Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Kobra with a Jett 46??

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Old 07-04-2006, 06:53 PM
  #1  
pilott34
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Default Kobra with a Jett 46??

Im normally a turbine flyer, but my interest has been sparked lately by a fast prop plane. Has anyone tried a Kobra with a Jett 46?? I thought this might be a little overkill, but hey its extreme speed right? It would probably be nose heavy but I may try and compensate by putting the battery pack and elevator servos aft of the CG. If not a Jett 46...which engine. My goal is a rocket. Im also considering using a skid vice gear sort of like the magnum. May also make the rudder non functional for ease of construction and save a little weight. Any thoughts?

Mike
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Old 07-05-2006, 12:13 AM
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Razor-RCU
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Default RE: Kobra with a Jett 46??

Sounds good... The Jett is always a good choice the West-50 would be quick too especially on a small prop like 8x8 APC
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Old 07-05-2006, 01:14 AM
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Default RE: Kobra with a Jett 46??

Cool....just ordered the plane. I was looking at the OS 50SX only because I could order the plane and engine from Tower, but I held out for the Jett. A friend of mine has the Jet 50 on a Patriot and its not all that fast, although I think he has some more fine tuning to do.
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Old 07-05-2006, 09:06 AM
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Default RE: Kobra with a Jett 46??

Look up Crazy4Flight on here. He has a Jett 46 powered Kobra (do a search, there are some photos in here somewhere).

Just watch the CG, maybe move the firewall aft a little bit during construction.

Of note, a straight Patriot 40, with a SJ50, retracts up, will hit a top end in the 115-120 mph range in level flight. Some have pushed in excess of 130 on occation. APC 9x8, 9x9 prop recommended.
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Old 07-05-2006, 09:31 AM
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Default RE: Kobra with a Jett 46??

Thanks Bob... I think thats close to what he is getting. He has a tuned pipe on it and maybe it just looks fast on the ground. It just looks like it should be doing 150. Ill look up C4F on here. Do I contact you to order the Jett engine?

Mike
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Old 07-05-2006, 09:44 AM
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Default RE: Kobra with a Jett 46??

I think this is the plane Bob is talking about. Not sure who's it is but nice setup
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Old 07-05-2006, 10:04 AM
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Default RE: Kobra with a Jett 46??


ORIGINAL: pilott34

Thanks Bob... I think thats close to what he is getting. He has a tuned pipe on it and maybe it just looks fast on the ground. It just looks like it should be doing 150. Ill look up C4F on here. Do I contact you to order the Jett engine?

Mike
Engine orders through the jettengineering.com web site

Be advised, Dub will be at the Nationals in Muncie for about the next week. So delivery of the engine will likely be following his return.

Bob
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Old 07-05-2006, 10:52 AM
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Default RE: Kobra with a Jett 46??

cool thread,
got a kobra with a supertiger 40 in it and it totally screams. over 110 plus the last time it was clocked. i think that im faster now but no radar gun has been put on it since i got it all smoothed out. anyway, i have retracts on it (mechanical) and moved the battery pack back and both tail servos aft to compensate nose weight. i did widen the fuse by 1/2 inch and extended the length in the rear by an inch. i sheeted a little extra on the wings to strenthen them and help with the retract mountings and ran individual aileron servos. inside the fuse i have the fuel tank mounted on the CG, front retract servo, and the reciever.
thought it would be a sled in the air but she tracks extemely well and as soon as in suck the gear up she takes off. i am also looking at putting a jett in this on this winter. im sure i could go super sonic with that set up. for now (summer) the ST works really well. turning 14.6k with a 9x6 prop and burning holes in the sky.
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Old 07-05-2006, 12:28 PM
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Default RE: Kobra with a Jett 46??

Ah... found one...
http://www.rcuniverse.com/forum/fb.asp?m=4317519

its the white plane.
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Old 07-08-2006, 09:37 AM
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Default RE: Kobra with a Jett 46??

Hello frikinstik !

Can you give me more pictures of your Kobra? I am interested how do you install thr retracts. Wich company produkt of retracts do you use?
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Old 07-11-2006, 04:07 PM
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Default RE: Kobra with a Jett 46??

i4ni.
wilco. let me get some good pics for u. the retracts are standard Hobbico type mechs and i run 2 JR RT88 low profile retracts. not to hard to modify if you are building a kobra. more to follow.
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Old 07-12-2006, 09:20 AM
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Default RE: Kobra with a Jett 46??

Hello frikinstik!

Thank you for your answere. Sorry, I am from Germany and I don't understand you at all. Hobbico and the JR SPORT - Servo, Retract RT88 (JSP-20080) is a good tipp for me. Thank you.
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Old 07-12-2006, 09:45 PM
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Default RE: Kobra with a Jett 46??

Bob27

Correction it is a Jett SS 40 in my Kobra. Kit bashed to a tail dragger with Robart mechaniacl retracts. It likes to nose over on taxi and take off. I bought it 85% done. So it will be a chore to move the mains forward. But first I will move the CG back a little.

