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Fast Lad Performance . Esprit Model . Thunder Power RC

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Main Discussion > 2 part epoxy just caused a mid flight failure, what do you use as a good adhesive?
 
 
speeddemon370
Veteran
Location: Spruce Grove, Alberta, Canada

Ok so I switched my collective to +12 -12 a while ago but haven't gotten to fly it till today. Man was I having fun. Inverted climb outs, some inverted hovering, some really out of shape tic tocs, mostly just punching the collective back and forth and having a blast. On the second battery pack I noticed that I somewhat suddenly had to be quite heavy on the right rudder. I broght her in for a landing and after a thorough investigation shrugged my shoulders and put on another 2 points of right rudder trim. I thought it might be all in my head or the extra pitch was constantly making it torque to the left for some reason. So I'm back up in the air about 60ft off the deck and inverted when the whole thing just loosens up and blasts into an uncontrollable pirouette. I fluked out and somehow brought it back rightside up and tried to weathervane it through fff into a skidding landing (crash landing). No dice, It was spinning pretty fricken fast when it hit....After a whole lot of cussing and head scratching I found the culprit. What type of glue would you guys reccomend so I NEVER EVER have to go through this again. The glue on here is 2 part epoxy that already has at least 30 flights on it. Maybe more but I don't keep track. It's the eflite ball links and a piece of generic carbon rod.

Thanks in advance. I'm gonna go repair the obvious damage and look for more:
Bent feathering shaft, bent flybar, most control rods appear to be slightly bent, and one separated push pull linkage that I am going to BURN in a pool of gasoline and smile the entire time!

with 2 ears and 1 mouth you should listen twice as much as you talk
05-07-2008 05:15 PM
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speeddemon370
Veteran
Location: Spruce Grove, Alberta, Canada

Sorry for the duplicate post. Cookie issues.

with 2 ears and 1 mouth you should listen twice as much as you talk
05-07-2008 05:17 PM
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jphilli
Senior Heliman
Location: Marietta, Ga.

I always used super glue. But some people will advise against that saying it's too brittle although I've never had a problem.
05-07-2008 05:18 PM
 
 
Brokenlink
Senior Heliman
Location: Oakdale,Ca.

You need to get some of the epoxy on the inside of the link.If it is too tight it will just push it off and you will end up having what you have right there,only on the end of the link and the rod.You can see now that it wont work so hot.
05-07-2008 05:23 PM
 
 
rstacy
Key Veteran
Location: Rochester, NY

Its hard to tell from the picture but it looks like the problem is more application than glue.
You don't have enough of the rod inserted in to the ball link to get a good grip.




www.kylestacy.com
Team MAPTERGY.... nuff said
05-07-2008 05:24 PM
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RappyTappy
Elite Veteran
Location: Las Vegas, NV

From what I can tell by your picture, the stud looks to be still in the carbon, it looks like the ball link stripped off the threads.

It looks like you may have had enough threads in the link (at least 5 threads onto the stud is recommended) so you may have accidently over tightened the ball link once it bottomed out on the control rod which ended up stripping plastic out of the ball link. A tip, when threading on a plastic part, once it bottoms out stop tightening or it will strip.

I've been flying for 10 years on 2 part epoxy control rods all the way up to 90s and I've even split control rods in flight and the epoxy held it together to land.

Chris
Rex 500
Burning them electrons :D

Forever Brothers
Mickey Tylo
05-07-2008 05:24 PM
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xcellgasman101
Elite Veteran
Location: WOODWARD, OKLA....

