Wood grain absorbs glue - different woods and grain cuts more or less. If Titebond is applied to an end grain much or most of it could wick into the end grain leaving little for bonding to the 2nd piece of wood. Double gluing is the application of glue onto bare wood, allowing it to be absorbed (filling the grain) followed by a 2nd application of glue to the "previously glued surface" resulting in a much more consistent and strong bond.

The red line is the glue used for the butt joint.
The purple fillets are of glue and are simply applied / spread with your finger. If you're using Elmer's glue - you can like your fingers - yum!

Now for Zor to tell me that I'm clueless! Won't be the 1st time nor the last ...

pkoury

Did you ask
Please explain double glueing. What were the fillets made of?

Double glueing involves that after a joint has been glued and cured we apply a second application of glue in the corners to create a fillet. The fillet is made of the same glue.

The idea is to increase the binding area of the joint.

As you look at the attached pictures you can easily figure that the binding areas can become 5 times the area of the parts in contact..The added weight of the glue is negligeable but the strength of the joint is considerably increased.

Zor

John,

I remember paying you compliments but your last line above bothers me.
I do not remember having said any such thing or similar things to you.

If my memory is failing me in my old age then I apologize.

I have always considered your postings appropriate, informative and well written..

Zor

The OP was asking for an opinion on what glue to use. I not only gave my opinion but experience what has worked for me.

I respect your opinion and point of view as well. I enjoy these types of discussions as they help each of us make our own choices on how to build our models.

Didn't know there were 'glue divas'.

Thanks for painting with a broad brush!   I can't tell which glue is used by the finished product, and I doubt you could, either. If used properly (like any glue), CA is fine for the entire aircraft. Same goes for AR. If built and covered properly, it's not an issue at all. 

I've been building since the mid-60's, and hopefully my building has improved with each model. I've used and tested almost any glue you can think of.  I've yet to see a bad glue joint cause the loss of a model. To imply that the CA joint won't hold up is preposterous. It may be more brittle in the event of a crash, but I don't build for a crash. I have seen aircraft built with AR rekitted so badly, we had to use a rake to clean it up. If you're a hack, in building or in flying, it shows.

Perhaps 'glue dilettantes' is more..., fitting? [8D]

If you are going to join the root ends of each wing panel then no you cannot use CA glue for that you will need 20 or 30 minute epoxy. But if you are just building the wing as in laying and pinning the spar to the building table and then setting the ribs on the spars well this is where you can either use elmers wood glue or CA this is purely for which one you choose to use but either glue is fine. The other builders speak of "brittle glue joints" well I have no idea what they are talking about, yes CA glue goes into the pours of the wood this is how CA "kicks off and cures" and builds the strong joint between the two joined wood pieces. I have a Great Planes Ultra Sport 60 that I built back in 1991 still in my hangar in flying condition and was built from CA medium viscosity for glue joints and thin viscosity for the CA hinges and epoxy for the firewall, wing root and wing joiner and tail feather. I can only suggest that you follow the build manual and follow its "glue type directions" to get you the proper glue for the area of things to be glued. Good Luck. If you like inbox me with a picture of what you are working on and I can help with your glue question.

pkoury,

Did my pictures and the drawing by JohnGilmore satisfy you as a proper answer to your question ?

Can you see how the filleting adds little weight while increasing the binding area up to five times or in accordance of how the fillets are made and extended ?

The two pictures I posted of thered piece may have appeared funny to some viewers.
That part is a cover on the nose top with an IC engine that did not use a muffler in the old days.
that part was treated for resistance to the exhaust residues. Some of the glue fillet were colored red to help evaluate the deposits from the exhaust on the glued joints. That part was built in the late 1950s. You can see the date of the picture at its bottom right corner. It was still undamaged at the date of the picture after that model crashed dozens of times.

It is part of my experimental radio control model that used to crash as often as it had a nice landing. The nose of that model never colapsed. It has a shaped steel nose piece backed by hardwood engine mount that goes all the way to be in line with the trailing edge of the wings. That plane weighted 8 (eight) lbs.and has a span of 72 inches. It is still in my hangar.

