opjose

Those look pretty nice. I was thinking of using them for another project.

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BTW: Anyone here running the Graupner 11x8 props?

I noticed that the warnings from Graupner indicate that these props should not be run faster than 12,275 RPM lest they break apart!

With the GMS or Tower engines, we can crank them up WAY beyond that.

CrashPro

My Feedback: (1)

Yeppers on that opjose.....after trying all the other available pusher props (and that includes the 3 bladed props)....came to the conclusion that I was getting the most speed with the Graupner 11x8 prop....

patzane

where can you get a Graupner prop from I like in AZ and none of the LHS here carry them

patzane

So them retract should work on this bobcat. What about motor. OS 55 vs Tower 75 which will give you the most speed

doubledcom

My Feedback: (49)

I ordered my graupner pusher props from hobby-lobby international

opjose

If you go back somewhat in this thread there is a comparison of the two.

If I remember correctly the OS 55 does very well especially when combined with a pipe.

However it's performance is about on par with the much cheaper Tower 75 or GMS .76, so you can save your dollars if you wish.

The latter two work fine with the included muffler.

opjose

Have you had any indications that I should pay attention to Graupner's warnings about the max RPM speed on the 11x8 prop?

According to their included warnings, we should NOT be spinning the prop that fast lest it break apart.

AGR413

My Feedback: (1)

Here is the link to the os 55/tower 75 comparison.

http://www.rcuniverse.com/forum/fb.asp?m=6690701

Meekskin

I would offer the Magnum 52...cheap but very good motor....look at my pics on eariler post. You can get 16k with regular prop and 15500 with pusher prop. You will like the speed.

Stick Jammer

The elevator is one piece, the rudders are separate. The stock servo configuration is set up for dual mini's on elevator and rudders. Go back to page 99, post 2461 for an option using a single standard servo for elevator and rudders.

Stick Jammer

I modified the tailboom servo bays for standard servos and went with a single on elevator and a single for rudders. I used Hitec HS-475HB's all around. With a 5-cell pack they are rated at 76 oz/in torque. 100 bucks gets you all six, big savings over the stock set up using mini's.

doubledcom

My Feedback: (49)

Opjose....Just got the graupners....but have not used them...It's going to be quite a long time before I get to test them out .....we just got another 12 inches of snow and gusting winds of 30+ miles per hour....couple days ago we had temps of 20 below zero......I hate winter....

CrashPro

My Feedback: (1)

Haven't had any props come apart on me opjose....I had canopy screw come off and hit the prop and take a chunk out of the prop,...but it still didn't break.

Lopi

Here is my Bobcat...
I make a new Canopy and i think there is a better one...

BillS

The canopy looks good. I am attempting to come up with a better method to attach the canopy and am interested in your approach.

Bill

hapyjac2

My Feedback: (927)

Bill,
I have used the rear catch and pin thru the nose method on mine. It is simple and very strong. My Bobcat is turbine powered and the canopy has never even shown signs of being loose. Also allows quick entry to the interior, a must for a turbine powered jet.

There is a conversion article on my web site which shows how it's done. check it out. [8D]

www.southfloridajettogether.com

opjose

Here's what I did on my Bobcat .25... it works great. The canopy has never fallen off even though I have the plane screaming through the sky with it's .46 equivalent electric motor.




The magnets are unneeded. They are holder-overs from my first attempt which did not work well.

PhilLin

Oh yeah. I found out magnets do not work well when in the shear position. I used 2-pairs of 3/16" dia rare earth magnets which worked well after changing them to pull against their flat circular faces. Always had a nagging suspicion that the added stray magnetic field might cause Rx problems close by so had the Rx wrapped around with alu foil; & was able to have good Rx performance.

@Opjose, care to give a bit more detail on your electric version?

Phil

ps: @Opjose, I like the way you mounted your canopy.

Stick Jammer

I've seen a few clever canopy installations in this thread, they all looked good. Personally, with a glow engine and bolted on wings, I don't need to get into the fuse very often. When I do need to access the interior I don't mind removing a few screws. Keep in mind that with a pusher prop anything that comes loose in flight has the potential to do major damage.

opjose

On the Bobcat .25 I'm running a pair of 3900mAh batteries in a 6S configuration ( 22 volts ) driving a 893KV motor, a 10x7 pusher and a 60Amp ESC capable of dealing with the 22volts. Fortunately the ESC was more than able to handle all of the micro & mini servos used.

