HeliTB

Here are the pics of my completed BobCat. I finished it today. I will attempt the maiden on Sunday.

I forgot to ask. If you look at the 3rd pic of the sideview. Can someone tell me if they think I need some downthrust (to the rear) in the engine?

BillS

Very pretty airplane.

My Bob Cat needed up thrust on the rear (prop end) of the engine. Needed to hold a lot of down elevator at high throttle. Yours may be different.

Good luck on the maiden.

Bill

hutt

Hi HeliTB
Do you have any pics of how you ran the nose leg steering cables and where you put the servo ?

Many Thanks

HeliTB

hutt...I'll try to post some pics for you tomorrow on how I did mine.

Ed

What are you using for covering, and paint John ?

... zak

Boomerang1

On the tailplane & booms I covered them with brown paper/white glue followed by automotive grey primer. I filled in the cut-outs on the tailplane before covering so it's completely sheeted. As well I covered the tailplane bottom surface & around about 3/4 inch onto the top surface with self adhesive aluninium tape.

I did not want to fill all the openings in the wings so I covered them in Sig Coverall fabric sealed with dope followed by grey primer.

On the fuselage I had to do a few repairs (the model was bought damaged) then sanded some of the paint off & grey primer.

The canopy was broken & I did not like the chances of getting a spare in Oz so I patched it & primed it as well. I will probably go for a WW2 German colour scheme like the similar Focke Wulf Flitzer.

Jet fuel is not very aggressive to paint & little exhaust residue ends up on the model so I will do what I did on my last jet & paint it with oil based enamel paint. The orange is Humbrol enamel, the black & white from pressure pack cans. - John.

HeliTB

BillS...Be very careful with canards and elevator. Be sure to have the canards active at all times. If you look at my avatar I had another plane with canards just like it. The issue I had was the canards were fighting the elevator if they are stationary. It would not want to let the plane dive or climb based on elevator input. It all of a sudden pitch or down, that was scary so I made another model without canards.

Dig it

For parts, try Texas RC. The fellah there is great to talk to and he had a canopy in for my yellow 50 size. Now, it was a little pricey but if ya done broke it, ya gots to pay fer it to get fexed.

Dale

moto-x

Well Gent"s I flew the Bobcat with the Supertiger 51 until I was just about bored with it. It flew great and landings were perfect. It wasn"t slow by any means but I just thought I could get a little more as for the butt pucker factor was gone. I came across a Webra speed 50 with a tuned pipe brand new for $75.00. I put the motor on the test stand to run it in. After 6 tanks I started tweaking the needles. I reached 17,000 rpm static with a 10/6 pusher Graupner prop. Well, I mounted the motor and off to the field. Well long story short, the butt pucker factor is back, I picked up quite a bit of speed and the sound is awsome.

HeliTB

hutt...Here are the pics I promised.

sbrackets

Hey HeliTB

Thanks for posting those pics. It gives me something to go on now in hooking up my pull/pull nose gear.
What retract are you using? Are they Robarts? and if so do the mains fit without much trouble?
I was thinking of ordering a set of the retracts from Hobby City, but there the air/air type and I'd perfer the Spring/Air type instead.
Your thoughts would be appreciated.

Thanks, Jim

hutt

HeliTB
Pics proved very helpful, many thanks.

davej78

[email protected] Are doing a clear plastic canopy for the Bobcat 50

HeliTB

sbrackets...They are Robart 520w1 from Tower. They are the air up/spring down type. They mounted without issue. They seem to be a direct drop in for the Bobcat. I think Tower has $20 off an order over $149, which will make the retracts $20 less. You will also need a pump as well which is $35, but it has a guage. Also you will want to get the brass T's, because the plastic ones leak. Well the ones I had any way, once I switched to the brass no problems.

sbrackets

Thanks HeliTB
That's what I needed to know. I already have the pump, but will order the brass tee's as you suggest.

Regards, Jim

HeliTB

Okay All, I'm ready to report my maiden flight from yesterday. Weather conditions were overcast about 90F degrees, winds about 10-13 mph cross winds.

My Setup:
OS AX .55 w/11x7P and stock muffler turning about 12.8k on the bench, probably 13k in the air. I wanted to see what the stock muffler did before I put on the tuned Ultrathrust pipe shown in my earlier post above.

Hitec Analog servos all around. HS475 on Ailerons, HS325 Throttle/Steering/Retract Valve, HS225 on the Rudders and one HS635 for the Elevator. Using 20lbs Leeder line and #2 sleeves(fishing stuff) for Pull-Pull on the Nose wheel.

Robart 520w1 Railmount Retracts w/struts from HobbyCitee (City). Retracts also have quick disconnects on the wings air tube, since they are removable.
Hangar 9 2-1/2" Pro-lite wheels

Futaba 2.4GHz R608FS 8-Channel receiver, powered by a A123 2300mAh battery.
Ch1 - Rt Aileron
Ch2 - Elevator
Ch3 - Throttle
Ch4 - Rt Rudder
Ch5 - Retract Valve
CH6 - Lt Aileron
CH7 - Lt Rudder
CH8 - Steering/Nose Wheel

Ch1 and CH6 - Flaperons of course
Ch7 is mixed to Ch4 as Slave at 100%
CH8 is mixed to CH4 as well but 30%, also mixed on the Retract Switch so when the retracts are up the Sterring/Nose wheel is not active. Only active when Retract switch is off.

