CA vs. wood glue. Weight?

[marc 540]

Hi all,
How can wood glue be lighter than CA? I know CA is more brittle but I just don't understand how wood glue is lighter than CA. It seems like CA just soaks into the wood without adding any weight. Forgive me if this is a stupid question but I really don't get it. :confused:

Marc 540 :)

[GDbot]

I am taking what I read a little on faith but my understanding is that the water evaporates from the wood glue. Some of the wood glues have some flex and will give a more resilient wing.

[wingsnapper]

The weight of ca stays the same while wood glue lightens as it cures.

[Phoebusflyer]

I guess the difference is HOW MUCH wood glue you use versus how much CA you use. Do you use 2 or 3 ozs. of ca for a whole plane? Do you use twice that for wood glue? I guess the only way to know is start with a fresh bottle of each and see how much you have left when you finish the plane!!
Water evaporates, but how much does wood glue leave behind? Anyone know?

[schrederman]

Wood glues are about 50% solids by weight. CAs are about 90% solids by weight. Polyurethane glues are 100% solids. CA seems to disappear but soaks deeply into wood grains. However the weight remains. All of these glues, and epoxies, etc. have their places. I like to use wood glue cut 33% with distilled water, except in places like spar cap to shear web joints. I use it full strength there. I usually like to apply it with a small paint brush. For CAs I use a pipette in an attempt to only wick in what's needed.

Remember, glue belongs in the joint, not on it... and if you add a lot of beef, it'll fly like a cow...:p...:D

Jack

[schrederman]

Oh... and there REALLY are no stupid questions...

JW

[scaflock]

WHat Jack said! (In BOTH of his posts!)

Jeff

[TLyttle]

I don't know what the weight is of the water is, but I don't think that is the point. One isn't really adding any percentage to the weight of a model in glue! Even tripling the weight of the glues is not going to add as much weight as one's choice of covering material.

Besides, having the RIGHT adhesive is far more important than how MUCH adhesive: epoxy has its place, as does contact cement, and CA has its uses. I use aliphatic for a number of reasons: it is cheap, it works properly, it is non-toxic, and it is available. My closest hobby shop is 80 miles away, so my choices are limited!

I take longer to build than some because I like to pre-glue joints. It isn't really necessary (mostly a habit), but I am in no hurry, and any structural failures are of the material, never the adhesives.

[dion9146]

I take longer to build than some because I like to pre-glue joints. It isn't really necessary (mostly a habit), but I am in no hurry, and any structural failures are of the material, never the adhesives.

OK, in the vane of no stupid questions, what do you mean by this?

I use white glue as my main wood glue, then use CA and epoxy for specialized joints, surfaces, etc. When I am dealing with end grain or very soft balsa, I always glue the joint, take it apart after the glue has soaked in (usually just a few seconds) and reapply if needed. Is that what you mean?

Thanks,

Dion

[schrederman]

That's exactly right... the correct adhesive for the job is very important... more so than what it weighs...

Jack

[rdeis]

When I am dealing with end grain or very soft balsa, I always glue the joint, take it apart after the glue has soaked in (usually just a few seconds) and reapply if needed. Is that what you mean?


My old rocket kit instructions defined "preglueing" as applying glue to the parts separately, letting them dry, and then sanding the joint smooth. After cleaning up the dust, apply new glue and then join the parts.

They said it was important for getting a strong joint in endgrain parts (like a balsa fin against a body tube.)

[rogerflies]

"My old rocket kit instructions defined "preglueing" as applying glue to the parts separately, letting them dry, and then sanding the joint smooth. After cleaning up the dust, apply new glue and then join the parts."

That sounds like a sure-fire way to have a weak joint. Most of the wood glues are at least a little water resistant after they dry, so the second application wouldn't really bond to the first.

dion1946 had it right:
"...glue the joint, take it apart after the glue has soaked in (usually just a few seconds) and reapply if needed." It's not just for end grain and soft wood, though.

I usually put a small fillet of glue around the joint so it can be drawn into the joint as the glue soaks into the wood.

Weight is the least of my reasons for not using CA.

Roger

[scaflock]

CA does have its place. For example it's great for fast field repairs, tacking parts into place etc. If a kit calls for CA then use CA. Just make sure you're using the right type is all. Thin CA will soak into the wood much easier than medium or thick CA will. If a plan calls for epoxy, then use it in those locations. If you're going to use CA then you should also have a bottle of de-bonder. It's great for cleaning the CA off your fingers as well as taking mistakes apart when needed. (I've never made a mistake on a kit!! NOT!!!)

