I was wondering if it were to be a good idea to substitute Elmer's wood glue for slow CA. It's for the main spar on an LT-40.

as long as you can keep the spar in place tight against the ribs that glue selection would be better! Wood glue would stay flexible and move with the wing, where as the CA would be a more brittle bond.... both are acceptable, its really a matter of how long do you have to sit and watch glue dry!


Rod

I use aliphatic resin (Elmer's, Titebond, etc.) for nearly all construction joints.

If you want to read more about types of glues and their applications, see AirfieldModelsAdhesives

hmm...it says not to use for high stress areas. Would a main spar not count as a high stress area?

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Aliphatic type glue is the only logical glue to use.

Ca to be used for tacking only.

Epoxy for high strength locations.

You do not have to watch the glue cure. There is always somethng else to do while the glue cures.

Who use CA for all their build to save time also end up saving time for the life of their model.

All old timers know that by experience.

Good gluing practice and covering that does not tear is always worth any extra effort while building.

Zor

Zor - not sure what point you're trying to make. Will you please say it a different way? Thx.

Hee Hee ___laughing ___.
Semantics is a great thing.

The point I am making is that if a builder use CA for saving time in his build the model will also have a short life because its first crash will result inmany individual pieces instead of remaining in one piece easily repaired.

The model will also save time having a short life. .

Zor

I've seen more pilot and radio problems crash more planes than any type of glue joint.  If you look at crashed planes most of the broke pieces are of single wood parts and not the glue joints.  Now if its a weight thing Aliphatic glue is lighter than CA.

That being said I just built an LT-40 over the winter and used slow CA on the main spar and it's rock solid.

I have to disagree with this statement. My Smith Miniplane was constructed entirely with CA, and 6 years later is still like a tank. And I am not gentle with it, either! [>:]

A different twist - Zor referred to "all old timers"

Before ARF's everyone built. The ones that were in a hurry built their models "in a hurry" disregarding attention to details. They also used CA BECAUSE they were in a hurry. As a result the finished product reflected them being "in a hurry". Probably didn't last long.

Today, the fliers that are "in a hurry" buy RTF or ARF products. Those of us that build are NOT "in a hurry" and we pay attention to details whether we're using CA, AR, epoxy, hot glue, or any other adhesive. As a result, pilot error or an occasional radio hit (or other pilot hit) are the reasons that today's kit airplanes fall out of the sky NOT because CA was used.

Hope that that makes sense ... (it did when I typed it )

After thought - the only airplane component failure that resulted in a lawn sale was my 1st plane - SIGKadet Sr. ARF - the wing collapsed just outside the "main spar doubler". Bob Nelson of SIGsaid that there were "build"problems with the wing and if I'd send it back SIGwould replace the plane. Oops - I field stripped all of the serviceable bits and tossed the rest in the field's dumpster. Arrrggggg - there is a lesson here ...

Congratulations for being a good pilot and not crashing your Smith Miniplane for 6 years.
I suppose you have had many hours of enjoying flying it.

As I said before, it is in a crash that we see the difference.
If you havea badluck you may agree with me and count the number of pieces your tank has produced.

Of course the number of pieces will vary with how hard it hit the obsruction.

I never forgot the fellow who wanted to recover his ARF to change the color scheme.
Pulling off the covering he found that the covering is what was holding his frame together.



Zor

I would suggest epoxy if at the wing root.  Either CA or aliphatic for the rest.  If only because epoxy is completely fuel and water proof and not brittle.  All will work for a few years, but the stress would eventually get to CA or aliphatic.  It depends on just how much and how often it is stressed.  They might work, but why take a chance?

I referred to "old timers" as the fellows that had to build their model if they wished to fly before ARFs and RTFs were available.

Your second paragraph illustrates exactly the point I was making.

I certainly DIDNOT imply that models fall off of the sky because they were glued with CA.
I only referred to the results of a bad crash.

What you wrote does make sense to me.

No doubt there is a lesson from your Sig Kadet wing folding. However we do not really know the reason for the folding. It may have been poor glueing but it could also have been weak spar material or a covering that did not add strength to the frame.

Zor

I respect your opinion of being "rock solid" but it remains just an opinion ___does it not ?

Weight wise ___I cannot see any advantage of saving on glue.
I built an 10 1/2 lbs model and used less than 4 weight oz of glue and that is with double glueing and making fillets at all glued joints.

