stunthanger.com
Design => Stunt design => Topic started by: Jim Oliver on July 09, 2006, 08:21:05 PM
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Hey You Design Guys,
I have this weakness for Hurricanes. Presently have the RSM kit and Larry Richards Veco Hurricane kit.
A note on the RSM plans comments on the low position of the wing relative to the thrust line and suggests .75 in. of dihedral under each tip.
I have (at least) two questions:
1--Should the lead-outs be installed the same as if there were no dihedral; should
they exit the tip in the same place as if there were no dihedral?
2--Would there be any advantage/disadvantage in raising the wing so that the chord
line of the wing would be closer to the thrust line? The chord line is now 1.5 in.
below the thrust line.
Thanks,
Jim Oliver
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Jim,
Answers are:
1 - Yes
2 - Yes
I defer to Al Rabe to give technical details regarding dihedral, although, Brett Buck, Ted Fancher, Bill Netzband, Pete Soule, Larry Cunningham and a bunch of others can provide most of the nuiances as well.
Jim Pollock, Adacter et Strenue
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I'd expect that Pat Johnston drew the CAD drawings for the RSM kit. Most of his stunters are semi-scale and most have dihederal. If you see his name on the plans, I would take that note as gosphel. If you think it could benefit from more dihederal, you might raise the LO's in the tip, and I'd encourage you to contact Pat...he's a good guy. I also have the Larry Richards "Hurricane" kit. ;D Steve
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if you put the bellcrank platform under the top spar,and the leadouts flat theyll come out 3/4 lower at the tip.
dosnt work on a Corsaior wing !
You basically get the bellcrank up so the ends almost miss the C/S sheeting,
and if you had 13 ribs it d be 1/16 down oon ea rib,for 3/4 " , as theres 12 'between ribs'.
you can actually fit the guide to the bottom of the tip rib,for max. diheadral.
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My two cents worth, Pat and I have talked abou dihedral at length. on Semiscale ships, wherre the wing is low, the dihedral gets the vertical cg in the right place for trimming purposes. the Brodak P-40, also designed by Pat, also needs dihedral to trim properly. There are some that move the wing up it will basically accomplish the same purpose. HOWEVER, now it wont look right! I guess it depends on how you feel about the appearance of your finished plane as to the direction you go. Myself, the dihedral isnt any big deal to incorparate so I followed the designers reccomendations. besides that, a low winger with dihedral just looks cool! and any one who has flown any of Pats designs can attest to the fact that he has the knack for getting it right. The bellcrank mounted centered in the wing hasnt any impact on the situation except allowign a better installation . the leadouts will not have any problems negotiating the "turn" as they exit the tip. If you move the leadouts to the bottom of the tip, it will negate the purpose of the dihedral. the dihedral is ONLY there to get the LEADOUTS to a position that balances the vertical cg, put em in the center of the tip.
long story short,
1# leadouts centered in the wing, without question and use dihedral
2#dont move the wing, use the dihedral, it willnot be a hurricane if you move the wing!
for more on this, there is quite a dialog in the "arf" section on this forum. discussing the Brodak P-40, actually two threads on it. Pictures about how I put dihedral in the ARC wing. If you are building from scratch its way way easier
My vote, put the dihedral in leave the wing low.
just my thoughts
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Thanks for the recent comments---I had previously decided to put in the dihedral but had concerns about leadout/bellcrank location.
Thanks for the info.
Jim
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Doesn't matter where the bellcrank is located. The only thing that counts is the exit point at the wingtip and the vertical CG. I also use dihedral on many of my models and it has no effect on how the airplane flies. Only on how it looks (cool). I have just drawn up a profile Corsair and it has the requisite gull wing with leadouts "going around the corner" to get to the tip.
Don
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Isn't the RSM kit based on Mr. Palmer's Hurricane? If so, something in the back of my mind tells me that his original had dihedral. I know his Skyscraper does.
Bill <><
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>>I also use dihedral on many of my models and it has no effect on how the airplane flies. <<
I would argue that it in fact improves the flight profile. The dihedral adds some additional roll stability. Pat's planes often use the Rabe wiggly rudder too.
And as noted, it just looks right.
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Bill,
The RSM kit is from Jack Sheek's "design bureau".
Cheers,
Jim
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Bill,
The RSM kit is from Jack Sheek's "design bureau".
Cheers,
Jim
Thanks, Jim. For some reason I had Bob's plane in mind! ;D Dag gum, Jack designed SO MANY planes, I surely can't keep up with them all. n~
Bill <><
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>>Jack designed SO MANY planes, I surely can't keep up with them all.<<
Boy, isn't that the truth. I can remember as a teenager hardly being able to wait for the next edition of Flying Models and whatever new wonder Jack had come up with.
Remember the Bewitched? Or the Bishop? #^
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Thanks for the recent comments---I had previously decided to put in the dihedral but had concerns about leadout/bellcrank location.
Thanks for the info.
Jim
To my mind (and arm) ,when the planes trying to take your arm of,or pull you of your feet,
there'll be a 'straight line' from the handle to the bellcrank.
If the plane was pulling one G (its own wt. at the handle) it might be 50/50 lateraly banked,
if the leadouts are diheadraled.
i pessume Flat leadouts,with the bellcrank close to the vertical C.G.,
will result in the plane flying square to the lines ,lateraly.in a diheadraled wing.
Thats how Ive fitted it in 1/2 doz. low wing / diheadral ships.
Bellcrank up at the top spar.Leadouts horizontal.
Only bank seems to be yaw induced,which is actually Roll !
M.S.