Glue fillet holes.

[darthgriffin]

My first non-plastic kit is an Estes Photon Disruptor and I'm having a glue problem. The glue fillets are drying with holes in them. What am I doing wrong or how do I prevent this?

 

[fyrwrxz]

Okay... first, looks like wood glue-good choice! second, you may want to thin it *just* a bit. Third, drag a wetted finger or stick or tool of your choice (I've heard spoons are good) over the fillet to eliminate the bubbles and give a smooth surface. Lastly and just FWIW, you may want to rethink the grain direction on the fins...they should really never run parallel to the body tube, but these are small enough it shouldn't make that much difference. Just my farthing's worth! Keep building and keep posting, we all want to see the finished product. ( we live vicariously.....) Straight smoke and good chutes!

 

[[POW]Eagle159]

Also try a few thin fillets....The thicker it is the more it will shrink when it dries. I like to put a thin bead of glue on and then smooth/wipe off extra glue.
And as stated above the balsa wood grain should go perpendicular with the body tube....or with the leading edge of the fin.
Nice build!:horse:

 

[les]

You can easily fix it by doing another layer. I just use my finger to wipe across the filet. If you still see bubbles, you can also use a pin.

 

[luke strawwalker]

This is VERY common with wood or white glue fillets. The trick is to lay them on VERY VERY THIN in multiple layers. White and wood glue shrinks as it dries (Yellow wood glue shrinks more than white does, but both will do this when used thick on fillets) and this opens up voids in the glue application as it dries.

You can always go back and just fill in the voids with more glue and fix it that way, but usually you'll have to do this two or three times at least before you get all the voids closed up permanently.

The best way to fix this is to use a glue that doesn't shrink appreciably as it dries. Next time you're in the lumberyard stores (Lowes, Home Depot, Menards, ETC) pick up a bottle of "Titebond Moulding and Trim Glue" over on the shelf by the wood and white glues. It's in a gray bottle/label with black printing. Use this stuff for your fillets and they'll go on beautifully, stay put without running (unlike regular "thin" wood or white glue which tends to run or sag before it sets up) and there shouldn't be ANY voids or pits in the finished fillet... best of all it's a thickened water-based white glue, so you can smooth the fillets down with a damp finger, unlike using epoxy or other glues that shouldn't contact your bare skin. The Trim Glue dries almost clear and is really the cat's pajamas...

Later and good luck! OL JR

 

[o1d_dude]

What Luke said.

The Titebond Molding and Trim Glue has recently been repackaged/renamed so you may have to look for "Titebond Molding Wood Glue" or some variation thereof.

It still says "Molding and Trim" in faded letters near the top of the label but really emphasizes the "Wood Glue" in large bold print.

Good stuff. I did some filleting tonight and laughed recalling that Luke originally set me on to the "wet finger" method a couple of years back.

 

[Marc_G]

+1 for TMTG!

 

[gpoehlein]

I've found that Aileen's Extra Thick Tacky Glue is also really got for one application fillets. It is really thick that it doesn't shrink much when it dries (that's what causes the holes).

On larger rockets (I don't bother with models less that BT-60 and anything smaller than a 24mm motor mount) you can also use epoxy for fillets. I apply masking tape (use a good masking tape like 3M Blue) about 1/4inch from the joint on both fin and body tube. Then use a stick to apply enough epoxy (5 minute is OK, 15 minute is better) to make a fillet there. Do just two fillets at a time on adjacent fins and don't move until it sets (you want it to settle into the fin root by gravity). Oh, and remove the tape as soon as the epoxy sets and don't wait until the epoxy dries. After the epoxy is set on the first two fins, rotate to the next pair and repeat (yeah, it's easiest to go ahead and mask all the fins before you start and then just take then off as you work around the rocket). Don't put too much epoxy in each fin joint - you want enough to go to the tape but not up on the tape. The tape is really more for keeping the edge straight and keep dribbles of epoxy off the fin ad body tube.