Zor

Zor - SIG told me that it was a "wood specification" that needed to be upgraded. If I understand that statement correctly, it was built with a lower quality grade or perhaps smaller in dimension than it should have been.

Also, the manufacturer used hot glue. It's my understanding that hot glue creates a "bond by interference" joint rather than an "bond by absorption". Every time I handled the wing or fuse and heard a faint "crack", unknown to me but a joint has just failed.

On some rather large models, yes, a wing spar is a bit more stressed than a single rib for example. But on an LT 40? This thing weighs, what, 5-6 pounds maybe? The spars are lightly loaded in this situation and Elmers works great ....

Like any glue it can be misused.

MinnFlyer (RIP) shared advice given to him by his father when using AR - apply the glue and wipe it off with your finger. What remains is enough glue.

Of course - technique does NOTapply to CA

The only thing to use is Slow Cure Epoxy.

You just hit a wasp's nest with a broom ...

The wing's main spar is the highest stress point in any aircraft. Every other component (part) of the aircraft rides on it and depends on it's integrety.

I tool a look at the LT-40 kit build manual (http://www.sigmfg.com/BuildManuals/S...detLT40P2.html) in reference to building the wing. I see that the wing spars are hardwood and that there is a balsa doubler bonded to the hardwood spar. Is this the area that your questioning using slow CA on?

Which type of glue to use where in building a model will turn your simple question into pages and pages and pages of endless debate. To a certain degree, the type of glue you use is personal preference. There are some glues that work best and should be used in certain applications. The Airfield Models presentation on adhesives that John Gilmore posted a link to is a great reference. This reference will help you build a knack for what type of glue to use where on your model builds.

Personally - AGAIN - personally, I do not like what CA does to balsa. By nature, it works itself into the pores of the wood and hardens, thereby hardeneing the wood. I've been building by the rule of thumb that if a balsa area must be sanded, I do not use CA. I don't use CA in high-stress areas because CA depends more on it's own strength instead of the strength of a adhesive/wood bond like in the case of aliphatic resin or epoxy. Once again, this is my personal preference. I can point to one large-scale (1/4-scale, 1/3-scale) VERY skilled scale builder that builds his models primarily using CA and has not had any problems. Here in this thread Dope Fiend reports that his Smith Miniplane is just fine. Can't argue with sucess and experience.

I build primarily using aliphatic resin (aka: "carpenter's glue") and Titebond is my brand of choice. It spreads and sands nicely. For high-stress areas (firewall, landing gear, etc.) I use :30-minute epoxy. Again, to each his own. The main thing is that you use the best adhesive for the application. In your case, I would bond the balsa doubler to the spar using aliphatic resin. My technique is to put a small amount of glue in a small plastic mixing cup and spread the glue on the woods using a small, flat artist's paint brush. Easier to control than applying straight out ofthe bottle.

Speaking of wing spars, here's an interesting video on the B-777 wing spar stress test:

http://www.youtube.com/watch?v=Ai2HmvAXcU0<br type="_moz" />

Well I have Elmer's Glue, Sig Bond and Sig Epoxy...and I'm thinking either the Bond or Epoxy, but leaning more toward epoxy at this point. I have realized, however, that I probably need to put some fillets with the Elmer's on the horizontal and vertical stabs, cause the CA fillets aren't that great.

FT6 - SIG bond is a great wood glue whose joint sands beautifully - however - it is not one of the stronger ones. In the LT40 wing spar glue - Elmer's or epoxy would be my choice.

Sport epoxy is not fuel proof. if you have every noticed that firewalls coated in epoxy will eventually turn color because the fuel soaked into the epoxy. besides all this does is add weight to the plane.
Acrylic paint is the most fuel proof product that i can think of.

OP as far as super glue goes you can use it on the spars and the whole build of the plane except fire wall and wing hold down blocks. do not use kicker on the super glue as it will reduce its holding strenght a lot. use slow gap filling on the spars ribs and what ever else and dont worry. you must let it cure before you remove the pins/ta[pe or what every you use to secure.

for any kit i build i only use elmers wood glue on everything including the firewall, wing hold down block and even to join wings. to me this glue is the best out there for wood kits.............

Old timers used Ambroid!

Explain double glueing. What were the fillets made of?