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Which glue

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Old 01-31-2013, 06:24 AM
  #26
JohnBuckner
 
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Default RE: Which glue

Old Fart if what you mean by balsa cement is the cellulose cements of the past such as Testors, ambroid and so on, then I would not recomend its use. In the past among all its other problems the critical one is its durability over time. It typically would only take a few years for the cellulose to harden and become brittle compromising the long life of your airplane.

After all even the motion picture industry figured out anything made of celluloid has a short life span unless extraordinary storage measures (temperature & humidity) are taken.

John
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Old 01-31-2013, 08:34 AM
  #27
Rodney
 
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Default RE: Which glue

I can attest to the fact that those old cellulose glues do not hold up. After having a model built with them fall from a hanger (after hanging there about 5 years) all the joints parted company without any wood breaking. I have also had old silk and dope finishes become so weak that if you touched them the covering fell apart. I think the silk actually rotted away leaving only a dope skin.
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Old 01-31-2013, 10:12 AM
  #28
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Default RE: Which glue

How heavy is the Elder anyway? It sounds like a 40 sized trainer type to me. How much force do guys think exists on the stab when the model is flying?

The thing to remember is contact area. If you only have 1/8" balsa edges to glue on and only one side of the stab at that, I don't care if epoxy was used, at some point the stab could part company. The joint will be intact but the balsa fuse side will possibly give.

If thereare at least 1/4" wide fuse sides at the stab location, epoxy, titebond, gorilla glue will all do the job fine. If the fuse side is thin, let me suggest that it bethickened to 1/4" or a bitthicker first. Or if the stab is also attached on the top side, ie-fully captured, thinner wood will work fine too. There is no need to overbuild this area because weight here has nearly triple the effect on the nose. But some judicious use of doubler stock is weight well spent.

Dowels or pins basically add contact area
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Old 01-31-2013, 12:08 PM
  #29
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Default RE: Which glue

I'm using Sigment and being very selective where and what gets glued with it. I'm building a small electric Ultimate and so far used the Sigment on the hardwood fuse doublers and a few other places. It is brittle though and when I was fitting the cabanes through the doubler slot, a very tight fit, the glue let go a little with a snap. Back in the 50s through the 80 I was still using Ambroids. It was the late 80s or early 90s someone put me onto CA so CA and epoxy have been my main glues of choice. I have about 6 different types of glues on my bench and all have there place but I do like to try new and go back to the old sometimes. I used to pick up test samples at the shows and events though then give new products a try.
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Old 01-31-2013, 01:19 PM
  #30
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Default RE: Which glue

Hi!
MTK is right! Doesn't matter what glue you use if the wooden area isn't large enough.
On such a small and slow flying model like the Elder any glue will work...but see to that the glue area is large enough. Gluing a stab to two 3mm balsa longerones isn't enough! Putting some additional 3mm balsa sticks parallell to the longerons at the rear will be just enough gluing area...and then any glue will work. 30min epoxy or 5min doesn't matter.
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Old 01-31-2013, 02:48 PM
  #31
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Default RE: Which glue

As stated earlier I had to take something apart that was put together with 5 minute epoxy and it just snapped apart without taking any wood with it.  Looks like the price of fast is weak.  I think the 5 minute stuff didn't have time to soak into the wood.  Worked great mixed with alcohol for fuel-proofing.  Had to work fast!  I have gone over the Elder 40 build threads and nobody mentioned that they were concerned with the tail feathers staying on.  No mention of them falling off either.  At any rate I did add a few braces to increase the glue area.  If it's too heavy to get off the ground I'll just call it a next generation tank. 
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Old 01-31-2013, 07:27 PM
  #32
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Default RE: Which glue


Quote:
ORIGINAL: 33willys

As stated earlier I had to take something apart that was put together with 5 minute epoxy and it just snapped apart without taking any wood with it. Looks like the price of fast is weak. I think the 5 minute stuff didn't have time to soak into the wood. Worked great mixed with alcohol for fuel-proofing. Had to work fast! I have gone over the Elder 40 build threads and nobody mentioned that they were concerned with the tail feathers staying on. No mention of them falling off either. At any rate I did add a few braces to increase the glue area. If it's too heavy to get off the ground I'll just call it a next generation tank.
It snapped apart because 5 minute epoxy cures very hard and brittle, unlike a very slow curing epoxy glue or stuctural adhesive that cures very tough. That is why you should never use 5 minute epoxy for highly loaded bond lines, especially if subjected to high vibration while loaded.

Bob
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Old 02-01-2013, 01:46 AM
  #33
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Default RE: Which glue

Thanks for the answer yeah i think i was getting sentimental,we used to spray cars with nitro cellulose laquer and that had a short lifespan too
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