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Conference vmszoo::rc

Title:Welcome To The Radio Control Conference
Notice:dir's in 11, who's who in 4, sales in 6, auctions 19
Moderator:VMSSG::FRIEDRICHS
Created:Tue Jan 13 1987
Last Modified:Thu Jun 05 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:1706
Total number of notes:27193

1611.0. "Plastic cub does axial roll on takeoff" by CSC32::HAGERTY (Veni, Vedi, $Cmkrnli, Rebooti) Tue Jun 28 1994 12:42

    Well, the notes biz seems a bit slow of late, so I figured I'd enter
    something that falls in the "doesn't matter, but maybe interesting
    to talk about" category.
    
    I and 4 others got the unequalled opportunity to try (word chosen for a
    reason) to launch a Cub owned by a fairly new modeler who was just
    transferred here.  I'd never seen this particular model, but it was
    all plastic (hard plastic) with perhaps a 50" wingspan.  It was powered
    with a .40 OS FP.
    
    Try as we might, it wouldn't get into the air.  At one point, it lifted
    off, but did the most wonderful roll (not loop) you've ever seen.
    It had the twitchiest rudder on the ground you've ever seen.
    
    I got it to the point that it was rolling down the runway straight or
    fairly so, pulled up, and it lurched heavily to the right.  Any
    amount of trim or cajoling did not correct this tendency.  One of
    the other guys got it up and it did this perfectly executed axial roll
    about 5 feet off of the deck.
    
    We had to fool with the gear to get it to roll right, but it still
    isn't right.  This tendency to roll to the right on takeoff is not
    something that endears any of us to it. :-)
    
    First off, does anybody have any idea what plane this is?  It looks
    like a standard cub in yellow.  It has a conventional landing gear
    but is all plastic.  In fact the material sort of reminds me of a very
    heavy canopy.  Needless to say it's virtually indestructable.
    
    Secondly, any speculation as to what's going on with this plane? 
    I suspected wing warp, but something this dramatic would be obvious
    to the unaided eye, or so I would have thought.
    
    The owner has retired it to his attic (thankfully)
    
    							Dave()
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1611.1VMSSPT::FRIEDRICHSI'd rather be flying!Tue Jun 28 1994 13:0315
    I saw one of these for the first time Sunday morning during our
    beginners time...  Sorry, I can't remember the name of it.
    
    Mike flew it and even in the wind he was fairly impressed with it.  
    He said that it handled quite well.  The only thing was that it took
    quite a bit of down trim, if I remember right.
    
    FWIW - This (now) poor guy bought the whole setup at Eric Fuch's 
    Hobbies (the "hobby" store chain located in many malls around here).
    I didn't dare ask what he paid for it, but I suggested that there are
    other alternatives...
    
    cheers,
    jeff
    
1611.2UNYEM::BLUMJTue Jun 28 1994 13:131
    Sounds like the CG may be much to far aft.
1611.3He said it had flown beforeCSC32::HAGERTYVeni, Vedi, $Cmkrnli, RebootiTue Jun 28 1994 13:496
    I thought this, too.  Several of us balanced it on the (virtual) spar,
    and this not seem to be the case.  Admittedly, the absence of a
    physical spar could be a source of error, as we had to guess where the
    CG would be.  He bought it used with no instructions.
    
    He claimed it flew and flew well where he brought it from.
1611.4WRKSYS::REITHJim WRKSYS::Reith MLO1-2/c37 223-2021Tue Jun 28 1994 13:512
If he bought it without an engine then the right and down thrust might be
screwed up. The roll might have been due to torque
1611.5aircore...GALVIA::ECULLENIt will never fly, Wright !Tue Jun 28 1994 14:056
    Probably not but it sounds similar to the AirCore kits, made of
    corrigated (?sp) plastic.  One of our club members has one. Flys well
    and is indestructible. You basically fold the pieces together and viola
    one airplane. 
    
    Eric.
1611.6CIM::LORENI <heart> OOPSTue Jun 28 1994 18:017
    Does it have a covered wing?
    
