Its Bobcat nice
01-09-2008, 01:33 PM
#476
RE: Its Bobcat nice
I can attest as well, it should be nose high to rotate. Mine went 1/4 mile across a dry lake
at full speed and would not rotate. I had to raise the nose all the way, and it was OK. But,
mine was nose heavy because of the wrong c/g setting, and that was part of the problem
as well.
Even now, It shoots straight up when it does take off. You must hold full up on them for
some reason. I made some wider gear for mine, and moved them forward as well so it
is easier to lift the nose wheel.
FBD.
at full speed and would not rotate. I had to raise the nose all the way, and it was OK. But,
mine was nose heavy because of the wrong c/g setting, and that was part of the problem
as well.
Even now, It shoots straight up when it does take off. You must hold full up on them for
some reason. I made some wider gear for mine, and moved them forward as well so it
is easier to lift the nose wheel.
FBD.
01-09-2008, 01:47 PM
#477
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RE: Its Bobcat nice
ORIGINAL: z06kal
How bad was your negative incidence? Ie difference in inches between mains and nose?
How bad was your negative incidence? Ie difference in inches between mains and nose?
I believe it was about -2 degrees or so, though.
Now I have about 2-3 degrees of positive incidence.
Change your incidence. Make it positive.
While you may want to avoid making the change, you'll be glad you did.
01-09-2008, 02:16 PM
#478
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RE: Its Bobcat nice
I must have a different plane lol I don't touch the elevator and at speed mine will lift up into the ground effect and I then apply elevator. Go figgur?
01-09-2008, 02:19 PM
#479
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RE: Its Bobcat nice
ORIGINAL: AGR413
I must have a different plane lol I don't touch the elevator and at speed mine will lift up into the ground effect and I than apply elevator. Go figgur?
I must have a different plane lol I don't touch the elevator and at speed mine will lift up into the ground effect and I than apply elevator. Go figgur?
01-09-2008, 02:25 PM
#481
RE: Its Bobcat nice
....wierd. Even though I have mine is nose high and balanced, and I still must pull lots
of "up" to get it airborne. [X(]
Most of them need 1/8" "up" trim in the elevator as well for level flight. So maybe the
wing has negative incidence relative to the horiz. stab. The nose high "angle of attack"
is off-setting the negative incidence in the wing ???
of "up" to get it airborne. [X(]
Most of them need 1/8" "up" trim in the elevator as well for level flight. So maybe the
wing has negative incidence relative to the horiz. stab. The nose high "angle of attack"
is off-setting the negative incidence in the wing ???
01-09-2008, 02:43 PM
#483
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RE: Its Bobcat nice
Mine will fly level with the trailing edge of the elevator, level with the top trailing edge of the horizontal stabilizer... or just beyond that.
However relative to the fuse it appears that I have some positive incidence to the wing.
However relative to the fuse it appears that I have some positive incidence to the wing.
01-09-2008, 03:25 PM
#484
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RE: Its Bobcat nice
ORIGINAL: Flyboy Dave
....you're talking about the angle of attack, with a nose high attitude.
ORIGINAL: AGR413
Positive nose incidence of course, I was thinking of FBD's reply when I typed that.
Positive nose incidence of course, I was thinking of FBD's reply when I typed that.
....you're talking about the angle of attack, with a nose high attitude.
My elevator is within 1/16-1/8 of being level with the top of the elevator at neutral. Balance is at 10.3-10.5 aft of leading edge meeting fuselage measured right side up (not upside down). I know I know. Mine is right on the margin for CG, if it gets started going up it wants to keep going up but displays no other bad behavior which is no big deal because this plane should be "flown" everywhere it goes anyway. There may be a motor incidence issue in there somewhere to but I'm not going to go digging it flies just fine. However those of you that came up with the spoileron solution my hat is off to you. I have many many flights now with the spoilerons and I am one happy camper. No more "O GOD ITS TIME TO LAND THIS BEAST" I on the switch just before I reach the end of the runway and flare just before touchdown (looks just like I know what I am doing, even though I don't shhhhhhh)
01-09-2008, 03:36 PM
#486
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RE: Its Bobcat nice
I was waiting for your reply, I think the mounting of the booms (which affects elevator incidence) is very subjective on this plane. The tips of my booms don't sit flush on the wing (very slight gap) but the rest of the boom sits snug on the wing, this seemed intuitively more correct to me. Maybe this plays a role as well. The relocation of your landing gear may (may) play a role as well?
