I must have hear a hundred times that if you put ????? in a gap and drop some CA on, it make a greag strong gap fillier. My problem is that I don't remember what the ??? is. Corn starch, Baking Powder, Baking soda=???? Iremember it was a common kitchen product.

The reason I ask, is that i whacked a wing tip and broke the "hardwood joiner" for the wing half's on my Cermark SU-31. I didn't discover it untill I was cleaning up after three filghts after the repairs to the cowl and landing gear. After fixing the broken joiner and replacing a pulled aprart root rib, I decided to completely skin the wing and see what else happened that wasn't obvious. It turns out that there is an 8" crack in the LE sheeting on the top and about a 4" crack on the bottom there is no LE damage or rib damage though. One of the cracks has opened slightly, just enough that I would be happy with just thin Ca for a fix. Iremember that one of the above powders packed into a crack and the hit with CA gives a strong repair. Which powder???

Don</p>

Through three decades of experience I have found that the "best" filler comes from sanding. I save the dust in a container and then pack it in a crack with the back of an exacto blade then use thin CA over the top. Sands well and seems to be structuraly sound, as in I've never had a failure attributed to it.

It is baking soda. The old fashion Arm and Hammer is fine. Remember putting CA on the baking soda will make it had like a rock and it not very easy to sand. Over the crack you might consider trying some light fiberglass.

Yeah, Don. I tried the CA and Baking Soda mix but it comes out like crystal and is really tough to sand down. But, it is lightweight. For a quick fix, I'd go with the sawdust and CA... probably just as light, or for an overnight thingie, sawdust and epoxy, which may be a tad bit heavier. For Glow, well, that won't matter much. Electrics, well, used sparingly it should be fine.

CGr.

Baking soda as a filler only works if the gap is closed at the bottom. Even a microscopic space will let the baking soda fall through. As pointed out, the filler will be very hard when cured, so I carefully wipe off excess baking soda from the surface before applying the glue. And do not let the tip of the nozzle touch the baking soda or it will be instantly clogged. I only use this technique for filling where the issue is structural and not cosmetic.

That's probably why sawdust and epoxy or something like Elmers would be a better choice. Just mix up a mud mix and fill in the cracks, smooth it out, then sand it lightly once it's all set.

CGr.

Thanks for the replys. Wouldn't you know it, I just vacuumed up the sawdust on my bench yesterday. I guess it wouldn't take long to manufacture another bit though. Ithink I'm going to see if I can get my finger into the wing and glue some 1/16" balsa backs under the crack, then just fill the crack with balsa putty. A closer inspection showed that only the last bay at the tip, had the crack running away from the LEstock. That is where the backing will be needed.

Don

Ha.. well, cleanliness is next to ..... ok.. ok.. [sm=49_49.gif]

Sounds like a plan, Don.

Ah, you are near Vandenburg, I see. Nice area. I worked there several times, both for the Coast Guard, installing Differential GPS and for the FAA doing RADAR stuff at the site near SLC6.

CGr.

i use sanding dust as a filler.baking soda get hard like a diamond,real tough to impossible to sand down.if you plan to sand use wood sanding dust with a wood glue like titebond.i mix some glue in a cup with the dust into a sorta paste and push it into the crack,after it dries you can sand it real sweet..strong as heck.

+1 for the sawdust/ca, works much better than anything ive tried

We are not to far from Vandenburg. We've seen some really interesting rocket launches. One was just after dark, and when it broke into the sun lite, it was the most awsome sight I believe I ever say. From a gold glow to a huge ring with cross hairs and the rocket was in the center of the cross hairs. For some reason, we just don't see them or the noise is so low that we don't hear them any more.

If you ever get back out this way, give me a shout and I'll take you out to our field.

Don

Will do!! Thanks for the invite!!

Because both sites I worked at were near the space launch complex's (SLC's), we were not allowed to go in to the sites if there was a scheduled launch until at least an hour after the launch. We could hear them, but never saw them because they were on the other side of the "mountain".


CGr

Use Duco cement. It is sandable and shrinks when it cures. This will render the crack imperceptable because it will pull the crack closed. CA on an outer surface is a no- no unless you don't give a rat's butt what the airplane finish looks like! CA won't sand at an equal rate to its surround so the end result is a bunch of high and low spots.

Although it doesn't completely solve the CA sanding issue, it goes a long way. I use 320 wet or dry glued to "Craft Sticks" (popsicle sticks without the popsicle) with 77 spray adheasive. I then cut out the sticks from the sheet with and Xacto knife. The 320 does a fairly good and agressive job on the CA, but it really to fine to do much to the balsa unless you dig in an edge. The sticks get loaded up quickly though.

Don

Hi!
There is nothing compared to brown micro balloons and either 24 hour epoxy resin...or polyester resin.

We are way over the mountain here. If you happen to be looking at the right spot though you will see a big flash of light behint the mouuntain then it goes dark then the rocket makes it's apperance. Late afternoon, early evening are the best though. About five years back, we had one launch that lefta smoke trail that was lit up by sunshine and it looked like a kids scribbles, Loops and swrils. The colors were orange and purple. My son was living in Phenoix at the time and he saw it from there.

By the way, Vandenberg got a mild shaking this morning. We had a 3.1 just off shore at Lompoc.

Don