HeliTB

Opjose...Spoilerons Hmmm. How much down aileron deflection do you have programmed in for your Bobcat 50? I'm wide open for suggestions. I'm using a Futaba 9C.

TUMBLER

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orgive me guys but I did a search in the thread for (cg) and nothing comes up. The manuals are usually wrong, so can someone tell me what is the suggested cg?

Thanks!

Tumbler

HeliTB

CG is 10.3" to 10.5". Most guys are using this based on what I saw in this forum. I'm using 10.5" myself with success.

HeliTB

Just realized "Spoilerons" are up not down. I read in another thread that 1/8" to 1/4" up defelction for starter and adjust as needed. You will need to mix in some down elevator.

BillS

A little spoileron goes a long way and I would suggest starting at 1/16� or use a knob. I have had the CG at 10� and 10 1/4� but found that spoilerons were not necessary for high alpha landings. My airplane is heaver at 8 lbs and is working with a 10/6 prop.

I ordered pusher props and am changing to a larger engine hoping to avoid marginal take off performance.

Bill

Team_Monkey

Hello gents,
I've a lot pf catching up to do, last page I read was 124. Had a chance to do more work on my PlastiCat and finally got some in flight vids so I thought I'd share them with ya. Definitely need some spoilerons and more practice. I stalled it about a foot off the ground at each landing. Thankfully the L/G blocks are strong. they lasted uintil the third flight where I dropped in from three feet...but that's in the write up.

It would have been cheaper in time to just buy the ARF but I enjoy building so this exercise has been fun. Here's the write up and movies.
(Since it's been awhile... it is a Coroplast plane with 48" span and a GMS .47 for power.)

************************************************** **
Flew the 'cat a few times this weekend. Videos are being edited.

She has plenty of power and shot right up off the runway in short order. the winds were pretty heavy so that helped too. Stalled her a few times just flying along down wind. Ground speed looked ok but airspeed must have been low. It was scarey but I let the nose drop and flew it out of it. twice because I wasn't smart enough to realize what happened the first time. []She sure is pretty on a fly by. Odd thing was I had elevator at low speed and next to none at high speed. My landing on Friday was OK but the left main caught a hollow in the grass and biffed the nose in busting the foam. poly glue to the rescue and it was good as new.
So, thinking the elevator control and nose dropping was a CG issue I took two of the lead shots out of the nose. I also swapped out the HS-85 servo for an HS-311. (I don't think that was needed though, read on.)

Saturday or was it Sunday? Anyways, I flew it with the new CG and it seemed a bit better but still was weak on elevator. When I landed gravity looked at the rear stab and we could flex it pretty easy. His idea did the trick, we glued on another layer of 4mm with flutes at 90deg. to the first. Now the elevator had control! I had also swapped out the 10x6 for a three blade 9x7. She had gobbs of power and went vertical on take off like a 3D machine. :grin: OOPS! nose over and climb out was OK. But now the CG was too far rear with the bigger servo, extra 4mm and less nose weight. So I was flying her fast to keep ahead of the stall speed. and fast she is. Seems to really growl with the GMS .47 and a three blade prop. Rolls are pretty fast and the loops are tight with a cool mush on the bottom side like a jet.

But after 5 mins or so the power dropped. I think it may have leaned out a bit and heated up as the tank level dropped. With the tank leads facing forward I have about 8" of line to the muffler and carb. She started to stall and drop way out over the corn. I nosed her down to gain speed, begged for lift and had just enough to limp her straight at us. No time or height for a pattern approach, I was at 90deg to the runway. I flew between a couple trees, yawed in line with the active and touched down flat but a bit hard. Both main gear blocks busted (just yardsticks) but overall she is fine.

I gave it one more click rich for the next flight and de-fueled the tank. Still lots of fuel in there, over 1/2 I'd guess. Took her to the basement and that's where she rests. A couple more proving flights and she should be dialed in. It is a neat plane to watch fly but it does need to land a little faster than I'm used to. Need to dial in more spoilerons.

added videos:
and here's the videos
http://s324.photobucket.com/albums/k...sticatfilm.flv

http://s324.photobucket.com/albums/k...ticatfilm2.flv

-edit-
There's a title about the third flight in there that I forgot to delete so ignore that.

TUMBLER

My Feedback: (13)

Links to vids don't work for me.

Team_Monkey

Sorry Tumbler I just tried them and they work. Maybe your work is blocking photobucket?
They are large files so they might take some time to view on dial up.

..Oh, ya know what? you might have hit it before I corrected the original post. Try 'em again.

Xairflyer

My Feedback: (1)

Is there a noticable reduction in speed? I know the guys with the bigger version say that it comes in at walking pace with the fitted flaps.

I am in the middle of fitting flaps/airbrakes to mine, I have one side done and hope to have the other side finished today so I can fly it tomorrow.
I will post more pics later this eve.

Boomerang1

An airbrake will not lower the landing speed at all, the stall speed will not be altered by extra drag alone. What an airbrake does is make more drag, the opposite of thrust. What it means for me is the landing approach can be steeper without building up speed or, if I am making a flat approach, I have to fly in with some throttle on & can control the rate of descent better with the throttle.

With the engine I'm using it takes about 6 seconds for it to go from idle speed (55,000 RPM) to full speed (190,000 RPM). If I have to go round because I stuff up the approach & I already have some power on it takes only about 3 seconds to reach full power. Even 3 seconds is a long while if your model is descending towards the weeds!

