OhD

I kind of remember folks talking about building in a small amount of "roll" in the horizontal stabs, I would assume to correct for torque effects. I just bought an Oxai Acuracy and my Mark 1 eyeball tells me there is an offset built in. Has anyone else seen this and does it make sense?

Jim O

apereira

Do you mean there's a difference in distance between the forward stab tube(for example) to the top of each stab panel? The panels are identical on my Acuracy.

Regards

OhD

If I line up the elevators tips with the stab tip trailing edges, one elevator is well above the other at the root. In other words it looks like they do not have the same incidence.

Jim

TonyF

My Feedback: (92)

One elevator is warped. Or one stab half is warped. Pretty sure unintentional.

serious power

Hi Jim,
That would seem to be as Tony has said.
You might be lucky in that it is obvious, otherwise you might have a little twist and not realise it - a heart-breaker !!
It can be quite tricky to measure incidence on a tailplane with pre-installed elevators and Oxai stab halves are not independently adjustable.

Oxai are generally good at replacing stuff like this.

Brian

Malcolm H

Jim,

Very often the warped piece is only the fixed tip block that covers the outboard end of the elevator. If you have the servos installed so that you can use the radio to hold the elevator position relative to the stab, its relatively easy to measure the incidence from the inboard end to the outboard end of the elevator. If you are happy that the twist is only in the outboard tip block, it can be "moved" back into line by gently warming it with a heat gun and apply pressure in the direction you want to go and then quickly applying a wet towel. Be very careful with the heat as its easy to mark the Oxai paint with your fingers while its soft (don't ask me how I know this!) so its best to keep the heat low and do it a few times until you get it moved.

One other possibility is that the holes in the stab roots for the forward incidence pin are not in line and because the one piece pin passes through the adjuster this isn't easy to fix. It might be possible to make up an offset pin by epoxying a split carbon tube on one half of the pin, mounting the other half in a 4 jaw lathe chuck with the required offset and turning the modified side back to the required diameter. I know this sounds complicated but if you have access to a small lathe and the required skill its doable.

Malcolm

serious power

Hi Malcolm/Jim,

Malcolm, you're off your 'chuck'

At $4500 to $5000 I'd be getting a replacement if it is in any way twisted and especially so if it is bad.

Brian

OhD

Brian, I'm not sure what "off your chuck" means, but it sounds derogative. So I assume "on your chuck" is good. Malcolm, you are on your chuck.

I did as Malcolm said and aligned the elevators at the root and then checked at various distances out to the tip. The Acuracy with its flared trailing edges is fairly easy to check by laying long straight pieces of balsa on the high point and on the flare of the trailing edge of each elevator, parallel to the airplane's center line, and then sighting down the plane of the stab to see that the balsa "beams" are parallel. They were. So it looks like the tip blocks are the culprit, but after aligning the elevators the misalignment at the tips doesn't look too bad. I'll fly it before I try too heat the tips and bend them.

Thanks for the info guys.

Jim O

Malcolm H

Its OK Jim, Brian and I go way back, its a Scottish/Irish thing and he was attempting to make a pun regarding my suggestion to make an offset incidence pin. I will have plenty of opportunity to get back at him either in person next season or on one of these threads, right Brian? :-)

M

serious power

Hi Jim,
Joking aside, I really don't understand why anyone would pay $5000 for a competition class airframe and then accept twisted flight panels that need to be straightened from the get go.
If you mess with it you then can't show the supplier how it was, as supplied. I assume it is quite new, therefore may not be finished twisting yet.
You will ,henceforth, be very likely to have a doubt in your mind about what's what with the model.

I don't think that it is too much to expect to have straight components at $5000 a pop.
The more often we accept stuff like that the more often we will get stuff like that.

I'll get off the soap box now !

Brian

PS ; Malcolm, I have no doubt . However if it is/was so bad that it requires an offset pin to line it up, it is just not fit for purpose. It would be madness to do such work on a brand new model like this.