And it goes!!!!
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Old 07-12-2006, 09:51 PM
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Default RE: Kobra with a Jett 46??

pictures will upload if i send them in one at a time. [:@]
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Old 07-16-2006, 09:53 AM
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Default RE: Kobra with a Jett 46??

i4ni,
OK, got some pics that should help you out. first thing i wondered about is if you had already assembled your Kobra. if not, cool. if so, the wing can be modified pretty easily but the FUSE i have is 1/2" wider and 1 inch longer than the plans, including the front gear door addition that makes the bottom of the nose a little deeper to fit the front retract. the front retract still protrudes from the bottom but it was the only way to mount it, and butts up against the engine mount.
First pics depicts the mounting of main gear. mounted on line with gear placement on plans as well as when extended. i utilized hard basswood (4 total) between ribs. to re-enforce the ribs i utilized the plans and cut and sandwiched two 1/16 ply ribs from the main spar to the trailing edge. installed mouting blocks and stengthened with strips of fiberglass cloth. to make the gear bays I utilized 3/16 " balsa for the sides and 1/16 ply (easy to bend) to make the rounded wheel recess. to make this you have to cut through more of the ribs toward the root rib, and to strenthen them again i utilized 1/16 in ply cut to fit on each one cut and sheeted the wing out to the retract mount.

Next pics show the mounting of the retract servo. i used the low profile type because of limited space. this bay was originally for the aileron servo but works perfectly for the retracts. this also requires you to install individual aileron servos which get mounted on their sides and mounted using hatches something like i did. for the hatches i used 3/32" lite ply and wood screws.

For the Nose retract pics, this was the hardest one to make fit and what i did is use the plans and put my retract on them an traced it out, ensuring that the pivot point was centered exactly where the front fixed gear was. this causes you to have to cut up into the firewall enough to get it recessed but not to much so you can still get the mount on it. i utilized a piece of aluminum stock bent to 90 degrees and mounted this BEHIND the firewall. this strengened the amount of firewall removed and also gave more "meat" to mount the engine mounting screws. then i marked and drilled for the retract mounting holes and mounted the retract by sliding it nose in first and then down on to the aluminum stock. i only used the back to holes and use nylon locking nuts to keep in place.
for the nose retract, you have to move the fuel tank back (more pics to follow), and i made a mounting plate for it and the steering servo. not alot of clearance for either servo and i mounted the plate low enought to alow the retract servo with arm and control rod keeper to pull in a straight line. both the retract and stearing servo are connected to the reciever using Y-harness.

cant load anymore pics and i got to get flying so i will get back at this later. if i am unclear or you have more questions let me know.
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Old 07-16-2006, 10:20 AM
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Default RE: Kobra with a Jett 46??

Hello frikinstik,

Thank you for your great pics. My Kobra is not assembled already. This pictures and your words will help me when I build my Kobra.
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Old 07-17-2006, 10:51 AM
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Default RE: Kobra with a Jett 46??

any reason the main wheels are on backwards? Not retracting into the wheel wells ?
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Old 07-19-2006, 12:13 PM
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Default RE: Kobra with a Jett 46??

BOB27,
yup. with the wheels place out board they provide for better lock down out on landing. i have 3 sets of mechanical retracts and found that you can slide after landing and they keep tention on the control rods and keep them from collapesing if they get a little slop in them which they tend to do after a few landings. just my opinion.
saving my pennies to put a jett in this one too.
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Old 07-19-2006, 09:00 PM
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Default RE: Kobra with a Jett 46??

I think this plane is on the Jett web sight. If so it is a King Cobra with a Jett 90 if memory serves me right. I saw it at a swap meet several years ago and should have bought it.
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ORIGINAL: Cyclic Hardover

I think this is the plane Bob is talking about. Not sure who's it is but nice setup
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Old 07-27-2006, 02:28 PM
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Default RE: Kobra with a Jett 46??

I had a Kobra with a TT 46 in itand it was pretty darn fast I also clipped the wing one wing bay on both sides. With clipped wing it had a tendancie to tip stall if you tryed to land to slow.
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Old 07-27-2006, 06:39 PM
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Default RE: Kobra with a Jett 46??

Hi Frikinstik,
You really do have some nice looking models[sm=thumbup.gif]

This 1 & the F18 are a credit !!
Tony.
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Old 02-07-2008, 10:03 PM
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Default RE: Kobra with a Jett 46??

hi, does the plane require any mods in order to mount a 46 ax?
thanks
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Old 02-08-2008, 10:38 AM
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Default RE: Kobra with a Jett 46??

I first installed a Magnum 46, but leaked to much, so i dropped the 46 AX in. It fits but it is very tight. Fueling is a problem, but it does work. I made it a tail dragger and moved the elevator servo to the rear and the battery pack behind the rudder servo just ahead of the 3rd former. I still needed about a 1/2 oz of tail weight. It worked and at the weight of this plane it is very fast. I believe it to be much faster than the calc. boys are figuring. I have more pix if you need them.
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Old 02-08-2008, 08:14 PM
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Default RE: Kobra with a Jett 46??

what mods does the plane requires in order to convert it into a tail dragger, what other mods are needed in order to mount the elevator servo in the back?
thanks for all the help.
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Old 02-11-2008, 09:00 AM
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Default RE: Kobra with a Jett 46??

You will have to move the landing gear block forward of the spar-this includes cutting wing ribs. Also you need to figure out the steering, I made a pull/pull system but if I did it again I would just let the wheel caster. Takes off in 5' anyway.
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