Hi Xairflyer,

Not flown it yet but I’ve set spoilerons as GSK recommends. These will through increased drag reduce speed as well as reducing lift. I’ve used spoilerons on previous planes with success. Start with a only 2mm upward movement and increase with experiance.

The main problem that I believe exists with flapperons is the amount of up elevator required to maintain straight and level flight. There just doesn’t appear to be enough up elevator movement still available to flair for touchdown.


Eric

Hi Guys ,
Not replying to enyone in particular ,just relating my experiances.
The whether in the UK has been terrible as you may have seen on the news?
No flooding where I am but still been wet and windy . Not the ideal conditions for a first flight of my Bobcat 50 which has beem finished for a couple of weeks and intimidating me every time I go into the workshop.
The whether changed for a while and the wind was down the strip so I've now had five flights.
The first takeoff with the throws as recomended was a bit scary far to much movement.I got it under control and switched in rates which were 70% then all was fine. Seems absolutly viceless. Second flight had an engine cut at about 80 feet going down wind. I took a chance on pulling her round . There was no stall or wing drop and I got back to the strip. On the second outing I richened the engine fuel by 3 clicks and all has been fine . A really smooth flyer and quite fast.
My setup is : West 50 with a West pusher pipe , 11X7 APC , no retracts ( the retract version was available about two weeks after I bought mine!!!) Tank as supplied with the clunk at the rear ,as normal. HS MG's for the elevator . The only thing I've changed is I made new U/C legs from better wire ,reversed them, made the wings detachable using joining plates and bolts at the rear and screw eyes into the route rib throght the Fus side pulled together with a cable tie. Both U/c blocks have been replace with larger (glued in ) blocks!
Thanks for all th edvice everyone, Good flying

I also live in the UK and agree the weather has been poor.

I maidened mine on Sunday, had to put an 11x10 on due to noise restrictions at our site - I have a Jen 57 with CVEC tuned pipe.

Our strip is grass, about 50 metres long. It took a full run to get off the ground with elevator at the last minute.

I agree, the throws particularly on the ailerons were way too much. I've reduced these from 75% movement (that's the maximum throw according to the manual), 50% expo to 45% movement and 60% expo. Elevator and rudder I have left as per the manual.

I mounted my tank forwards and ran the tubes back over the tank. It appears to work but after 6 minutes of flying you can guarantee a dead stick. I might reverse the tank to point to the back and see. I did manage to pull the tube a bit too much when fueling and pulled it off the carb and flooded the inside of the fuselage.

I've also made the wings detachable, I put some captives in the wing and nylon bolts from the inside of the fuzz just before the 5/6mm rod that stops the wing moving. To help take the bolts out I glued some large washers in the bolts to turn easier.

My first landing was dead stick. I had to hop over a fellow flyer's plane who had just landed, everyone laughed.

Attempting a controlled landing I noticed the glide in was good but it comes in at speed, cutting the throttle on the approach might help a little. I did slip into the rough grass but all it did was bend the undercarriage. I suppose something has to give.

I might put an eight channel receiver in and program some flaps, it could help slow it down or at least bring it in slower without falling out of the sky. I have all 7 channels used:

ch1 - ailerons - on y lead
ch2 - elevator - left side
ch3 - throttle
ch4 - rudder - left side
ch5 - elevator - right side
ch6 - rudder - right side
ch7 - nose leg & receiver battery

It's useful to share experiences, a lot of information here is of use to people looking to do the same. It does help to get a successful first time flight and not black bin bag at the end of the day.

Jason

Jason,

Try holding the nose high, very high, on your approach. This plane being a pusher handles like a jet on landing. Nose high and throttle to adjust glide. Mine comes in very slow.

Mark

Cheers Mark, will try that and let you know.

Other than that it flies fantastic.

Jason

Just finished putting my bobcat 50 together and found it tail heavy. Have a Tower 61 on it. Had to hang 1 pound of lead on the nose to get close to balance. Instruction manual has CG at 175mm from leading edge. Could this be wrong or am I missing something?
Cliff

Cliff,
I balanced mine at about 10.5" from the leading edge of the wing at the fuse. If you go back through this thread,you will note that many have discovered that the balance point in the instructions was a bit off. You may have recieved a kit without the addendium.