    My father had a plane which acted like that. Looked fine, balanced
    fine, nice hand toss behavior but at speed it was a mess. Turned out
    that the monocoat had separated at the leading edge from one of the
    wing panels, and at speed would lift and mess up the airfoil...
    
1611.7our conclusionsCSC32::HAGERTYVeni, Vedi, $Cmkrnli, RebootiWed Jun 29 1994 12:4812
    It was a one-piece wing of a sort of hard plastic.  When it did the
    ground roll, it just scraped up the v-stab a bit.  Not a stick of balsa
    or ply in it that I could discern.
    
    We talked about it again and came to the conclusion that it must be one
    or a combination of the following:
    
    a) major league left thrust (a joy on takeoff)
    b) warp 1, Mr Scott
    c) flawed design to begin with
    
    						Dave()
1611.8VMSSPT::FRIEDRICHSI'd rather be flying!Wed Jun 29 1994 12:579
    Sorry, it can't be (c) as the guy that brought this plane out had
    no experience on how to build.  So, if we are talking about the same
    plane (and I believe we are), the design isn't bad.  I will try
    to get some more info about engine size, see if there is any thrust
    built in or what...
    
    cheers,
    jeff
    
1611.9A few more checks won't hurtMKOTS3::MARRONEThu Jun 30 1994 16:3920
    A couple of thoughts.
    
    Check out the lateral balance.  It won't fly well it one wing is
    heavier.
    
    Despite the "apparent" good CG, I'd move it further forward to see if
    anything changes for the better.
    
    Put an incidence meter on the wings to check for warp and for wash-in. 
    Either one will cause a problem, and I've learned NOT to rely on eyeball
    checks to determine if warp is present.
    
    General Comment:  I have never seen a plastic model that flew as well
    as a balsa/ply built up model. Period.  I don't know the reason why,
    but they just don't fly consistently well, and some days they are not
    bad, other days the same plane is unflyable.  The one exception I've
    seen is one of the Kyosho ARFs which could be favorably compared to a
    built-up.
    
    -Joe  
1611.10Junk is junk.CSTEAM::HENDERSONCompetition is Fun: Dtn 297-6180, MRO4Thu Jun 30 1994 16:448
    Garbage up - Garbage down!.
    
    I have seen one of these planes before. I think that Charlie Watt test
    flew it. It was too heavy.
    
    End of story.
    
    E.     
1611.11Yep, he rightMKOTS3::MARRONEThu Jun 30 1994 17:176
    Eric, you have such a way with words!!
    
    But these are my sentiments, exactly.  I was just trying to be more
    diplomatic.  
    
    -Joe
1611.12I AgreeLEDS::WATTMon Jul 11 1994 16:487
    Small heavy Cubs fly like SH$T.  I had a beginner show up with one that
    took all of my experience to fly.  Needless to say, he didn't get much
    stick time and I'm sure he quit the hobby before ever getting a chance
    to enjoy it.  
    
    Charlie
    
1611.13The end of the storyCSC32::HAGERTYVeni, Vedi, $Cmkrnli, RebootiTue Jul 12 1994 12:385
    Well, this story has a happy ending.  The guy *did* eventually commit
    the cub to the dustbin and bought a "regular" trainer. I took it up and
    it flew much more sanely.  He had quite a bit of time on it the
    other day when he bent it a bit on takeoff.  He's in the course of
    fixing it.   In other words, things are quite normal :-).
1611.14Nice to hear.CSTEAM::HENDERSONCompetition is Fun: Dtn 297-6180, MRO4Tue Jul 12 1994 12:425
    That is good news. It grieves me when I see guys get the wrong start. I
    think that clubs should write a "Primer" and leave it in all local
    model shops.
    
    E.
1611.15Right StartLEDS::WATTTue Jul 12 1994 17:0010
    The best advice I could give anyone is to  join a club BEFORE
    they buy any RC stuff.  I was lucky that I had a buddy that gave me
    good advice before I bought anything.  (he also taught me to fly)  Bill
    Lewis saved me much grief and got me started with the right equipment.
    	It's a shame when someone gets interested in the hobby and gets
    started off on the wrong foot.  Many will give up and never get the
    chance to enjoy RC flying.
    
    CHarlie