I have drilled a heap of holes in my airbrake to hopefully increase the drag some more, I cannot make it longer because it will scrape on the ground or wider because it will hit on the engine support rails. I could not fit them where yours are because of the retracts. - John.

cyborg1

Hi guys,

Maidened my bobcat already, and lost it on the same flight. I clipped the roof of a building on my landing approach, lost one of my retracts, and then it just didn't respond to any input after that. Result - broken leading edge of the left wing, cracked fuselage from the front to the center, elevator ripped out from the booms, both booms seperated from the wing. Anyway, fixed her up, and she's almost ready to fly again. I noticed a trait I found puzzling. When banking for a turn and grabbing the elevator to tighten the turn. the plane would nose up and start to climb mid turn. Has anyone experienced this? I found the trait to be unsettling, so I just opted for wide banking turns without elevator input. Any ideas on what causes this? BTW, I had a heck of a time trimming her out, as she required almost full up trim before flying level hands off. I had about 6 minutes of flying time, with about 3 of those minutes setting her up for landing in a crosswind. Happy Flying!

jrotor

My Feedback: (5)

may be this was already discussed, but
anyone used elevon to reduce servo count ?
I'm thinking about not using elevator and rudder.
Just 4 servos for throttle, nose steering, 2 elevons.
What do u think ?

Xairflyer

My Feedback: (1)

If a model points its nose up in a turn it says it is tail heavy, only other thing can be rudder deflection or boom alignment.
Does it do it if you turn the other way ?

Xairflyer

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Don't know if this would work with the high mounted tailplane, why not fit a single servo in the tailplane like I done (see pics in previous posts) and no rudders.

Xairflyer

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Went to fly my Bobcat yesterday to try out the new split flaps/airbrake but my EGT probe on my turbine was'nt reading so had to go home again !

I have attached pictures of what I done below.

The flaps are made from 1/16" ply, how to hinge them was the biggest problem, finally went with using bullet tape first on one side then folded back and done the other, amazing how strong it is, I tried it on my dead bobcat, that I keep for reference (rib positions etc) and I had to apply a lot of pressure to rip it off. I super glued the edges and punched holes so it glued into the wood below as well.

Using my dead bobcat I was able to establish the positions of the ribs and wing joiner tube so I could fit the servos to the measurements shown. Covered the tape with film peeled off the dead bobcat and then some red on the flaps.
I can get about 70deg with the servo arms/travel fitted at the moment but I think these will work more like the flaps on the larger falcon version so don't expect to use more than 45deg.

Will report back on the results when I fly it

BillS

Sure looks like the brakes should slow it down. What does the airplane weight?

I am finding a number of reasonably severe cracks in the fuselage between former # 2 and former # 3 in front of the servo tray. Probably should have reinforced the area with fiberglass before flying. Better landings would help.

Bill

TUMBLER

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That looks great!!! That will really help! On my turbine powered KAngaroo, it came at mach 3 until I got the linkage right so the airbrake would not get blown back. I couldn;t believe how that little airbrake made such a difference!

Tumbler

Xairflyer

My Feedback: (1)

It weighs now 9lb 13ozs empty.

Been wondering if I should use them as flaps or airbrakes, the guys flying the bigger version say it comes in at walking pace and they are set up as flaps with a max of 45deg.

I will try this first and then see how they work full down like airbrakes, but I think like this they will be too big and may need to be trimmed down. The airbrake on the boomerang is only about 30mm.

Xairflyer

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Flew it twice today, sorted my EGT problem, turned out to be that parameter 1 (gasper Fadec AU-540) was set at 252 instead of 49 ?? Speaking to gasper he said it can happen but very rarely, so if anyone has the same problem, check the EGT calibration parameter.

Well the flaps/airbrakes worked very well, I set them at 45deg with 20% down elevator (JR Tranny) makes a big difference on landing, a must do mod to help slow these things down on landing.

Going to try more movement on my second flap setting next day I fly it to see if it works even better.

Romulo

Does anyone have the Bobcat 50 manual in PDF format ?? I loose my paper manual !!

Thanks,

bob092

Romulo
Send me your email address I can copy my manuel and send it to you. Bob

HeliTB

XairFlyer...So are saying the Bobcat landed better with flaps instead of spoilerons?

BillS

After trying three engines on an 8-pound Bob Cat below is some information.

A .45 engine with 10 x 6 prop turning 12,500 rpm on the ground is very marginal on take off from grass. Take off from asphalt is OK and after up to speed the flight is OK.

A .50 engine with 11 x 6p prop turning 12,500 rpm on the ground is very marginal on take off from grass. After up to speed the flight is good.

A .50 engine with 10 x 7p prop turning 13,500/13,600 rpm on the ground is somewhat marginal on take off from grass. A couple of rich clicks on the needle can be dangerous.

I used engines that I had. All setups flew OK after the airplane is up to speed. The airplane would benefit from more wing area.

Bill

Xairflyer

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Not sure what you mean by spoilerons, they are fitted to the top of a wing and I dont know of anyone who has tried them but may be another idea.

I have found with adding the split flaps to the bottom of the wing it slows the plane down alot, and I intend to explore it further with more down deflection

HeliTB

XairFlyer...What I mean by spoilerons is that both ailerons raise up instead down like flaps. This is done on planes that don't have seperate flaps and ailerons. I'm not sure of which post, but there was a post maybe no more than two pages back that mentioned spoilerons.

BillS...When you say 10x7p and few clicks rich can be dangerous do you mean "Fast"? Reason I asking is I have both the 11x7p and 10x7p, I've flown two flights with the 11x7p and think thing is Fast. I haven't tried the 10x7p yet. I believe when I tached the 11x7p on the ground it was hitting 12.5 to 13k.