bencav84

Good evening all.

Throwing together another ARFT at the minute, and after gluing the wing halves together using cold thick 30min epoxy, I was wondering of a suitable white glue would work as well? The Glue I have is waterproof 'wood glue' slightly flexible when dry (much the same as 30 epoxy) but much easier to get to soak into the wood. Any thoughts??

I am not sure if this is the same as (elmers???) yellow glue that you use over the pond, all I know is that t is a polymer UPVA glue.

Cheers!!

BC

p.s. Wasnt planning on using for joining wings, just to glue the vert and horiz stabs in place!!

Texastbird

A couple of ARFs I have built lately said to use CA on the tail feathers, but I stuck (no pun intended) with epoxy. If it is a good tight joint, I don't see why ithe waterproof wood glue wouldn't work just fine. On some loose fitting joints I have used polyurethane "Gorilla" glue with good results. I do agree with the epoxy on the wing joint. I have seen some come apart that weren't properly joined in this area.

carlosponti

My Feedback: (1)

the conventional wisdom i was taught was that use epoxy in high strength areas like joining wings and installing vertical and horizontal stabs. having said that I have read from plenty of forum members about using wood glue for the stabs. frankly from what i have learned about glues from my woodworking is that wood glue is sufficient for alot of areas and epoxy good for adhering dissimilar materials. I have glued table tops together with nothing but a butt joint and some wood glue, and if you make sure to use a planer or jointer to smooth the joint its a sufficiently strong bond. I would personally have confidence in using wood glue on the stabs because its basically a [link=http://en.wikipedia.org/wiki/Dado_(joinery)]Dado[/link] joint. i have the problem though that i don't have the confidence sometimes and fall back to the conventional wisdom. sure the epoxy is a strong bond but i have my doubts its any stronger than wood glue in the situation. for firewalls and such you are really joining dissimilar materials, ply to balsa, which result in weaker joints. You will get all kinds of different answers on this subject.

On the subject of white elmers glue to yellow glue. its bit confusing because some yellow glues that are advertised as wood glues are Aliphatic resins and some are PVA's. I use titebond for building airplanes as well as woodworking projects. which is an Aliphatic resin but titebond II and III are PVA the waterproof titebond being something different all together. the elmers yellow wood glue is a PVA as well.

opjose

And what is the white Elmer's?

aussiesteve

White Elmers is "Aromatic" PVA, Yellow is "Aliphatic" PVA.
The two terms refer to the bond linking of the polymer chains.

I have always worked on the principle that as long as the glue is sronger than the material it is gluing - it is strong enough. Try using the glue to join two bits of the material and when it is properly cured - pull the joint apart and see what gives - the glue or the wood. If it is the wood - then the glue is adequate. - NOW FOR THE DISCLAIMERS

Chemical resistance also plays part - that is one of the reasons for Epoxy anywhere near an Engine bay and why I wouldn't use personally use aromatic PVA on a float plane (Water resistance).

As has also been very well stated - Joint design and fit is also important. How many firewalls do we build where pretty much the entire glued joint is under tension? Such as the ones where there is a bit of Tri Stock Behind the firewall onto the flush cut fuselage sides? - in those cases you want a glue with good tensile strength (usually we use epoxy for that reason too). If the glued area is only under shear or even better - compression - then the glue can be just about anything as long as it is as strong or stronger than the material being glued.

Then there is fatigue resistance of the glue to consider too.

I have had this argument with some of the ARF manufacturers when I have seen weaknesses in their design coupled with the glue used.

bencav84

Thanks fellas, I would totally agree with, and indeed it was this fact that prompted mt thoughts, that wood glue ios generally stronger than the wood itself. I have tried the glue 2 bits opf pine together then break when dry - always the pine which gave way first.

To add another twist, elmers glue isnt the big fish in the UK (at least not with model people anyway) the brand of choice is EVO-Stik, which is a waterproof PVA white glue - goodness knows what the heck it is made form!!

I always use a star calmp on the tale feathers to ensure the forks in the fus are clamped to the stabs, so white glue it is!! I hate gluing the clamp to the airframe!!

Cheers agian!!

Ben

fhm101

Any thoughts on Devcon gel epoxy? I'm new to planes, but I've been building fishing rods for years and Devcon 2 ton is the best thing I've found for attaching cork grips to glass or graphite blanks.

My first plane is a Lil Rascal and the horizontal stab simply lays on a notch cut into the rear of the fuse. Aside from driving me crazy with alignment issues, there are also what I would consider some largish gaps that I want to make sure are filled and I'm afraid my trusty 2 ton is too thin to get that job done.

I thought about changing the assembly sequence by joining the vertical and horizontal pieces first as this would really help with the alignment issues, but then I have very little surface left on which to rest any weights to hold the assembly to the fuse when it's glued up to insure horizontal alignment.

Any and all thoughts and/or advice on both glue and assembly method would be greatly appreciated.

bencav84

Dont use glue to take up gaps, adjust the wood to get good face to face contact, epoxy is very brittle when used as a filler, it only gains strength ehrn it has seaped into wood.

Alternatively, mix some milled glass fibre with epoxy and use that to take up any small gaps.

Never heard of the devcon gel, but how is it thin if it is a gel?

BC

fhm101

I've never used the gel either. I've been using Devcon 2 Ton and 5 minute which is thin enough to run before it sets. Thanks for the tips on gap filling though.

pdansalvish

My Feedback: (23)

Before PICA when out a business, I used their Glueit. They actually had you do a test between it and epoxy, using two pieces of plywood. I could break the plywood but never the joint. But, I still admit I use 30 minute epoxy for gluing wings together and Titebond II for most everything else. I try and avoid CA as much as possible.

captinjohn

I have heard of using Titebond glue thinned down a bit and brushed into places that look a little lite on glue. Some ARF,s are lite on glue in places. A small 1/8 inch brush can reach into tight places. Best regards Capt,n

jship

My Feedback: (4)

I take a large cup and put 2" of water in heat it up andf then place the 30min epoxy in it. No longer working with cold thick 30min epoxy.[>:]

John

bencav84

Cheers John. I will gove that a go next time!!


For the record, I ended up using wood glue. Doing a rather exagerated pull test, the only movement weas the back of the fus merrily bending under strain. I think it is safe to say the wood glue is strong enough!!

one thing I did notice though, wood glue has very little grab so lots more pins and tape were required than if using epoxy. Not a problem....if you know about it first, more hassl;e if you dont have any pins at all and the tape is in the loft!!!

BC

NM2K

My Feedback: (14)

I too like aliphatic resin glue (Titebond) the best, but the joints must be near perfect for this glue to work satisfactorily.

Don't hesitate to CA pieces of scrap balsa into gaps, etc. You can easily trim it/sand it to the correct dimension. This gives the aliphatic resin glue a good purchase due to increased glueing area.

I too use a small 1/8" brush for applying the yellow aliphatic resin glue. If you want super strong joints with this glue and have already added balsa scrap to fill gaps and trimmed or sanded for a good surface - whew! -, apply a little glue with the brush, but make the coat very thin on all surfaces to be joined. Wait for a skin to form on the glue and then add a tiny bit more glue. It is now time to join the pieces, but be quick. This stuff will start to set up much quicker than one would suppose.

I use CA for tacking or filling with balsa scrap, but I try to avoid using CA as much as possible. I'm already sensitive to the fumes and if I get over exposed, I'll have a bad sinus headache for a few days if I'm not careful.


Ed Cregger