry!
 
What happens when epoxies sit is that they set up. The polymers begin linking to one another; your epoxy resin gradually crystallizes. However, you can break it back down and restore the semi-set epoxy to "like-new" condition by heating it up.

You need to heat it to 120-140º F. How to do this? Easy. Put a sealed can in the sink and run hot water on it.

Most catalysts (hardeners) do not crystallize and as long as you keep them sealed are good for 10+ years. The exception that proves the rule is some of the EZ-Poxy hardeners (in the 80 series). If these crystallize, they can also be rejuvenated with the hot-water trick.

Remember, you run the hot water on the SEALED can. You don't want to get water INTO your hardener.

As far as mixing is concerned, measuring by weight is the approved way to do it. Some epoxies come with a pre-configured pump that's supposed to give you a perfect mixture of resin and catalyst. You really should check the pump by weight every time you use it, though!

Changing the relative weights of resin and catalyst to adjust your setting time is a bad idea and you risk making an understrength part. Better to change the hardener (catalyst). For most any resin there are a variety of hardener speeds to be had.

On most any epoxy, a heated post-cure will increase the strength and stability of the part.

There's a lot of information out there. The Cozy and Long-EZ builders are an excellent resource for epoxy information. So are boatbuilders! (The guy that makes the elegant composite fuselage for the Mosquito XE was a yacht builder). Check your local EAA chapter for a Technical Counselor who has long-EZ or similar experience.

Hope this helps.

cheers

-=K=-
 
Dennis,

You mentiond that to bond aluminum, one must first use Alumiprep No. 33, P/N 09-01621, and then treat the aluminum with Alodine No. 1201 P/N 09-01625 and let it dry, and do not rinse. Was this part of the method that was used by Hughes Aircraft to bond their rotorblades? If so, what adhesive was used after the Alodine treatement?

Wayne
 
Dennis,

You mentiond that to bond aluminum, one must first use Alumiprep No. 33, P/N 09-01621, and then treat the aluminum with Alodine No. 1201 P/N 09-01625 and let it dry, and do not rinse. Was this part of the method that was used by Hughes Aircraft to bond their rotorblades? If so, what adhesive was used after the Alodine treatement?

Wayne

Sorry Wayne,
I have no reputable knowledge of Hughes Aircrafts' manufacturing procedures, and thus can not comment.
 
Alodine is a chemical conversion coating. It is important to rinse after application and NOT to let it just dry on the part. This is in all the instructions for the product.

If you do not rinse, you will loose bond strength as the surface of the treated part will have remnants of evaporated alodine. Whereas a rinsed surface leaves nothing behind other then the altered surface of the aluminum which is chemically bonded.

As far as a great structural epoxy is 3M scotchweld 2216 b/a. It is the same product as EC-2216 B/A which has been labeled, packaged, tested, and certified for aircraft and aerospace applications.

This is the epoxy used by rotorway in and helicycle in the construction of their blades. It is good stuff.

http://multimedia.mmm.com/mws/mediawebserver.dyn?6666660Zjcf6lVs6EVs666GGfCOrrrrQ-

It is also availableat AC Spruce:
http://www.aircraftspruce.com/catalog/cspages/3mAdhesive2216.php
 
Alodine is a chemical conversion coating. It is important to rinse after application and NOT to let it just dry on the part. This is in all the instructions for the product.

If you do not rinse, you will loose bond strength as the surface of the treated part will have remnants of evaporated alodine. Whereas a rinsed surface leaves nothing behind other then the altered surface of the aluminum which is chemically bonded.

As far as a great structural epoxy is 3M scotchweld 2216 b/a. It is the same product as EC-2216 B/A which has been labeled, packaged, tested, and certified for aircraft and aerospace applications.

This is the epoxy used by rotorway in and helicycle in the construction of their blades. It is good stuff.

http://multimedia.mmm.com/mws/mediawebserver.dyn?6666660Zjcf6lVs6EVs666GGfCOrrrrQ-

It is also availableat AC Spruce:
http://www.aircraftspruce.com/catalog/cspages/3mAdhesive2216.php

Rinsing is great when you are going to paint, but bonding to it is a different story, and you ain't going to read about it on the bottle.
 
I tried using the Magnolia epoxy included in my SH kit, but it was a real pain. It is very thick and the mixing ratio is awkward.

I wound up using West System epoxy, available thru Aircraft Spruce and most boat supply houses. It is easy to mix with the optional metering pumps and you add different fillers to thicken it for different applications. I had a can left from when I was building a wood aerobatic wing. It's very nice stuff to work with (for a smelly epoxy!).

Marc
 
Dennis,
I was not just referring to "instructions on the bottle". I was also referring to ANY reference material you can find on the application process. I am not going to argue this point with you.....but needless to say, I would rinse any critical application.
I only have one question. Can you explain how leaving behind contaminants on the surface would help in bond strength? The first rule of bonding anything is to thoroughly clean surfaces to be bonded.....but I guess that is just the "instructions on the tube" as well.
Mgoroff,
West system is a good epoxy resin for wetting fiberglass or bonding wood but is not a good structural epoxy for metals. It is too brittle and shears rather easily. Again...check out the scotchweld 2216. You will not go wrong with it.
If the ultimate in convenience is required, it is available in blister packs where you just break the seal and mix the two exact quantities...but the tubes are easy enough to use.

You know, this is one of the reasons I don't share manufacturing techniques or get into design discussions. There is always someone that has never done it before wanting to argue over something that you developed 20 years ago and have been using successfully since.

No, I will not explain why. Just ignore what I wrote, I don't know what I way thinking to give construction advice here in the first place.

The guy asked a question, I gave him an answer that would work for him, he can take it or leave it.
 
Mgoroff,

West system is a good epoxy resin for wetting fiberglass or bonding wood but is not a good structural epoxy for metals. It is too brittle and shears rather easily. Again...check out the scotchweld 2216. You will not go wrong with it.

In the SH, epoxy is used to bind a wooden block inside the lower rotor mast and to bond the fiberglass horizontal stabilizer to the rudder. I believe the main purpose of the epoxy on the wood in the mast is to seal the wood as the mounting bolts for the upper mast go thru the lower mast and the block and there's very little stress on the glue line.

The horizontal stab has an aluminum spar and spacer rings and a wooden spacer block at the rear. Epoxy is used to glue the spar and spacer rings together and to the fiberglass stab, as well as a locating pin between the wooden spacer locks at the rear. There is also a thru bolt between the spacers and the spar taking any rotational loads. Epoxy is also used to fillet the mating surface on the tail feathers. I don't think the glue lines are particulary high stress applications, so I expect any convenient epoxy will work. One thing I like about West System is that the resin is thin and can be thickened as desired with additives. It's very convenient for things like sealing wood glued inside the mast and filleting.

I would certainly be reluctant to use it to make structural lap joints in metal (like in my car, which is an epoxy bonded AL frame), but I have no issue with its use in the SH and it is particularly nice for filleting the fiberglass joints.

Marc
 
I agree that West Systems is a great product and in your application sounds OK. One reason I like it is the metered pumps as you said. I have a gallon in my garage along with one each of fast and slow hardener. As you said, when mixed with micro of flox, you can do many things with it. I use it all the time as a lightweight easy sanding filler.
 
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