CA was unknown in those days and the model was all double or triple glued to make fillets everywhere.

I hope this information is useful to new builders.
We ( you ) should do your own evaluation of this technique and disregard any postings made by some fellows that proclaim that CA is as good.

There is no doubt that CA and shrink film is fine while flying if used properly.
Some building instuctions are suggesting CA to back up their claim of a kit that is claimed to be built in only a few hours, so buy it NOW and fly in just a few hours.

It is in a crash that the difference is seen. The more pieces to be picked up, the more chances that you will buy anoher kit. That is good business for the industry.

You are always free to do things your own way. Not all modelers or fliers are rich and can afford to keep buying new planes whethr they are kits, ARF or RTF or BNF or pre-built by others.

Have fun and avoid crashing to the best of your ability.

Zor

How could it? The OP wanted input as to what kind of glue he should use to laminate a strip of balsa to a strip of hardwood. This lay-up has nothing to do with "double glueing" (or tripple, or quadruple, ad nauseum) or fillets.

In woodworking, the term "double glueing" means applying glue to both surfaces to be bonded instead of just one. Especially important to end-grain to end-grain bonding.

(All, stand-by for a demonstration to what John meant in his post #26... )<br type="_moz" />

That's more what I've understood it to be.

I'm no expert. But my Dad was, a fine cabinetmaker. He taught us to double-glue hardwood or dissimilar woods to get better penetration and a stronger bond. Glue and mate the pieces, separate them for an appropriate time (depending on density) anywhere from a minute or two to an hour or more, swipe a couple times with sandpaper then reglue.

Note to all readers,

My post #27 was addressed to pkoury and was in response to his question in his post # 25 .

I think most that followed the thread have realized that I mean (meant) a second applicstion of glue to create a proper fillet.

I even explained that in my post #27.

Zor

The gift that keeps on giving...<div>
</div><div>
</div>

</p>

eddieC,</p>

One of my posting is being criticized on semantics about the meaning of "double gluing".
You follow with a posting agreeing with the post attempting to correct my understanding of "double gluing".</p>

Then you explain _ _ _</p>

Glue and mate the pieces, separate them for an appropriate time (depending on density) anywhere from a minute or two to an hour or more, swipe a couple times with sandpaper then reglue.</p>

Is this not a second application of glue after a time lapse ?</p>

It sure appears to me that we can refer to this as a second gluing or "double gluing" as I was using the term which I had explained in my post.</p>

It is sometime very interesting how we can read peoples' reactions in this forum.
It is often reflecting the attitude of who is looking for an opportunity to criticize instead of being helpful and contribute with an explanation as was requested.</p>

JohnGilmore was helpful with his drawing that he posted while I was writing and finding the pictures I posted a few minutes after John.</p>

I will contimue to refer to the process as "double gluing" meaning a second application of glue to assure that all joints have a fillet of glue that increases the binding area.</p>

Zor</p>


P.S.: I do not know the purpose of the followingtext line inEJWash1 posting.
(All, stand-by for a demonstration to what John meant in his post #26... )

End

</p>

For a spruce spar, nothing beats good old PVA wood glue. CA doesn't bond to spruce very well. If it's a balsa spar, CA works very well, the glue joint will not fail.

Negligeable for an LT40 maybe, but it's a big deal on a super light performance 3d model or equivalent, especially the small ones where every gram saved counts.

I agree, semantics! Sorry if I offended, Zor. Didn't mean to, but I must have missed the 'separate the pieces' part.

There's more than one way to skin a cat, none of these techniques are set in stone.  Don't take these posts personally, either.  It's the Interweb. Have fun! [8D]</p>

EXACTLY! Thank you!

The point is that if you don't do it "zor's way", he comes back with some low-brow, classless remark like "avoid crashing to the best of your ability". Being that the OP is building an entry-level model, what a great morale and confidence-booster, eh? NOT!

