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Jun 05, 2007, 06:27 PM
Registered User
Quote:
Originally Posted by schweig1959
Here is my FunJet. Micro Dan Motor. AUW 18oz. Have not flown it yet.

Rich

Did a maidend with my FunJet this past weekend. All I can say is WOW. It is great flyinfg plane and no issues with the hand launch. Very stable at high speed. A couple of my club members where so impressed by the FunJet, I think they are ordering them right now. I had to answer a lot of questions about the set-up of the plane. One of the guys is a Heli pilot and doesn't even fly airplanes.

Rich
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Jun 06, 2007, 12:16 AM
Foamsmithing forever!!
crash test dummy's Avatar
We are hoping to get some better video this weekend. The camera we were using was Raynet11's, he just got it the other day. He still hasn't learned all the functions on it yet.

CTD
Jun 07, 2007, 03:13 PM
Registered User
Quote:
Originally Posted by Jurgen Heilig
I just came back from a test flight with a Cam Speed 5x5". I checked twice whether I mounted the prop reversed or whether it was slipping on the adapter, because the static thrust was really poor. Even in the air, the model was not faster than with the 5.5x4.3".

Jürgen
https://www.rcgroups.com/forums/show...postcount=2856

Try this and see if it improves the performance of the 5.2x5.2 for you too. I agree with TreeDriver that the 16/15/4 and 4s is a very good setup, I wont stop trying a few more though....!
Jun 07, 2007, 06:10 PM
Registered User
FD Pilot's Avatar
Smartarse88,

You and I think alike. If there is one major complaint with the FJ it's the large aft fuse and motor mount that messes with prop efficiency. This is one reason the MJs and ProJetis are faster for the same power. I cut-out the chevron darts in the simulated turkey feather nozzle/motor mount to get the flow in toward the prop hub. I may try a stick mount and get rid of the plastic mount all together.
Jun 07, 2007, 10:38 PM
Registered User
Jurgen Heilig's Avatar
Quote:
Originally Posted by FD Pilot
...
If there is one major complaint with the FJ it's the large aft fuse and motor mount that messes with prop efficiency. This is one reason the MJs and ProJetis are faster for the same power. ...
The airflow to the prop really isn't a problem. Both models - MJ and ProJeti - are just much smaller than the FunJet. MJ and ProJeti will fly already pretty fast on a standard Speed 400.

Jürgen
Jun 08, 2007, 12:04 AM
Registered User
FD Pilot's Avatar
Jurgen,

You are mistaken about the ProJeti's size relative to the FunJet. The ProJeti is bigger than the FunJet. The ProJeti has a 820mm span with a 15.5 dm^2 wing area versus the FunJet which has a 795mm span with a 15 dm^2 area.

For speed/watt the ProJeti is superior because of better "area ruling". Take a look at the ProJeti and you will see very agressive tapering of the aft fuselage well in front of the motor and prop (the reason the motor mount is so weak). The trailing edge area just in front of the prop disk is a smaller percentage of the prop disk area than with a FunJet. Speed data contained in these forums verifies the benefit of the ProJeti's cleaner aerodynamic design. Less disturbed airflow into the prop yields better propulsive efficiency = better speed/watt.
Jun 08, 2007, 12:24 AM
Registered User
Jurgen Heilig's Avatar
Quote:
Originally Posted by FD Pilot
Jurgen,

You are mistaken about the ProJeti's size relative to the FunJet. The ProJeti is bigger than the FunJet. The ProJeti has a 820mm span with a 15.5 dm^2 wing area versus the FunJet which has a 795mm span with a 15 dm^2 area.
....
I wasn't comparing wingspan or wing area, but the sheer size (=volume) of the models. The FunJet has a massive fuselage compared to the other two models, and in contrary to the ProJeti, the aerodynamic design was lower on the priority list.

Jürgen
Jun 08, 2007, 03:05 AM
Annoying people since 1970 :)
I have an unbuilt Thunder Tiger Velocity which is a 'similar' design to the Projeti but it will need some serious strengthening before it ever flys as the wings would snap off with a decent brushless set-up!
Jun 08, 2007, 07:14 AM
Gone Flying.
ChrisWNY's Avatar
Quote:
Originally Posted by FD Pilot
Jurgen,

You are mistaken about the ProJeti's size relative to the FunJet. The ProJeti is bigger than the FunJet. The ProJeti has a 820mm span with a 15.5 dm^2 wing area versus the FunJet which has a 795mm span with a 15 dm^2 area.