In answer to some of the other questions raised here... Water weighs in at about 8lbs per gallon. Pre-gluing is fine if using old school "white" glue. Titebond types of glues are water resistant when dry so they won't grab to a dried patch of glue as well as most people think. As long as the first coat is still a little damp the second coat will bond with it fine.

I use the same gluing style as Jack in applying it with a small brush. I keep two "Glue pots" on the building table. One full strength and one that's been thinned with water to about 66%.

On wings I don't worry too much about using CA. On tail feathers I always try to use wood glue to save weight, Usually 1 oz of weight at the tail will require 4 oz of lead in the nose to counter balance it.

Jeff

[kc2iso]

Great info here. Thx for that. That would have taken me about 5 yrs in the hobby to figure that one out....hehe.

[slopemeno]

I built my Gentle Lady 12 years ago on my lunch breaks from work. I used Titebond, and then used a paintbrush and thinned Titebond to make a small bead around the glue joint. That wing survived a dead-battery full-speed dive into some heavy coastal brush that has destroyed lots of other planes.

Titebond is amazingly strong considering how inexpensive it is. I built it so I would glue up say, the ribs and spars, and then head back to work. I'd come home four hours later, and glue something else. It actually goes quite fast if you work around the drying time, rather than fight it.

That Gentle Lady still flies great, btw.

[glidermang]

Titebond (yellow aliphatic) on wood - I love it, it really holds well.

CA for composites - I love it, it really holds well.

Epoxy for special, localized applications - I love it... well, you know.

And so forth for 3M-77, goop, gorilla glue and all the others.

But, they are all HEAVY.

Yours, Greg

[johnsocj]

- On the previous subject of pre-gluing, the reason the rocket folk do it is because of the fin-tube junction. The fin usually has end grain balsa, which soaks up the glue quickly, whereas the tube is a phenolic coated/wrapped paper.

The tube ends up glue starved, and the fin ends up glue heavy. In this instance, pre-gluing allows the modeler to apply a small amount of glue to the fin, to keep it from soaking up the glue used for bonding. In addition to the glue left on the (now roughed up) tube surface, the resulting final joint is much, much, stronger than one done a single time.

A balsa2balsa joint could have similar problems (balsa wicking and starving the joint) especially in rib 2 leading edge joints. Pre gluing could help control the glue used, and yield a stronger joint, however, you also need to ask yourself just how strong does this particular joint need to be?

[scaflock]

The answer to that question is easy. The glue joint needs to be strong enough that it's the material around it that fails before the glue joint does. Balsa should always fail before the glue does, no matter which glue is used.

Jeff

[kzimmerm]

That's exactly right... the correct adhesive for the job is very important... more so than what it weighs...

Jack


I learned this lesson long ago when I built an Aquila Grande using almost 100% CA, including the spar. What a mistake. What I found is the CA doing a great job soaking into the wood made that wood very brittle. Very poor combination for a main support structure in the wing. (I was young and foolish and thought I knew everything..... lol)

As Jack pointed out, you have to use the right adhesive for the right job. Ever since I "discovered" this on my own I have never had a issue/problem with structure failures... only pilot errors.. which, well, I don't think there is a cure lol..

The one thing I've never done was to cut wood glue with distilled water. If I were looking to save some weight I guess I could do that. I can envision several places where I can do that and not have a concern with structure failures such as coating ribs & sheeting/rib caps before I bond them with heat.

AS point out above....
Like Jack Said :D

Kurt

[Ricardo RW]

... I used Titebond, and then used a paintbrush and thinned Titebond to make a small bead around the glue joint...

Do you mean like a fillet? Do you have a picture about it? I'm curious about it.

Thanx in advance.

[scaflock]

The one thing I've never done was to cut wood glue with distilled water. If I were looking to save some weight I guess I could do that.

AS point out above....
Like Jack Said :D

Kurt


Thinning the glue isn't done to save weight but rather to allow it to soak into the wood easier. Kind of like using thin CA instead of medium or thick.
Jeff

[dion9146]

I was thinking about this thread yesterday as I built the stab for my Sagitta 900. I used white glue for most of it, CA glue to bond a couple of areas that I needed to have instantly attached, and epoxy for the pivot rods.

Dion

[harlequin]

I use a small brush to apply Titebond. I keep the brush in a container of water to prevent the glue from hardening on the brush. I keep a rag nearby and dry the brush before use depending on how much I want to thin out the glue before applying. The water in the container gets contaminated with the disolved Titebond, but I figure that's a Good Thing!

Larry

[PizzaHunter]

For a long time I used only epoxy and CA, mainly because of time, but now I try to except CA usage, cause it smells badly. Very good fitting detail + titebond = strong, but ellastic bond. CA is not ellastic.