But check back about 40 to 50 pages and you'll see what people have found.
Boy has this thread gotten long!

Jgwright - is that a STOCK bobcat 50 by Dave Wilde with the Wren 44 or has it been modified somewhow ? strengthend maube ?

corrected CG in later instruction [
Maunal

Dave's Bobcat has had very little done to it. He wanted to see how it would stand up to being powered by a turbine. He did use stronger pushrods and better clevises, but the structure of the plane is pretty much as supplied.

John

Yes, 10.5 inches is the measurement for CG, that's where I balanced on according to my manual.

That's 26.67 cm or 266.70 mm.

Jason

CG at 260mm sounds a lot better. I knew some thing had to be wrong. Thanks Cliff

Did everybody glue the horizontal stab in or did they just bolt it into the booms? The instructions only show bolting it in but those instructions are almost worthless. I am going to replace the nylon bolts with metal ones but I am un-decided on whether I should glue it in too.

thanks.....

My 20 hour Bobcat to build that is taking 20 months to complete......
retracts are in.
robart struts installed
wings has been re-covered where the covering was taken off
wing mod is done
boom mod is done and booms installed.
all control surfaces are hinged
wing, rudder, and elevator servos installed
rudder and aileron pushrods threaded. Elevators will be threaded once I decide what to do with the stab.
Glued maple blocks in for the motor to mount on

I used Loctite extreme repair on the ends of the horizontal stab in addition to the bolts.

Just bolted my stab with loctite. I did need to dip into my stock for a longer bolt on one side.

I have a question about flaperons. I have a Bobcat with a MW44 on it. I have flown if off of concrete and grass but it is hard to get it up off of a grass runway. I moved the main gear forward, raised the nosewheel and tried flaperons the other day. It took off much quicker. I landed the first time without flaperons and had no problem but on landing the second time with flaperons on it pancaked in and broke one of the landing gear blocks. I have been reading earlier threads that flaperons cause it to dive because they work like an elvator. That may be what happened on landing, however, it was pretty windy so I'm not totally sure that was the problem. I am going to try reversing them on the next flight. What I am wondering would that also help on takeoff since they seem to be working as an elevator?

Thanks for any help.

Hal

What did you do for your nose gear steering linkage?

SUCCESSFUL MAIDEN FLIGHT TODAY!!!!!

I'm a happy camper for sure! Here's some good info for you guys building:

I have the retracts version, and I'm using Cermark Mains from Robert at http://www.EJF.com These are gear made for the Cermark F16. The mains are fine, the front doesn't work, as it's made to sit recessed in the fuse (with gear doors). So I have a Robart up front.

I am using a Venom 6V 1200mAh battery, that is in the second bulkhead area from the nose, and I packed in soft foam to stop it from moving around. The can for the air is up there, too. I have an OS 55 AX for power. It balanced a bit nose heavy at 10 3/8" from the leading edge where it meets the fuse. NO EXTRA WEIGHT REQUIRED.

It is REALLY important to NOT USE THE PLASTIC BOLTS for the tail booms! In the little baggie of hardware, there's 2 metal bolts that fit in the rear perfectly, but nothing but the plastic bolts fit the f$%#ing Chinese blindnuts, so I used them in the front. I have been to 2 different Ace hardwares, and 2 hobby shops, and nobody can find a bolt that will screw onto the screw - either metric or SAE. The plastic screw UNSCREWED itself in flight. The metal one held, so I consider myself LUCKY, and yes, I'm going to buy a single $1 lotto ticket today since I'm very lucky that the plane landed safely!

Anyway, I was talking with another guy at the field today that has the bigger one - same crap for the booms. He told me to use a heat gun, soften up the glue, pry the blocks out and change the blind nut to 6/32, and then of course you can use a metal, hex head bolt. He also put 1/16 ply plate on the underside of the wing to prevent anything from digging in to the soft balsa. Sounds like good advice, so I'm going to do that tonight.

I thought the elevator felt "mushy" in flight, and I had to switch it to higher rates, as it nosed down pretty hard in turns. I'm thinking that this is a combination of the booms flexing with the plastic bolt, and I'm a little nose heavy. I was also running the new motor pretty fat (rich) and was not yet impressed with it's speed. It flew fine - roll rate was good, and it held knife edge during a 4-point roll pretty well.