This turned the little Bobcat .25 into a little screamer of a plane.

It draws about 700+ watts 38Amps, so it is roughly the equivalent of a .40+ glow engine.

Unfortunately it is a non-retract plane due to it's size.

The canopy mount I used above enables quick access to the battery packs.

I had to remove one of the formers to get both of the batteries to fit.

The clips I used are from Dubro. Two pairs could be used to firmly attach a canopy for the larger sized Bobcat.

BillS

Thanks for the canopy mounting information. Parts of both ideas will be used.

The South Florida Jet site was very interesting. The canard's were particularly interesting.

Bill

gooseF22

Im turning that prop 15000 rpm with a super tiger .90 on a Jett pipe. Make sure to balance it, and if you nick it, toss it. I had one come apart that had a little nick in it. It was pretty impressive when it let loose. It went right through the keel. But we dead sticked her in and had her back in the air that day....a little packing tape and a new prop. I was flying a keecat, but same idea.

gooseF22

Talk to Dub Jett at www.jettengineering.com I have a modified jett pusher muffler and its simply bad *****. Its on my super tigre .90. They will close the back end and put a nipple out on the front to make for pusher. it added 1000 rpm. Im turning the graupner to the limit of its ability.

Nobody stands near the prop!! I can tell you that! it screams!! I run 20% ys fuel and run it on the rich side, just as it begins to lean. It will unload more in the air, so be careful when turning this prop fast, the blades are a bit too wide for speed as it will unload more than an APC. But it pulls like a truck.

I cannot find a better pusher prop for my ST.90 either. I wish someone made an 11x9 pusher.

opjose

I've been asked twice how I did the mod for the GMS or Tower engine exhaust, ( an improved version of what you see in the picture below ) so I'm posting this here.



I mounted the muffler in place with the exhaust facing down.

I obtained the longest stock exhaust deflector I could find.

I used the Venom deflector. This one: http://www3.towerhobbies.com/cgi-bin...?&I=LXRHS9&P=7



I temporarily installed the deflector on the muffler.

I drilled a hole the same size as the deflector just past the "bend" on the deflector. The Center of the hole was just past the bend point about 1/8".

I removed the muffler, then using a GP engine center hole marker/finder ( so as not to rip up the wood ) I marked the center point on the lower wing drilling through it with the GP Hole finder tool.

I then opened the hole up to size from the bottom of the wing.

I then CA'd the wood around the now open holes, by dripping in THIN CA from the other side. This hardened the wood for the next step.

I had on hand some brass snap rivet rings of the right size which II ended up using but I had ordered these, which should work as well.

http://www3.towerhobbies.com/cgi-bin...?&I=LXRHP4&P=7



The rings were epoxied in place to prevent the wood from cracking with any vibration from the deflector.

Once dry I installed the muffler and deflector ( through the rings ) back onto the plane.

I wire tied the deflector to the muffler.

I then put silicon canopy glue on the deflector both top and bottom to prevent fuel from seeping into the inside of the wing.
Canopy glue is removable but impervious to glow fuel...

The top and bottom had to be separately done as the canopy glue runs... so the top was done first one night and the next I did the bottom.


The deflector was exposed about 1/8 to 1/4" of the deflector UNDER the wing. The first time I flew it I found that some fuel would end up smearing across the wing itself, which I did not like...

soooo....

I got one of these: http://www3.towerhobbies.com/cgi-bin...?&I=LXRHR9&P=7



And epoxied it just to the stub of the deflector ( not the ring ) that was sticking out of the bottom of the wing... that way if I ever want to remove or replace the deflector I merely cut the deflector from the top of the wing, then pull it through.

The coupler angles back.

The whole thing looks pretty good and it keeps the plane perfectly clean.

Meekskin

Opjose, Nice looking system but how fast does it fly. I flew mine today and could not believe the radar gun reading. Top speed today was 122mph....this is with my magnum 52 weston pipe and of course retracts. I really like the way my bobcat flies and I know it will go faster. If I could enclose the wheel wells I'm sure my speed would go up. Anyway, the 122 mph is the fastest for our club. Lets see what other bobcat owners are getting. POST your speed here.....