01-09-2008, 05:04 PM
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RE: Its Bobcat nice
Okay I redid my retracts. Unfortunately I had to cut a slot in the nose wheel wheel well for the wheel to go down further. Oh welp more cooling for the 3.5 pounds of batteries LOL. Right now my nose wheel is about 3/4" longer than my mains. Is this the ammount of up incididence I want or more or less?
01-09-2008, 05:25 PM
#489
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RE: Its Bobcat nice
As long as the wings sit either level with the ground or the leading edge is higher than the trailing edge you'll do fine.
Remember that this is along the wing chord.
Add spoilerons too! You need them with this plane.
Remember that this is along the wing chord.
Add spoilerons too! You need them with this plane.
02-12-2008, 11:25 AM
#492
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RE: Its Bobcat nice
ORIGINAL: AGR413
I was waiting for your reply, I think the mounting of the booms (which affects elevator incidence) is very subjective on this plane. The tips of my booms don't sit flush on the wing (very slight gap) but the rest of the boom sits snug on the wing, this seemed intuitively more correct to me. Maybe this plays a role as well. The relocation of your landing gear may (may) play a role as well?
I was waiting for your reply, I think the mounting of the booms (which affects elevator incidence) is very subjective on this plane. The tips of my booms don't sit flush on the wing (very slight gap) but the rest of the boom sits snug on the wing, this seemed intuitively more correct to me. Maybe this plays a role as well. The relocation of your landing gear may (may) play a role as well?
"The tips of my booms don't sit flush on the wing ..." Same and I put it together anyway hoping for the best.
The airplane requires 16 1/2 oz. sitting on the stab to rotate. Used fixed gear and mounted the wheel CL 2" behind the CG (10.3) because I suspect it would not rotate on demand. Initial balance is 1/4" forward of 10.3". With standard servos all around and Sub-C batteries up front the all up weight is 7 pounds 7 oz.
Through bolts were used on the booms thinking that I might move the booms forward 1/2" at a time experimentally after the flight characteristics are understood. Used an old Royal .46 with removable front housing and ran it backwards to avoid the pusher prop hassle. Booms moved 3" forward would allow a 10 oz. heavier engine without adding weight to the nose or would allow lighter batteries without changing the CG. And I have a ST .90 with removable front housing. The two engines that I ran backwards on the bench ran remarkably well.
Finished and ground handling tests should be this week. This has been a fun project with endless experimental possibilities. If my building skills were better a small canard would already be mounted to the nose wheel former. A canard might allow minimum stabilizer and elevator and reduce weight in the tail. Maybe after the flight characteristics are understood.
Bill
02-12-2008, 01:19 PM
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RE: Its Bobcat nice
I used a Laser incidence meter to check mine. The very tip of the boom wasn't quite flush with the curved top of the wing. However most of the boom layed perfectly flat against the wing. Incidence was very very close within 1/4 of a degree.
These parts are all laser cut so it is pretty hard to throw off the incidence by a large ammount. If you were to shim the front of the boom even a small amount it would be very obvious in how the rest of the boom sits against the wing not to mention the balsa will easy crush/flex this ammount if you screw it down hard to seat against the wing.
Mine is electric. All up weight is 11 pounds.
http://www.rcuniverse.com/forum/m_69...tm.htm#6970911
These parts are all laser cut so it is pretty hard to throw off the incidence by a large ammount. If you were to shim the front of the boom even a small amount it would be very obvious in how the rest of the boom sits against the wing not to mention the balsa will easy crush/flex this ammount if you screw it down hard to seat against the wing.
Mine is electric. All up weight is 11 pounds.
http://www.rcuniverse.com/forum/m_69...tm.htm#6970911
02-12-2008, 03:11 PM
#494
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RE: Its Bobcat nice
ORIGINAL: BillS
A very small change in the boom has a large affect on the stabilizer incidence. A 1/64" shim at the front boom mounting hole would change the stab incidence by 6 degrees.
