Conference vmszoo::rc

        Re:< Note 268.0 by BARNUM::WALTER >

        Dave,
        
                I ahev  always  been able to remove warp by �having a
        friend or relative  hold  the  plane and bending the culprit to a
        little the other way  past straight and running over the monocote
        with a heat gun.
        
        Anker

    About your faith in engineering.
    
    The fact that the plane has been crashed a number of times, and
    probably on the same side each time since the plane is pulling,
    makes the "errors" in the warping "NON-independent".  If the structure
    is being stressed in one direction in the majority of the crashes,
    how can the errors cancel each other, or follow statistical theory?
    I don't think that it can be expected to.


    Chuck Owen  (not ready to throw out my engineering degree quite yet)

    Do as Anker suggested in .1, as if you were adding "washout".  It
    takes two people.  Have a friend hold the wing while you twist/bend
    it while heating both sides with a heat gun.  You may have to repeat
    this a few times to get it but it works great.  Don't forget to
    measure it on a flat surface, do not trust your eyes and use a straight
    edge where needed.
    
    G' Luck
    Chris Spohr
    

    By all means, follow all previous replies and do EVERYTHING possible
    to remove the warp from the structure.  However, If the surfaces
    have been badly enough misaligned (in the course of many repairs)
    as to make this impossible, consider trying bendable trim-tabs.
    
    Thin brass sheet or even beer-can stock can be used.  Just CYA the
    tab into an X-acto knife-slot and bend it up/down to compensate for 
    the warp.  This will, of course, create some miniscule amount of
    extra drag, but it WILL correct the adverse affects of a warp and
    trim the bird to fly straight...that's whay they put 'em on full-
    size aircraft.
    
    Adios,	Al

    OK, I'll try to bend the warp out with a heat gun first. If that
    fails, then maybe the trim tabs.
    
    Re: .2  Maybe I should be moaning more about Murphy's Laws than
    statistics. So far, I broke the left half of the wing and the rudder
    when it fell out of a tree, the right half of the wing and the right
    half of the stab when the hi-start hauled it down out of the sky
    faster than it went up, and the fin broke on some crash I can't
    even remember now. So it's pretty evenly cracked up.
    
    Dave Walter
    
    

Well, by Gawd, it worked! I took the advice on ironing out the warps, but
this time I was more patient with it, and I used a ruler and a flat table
to keep tabs on my progress. I found that due to a slight skew where the
two wing halfs meet, it will never be perfectly straight, but I was able
to get it close. As for the stab, it was so bad that no amount of ironing
was going to help, so I had to cut out the offending piece of balsa and
glue a new one in. 

And what a difference it makes in flying it. It practically flies itself
now, and I can even make right AND left turns! I got in a good dozen or
so flights today, and for the first time it came home in the same condition
it left. A personal milestone.

As long as I'm writing, I have a question on frequency bands. Somewhere
else in this notes file someone mentioned that planes are on different
frequencies than ground vehicles. The box that my radio came in says "4
channel system, aircraft", but right next to that is a sticker that says
"channel 74, 75.670, boat and car only". To further complicate things, the
instructions inside are for planes, and the receiver servo outputs are labeled
rudder, elevator, ailerons, etc. as if to be used on a plane. So, am I on
the right band or not? If not, can it be retuned easily?

Dave Walter

I think that you've got a surface radio there; channel 74 is a
surface frequency.  All aircraft radios in that band are on 72
MHz.  The fact that the receiver outputs are labeled as for
airplanes is probably due to the manufacturer not having an
alternate silkscreen  for surface (never thought of it before;
what are the surface radio outputs labeled as?). 

Any labeling to the effect that the radio is for aircraft is
false. 

You may be able to have the radio converted, depending on the
brand.  A radio shop should be able to tell you right off.   One
good thing, if you can't convert it, there's lots of folks around
who use the surface freqs.  Hope it works out ok for you.

    I've just revisited one of those unfinished projects that got parked in 
    the hanger about a year ago. Its a polyhedral pair of 12ft foam/veneer 
    wings (blue inners and white foam outers) which weren't stored as flat 
    as they should have been. The result is that the outer sections are
    twisted: one washout and one washin + some outher minor distorsions of
    the trailing edge.
    
    I have set them up in the garage (thats where they were stored
    originally) with the opposite twist, but I imaging it could take the 
    same period (abouta year) to correct the fault.
    
    Has anyone any suggestions straightening foam wings?
    I think my idea will work but how can I speed it up, (I would like to
    fly these this year) 
    
    regards
    trevor

The quickest way would be to slice into the grain direction with a knife and
rub epoxy into the slices and twist in the corrective warp. If you slice with
the grain it allows a bit more movement and the epoxy will freeze it back in
place. You can also use a heat gun but you have to be careful you don't cause
delamination that way.

Jim

    Thanks Jim,
    
    I asked around and several people confirmed the sliting method.
     
    The additional advice was: Don't cut right through both skins and only 
    use a small amount of adhesive/epoxy (especially if you're going to 
    glass anyway)
    
    Trevor

I would only do it down to the foam, not through the entire wing. The foam
won't cause any problems. You just want to allow the skins to skew a little
bit to allow the skins to de-stress. You might be able to get away with just
doing the top surface. I did on the one that I had to do this with. I just
forced enough epoxy into the slits to reseal them when I was done. Here in the
states I'd use Hobbypoxy Smooth and Easy since it has great sanding qualities
and you don't want to put in a lot of effort and change the profile of the
airfoil when cleaning up.

Jim