As you can see no Y's needed. Servo Extensions used (2) Aileron 12", (2) Rudder 18", (1) Elevator 18". Looking back I should have used 18" on the Ailerons and 24" on the Rud/Ele.

C of G - I used 10-1/4" or 265mm for my Bobcat which is slightly nose heavy, probably due to the nose wheel retract.

AUW 7.4 lbs

Flight Report
OS 55 AX fired on the first shot at factory setting and purred like a kitten. We then twinked/leaned the low end needle for a little more throttle response. Once that was doen we headed for the runway. Me being an above the knee amputee (Motorcycle accident 3 yrs ago) I needed the help of my good friend James (JBEN, checkout out his Giant Super Sportster here on RCU, really!!! He a master builder in my eyes) to get the running Bobcat off the bench (subsquent starts will be on the ground). Taxied up the runway, look back the wind sock to see which runway to use, lined up, full throttle, boy does that thing move. Ran about 150 to 200 feet and pull back full elevator (not needed) and the Bobcat launched into the air with the nose straight up like it was a rocket, this is not good. Quickly began levelling out so that I trim the Bobcat. It took about 7 clicks of left aileron and 6 clicks of up elevator (remember slightly nose heavy) and she was flying level. All I heard form behind me, "Boy is that thing fast." That was with the retracts down. I need to dial a little more expo on the controls, I'm at about 50% I will go to about 70%. My good friend, JBEN, says okay that looks great let's get her down so we won't have to dead stick her (new engine first flight), I thought great idea. Begin my line up approaches. Did this about 4 to 5 times to judge the speed and distance I needed to land. Remember the crosswinds. On my final approach I was lined and looking good, I was about 10-15 feet off the deck. I committed a no-no, the Bobcat was moving so fast on landing I thought I was going to miss the runway so I helped it down by giving a down elevator input. When I got about 5 feet I decided that down input was too much, by the time I gave up it was on the ground. The front strut shaft got bent, the right main retract got ripped out and the left main was about to be ripped out. Good news no damage to the plane, not one sratch. I assessed the damage to the gear, the right main rail blocks came out clean, so they only need to be epoxied back in, the left had one block come out clean and one cracked, so I will epoxy the one block and replce the other. Nose strut only needs a new shaft which I have since I ordered an extra strut anyway. I'll be back up in the air tomorrow, maybe even this afternoon. I don't think the mains broke or came loose do to the hard landing, I believe it was due to the cheap hot glue giving way and cheap wood. I will put epoxy over everything I can see.

Thanks for reading this lengthy post. I will post a shorter second flight report, if nothing goes wrong.

BillS

I like to put engine kill on a switch for emergency purposes.

I did manage two flights with fixed canards but was disappointed with the performance as the airplane left the ground. It took forever to reach safe flying speed after which the flights were OK. The canard probably added extra drag to a marginal power condition. The canard was on a knob but I didn’t have enough hands to work the knob.

I temporarily removed the canard and am shimming the tail plane up so the elevator will be parallel to the horizontal stabilizer during level flight. Will try the canard again after more experience with the airframe and maybe a larger engine.

Bill

HeliTB

Bills...Canards means butt first. I'm a Minister so I didn't want to use another word. But anyway, with canards you have two elevator control surfaces. The canards will fight the rear elevator movement if they are stationary. In order to get them to be efficient they must be active during flight, which means they must be moving to help the loop or lift of plane.

I tried this on my foam jet, that's how I know. I removed the canards and my jet flew like it was on rails.

BillS

Anyone know the weight of a very old HP .61. Found one with a removable front housing but didn’t have a scale to measure the weight.

Bill

TUMBLER

My Feedback: (13)

Since you guys are facing the tank towards the nose, aren't you having trouble drawing fuel so far with such long fuel lines?

Tumbler

BillS

I used a small header tank behind the main tank.

Bill

HeliTB

Tumbler...I didn't seem to have a problem drawing fuel for my 5 min. maiden flight. But a header tank is awesome idea.

Good News!!!! The Bobcat is repaired and ready for flight. I epoxied the rail mount back in real good and put epoxy on other high stress joints that I could get to. I also thinned the rail some to further recess the retracts so that it disappears. Didn't do the front since the nose wheel needs to be taller than the mains to give the proper incidence needed for lift off.

TUMBLER

My Feedback: (13)

Thanks guys. I actually just hollowed out the rear former and pushed the tank all the way back to the engine block, so no header needed.

I have built the 120 with a turbine and 25 size with electric and both had bolt on wings. Looks like the wings just get glued on this one. IS that what everyone has done?

Thanks!

Tumbler

BillS

I bolted the wings on in case a repair might be necessary.

Bill

HeliTB

My wings are bolted on as well. They already had the bolts and the blind nut mounted. Instructions say glue, but I think they didn't update the manual with the updated kits.