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Oct 23, 2012, 03:43 AM
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Seagull Models Ultra Jet


Hello All,

I am hoping someone could give me some advice.

I am setting up this model:

http://www.jperkinsdistribution.co.u...%20-%20Seagull

I am researching a brushless outrunner 12s motor.

I have an ultra funjet with a stock powerset which is good for 125mph.

I would like this to be a larger and hopefully faster version of the funjet ultra.

What are people's experiences with large pusher prop models? The AUW of the model should be around 3-3.5 kg. Can I expect to push this into the 150mph+ zone with 12s?

I have a Kontronik PowerJazz 120 and a Pyro 700-520 kv motor as a starting point.

What type of prop speed is realistic in this type of model?

I have attached the manual.
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Oct 29, 2012, 03:04 AM
Registered User

TwinJet


At first look, this has a planform close to that of the Multiplex TwinJet but with a symmetric wing section.

The TwinJet is a great flier, but ultimately runs out of power because it's such a draggy airframe. It's foam, so has some surface resistance, but it's also got a bulky shape.

It compensates by being a steady slow plane, and by changing direction rapidly. It's a good all round plane to test the air, and to enjoy the start of a flying session.

This is a lot bigger, and potentially more complex plane to operate, so it won't be so relaxing. Personally, I would not waste too much time on ultimate speed since there will always be a carbon hotliner ready to leave you for dead. And MicroJets are quick too.

So, I would be keener to gear up for acceleration rather than speed, so a bigger, finer pitch propellor and lower Kv motor might be more fun. With a high speed setup you are so much more restricted. It's a one trick pony. It reminds me too much of muscle cars where owners put in larger and larger motors to get speed, but find they are hopeless in corners.

With a plane geared for acceleration you get the feeling of performance as you accelerate from low speeds. Acceleration is more important than top speed, as any Formula 1 driver will tell you.

You might then be tempted to separate out elevator and aileron functions, add twin rudders that give you air brakes and see how you could arrange for some flaps or crow brakes. Additionally, a rear mounted motor gives so much more chance to play with thrust vectoring, and with the symmetric wing, you have so much more chance to test out the aerodynamics.
Oct 31, 2012, 07:29 PM
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Thread OP
Thanks for the reply Michael,

Well I have the machine setup. I have gone with the equipment I had and used a 510 kv 700mx motor from a heli.

I have 2 props to try a 11 X 9 and a 14 X 12. I have a feeling the 14X12 will be nice but may need to limit the throttle curve as it would be too powerful at WOT (over 4500 watts)

I have the retracts working well and CG more or less dialed in at 250mm from the leading edge (scaled up version of the funjet ultra from what I can make out)

Attached are some pictures of the build. I will be maidening at the weekend. Will report back how sher flies. I think she is a nice test airframe for bigger faster machines. My Goal is to work up to the CARF Ultra Flash before the year is out.

Thanks again,

M
Nov 06, 2012, 10:35 AM
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HobbyTechnology's Avatar
It seems too 12S, would have a high wing loading, I would try to 8-9S with an engine with more KV
Nov 08, 2012, 05:47 AM
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Excellent


That is really impressive!!

I just drew up some plans for a 48inch span version of the MicroJet, so this looks just right for me too.

I love the MicroJet (I have five) and its TwinJet big sister, but not flown the FunJet that you have in the picture. I really would like something bigger, so ....
Nov 13, 2012, 04:47 AM
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Thread OP
Here's the video:
Seagull Ultra Jet (4 min 42 sec)
Last edited by MikeAlphaXray; Nov 13, 2012 at 05:07 PM.
Dec 07, 2012, 05:57 PM
Registered User
Quote:
Originally Posted by MikeAlphaXray
Thanks for the reply Michael,

Well I have the machine setup. I have gone with the equipment I had and used a 510 kv 700mx motor from a heli.

I have 2 props to try a 11 X 9 and a 14 X 12. I have a feeling the 14X12 will be nice but may need to limit the throttle curve as it would be too powerful at WOT (over 4500 watts)

I have the retracts working well and CG more or less dialed in at 250mm from the leading edge (scaled up version of the funjet ultra from what I can make out)

Attached are some pictures of the build. I will be maidening at the weekend. Will report back how sher flies. I think she is a nice test airframe for bigger faster machines. My Goal is to work up to the CARF Ultra Flash before the year is out.

Thanks again,

M
Any idea of the top speed achieve with your power setup? I got one on the way and plan to use a Scorpion 4035-500kv propped with the APC 12x12. This system can handle 8 cells with an approximate output of 3.5kw. Just curious if the plane can reach 140-150 mph?
Dec 17, 2012, 10:47 AM
Registered User
Any more news on the plane, any more flights by anyone? Just received one last week, and should have it ready to go by this weekend once the retract issue gets resolved. I would like to know how much deflection is being used on the control surfaces/ aileron and elevator(roll and pitch)?
Jan 11, 2013, 02:57 PM
Never Stop Learning
Jaguar22's Avatar

Any Updates?


So any more updates on this plane, builds?

I will be starting assembly on mine next week and post some of the setup or issues found.
Feb 25, 2013, 08:59 PM
CV1
CV1
Registered User
Quote:
Originally Posted by Vantagepoint
Any more news on the plane, any more flights by anyone? Just received one last week, and should have it ready to go by this weekend once the retract issue gets resolved. I would like to know how much deflection is being used on the control surfaces/ aileron and elevator(roll and pitch)?
I have just completed and test flown today. I replaced the crappy retracts with E-flight 60-120 size electrics. Powered by a E-flight 60 with castle 80 amp HC using a 12x12 apc prop on 10 cells 5,000 ma. MY GPS displayed three flights of 150 mph with 4 min flight times. Again 150 mph out of a 10 lb pusher plane and unlimited vertical. I need to install air brakes for shorter field landings.............very hot landings. Needs at least one inch up and down on both ail and elv. Oh yea, long roll outs on take off.
May 28, 2013, 08:54 AM
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How are you able to use 10 cells on the Power 60 motor? It is rated top 7 cell. Just curious because I am looking to assemble a similar setup.
Jul 06, 2013, 07:14 PM
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vewdew1's Avatar
Where did you guys set the center of gravity? If I set mine to 250mm like the manual states, it seems very nose heavy and requires a lot of led up front.
Jul 07, 2013, 09:21 AM
Registered User
Have you computed the speed of the propeller tips? If you are trying to turn the prop with the tips going faster than the speed of sound, then you will hit a brick wall.

My guess is that you could get about 80 mph with a 500kv motor and 6S and a 12 inch bite prop. Maybe you can keep prop speeds below the speed of sound with a 10S battery.
Jul 08, 2013, 02:53 PM
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vewdew1's Avatar
Just an FYI, since I've not yet gotten a response. I did some more research and found some guys on another forum who've built this model up with turbines. It appears to be all in German, but with a little help from Google translator it seems that their consensus (verified by multiple calculators) was that the 250mm CG stated in the manual is way off (and I concur). It appears that it should be much closer to 300mm.
Jul 26, 2013, 04:13 PM
Registered User

my seagull ultra jet


setup:
12s 3300 30c
BL 700MX 510kv
ice 160hv
60-120 eflite ret.
11x8.5 prop
custom motor mount
HV,H.speed servo





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