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Old Dec 30, 2005, 08:36 PM
SoCal, Year Round Flying!
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Scorpio Dornier Jet S2075

I picked this up at a hobbyshop today, looked like its been there for a few years. All parts appear to be there including 2 Cox fan units. anybody build one of these lately?
Any advice on going brushless or is 3S lipos possible with the stock motors?
I figure on first building it completely stock and running lipos, Should fly well with the lighter than stock weight.
Instructions say 10Amp ESC, 6 cells 350-600mah
Bruce
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Old Dec 30, 2005, 10:24 PM
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Quote:
Originally Posted by bmiller
I picked this up at a hobbyshop today, looked like its been there for a few years. All parts appear to be there including 2 Cox fan units. anybody build one of these lately?
Any advice on going brushless or is 3S lipos possible with the stock motors?
I figure on first building it completely stock and running lipos, Should fly well with the lighter than stock weight.
Instructions say 10Amp ESC, 6 cells 350-600mah
Bruce
I have sold mine but I do have plenty of experience with the stock fan/motor.

The stock fan and motor is widely used on many Cox single and two channel EPP planes. They are good for their price and size. You cannot go with more than 2 cell LiPo or you will fry your motor very quickly.

Twin fan wired parallel can probablly take a little more voltage but I recommend to monitor the voltage under load and do not go over 7 V at full throttle. The optimum power is about 20~25W per fan unit generating about 2~2.3 oz thrust each.

Although thrust is not high the pitch speed of these fan is quite high and if you build your model light you would get very fast and sporty jet like performance with no problem.

Unless you figure out a way to put landing gear on it or is good enough pilot to catch the plane by hand you should reinforce the nacelles and nacelle mount because they hang lowere than the fuse and will be the de facto landing gear and take all the landing shock. If the nacelle gets caught on something during landing it would also tend to get ripped off.
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Old Dec 30, 2005, 10:34 PM
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Thanks, thats good info! so I'll get a 2S lipo in the appropriate size(680-1320mah) and keep it under 7V which I'm guessing should be close to 4/5s throttle. As for landing gear....a gws setup maybe? I'll have to dig thru my old unused stuff drawer!
Bruce
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Old Dec 30, 2005, 11:22 PM
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Quote:
Originally Posted by bmiller
Thanks, thats good info! so I'll get a 2S lipo in the appropriate size(680-1320mah) and keep it under 7V which I'm guessing should be close to 4/5s throttle. As for landing gear....a gws setup maybe? I'll have to dig thru my old unused stuff drawer!
Bruce

Yes that sounds about right size for battery. The motor is happiest closer to 6V but that is too close to cut off voltage for 2 cell LiPo for comfort. Thus you still want to be conservative on your full throttle use. If you limit your throttle you are actually going to see higher voltage under load because you are giving the lighter load. Keep the watt under 30W per fan or perferably 26W per fan for longer motor life. Also the motor is fully enclosed in the fan. Good for aerodynamic, bad for cooling. Give the plane plenty of time to cool down (count hours) after one flight before you fly them again.

The body is all depron and you can't just glue a GWS landing gear plastic holder and hope the thin depron foam to hold for any landing except the lightest one. You definitely need to reinforce the landing gear mount area either by glassing or wood/carbon reinforcement or both. Probablly adding formers at the landing gear location is a good idea.
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Old Dec 30, 2005, 11:46 PM
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Just dremeled the lips off both fans to fit in the nacelles...
How about drilling some holes to get air to the motors? Done it on my alfafan, easy to do...
Should extend the motor life by alot. I don't really want to wait hours tween flights...
I plan to use fibreglass cloth and wbpu w/ some balsa for landing gear reinforcement.
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Old Dec 31, 2005, 12:09 AM
SoCal, Year Round Flying!
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Just read that park370 in a cox edf thread...sounds like a great future upgrade.
how about 2 5400kv on 2S or is the 4200 on 3s better you think?
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Old Jan 01, 2006, 04:39 PM
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Well the rain started again....Only got 2 flights with my SU-27 so I might as well start building .....
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Old Jan 01, 2006, 05:12 PM
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Quote:
Originally Posted by bmiller
Just dremeled the lips off both fans to fit in the nacelles...
How about drilling some holes to get air to the motors? Done it on my alfafan, easy to do...
Should extend the motor life by alot. I don't really want to wait hours tween flights...
I plan to use fibreglass cloth and wbpu w/ some balsa for landing gear reinforcement.

I don't think you should drill holes in the nacelles. The real problem is the motor housing. You may want to drill holes in the motor housing but you need to be careful not to damage the motor inside. The motor is not a cylinderical shape, rather it has two sides flattend. There is room to make air flow in the flattend side but it is difficult to locate the flattend side without opening up the motor housing. The rear cone can be removed to expose the motor but the cone has aerodynamic function you would like to keep it.

Looks nice. Do remember to take pictures of your landing gear reinforcement and setup I am very interested.
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Old Jan 01, 2006, 05:14 PM
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Quote:
Originally Posted by bmiller
Just read that park370 in a cox edf thread...sounds like a great future upgrade.
how about 2 5400kv on 2S or is the 4200 on 3s better you think?
I have great success with 4200 on 3 cell. 5400 on 2s should probablly also work.

To remove the stock motor, first pull off the impeller (it is only friction fit). Remove the screws. Cut the rear cone and pull off the stock motor. You then need to dremel the motor housing to fit 19~20 mm brushless motor.
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Old Jan 01, 2006, 09:34 PM
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oh no I meant drill the motor housings. The tailcones aren't glued yet so its easy to see the flatside of the motors. I think I'll use silicone for glue so I can disassemble the fans later for any upgrade. Thanks for the motor advice and also the impeller removal, I was wondering about that!
For the main gear, theres a balsa support on the front of the battery tray that looks about in the right spot for the wheel wire to hold on to. I found some pics online to see what the real thing looks like and I'll try to retain the scale look somewhat. The nose gear will need a balsa support plate at least. I have to dig thru my spare gws gear and see what I can use.
Bruce
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Old Jan 02, 2006, 12:44 AM
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Heres what I whipped up for fixed gear.
The nosewheel is actually a tailwheel assembly from an old wattage kit.
I had 1"1/4 foam wheels laying around but may get some smaller ones later.
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Old Jan 02, 2006, 02:35 PM
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Looks good Bruce, very nice kit !!
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Old Jan 02, 2006, 04:33 PM
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Thanks Herb!
I'm trying to do a decent job on it.
Who'd a thought we'd have 3 straight days of rain!!!!Arrggghh!!
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Old Jan 03, 2006, 05:20 PM
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Landing Gear Installed

Rear bulkhead and servo tray installed, Wing spar and wing retainer done.
Cut a slit in the fuse for the maingear wire and epoxied it to the servo tray/battery support, Nosegear screwed thru fuse into another ply plate. Seems pretty sturdy with no other reinforcement.
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Old Jan 03, 2006, 07:20 PM
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Question???

This is an upside down pic of the joint between the nacelle and wing. The installed spar spaces the nacelle away from the wing.
Should I make the nacelle lie flush w/the wing?
or is it supposed to be like that?
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