I have my plane setup with flaperons - about 1/4" down, with about 1/8" of up elevator mixed in, but I didn't test them out yet. There's definitely 2 schools of thought here on flaperons vs. spoilers, and I'm going to setup a mode for both for I can play next time out. I will say that without any flaps or spoilers, it still landed like "butta". It does take a while to slow down, so brakes might be the call here...but then again, I was a bit hot coming in because I didn't know what to expect.

So I'm trying to really decide about the booms...to epoxy permanently, or not. If I epoxy. I don't need to worry about "fixing" anything...and I'll still leave the stab screwed in with the 4-40's and locktite so I can at least get the wings off.

I'm hoping that when I lean out the motor, it goes faster. Most of the flight was a full throttle, and it flew fine, but nobody said "Wow! Thats fast!". I'm using a Zinger Wood 11x8 pusher. I will try APC 11x8 and 11x7 and see how that works...and someone else told me to try a 12x6. So...overall, I'm very happy, and would recommend this plane.

I'll post pix now that it flew....I'm superstitious and never take pictures on first flight day!

Thanks everyone for all the help!
Mark

OPJose - I setup Pull-pull on the rudder. When the gear retracts, they go slack, when the gear extends, I have enough tension on the steeing assembly so that it feels great.

Also - I didn't feel comfy having 3 servos on one channel, so I put the steering on Aux2 (disabled the switch) and have it set to mix at 65% with the rudder. It's active all the time, but of course when retracted, there's not enough tension on the lines to try and move anything. Terry posted pix a few pages back...I had to dremel a bit to allow for the actual steering arms to lay down, and I shortened them to only the first hole. (You don't need much throw).

See the pix on Page 99. THANKS TERRY!

I'm really looking forward to flying again tomorrow!
New Jet, later today my wife picks up her new 328i, and I got lucky with the tail boom (read my earlier post)....so today *IS* a good day for sure!

I sure learned a lot working on this plane from everyone on this forum! It was my first time with Air retracts, and I'll tell you that I will NEVER do mechanicals again!

Cya!
Mark

Mark

Spoke with Al and he is using an 11X7 on his OS 61 and his runs fine. Maybe the prop your using is a bit much for the OS 55. Then again I have no experience with the glow engines.

Just my 2 cents.

Re: Retracts.

I was not comfortable doing as the picture shows on mine, which is why I asked.

There is too much wood removed from the anchor block IMHO.

Instead I moved the control horn further Down ( or up when the plane is inverted ) the gear, so that it folds in past the firewall. Of course this required a cut in the fiberglass to accept the horn when the gear retracts.

Re: 3 Servos on one channel.

Since the servos merely receive a signal the limit to the quantity is more of signal degredation as you extend the line.

There should otherwise be no problems putting in three or more servos on one channel, as they do not draw power from the RX, rather they draw directly from the battery.

I have several biplanes with have four servos hooked up to the one aileron channel. This is pretty standard.

However now that you have the stearing on one servo, consider setting up the radio to disable attempts to move the stearing linkages when the gear is up.

I did this with my JR radio's mixing functions.

It means that I have one less servo consuming power when the plane is in flight.

OK, makes sense... Good idea about disabling based on the gear switch position - I'll do that tonight.

Can someone PLEASE tell me the exact specifications for the screws that hold the booms on?

It's really going to be hard to get to the forward blind nut without performing surgery...

Thanks!

Thanks AGR413 and MMallory for the replies. I did plan on using locktite on all of the metal bolts.

marktur

I replaced the front bolts on the booms with a 4m x 50mm hex bolt and a 1/8 x 3/4 fender washers. I had to use the long bolt from the bottom of the wing all the way through because the Monday built side of the plane, the bolt was going all the way through and coming out the top of the boom. The Friday side was working as designed as the bolt did not go all the way through like it other side did but I made it the same for both side for cosmetic purposes. I did not want to do the surgery on the booms to get the blind nuts out. I used the fender washers to make sure the compression from tightening the bolts was spread over a larger area and to make sure the hole in the wing was covered.