Looks like to me,,, you didn't have enough of the ball link on the rod,, Here is something else you can do to keep this from ever happening again,, Once you have the ball link glued on,, drill a small hole thru the link and rod out the other side, then mix up some more epoxy, with a toothpick, and push it thru, then cut it off flush then it will never come off again,, unless you break it,, Good luck,,

Also.. did you hit throttle hold??? if not why??? Always hit throttle hold when you get a uncontrollable piro, this will take the torque off and let the tail stop,, Well maybe not if the rod gets unhooked, like yours did,, but it will help.... XGM/VGM

John Crotts
www.soonerhelicamproductions.com
05-07-2008 05:39 PM
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speeddemon370
Veteran
Location: Spruce Grove, Alberta, Canada

Thanks guys,

To answer some of your questions it's not a threaded rod. It's a homemade link. Lot's of the guys use them at the field and apparently nobody's had a problem yet. I agree that there probably should have been more of a stud through there. I'm certianly going to use xcellgasman's tip of drilling a hole and putting more epoxy on it. I like that one. I'll also be sure to make it so it's not such a snug fit so I can potentially get some more surface contact and a deeper insertion (get your head out of the gutter).

I did hit throttle hold, right before I hit the ground. I didn't wanna have it freefall from that altitude by itself so I brought it down as gently as I could and flicked it last possible second. It would have landed fine except the vertical stabilizer snagged the grass as it was still spinning and I had a minor tip over. I almost have it all back together now and the only casualties were the flybar and feathering shaft so I'm pretty happy about that. I even tried (tried in real life as opposed to the sim) a new tecnique today, modifying my cyclic input at a certian point during each piro. So it was a somewhat "lol" controlled crash.

Man am I ever thankful for my sim. Otherwise this would have most certianly been a lawn dart creates small crater crash with way more casualties. Boom, tail, tailrotors, probably stripped servo or 2, rotors, canopy, spindle, mainshaft, blade grip or 2......... man the list goes on and on. Whew, I think I dodged the bullet on this one. Better go buy a lotto ticket!

with 2 ears and 1 mouth you should listen twice as much as you talk
05-07-2008 07:03 PM
HOMEPAGE  
 
 
RappyTappy
Elite Veteran
Location: Las Vegas, NV

You can't expect epoxy to adhere to the plastic unless you rough up the surface of the rod and the plastic on the inside to give the epoxy something to grip onto. Well, I think any guy whos been in this hobby for some time has had some hard lessons to learn that ended up replacing parts.

The toothpick method sounds good and all, but drilling a hole through that small of rod will be real fun if you plan on doing it by hand. You'll need something to hold the rod steady, like a vice and then a press to keep the drill bit straight and steady. Even then it will take a while to get right, if at all because its such a small rod.

You would be better off and much easier to just get a threaded rod imo.

Chris
Rex 500
Burning them electrons :D

Forever Brothers
Mickey Tylo
05-07-2008 07:10 PM
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Dr.Ben
Elite Veteran
Location: Richmond, VA, USA

There is no situation that I'd trust any expoxy adhesive to bond a rod up into a plastic link. Use a threaded rod. JB weld or slow CA it into the carbon rod and then thread the link onto the stud.

Ben Minor
05-07-2008 07:15 PM
 
 
xcellgasman101
Elite Veteran
Location: WOODWARD, OKLA....

I agree with the threaded rod,, and yes I do use a drill press when pinning a part, but it's not that hard, just make sure you use a small enough drill bit, that will go thru the inserted rod, but not so big, it cuts the inserted rod into,, Hope this helps,,, XGM/VGM

John Crotts
www.soonerhelicamproductions.com
05-07-2008 07:16 PM
HOMEPAGE  
 
 
ferincr
Senior Heliman
Location: San Jose - Costa Rica

For plastics I love a glue from Devcon called PLASTIC WELD it comes in one of those siamese syringes like some epoxies, it is a two part but it's a methacrylate (or whatever it spells) smells like melted acrylic (like the one the dentists use for temporary refills) and it glues almost any plastic.
Sometimes the glue is the least of the problems, meaning that the prep of the surfaces is most of the time more important than the glue itself (clean it thoroughly with a degreaser and scour it before gluing) better yet (as people suggested above try to use some sort of threaded end into plastic ball links

Intelligence chases me, but I'm a lot faster! Fernando
05-07-2008 07:22 PM
 
 
tchavei
rrProfessor
Location: Portugal

Quote 
To answer some of your questions it's not a threaded rod. It's a homemade link

You're kidding right? Even if you build your own tail linkages (like I do), minimize the need of glue. Carbon and metal will glue very well together with the use of epoxy and some creative cutting on the metal but a plastic ball link will never form acceptable bond with a piece of flat metal no matter what glue you use.