[lincoln]

If you're doing joints across the grain in very light balsa wood, then Ambroid is very convenient. I hear it's supposed to sand well too, although I haven't tested that part. A preglued end grain joint with Titebond in balsa can be stronger than the wood if done properly. I've seen it (break was near the joint but not at it) but I haven't done it myself.

[schrederman]

Ambroid is great for sheeting splices because it sands just like it wasn't there, but where can anyone find it these days? I haven't seen Ambroid in several years. I hate ca for splices and joining 2 sheets to make it wider. I always end up with a hump where the ca hardens the balsa, no matter how carefully I wick it in... :( :( :( I sometimes use thinned Titebond but, alas, I am impatient... :rolleyes:

I have a Houston Hawk project going and will use 4 different adhesives. I'll use some CA, lots of Titebond (thinned and un-thinned), Epoxy where appropriate, and polyurethane for the upper sheet/rib joints. I have some new PU glue that is supposed to foam less and be stronger than the Gorilla Glue and others that came before. I'm testing it before I use it...(what a novel idea :rolleyes: )

Jack

[seanpcola]

Jack,

Aircraft Spruce carried ambroid the last time I looked. I'll check the catalog tomorrow at work.

[markdrela]

Ambroid is great for sheeting splices because it sands just like it wasn't there, but where can anyone find it these days? I haven't seen Ambroid in several years. Duco Cement is basically the same stuff, but without the amber coloring or the noxious anti-sniff ingredient. Most hardware stores carry it.

[schrederman]

Thanks... I wouldn't know how to act if it didn't stink like Ambroid...:D

Jack

[slopemeno]

Jack- the forum "Small Flying Arts" has lots of Amberoid users, since it works great for small FF planes. Amberoid is now often only available in one tube size. I've found Duco at my local Orchard Supply, but I'll grab a tube of Amberoid when I can find one. The Duco does work well.

My Dad built his Gentle Lady with Amberoid about 1992 or so, and he put a lot of hard use on that plane, but it's still fliable today.

[FrogChief]

Ambroid is great for sheeting splices because it sands just like it wasn't there, but where can anyone find it these days? I haven't seen Ambroid in several years. I hate ca for splices and joining 2 sheets to make it wider. I always end up with a hump where the ca hardens the balsa, no matter how carefully I wick it in... :( :( :( I sometimes use thinned Titebond but, alas, I am impatient... :rolleyes:

I have a Houston Hawk project going and will use 4 different adhesives. I'll use some CA, lots of Titebond (thinned and un-thinned), Epoxy where appropriate, and polyurethane for the upper sheet/rib joints. I have some new PU glue that is supposed to foam less and be stronger than the Gorilla Glue and others that came before. I'm testing it before I use it...(what a novel idea :rolleyes: )

Jack

Your new poly glue wouldn't happen to be Loctite "Sumo" glue would it?

[schrederman]

Yes, Froggie, it is... know anything about it?

Jack

[rogerflies]

A Google search turned up several hits for Ambroid at hobby stores. The Ambroid catalog number is 1511.

Do a search for: Ambroid 1511 original

Roger

[John255]

White glue has it's place, and getting it into small places without overflow is not always easy.

Using one of these bellows syringes is a real pleasure, especially when applying glue to ribs before pulling sheeting down on D-tube wings.

Here for $1.99:
http://www.ptreeusa.com/glue_products.htm
Regards,
John255

[Speedo125]

Many years ago, when I was a kid. I spent a great many hours hunched over my building table gluing Berkley, Scientific, Goldberg, Jetco etc. control-liners and gliders together with Ambroid. I loved using the stuff and can't recall ever having a joint failure. I can still recall the smell of the stuff.

However, my mother used to say that I was always a little "loopy" when I came downstairs for dinner. It never seemed to affect my building though. My models usually came nice and straight.

[TLyttle]

Hahaa! My buddy and I used to build in his bedroom (which wouldn't qualify as a closet today), including doping. Many, many times I went home with a feeling that I now know as being drunk, really drunk. We both survived, neither of us seeming to suffer adverse effects from those "binges", nor did the models...

[lincoln]

I've seen Testor's wood model cement in several hobby shops around here in the recent past. If it's the same as when I was a kid, it's a lot like Ambroid. I think sometimes stores will have a general purpose glue which turns out to be a lot like Duco.

