Loctite

[PappaBear]

We are often asked about the use of Loctite, especially with plastic parts. Please be aware that Loctite is NOT recommended for use where it may come into contact with plastic parts. Please see the link below. You will see this is a Loctite product and it clearly states not recommended for use on plastic. Blue Loctite will react with the plastic, and the parts will fail. This goes for any of the plastic parts in any of models supplied by Motion RC.

If you really want to lock a part in place, use Foam Tac. This is more than adequate for securing nuts and bolts on a foam model. Electric models are not subjected to anything like the same level of vibration as that of a glow or gas engine.

http://www.loctiteproducts.com/p/10/15/t_lkr_blue/overview/Loctite-Threadlocker-Blue-242.htm

Martin.

[Alpha]

Good topic, Martin. We hear at least twice a month of someone using Loctite on plastic. Metal screws into the propeller, for example. That Loctite corrodes the plastic propeller backplate and you can guess what happens on the maiden flight. I'm quick to point out that even on a metal to metal joint, for example on the Strega's wing bolts, where a metal machine screws threads into a threaded metal receiver, there is still the risk of Loctite oozing out and touching the plastic mount that molds that threaded metal receiver. I've seen where the screw remains in the threaded metal receiver, but the threaded metal receiver itself pops right out of the corroded plastic mount. Goodbye, wing!

The bottom line is, never use Loctite anywhere near plastic, period. It isn't worth the risk, even if it's only close but not actually touching. Foam Tac is a good alternative. But personally I've never used any additional screw fixative on a foam electric fixed wing aircraft.

[doctormike]

Thanks for the warning. I'll be using E- 6000 now if the screws are anywhere near plastic, which is most of the time. Doc

[farmflyer]

I hadn't thought about using foam tac for this but it makes good sense. I think I'll be using it more for basically all of my gluing and thread lock on all applications in the future except for the occasional use of hot glue.

[Teeks]

Great advice Martin. I've seen many of the ugly results of Loctite on plastic parts and it isn't pretty.

[Dewey H Lee]

Thank you Martin. I'm a retired machinist and just have a question for on the loctite. Can you apply loctite and allow it to dry and then install set screws ect. We use to do this a lot in the experimental machine shop. Most of our set screws were going in aluminium and plastic. The cured loctite still held the fastener even after drying. Please advise. Thank you.

[boomer108]

Hey everyone!

I recall reading about a guy complaining about the wing coming off his Waco because the cabanes came loose. He said he couldn't figure out why the screws came loose because he used loctite on them!! Bad stuff on plastic. I've used Welders adhesive with great success which is the same as Foam Tac which I also use on foam and plastic.

Roy B.

[owyheeguy]

If you have already done it is there a fix?

[boomer108]

If you have already done it is there a fix?

That depends one what part or area your talking about on the plane.

[fhhuber]

Can you apply loctite and allow it to dry and then install set screws ect. We use to do this a lot in the experimental machine shop. Most of our set screws were going in aluminium and plastic. The cured loctite still held the fastener even after drying. Please advise. Thank you.

there is a commercial version loctite made for this... Normal doesn't work correctly this way.

Note... the "cured" loctite still attacks plastic.

**************

Once the loctite has been applied to the plastic its too late. Its a chemical reaction that makes the plastic brittle. Its going to crack.

[Konrad]

As to the plastic nothing, the loctite damages the plasticizer particularly thermo plastics. So the parts need to be replaced or reinforced. Some times you can remove the damaged plastic and use a threaded insert. But often there isn't enough wall thickness to allow this.

I damaged the elevator horn on my Splendor and had to come up with this fix (fiberglass plate) or spend another $20 on a replacement part.

[Konrad]

Thank you Martin. I'm a retired machinist and just have a question for on the loctite. Can you apply loctite and allow it to dry and then install set screws ect. We use to do this a lot in the experimental machine shop. Most of our set screws were going in aluminium and plastic. The cured loctite still held the fastener even after drying. Please advise. Thank you.

Loctite is a brand name. They make and market a wide variety of compounds. I assume we are talking about anaerobic thread lockers.

As they are anaerobic they don't dry (oxide or evaporate) to cure. There are cleaners and primers that help with the curing in certain material. (copper in the alloys really helps, some of these primers have a .2% copper sulfate compound for this) But as it has been noted these thread locking compounds will fail most (not all) plastics, particularly thermo plastics.

[Konrad]

I'm thinking that this might be better placed in tips & tricks.

http://www.hobbysquawk.com/forum/rc-airplanes/airplane-tips-and-tricks

[owyheeguy]

Good morning Boomer108. there are tiny screws attaching the plastic wing struts to the wing on my J-3 Cub. I think I'll coat those areas with epoxy. I don"know if the struts are functional of just cosmetic on this model.

John N.

[Konrad]

What brand and model of the cub?

[boomer108]

Good morning Boomer108. there are tiny screws attaching the plastic wing struts to the wing on my J-3 Cub. I think I'll coat those areas with epoxy. I don"know if the struts are functional of just cosmetic on this model.

John N.

I would think they are functional to give some some rigidity from vertical movement,but not knowing the plane that's just an educated guess.

[owyheeguy]

Hi Konrad, it's a Hobby King J3 Cub, 55" wingspan.

[StormyDog1962]

Clear nail polish is a good option, simple to apply and gums up the threading to keep them screws from backing out. Tiny bottle stores easily just be careful your buddies don't see it in your flight box. Might start talking about ya!! Use clear as Pink raises too many questions!!

[fhhuber]

Careful with nail polish and plastics... They generally use acetone based paint for nail polish. This can attack some plastics.

[boomer108]

Hey Guys!

Use Foam Tac or Welders adhesive. It doesn't hurt foam so it won't hurt plastic.

Roy B.