TimBle

Hi,

I want to use an alternative control rod device than the bent rod into a wooden stick method so many models use. I found Du-Bro Lazer rods at a LHS and the owner swears by them. trouble guys at my club tell me I need to support them in the middle as well yet Du-Bro says explicitly not too!.

So what to do. I don't want to cut the fuse up to get some sort of support in the middle. I can epoxy the lazer rod guide sleeve as the instructions says at both ends. my brain says that enough but the warnings from allegedly experience pilots (although not in Lazer rods) says "No".

does anyone here have expereince with these rods and do they work well in an ARF.

I can;t really see any fault with the installation instructions.

experience sharing and advise welcome.


Thanks

Tim

smithcreek

My Feedback: (25)

I can't believe Dubro says not to support them, I say absolutely support them. Once near the servo and at least one more time between the servo and exit. It's not the hard to do without cutting the plane up. Make two supports out of 1/2" wide 1/8" thick hard balsa or lite ply, long enough to mount across the hole in the former near the servo and one about half way back in the fuse. Drill a hole large enough for the outside tube to fit in, approximately where it will keep the tube straight when installed. Slide the supports on the outer rod. Put the outer rod in place, with an inch or so sticking out the exit. Then slid the supports up against the formers and glue. You may need to put thick CA on the one that goes in the middle of the fuse first, then slide it in place.

TimBle

Du-Bro advises to support the lazer rods only near the servo and at exit from the fuse. it should make no difference what happens between those points though.
its sort of like an hydraulic line but with a plastic load transfer medium..

I have the Lazer rod exit shrouds and will be bonding those down with epoxy probably.
I have made a support at the first bulkhead after the servo tray. So between that bulkhead and the exit shroud I should not require any further support, which is how I understand your comment.

Somewhere inside the fuse I have decided that I will use some heatshrink to join the rudder and elevator control rod sleeves so that they provide some support for each other.

good?

TimBle

however i have just had a revelation!

I can simply fill the entire rear fuse with expanding sealing foam like that used for filling cavity's in walls.


problem or at least fear, resolved.

This way there is no where for those outer sleeves to move and I don;t need to be assembling an engine through the muffler.

Steve Percifield

My Feedback: (14)

Do not fill the fuse with expanding foam. It is heavy and your aircraft will be very tail heavy. I have used the lazer rods just like Dubro says, with no problems. Sometimes you just do what the manufacture recommends?

MinnFlyer

My Feedback: (4)

I agree not to fill with foam, but for a different reason... That stuff can expand more than you think and you can easily have it burst the sides of the plane.

That said, if you just squirt a little near the center of the rod, so it contacts the rod and at least one point on the fuse, you'll be good to go.

TimBle

yip thats what I intend to do.
have worked with expanding foam lots of times and the two part polyurethane mix stuff is pretty potent.
But the aerosol stuff used for general gap filling around the home is much more tame and still pretty light. Also I know to add some external support while injecting the foam e.g. velcro straps around the outside of the fuse.

Just did a trial run, and filling the centre of the fuselage near the centre of the rods will add 13grams of weight.

Not a problem.

But I agree with Steve, supporting it only at the ends should not present a problem. The fuselage is not volumous for the rods to bend so severely that they stop functioning. I think the fears have a lot to do with tradition.

I'll install as recommended but the foam is a wonderful back up if I need the centre supported.

TimBle

The foam is very very light, it will not add significant weight.

also the expansion ratio is 2.5:1 which is not nearly as severe as the two part mix PU foam. There is not enough pressure to burst the fuse.

MinnFlyer

My Feedback: (4)

I have exploded a wing by filling the retract area with spray foam - Believe me, there is MORE than enough pressure to burst a balsa structure!

cfircav8r

My Feedback: (1)

If both ends of the sleeve are held completely stationary then you will have no control issues. It works the same as a bicycle shifter cable. If one end breaks free then it becomes a pull cable only. If you support it in the middle as well and one end comes loose then it still becomes a pull cable only. Concentrate on securing the ends very well and do not worry about the middle, as they won't help and may cause them to bind.

TimBle

Thats exactly the way i see it !
Its sort of a plastic hydraulic system.

Thanks I'll get to work.

Minflyer,
if you exploded the wing then you overfilled the cavity and did not drill exhaust holes. I'\ve repaired many wings with expanding instead of recutting balsa. Just replace the load carrying members fill with foam. shape and resheet with balsa, cover. sorted.

MinnFlyer

My Feedback: (4)

Overfilled the wing... Obviously, yes. But that was intentional

This was in the rib bays where the retracts go. The holes for the retracts, struts and wheel wells were already cut out - so there were PLENTY of exhaust holes.

I intentionally overfilled the area (But not by much) to make sure I got full coverage, figuring that any excess would ooze out through the openings.

But this stuff doesn't work like that. It keeps expanding AS it hardens. So while some oozed out, the rest stayed in place, expanded and exploded the sheeting [:@]

I'm just passing on my incident to help others avoid making the same mistake.

TimBle

Ok but it would help to understand where the mistake was made.

I finished repairing the wing to my Tempo last night and filled in the damaged area with  Sista Polyurethane expanding foam. Foam risers everywhere I made exhaust holes his morning but the wing is intact.

what type of expanding foam did you use. The aerosol or two part mix. The later needs each of the two parts to be weighed carefully to ensure no over expansion.

Any way wings repairs, lazer rods are fitted to the STIK and they work just fine without central support.

Next weekend I will maiden it and see. I have no doubt the Lazer rods will work better than the sloppy wood/metal control rods in the Tempo.
I may just convert the Escapade over as well as I have sourced the parts for dual elevator element driving.

F. G. Opperman

Hi Tim
I have the same plane and are batteling with the cg. anny advice.
Gerhard

AMA 74894

My Feedback: (1)

hmm that last post is almost 4 years old..
you may want to re-post your full question, or start a new thread