 

[darthgriffin]

This is in fact my wife's Elmer's wood glue. The one I have in the garage dries more clear, but creates the same voids. I've found it also doesn't want to come out of the bottle below 40* F. I started out with less glue and wiping clean, seemed the right way, but it almost disappeared once dry so I tried to overcompensate.
Thanks to all who pointed out the wood grain orientation is wrong. Good job, Estes! The larger fins were cut properly though, and I'll be sure to remember that tip when I start rolling my own. This may be a little too ambitious for my first wood-fin kit, but hey it was on clearance. Who can pass that up?

Ok, now do I have to fill in these voids, or can I sand/dremel this down and start again with a flatter surface?

 

[o1d_dude]

Many wood glue formulatins will not set up properly at temps below 50 degrees.

Warm your glue up to normal room temps before use.

 

[darthgriffin]

That's why I used my wife's. She keeps her craft stuff in the house.

 

[luke strawwalker]

This is in fact my wife's Elmer's wood glue. The one I have in the garage dries more clear, but creates the same voids. I've found it also doesn't want to come out of the bottle below 40* F. I started out with less glue and wiping clean, seemed the right way, but it almost disappeared once dry so I tried to overcompensate.
Thanks to all who pointed out the wood grain orientation is wrong. Good job, Estes! The larger fins were cut properly though, and I'll be sure to remember that tip when I start rolling my own. This may be a little too ambitious for my first wood-fin kit, but hey it was on clearance. Who can pass that up?

Ok, now do I have to fill in these voids, or can I sand/dremel this down and start again with a flatter surface?

I wouldn't... (Sand and restart).

Just fill in the voids with more yellow wood glue. The stuff will probably shrink and in the larger voids it will probably open up a smaller pinhole again, but you can make another pass or two and fill these in until they close up completely.

I learned one time not to go TOO big of a fillet, even with TMTG (Titebond Moulding and Trim Glue). The stuff doesn't shrink appreciably during curing, but on a large enough fillet it WILL still open up a void... I was filleting between 3 BT-50 tubes joined side to side (gluing "SRB's" on a center tube) and the fillets were kinda big so that I could get a finger down there in between them to smooth it out... opened up voids bigtime... had to refill about 6 times before I finally got them all closed up and smooth. First and only time I've had that happen.

When I did the Zooch EFT-1 build, https://www.rocketryforum.com/showthread.php?t=29228&page=2 I made a tool to inject and smooth small glue fillets between the three tubes, using a kid's medicine measuring syringe (which I get freebies every time I pick up a prescription for Keira) and some Testor's Gluing Tips that I picked up at Hobby Lobby. Then smoothed the fillets with a bamboo skewer and used the sharp end to prick any bubbles from air trapped under the fillet. Seems like no matter how careful you are laying down a fillet, there WILL be SOME trapped air underneath it that seems to migrate and force it's way out, creating these voids and holes in the fillets that we see with yellow or white glues... it doesn't seem to happen with epoxy, probably because epoxy cures uniformly through and through, whereas white/yellow glues cure from the outside in via evaporation...

Later! OL JR

PS. BTW, you might want to check out papering fins... it's REALLY simple and easy to do and makes fins EXTREMELY strong, for VERY little additional effort and weight. There's pics and a description of the process in my Zooch Vanguard Eagle beta build thread... https://www.rocketryforum.com/showthread.php?t=13600

 

[o1d_dude]

That's why I used my wife's. She keeps her craft stuff in the house.

Wait. It gets down to 40 degrees in Mesa? LOL!

 

[darthgriffin]

Wait. It gets down to 40 degrees in Mesa? LOL!

I do most of my stuff around midnight while the kids are sleeping. 40 would be the low. I haven't even gotten my jeans out of the closet yet. We can wear shorts year round.

 

[Winston]

I second the praise for Aleene's Extra Thick Tacky Glue and also have great success with Aleene's Fast Grab Tacky Glue. They're both available in virtually any crafts section including those at Walmart's, it's cheap and works fantastic for bubble/gap-free model rocket fillets.