For the rear bolts I used 4m x 30mm socket cap bolts and fender washers. I used the fender wahsers here for cosmetic reasons to match the other two.

I got them all at Lowes. Cost me about $8 for everything but I did buy more than I really needed. Should run you less than $5 if you buy only what you need.


You can also do what this guy did. Drill out the blind nuts and runs a bolt all the way through and a nut on the bottom. [link=http://www.rcuniverse.com/forum/fb.asp?m=4920007]click here.[/link]. You would need about a 2 inch bolt for the front.

THANK YOU, BLUE MAX! You da man!

I found an old bolt that looked "close" but had paint or epoxy on most of the shank...pulled off the boom, and just tried to turn it in for kicks, and lo and behold IT FIT! Couldn't find another in my box-o-bolts, though. So I put that one in, and it locked the boom down nice and tight. The other side the plastic screw was holding very well, so I decided to go fly again.

I took all the expo out of the elevator, and gave it a bit more throw, too. (Felt way too mushy yesterday). I also realized that I had a couple of MM's of droop in the ailerons (like flaperons), so I readjusted that to be perfectly aligned with the wing. With that change, I decided not to change too many other things - especially the CG, and fly it again. BIG DIFFERENCE! I had to put down trim in it (started with the settings from yesterday). So that was a good sign. I also switched from the 11x8 Zinger wood to an APC 11x7, and leaned out the motor (yesterday it was running at break in settings - two-stroking, but still spitting a lot of oil... It flew MUCH better! I didn't have to keep it at full throttle the entire flight, which was good. It had decent speed - still not HOLY ***** FAST, but very acceptable.

I will let the motor continue to break in - see what it's like after the first gallon. If I'm still wanting that speed, I think I'll need to upgrade to an OS 75 AX ringed motor. Has anyone compared this to the Tower 75 ABC? It's about $100 apart in price...but the real question is performance?

Anyway, my second gallon, I think I'll switch to 30% Cool Power Heli fuel - which is great for motors that are not cooled by the prop-blast, plus, it's got twice as much nitro, which will add more power AND cool it more. So we'll see... I will also try the 11x8 again now that it's breaking in more...

The plane flew as expected today...nice and smooth. Low passes with the gear up were SA-WEET! Landings were nice, it settles in really nice with just a click or two above idle. It's a keeper for sure!

Can't wait to go again tomorrow....just wish we could get an overcast day already...it is HOT HOT HOT here in Palm Beach, FL!

Cya!
Mark

Your question made me curious so I did some research:

O.S. .75 AX ABL Engine

SPECS: Displacement: 0.75 cu in (12.3cc)
Bore: 1.02" (25.8mm)
Stroke: 0.93" (23.5mm)
Practical RPM: 2,000-16,000 r.p.m.
Power Output: 2.4ps/15,000 r.p.m.
Weight: 20.39 onuces (578g) w/o muffler
26.46 ounces (750g) w/ muffler
Recommended Props: 14x6, 14x8, 15x7
1 ps = 735.499 watts, 2.4px*735.499 = 1765.1976 watts output at 15,000rpm




Tower Hobbies .75 Ball Bearing ABC Schnuerle & Muffler

SPECS: Displacement: 12.21cc (.75 cu in)
Bore: 26mm (1.02")
Stoke: 23mm (.91")
Horsepower: 2.2 BHP at 15,600 RPM
Weight: 652g (23.0 oz) (with Muffler) (jl10/00)
Weight: 535g (18.9 oz) (without Muffler)
Recommended Props: Break In: 12x6 or 13x6
1 BHP =745.7watts, 2.2BHP*745.7=1640.54 watts @ 15,600 rpm


So if you look at pure watt per rpm efficiency the OS is 10.64% more efficient than the Tower motor.

@ 13,000 rpm that is a difference of 162 watts. The OS will spin a larger propellor which may be where you will see the advantage of the 10% greater efficiency. Not to mention those large props won't fit between the booms of the Bobcat. In this case I seriously doubt you will see the benefit of your extra $100 bones by buying the OS, the OS is also heavier than the Tower motor which means you will need more nose weight and make wing loading that much higher.

I would like to see what the Tower .75 would do with a tuned pipe on this plane.