NO NEED to apologize to a person that would write such a thing!<br type="_moz" />

PRICELESS!</p>

Zor,
This is what you posted, and I didn't see anything after all about what I'd call 'double glueing', so my first post stands. Your technique is better termed a 'glue fillet'. Folks should be aware that glue of itself doesn't make a strong medium, especially when stretched to '5x'. Were that so, we could build the entire airframe from glue.

Let's not lose sight of the big picture, that there's a huge variety of glues available, and nearly as many techniques as builders. My oldest brother was a part-time luthier (builder of stringed instruments, he repaired guitars for rockers, a few big time), and he used horse-hide glue among others like Titebond. The horse-hide was the strongest by far, over 3,000 psi til failure IIRC, but I haven't seen any in over a decade.

For those who don't know, here's an image of a glue factory:

Thus the reason of the block icon at the bottom of a person that makes a post, i have several people on block so i dont see their posts

EddieC,

Since you posted your father's glueing technique, I've been trying to remember where I've seen or read it before. So much for memory!

So, to be clear, your father's technique was to apply glue to both surfaces to be bonded instead of just one (known as "double gluing" in woodworking). Both pieces are mated (put together in their appropriate locations) and held in place (or lightly clamped?). The reason being so that the glue penetrates the wood in the area that the two pieces will be bonded to one another, correct?Then the pieces are separated from one another and the glue on each piece is allowed to dry for a period of time. Obviously, this is where the skill and experience of craftsman come into play. After the pre-applied glued pieces set apart from one another for the determined period of time, a fresh coat of glue is applied to both and they are joined and clamped to set. Do I have this right from your recollection?

When joining end-grain to end-grain, I apply glue to both surfaces, i.e.: "double gluing", but I've never tried your father's technique. I'll have to give it a try.

I don't see what you presented being a matter of semantics. What you presented has nothing to do with "slurry gluing" a wood joint...

For some, the poor horse is not dead until it is paste....<br type="_moz" />

Hide glue (and glue pots) are still out there:

http://www.woodcraft.com/PRODUCT/200...FegbQgodQCmsWg

I haven't come across anyone using hide glue in model aircraft building.

I do know of at least one luthier here on R/C U; Smith Creek. Think I'll drop him a note and get his position on it.

What a hoot! Thanks!
<br type="_moz" />

eddieC,

You did not offend me at all.

I was just curious why you agreed with the meaning of double gluing as defined by another fellow and then proceeded to explain that your father's technique involved gluing the same joint twice.

The word "double" is well defined as "repeating an action a second time" thus it is correct and appropriate to say "double gluing".

Let the argumentative people rest in peace and profit and learnby the knowledge of others.

Zor

Thanx! You are exactly right: Glue. join, separate, wait, reglue, rejoin. This gives maximum penetration of the glue into the wood. I seem to recall 'double gluing' getting a mention in the manual of a MidwestAerostar 40 I built in the late '80's, I was pleasantly surprised.
Zor's technique is OK because the second glue join/fillet repenetrates the join, but I'm not sure it gets to the center of the joint, especially on thicker joins or denser material.

Great link! This Titebond version was mentioned there also, I may give it a try just to see how it works:

http://www.woodcraft.com/Product/200...-Glue-8oz.aspx

eddieC,

The first applicatiion of glue has already taken care of the contact surfaces being joined.

The second application is to add and shape the extra binding areas as fillets.

I think the pictures I posted not long ago are well illustrating the end results.

I also mentioned in one of my postings that I often wait for penetration and joint the pieces when the glue just begins to thicken. The idea of that is that when the glue is too liquidy it can flow out or be squeezed out of the contact surface. There should be no air pocket or empty space between the contact area.

No matter how well we fit the pieces there is always the possibility of the fit not being absolutely perfect. Any tiny gap where the pieces are in contact should end up being filled with hardened glue .

It just makes sense.

Zor