New CA Over Old CA

[Dick Pacini]

I have a new stab and elevators to fit to my ARF P40 profile.  I have removed the old elevators by sawing through the hinges and part of the index finger on my left hand.   The problem is twofold, cutting exactly at the existing joint to maintain alignment when the new stab is installed and, can I re-glue with CA over the old stab seat, since it will probably have remnants of the original CA.?

[Dennis Moritz]

Use accelerator and it will stick. Otherwise it's very iffy. Probably won't.

[Tim Wescott]

You can hold the cut edges of your finger together and apply a bit of CA to that -- it'll keep you from leaking on your plane.

[john e. holliday]

Have to get smeone to hold the cut together so you can put the CA on or let them do the CA while you hold the cut.   

[Dennis Moritz]

Best thing to do is cut or sand the notch square. Check incidence. Very important. Stab needs to be centered along the chord line of wing. Lately I've been cutting a plywood platform, 1/16" will work or 1/32" to fit the bottom of the stab cut out. Again, check alignment and check squareness to wing, as viewed sighting over the stab from the back using disappearing wing technique. You know tilt stab up until the view intersects with the top of the wing. Fix alignment until top of wing disappears uniformly under the stab as you tilt. Use balsa wedges to hold stab in PERFECT alignment. My writing skills fail me at the moment to simply convey this common drill. Zap it with CA when everything is wedged PERFECT. I find that the plywood bottom piece keeps the stab truer or seems to keep the stab truer as plane is subject to the evil elements of humidity and temperature. Also the ply is a more stable platform when adjusting for incidence, squareness, alignment and etc. etc....

[Hoss Cain]

I have a new stab and elevators to fit to my ARF P40 profile.  I have removed the old elevators by sawing through the hinges and part of the index finger on my left hand.   The problem is twofold, cutting exactly at the existing joint to maintain alignment when the new stab is installed and, can I re-glue with CA over the old stab seat, since it will probably have remnants of the original CA.?

Man-O-Man, I would never do that. IMO Control surface joints deserve a slow (at least 15 minute) epoxy and 1/4 to 3/8 triangle support, at least underneath. Maybe I am into overkill a bit too much yet after all those years of cellulose cements, early epoxies, early "Hot-Stuffs" (CA) and even carpenter glues, CA is still not my choice for any joints significantly associated with any load function control surfaces or engine bearers, firewalls, landing gear main load mounts, and such. In the RC ARF world I have seen a number of these models come apart in the air and on the ground.
The worst being a guy tacking a G-38 from in front, which IMO should always be from behind.
That ARF, upon inspection, had a front end that I would not have even mounted a .40 on without substantial additional construction added. It  cost that person a thumb and a forefinger on the right hand.
Tail surfaces are subjected to significant load during maneuvers. That can cause a flutter which can cause a break at the fuselage. No real support sells ARFs.  

[bob branch]

Hoss

It turns out today's CA's are plenty strong to hold a tail on. Been doing it now for 9 years now since I returned to the hobby. In RC not only is CA the primarily recommended way of mounting them by the leading edge manufacturers (not the ones who wrote their manuals 15 years ago, they will still state epoxy) but many now recommend that the film covering NOT be removed from the glue contact surface. And this recommendation is on everything from small planes to 2 meter pattern ships. I think I saw the first recommendation for this method about 3 years ago. Been doing it ever since and not a single failure. When I kill a plane, I do not usually repair them. I destruction test them and break everything apart. I can tell you the glued over film method works from trying to pull it apart.

I know this will make a lot of folks nervous, but I'm just relating what is currently being done and what is working.

[john e. holliday]

Back in the day when I was playing with the twiddly sticks in RC the local hobby shop owner handed me a video, a kit and the various CA's.   Go build the plane and tell me what you think.  Need good tight joints and the proper CA for the intended use.   Lost count of how many hours were spent flying that plane.  At least four flights every time I went out with it for two years and back then I flew as much as twice a week.   Did it with a control line plane once before the CA got to me.  That is the only draw back is the CA fumes.

[Russell Shaffer]

Bob, do you poke some pin holes in the plastic film so the glue can get to the wood or just ca the thing together? 

[bob branch]

Russ

No its a direct bond to the film. I have noticed that all the planes that this is recommended with are covered in Ultracote. I do not think that means anything regarding the material per se. I think its just that most of the top arf manufacturers are using it now. I think only Tower's companies (Great Planes, Top Flite, etc use monocote any more. Anyway, Tower's companies are not on the leading edge of much of anything and I am not sure what their recommendations are on their stuff since I do not fly any of their models. But Top RC companies like Extreme Flight, Sebart, and 3D Hobby Shop recommend this method on their planes. Andy Jesky, Multi time US NATS Pattern champ tells me he has been doing it for years.

I was however, assembling a BiSlob arf this weekend and noted that the CA did not bond to the film as quickly as it does with utracote. I do not know if the slob is ultracote yet or not. The new Advanced level planes like T-Rex and SV-11 are. The stuff on the slob acted more like Brodak's own stuff which I do not care for. I was very suprised when I started in RC about 10 years ago that a very common structural failure in RC was horizontal stab failure. Usually it takes the form of a fracture of the wood right at the fuse.... right where the film would get cut. Companies blaimed it on an occasional piece of softer wood than specified and I used to strut all my tailplanes back when I started because of it. Some of the manufacturers felt it was from a stress riser from the cut thru the film and into the wood when the covering was removed. Thus the current recommendations. I have not struted a tailplane for several years now, since I started gluing to the film. But I don't stress a plane heavily. I mostly fly extreme 3D with low speeds and a lot of throttle management. Even pattern now is flown at slow speeds. Its the sportfliers who only know one throttle setting, wide open and zoom from one end of the field cranking in tight radius knife edge turns at each end with no throttle change that stress them.