[schrederman]

Well, I tried the Sumo brand of PU glue, and I don't think it's really any better. It's kind of a milky, translucent white when it comes out and cures into a firm white foam. In the joint, it's a bit harder than the gorilla snot but I don't think it's as strong as Titebond. I did the upper sheeting on the outboard panels of my new Hawk with the Sumo glue. After curing it seems to be normal strength. I did the inboards with Titebond. Of course I used stacks of phone books to hold pressure on the ribs-to-skin joints.

The thing I really didn't like about the Sumo glue was the bottle. It had already crusted over in the bottle from some moisture incursion, and I almost didn't get it to break. I had to use a small screwdriver to break it up and get the plug out of the tip after I cut off the end for the first time.

Anyhow... I thought some of you might like to know about this stuff... Your mileage may vary.

Jack

[smitty14]

Wow - I built two powered sailplanes with Ambroid, the orange stuff a long, long time ago. I haven't heard of anybody using it in years, but did no modeling for about 15 years. I am soon to start on my first big sailplane and planned to use Titebond, CA only to tack, and epoxy for any main joints. Tried Gorilla on a spar in a slope plane and hated the bubbles. Won't use it again unless somebody can give me a good reason?

[TLyttle]

You are on the right track Smitty. I had the same experience with Gorilla, threw out a nearly-full bottle...

Not sure why everyone is so hung up on the weight of glue; it doesn't add a percentage point to the weight of the model unless we start talking indoor models.

[smitty14]

I was hoping so. I like the ideas of using a pipette or syringe for the titebond though. Do these applications only work with thinned wood glue? If so, since there were two percentages suggested I'm wondering if they are for different structures? Does the thinning work better for ribs to LE,TE, spars? What about LE sheeting, concentrated or thinned? Thanks for letting me pick your brains.

[smitty14]

Oops. Just re-read the earlier posts. Both read thinned and cut for the same percentage 66% glue.

[Dennis Everett]

When i build a flat foamy 3d plane i glue the carbon spar in with polyurethane glue , (gorilla glue ect ), it only adds 1 gram to the weight of the wing/spar , epoxy on the other hand adds about 11 grams , A good way to sand super glue is to use wet/dry sandpaper with a few drops of debonder on it , if you need high strength use the slowest cure epoxy you can get , i used to on my high performance gliders , heat up 8 hr epoxy on a heating pad , brush the spar system with a paint brush , would add a little weight , one plane lasted me 12 years before i sold it...Dennis

[Cebola]

Thin Ca from Zap, applied on the joins and, aliphatic glue in the joint.
Ambroid like filler gap, whit some balsa dust.
The important is glue 100% of all surfaces, no matter the type of glue, and be sure to avoid week points.
Epoxy glue, only for wing joiner’s whit micro balloons.
And remember, aliphatic glue, after a long time gets brittle, the glue and the balsa around.

Cebola
Brazil

[TLyttle]

Aliphatic goes brittle? I haven't seen that yet, and I have built models, furniture, and a car using aliphatic. I am sure that any brittleness would have shown up in the car, but no sign after 18 years...

As far as models are concerned, none of mine ever last long enough to go brittle!

[rogerflies]

"....I have built ..... a car using aliphatic."

Can't let that go without asking for more info. Tell us about it, please.

Roger

[TLyttle]

I built this years ago, on a Toyota pigup chassis; it came out 40% lighter than the original truck. I used various thicknesses of ply, and aliphatic exclusively along with a few (very few) nails, and a box of screws. It turned out tough, quiet, very durable, and fun.

I abandoned it in the back yard for a few years (other projects), which is how I know about the durability of the aliphatic. The aliphatic far outlasted the adhesives used in the plywood itself.

[rogerflies]

That's neat.

I especially like the fact that you can switch the steering wheel from one side to the other. :D

Roger

[schrederman]

Aliphatic is used by all the major guitar makers... and some minor ones, too...

[TLyttle]

Hahaa! Sharp eye there Roger, one of these days I will flip that pic back... just not today...

I have rebuilt/refinished quite a few furniture pieces, replacing the old hide glue with aliphatic, but I doubt if I will be around long enough to see which glue lasts longer. I have found out that wood shrinkage does annoying things to glue joints, even when the wood is old.

[2milehighguy]

Which Titebond is best for RC? I seem to remeber three different kinds last time I was at the local hardware store. Thanks, Bob.

[schrederman]

I use Titebond II... I'm not sure which would actually be better. TB III is like weatherproof or something and looks kind of bad... more like a formaldehyde glue. I've never tried anything else in the Titebond brand. I have used Elmer's Carpenter's Wood Glue, but found it to be so nearly identical to Titebond that I couldn't tell any difference. Generally if I'm using Elmer's I refer to it as Titebond... just out of habit...

Jack