Glue Fillets
 

Hey everyone. Something I am wondering about is adding glue fillets to all joints after the majority of construction is done. Does everyone do this, or do some of you not bother. I have started construction on my first kit ( a 4*60 ) and am using Titebond 3. So far everything is going great. A couple of small mistakes, but to me and what I've read on other builds, nothing to sweat about. The wing halves are 75% done, but not joined or sheeted. I did put the dihedral brace in the wing halves, clamped them together and weighted one wing half down to my board and got 1 7/8 in. measurement on the opposite wing tip. Very little gap at the two W1 ribs at the joint. Both halves seem to be straight, so I guess I must be on the right track so far. I must agree with most of you when you say this is addictive. I am having a blast doing this build. Also, starting to think about the next kit.

P.S. If anyone has some good tips for the glue fillets, please let me know. I am planning on doing them.

Thankshttp://www.rcuniverse.com/forum/js/f...ular_smile.gif

RE: Glue Fillets
 

If you do them at all, be sure to wipe off any excess. Wood glues don't cure well if they are globbed on

RE: Glue Fillets
 

I use my index or pinky finger for fillets for I have much better control than a popsicle stick or similar. Also by the angle you use you can cover more or less of the joint. I will do fillets where the rib meets the shear web on one side of web, ot both or where formers meet fuse but thats about it. I don't recalll if the 4star 40 vertical tail has tri-stock at the base or not but for planes that don't have any support, I will usually add some small tri-stick in place of fillets at that location.
Mike

RE: Glue Fillets
 

Use Ambroid glue. Put it on, let it dry, then put a second coat on, thee joint won't ever break.

RE: Glue Fillets
 

And use your finger so you can chew the dried remains off later.

RE: Glue Fillets
 

You can also get one of these handy-dandy little oral syringes at your local drug store.

RE: Glue Fillets
 

Mmmmm.... Ambroid!

RE: Glue Fillets
 

I second the syringes!! EXTREMELY useful for tight places and controlling exact amounts and laying beads.

RE: Glue Fillets
 

These work great and you can stick a T-pin in the end and it's allways ready to use.

RE: Glue Fillets
 

Between builds, I take the glue out of the syringe and clean it with water.

DURING a build, I just stick the syringe nose-down in a glass of water and it's always clean and ready to use

RE: Glue Fillets
 

Hey Guys, Thanks for the ideas. I stopped in a the local Vet. yesterday and picked up a couple of 10cc syringes and a needle. Wasn't sure how hard the needle was but tried a file on it and it did cut. I filed the point off the needle, cleaned up the small burrs and mixed some glue (about 2 easpoons ) with a couple drops of water. The needle and syringe worked great but the glue was a little runny. Tried again with unthinned glue and it worked just great. I thought I would have to thin the glue to get it through the needle, but not so. The needle I got is .050 O.D. and approx .032 I.D. The needle sure makes it easy to get into all the tight spots without making a huge mess. I got a beautiful little bead of glue right where I wanted it. Takes a little practice to control the amount of glue, but this does work very well.

RE: Glue Fillets
 

I would recommend not using glue fillets on thin wing sheeting. Especially if the wood is low density contest wood. This is because most glues shrink and you can end up with a hollow "bones" look to the skin after construction is complete. The other reason is that it adds weight and the strength of the glue to the sheeting is more than enough.

I do add some fillets at higher stress areas like where the ribs meet the spars, but in general just depend on a good fit with minimal glue.

RE: Glue Fillets
 

Who said anything about sheeting?

RE: Glue Fillets
 

Isn't that the sheeting in post 6? I think he saying the fillet will shrink and cause a visible line on the outside, maybe I misunderstood what he was talking about? I never noticed the effect but it makes sense.
I don't worry about adding fillets, I believe you're better off getting the glue between the parts rather adjacent to. Fillets are sometimes necessary when the fit is not so good.
I would not use Tiebond III either on the complete build, only where strength is an issue, I find it doesn't sand very well or at all. White glue is all you need for most parts.

RE: Glue Fillets
 

Yes, but that picture was to show the syringe. And that is not thin sheeting

RE: Glue Fillets
 

Thin sheeting would be 1/16" balsa or thinner. Contest balsa would be under 7 lb/cu foot balsa. The localized stiffness of material is proportional to the thickness squared, so 3/32 balsa is slightly more than double the stiffness of 1/16" balsa.

RE: Glue Fillets
 

I do fillets! Fillets add strength with a worthy addition of some weight. As suggested above, apply the extra glue neatly. Aft of CG and tail, pay very close attention to amount of glue used to avoid balancing issues.

RE: Glue Fillets
 

Am I correct in my thinking that glue fillets are a simple way of building a mechanical mechanism to keep a butt joint in place?

Be forewarned that Titebond fillets dry to a dark amber color. If you are planning a transparent covering consider something else.

For what it's worth a local building guru uses aliphatic resin (Titebond original is his preference), a wet cotton swab to clean off all glue residue and finally thin CA on the inside corner of all the joints. Yea, he's pretty anal and goes to the extreme of cutting a dado joint in lieu of butt joints. All of his coverings are transparent - just to show off his craftsmanship. And how much time and patience do YOU have? ;)

RE: Glue Fillets
 

I got the patience but definitely not the time to that kind of work[sm=71_71.gif]

A glue fillet is a fluid type of triangular stock. Not as strong, but better than nothing...if you think there is call for reinforcing. Of course glue is to be applied first to the parts being fitted, THEN , on go the fillets.

RE: Glue Fillets
 

Here's my LT-40 wing with liberal Titebond Standard fillets ...

No transparent covering for THISwing!

RE: Glue Fillets
 

You have to be careful when using glue fillets. If they are too large, the glue will cure on the outside, but then it will have a center of still-liquid glue...kind of like a candy with a hard shell and a liquid center. It will take a very long time for that bit to cure, since the water will have to migrate out from the center, through the hardened shell.

If you are using fillets of glue to make a joint stronger, then you need just enough glue so that it's visible. Much more doesn't really add to strength, and it does add up to a lot of weight. If you run a fillet along a joint, and then use a cotton swab to remove as much as possible, the very small bead left is enough to insure a good joint. However, properly done, you need zero glue as a fillet. If you do any testing, you'll find that a fillet adds little to a properly-done glue joint. If you need to add strength, then glue in a bit of glass cloth or chopped fibers...even add a bit of wood stock to brace the joint. Those are ways to add real reinforcement.

RE: Glue Fillets
 

If you use a cotton swab, or any other tool, to eliminate the triangular shape of the fillet, you are defeating the purpose of the fillet.

True, it should be made using the least amount of glue possible.

Because the Triangle is the strongest geometric shape, then by adding glue fillets as needed, you will most definitely increase the strength of the structure.

RE: Glue Fillets
 

Hey folks. I thought I would try uploading a photo for the first time. This is how most of the fillets turned out using the syringe and needle. Of course some of the early ones don't look like this.

RE: Glue Fillets
 

Perfect

RE: Glue Fillets
 

Actually, the liquid glue left will form a small fillet with the typical curved surface. Too many people make the glue fillet much too large. It doesn't take much. If you're going to make them, the ones pictured a couple of posts up are perfect, as Minn said.