The proper way to do this is:

1. find 2 metal threaded inserts (2.3mm or 3mm). Plank guys is them alot to build piano wire linkages.

2. get a 5mm carbon hollow rod (5OD/4ID is very light yet resistant but 5/3 will do also)

3. find a 6mmOD/5mmID brass tube and cut pieces of 10mm

4. make deep cuts into the metal inserts with a dremel all around

5. make 1 hole 5mm from the carbon rod end

6. get some teflon heat shrink and place it over the carbon rod at the places where it will be in contact with the guides

7. glue the inserts in and make sure that some epoxy flows out through the hole you drilled into the carbon rod

8. while everything is still fresh put the 10mm brass tube over it to make a solid bond between the metal insert, carbon rod (through the hole) and the brass cover

9. let it cure for 24h (it doesn't matter if it is 30min or 60min epoxy, let it cure!)

10. get some 2.3mm ball link (or 3mm if you used 3mm metal inserts) and screw them on to the desired length and heat up the teflon heatshrinks from point 6 to hold them to the carbon.

11. go fly

my two cents

Tony


--------------------
"Perfection and patience usually walk side by side..."
05-07-2008 07:26 PM
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K-ROK
Heliman
Location: REDBANK NJ USA

Use JB Weld.
05-07-2008 07:45 PM
 
 
RappyTappy
Elite Veteran
Location: Las Vegas, NV

Everyone has their own taste, but personally I dislike JB Weld, I've found epoxy to be stronger in most cases for our applications.

Chris
Rex 500
Burning them electrons :D

Forever Brothers
Mickey Tylo
05-07-2008 08:02 PM
HOMEPAGE  
 
 
TwistedRotor
Senior Heliman
Location: Tulsa, OK- USA

Quote 
For plastics I love a glue from Devcon called PLASTIC WELD

+1, that stuff is awesome. We use it on almost everything plastic and it's tough as nails.

Another good epoxy that we use is a titanium epoxy also made by Devcon. http://www.devcon.com/products/prod...fm?familyid=124
It's even machinable.

The helicopter is a machine trying to commit suicide,our job is convincing her to fly...
05-07-2008 08:08 PM
 
 
speeddemon370
Veteran
Location: Spruce Grove, Alberta, Canada

Quote 
a plastic ball link will never form acceptable bond with a piece of flat metal no matter what glue you use.

Not quite sure where you were going with that but I'm not gluing plastic to metal, it's plastic to carbon.

I certianly appreciate your advice though and I'll keep your method in mind. It does sound a bit overkill for a mini but if it will save a crash I guess overkill is necessary. In the mean time I did come up with something that involves alot of the tips here plus an extra 1mm carbon rod epoxy'd over the joint to form a type of lap. It isn't the prettiest thing but I have alot of faith in it. I made 2 of them identically and tomorrow (I always wait 24h for adhesives to cure but still a good point) I'm going to do some destructive testing on the sample. You know, whack it on the ground a couple times, vibrate it, pull on it. Just to see how it holds up. If it dosen't, I'll go with your method for sure and the second one will never see the sky. The reason I don't do the "heavy duty" right off the bat is because I have to drive for about 1h one way just to get all the parts. It ends up being a very expensive trip just for gas so I try to avoid it whenever possible. (2002 dodge ram with 360 V8 and 36" tires, 8mpg)

On a side note, I thought JB Weld was only for metal?

I sincerely appreciate all the advice, wow, this forum is useful for something other than arguing after all.

with 2 ears and 1 mouth you should listen twice as much as you talk
05-07-2008 08:59 PM
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Main Discussion > 2 part epoxy just caused a mid flight failure, what do you use as a good adhesive?
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