"The tips of my booms don't sit flush on the wing ..." Same and I put it together anyway hoping for the best.
The airplane requires 16 1/2 oz. sitting on the stab to rotate. Used fixed gear and mounted the wheel CL 2" behind the CG (10.3) because I suspect it would not rotate on demand. Initial balance is 1/4" forward of 10.3". With standard servos all around and Sub-C batteries up front the all up weight is 7 pounds 7 oz.
Through bolts were used on the booms thinking that I might move the booms forward 1/2" at a time experimentally after the flight characteristics are understood. Used an old Royal .46 with removable front housing and ran it backwards to avoid the pusher prop hassle. Booms moved 3" forward would allow a 10 oz. heavier engine without adding weight to the nose or would allow lighter batteries without changing the CG. And I have a ST .90 with removable front housing. The two engines that I ran backwards on the bench ran remarkably well.
Finished and ground handling tests should be this week. This has been a fun project with endless experimental possibilities. If my building skills were better a small canard would already be mounted to the nose wheel former. A canard might allow minimum stabilizer and elevator and reduce weight in the tail. Maybe after the flight characteristics are understood.
Bill
ORIGINAL: AGR413
I was waiting for your reply, I think the mounting of the booms (which affects elevator incidence) is very subjective on this plane. The tips of my booms don't sit flush on the wing (very slight gap) but the rest of the boom sits snug on the wing, this seemed intuitively more correct to me. Maybe this plays a role as well. The relocation of your landing gear may (may) play a role as well?
I was waiting for your reply, I think the mounting of the booms (which affects elevator incidence) is very subjective on this plane. The tips of my booms don't sit flush on the wing (very slight gap) but the rest of the boom sits snug on the wing, this seemed intuitively more correct to me. Maybe this plays a role as well. The relocation of your landing gear may (may) play a role as well?
"The tips of my booms don't sit flush on the wing ..." Same and I put it together anyway hoping for the best.
The airplane requires 16 1/2 oz. sitting on the stab to rotate. Used fixed gear and mounted the wheel CL 2" behind the CG (10.3) because I suspect it would not rotate on demand. Initial balance is 1/4" forward of 10.3". With standard servos all around and Sub-C batteries up front the all up weight is 7 pounds 7 oz.
Through bolts were used on the booms thinking that I might move the booms forward 1/2" at a time experimentally after the flight characteristics are understood. Used an old Royal .46 with removable front housing and ran it backwards to avoid the pusher prop hassle. Booms moved 3" forward would allow a 10 oz. heavier engine without adding weight to the nose or would allow lighter batteries without changing the CG. And I have a ST .90 with removable front housing. The two engines that I ran backwards on the bench ran remarkably well.
Finished and ground handling tests should be this week. This has been a fun project with endless experimental possibilities. If my building skills were better a small canard would already be mounted to the nose wheel former. A canard might allow minimum stabilizer and elevator and reduce weight in the tail. Maybe after the flight characteristics are understood.
Bill
02-12-2008, 03:19 PM
#495
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RE: Its Bobcat nice
ORIGINAL: AGR413
Intriguing, you just gave me inspiration for an idea. I want to order one of these put canards on it, a vertical stab and get rid of the booms and elevator. It would look like a plane from the rocket racing league!
Intriguing, you just gave me inspiration for an idea. I want to order one of these put canards on it, a vertical stab and get rid of the booms and elevator. It would look like a plane from the rocket racing league!
02-13-2008, 12:13 AM
#497
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RE: Its Bobcat nice
ORIGINAL: opjose
Heh, yeah it would look a bit like one of these with canards!
ORIGINAL: AGR413
Intriguing, you just gave me inspiration for an idea. I want to order one of these put canards on it, a vertical stab and get rid of the booms and elevator. It would look like a plane from the rocket racing league!
Intriguing, you just gave me inspiration for an idea. I want to order one of these put canards on it, a vertical stab and get rid of the booms and elevator. It would look like a plane from the rocket racing league!
02-13-2008, 11:51 AM
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RE: Its Bobcat nice
ORIGINAL: AGR413
Yep except without that stupid looking flat thing on top of the vertical stab what do you call that again?
Yep except without that stupid looking flat thing on top of the vertical stab what do you call that again?