...
The FunJet wing span is only 0.5" (12.7mm) shorter than the wingspan of the Projeti. Overall, the FunJet fuselage is larger and heavier (hence more draggy), especially from front to back. Just place the 2 planes side-by-side -- the FunJet will appear almost equal in wingspan, but it is obvious that the FunJet is a larger aircraft in sheer size, overall.

I am in agreement that the Projeti flies faster with the same power set up - it is a more aerodynamic design, not as draggy, easier to build light-weight. One of our best electric pilots in my club has a Projeti (with a Mega 16/15/4 motor) and flies it quite often - he's encountered some warping issues with it, and has also run into some wing breakage issues on 1 or 2 slightly rough landings. I've landed my FJ hard a few times with no damage at all, so it seems more durable. I can also more easily see the FunJet when it's high in the air. The Projeti is so speedy on a vertical climb that I lose sight of it much sooner that I would the FunJet. Oh yeah, the Projeti airframe kit runs $110 at hobby-lobby (which is the only place, to my knowledge, that sells this kit), and I can buy a FunJet at my LHS for ~$60. I could crash 2 FunJets for the price of 1 Projeti.
Jun 08, 2007, 07:25 AM
Registered User
timhoffman's Avatar
Quote:
Originally Posted by Smartarse88
[IMG]I modified the motor mount a few months ago in the quest for speed. I did this because there is such a big difference when you use a larger prop with the funjet as the motor mount shrouds the props airflow a lot. I did it with a cone shaped sander and it was just to test the idea not to be neat. Surprisingly the stiffness has not been much compromised which is good.
There was a noticeable difference in thrust - especially at low speed and an improvement in top speed. The peak current draw also rose a lot! With a 5.5 x 5.2 speedcam on 4s2150 and Mega4t you could cause the prop to cavitate easily at low speed if you applied the throtlw quickly, with the mods the prop doesn't seem to stall.
The plane is fast with a Het 2W-25 with a 5.2x5.2 (using 4s3700's), my Jeti 66 reports peaks of 98amps at 15.0 volts - nearly 1.5kW! I have yet to put my micrologger in to confirm that, after the flight nothing is too hot..... However the laws of diminishing returns means that overall i have the most fun with the Mega4Turn on 4s.
My plan was to make a new mount that was effectively a reverse cone that would flow down to the same diameter as the spinner, that has not happened yet. Kinda figured it would release the airflow more aerodynamically, however the whold airframe is not that slippy so my HET F16 will now fulfill the need for speed!

-Scott[/IMG]
I am impressed with you squeezing the 2W -25 in the funjet, but i guess you are right about the amp demand making it a watt and amp hungry scenario.

Mine runs on the HET 3W, and 3s 2100's. I like the 5.5 x 4.3 prop for its efficiency with the shrouded motor cowl..

I wished now I had gone for your 4s 4wind option because the amps would be lower.. Mine would be drawing up to 36 amps...
Jun 08, 2007, 09:34 AM
BrainFart RC-Pilot
TreeDiver's Avatar
Quote:
Originally Posted by Jurgen Heilig
I just came back from a test flight with a Cam Speed 5x5". I checked twice whether I mounted the prop reversed or whether it was slipping on the adapter, because the static thrust was really poor. Even in the air, the model was not faster than with the 5.5x4.3".

Jürgen
Hi Juergen,

Well I can only confirm this.
The 5.5x4.3 is a great prop for this plane together with the Mega 16/15/4 and 4s.
At 3s and the Mega 16/15/4 the 5.5x5.5 is superb and great to start with.

You need thrust to "keep" speed.
See pictures of my FunJet and the "washers" I used to set the prop a bit more backwards, so that it grabs more air.

l8r

Rob

PS. see my BLOG with my beloved electro planes
https://www.rcgroups.com/forums/member.php?u=20015
Last edited by TreeDiver; Jun 08, 2007 at 09:50 AM.
Jun 08, 2007, 09:38 AM
Registered User
Quote:
Originally Posted by timhoffman
I am impressed with you squeezing the 2W -25 in the funjet, but i guess you are right about the amp demand making it a watt and amp hungry scenario.

Mine runs on the HET 3W, and 3s 2100's. I like the 5.5 x 4.3 prop for its efficiency with the shrouded motor cowl..

I wished now I had gone for your 4s 4wind option because the amps would be lower.. Mine would be drawing up to 36 amps...
The landings can be quite fast! I am trying to establish the actual current draw, the flights are short I should time them really. The Jeti Spin 66 I used reported 95amps peak but later on a static test that figure did not agree with my e-logger which reported less. Sadly at the end of the next flight the e-logger was somehow corrupted and refuses to do anything now! either way its fun and faster with the motor mount mod but not as fun as good ole 16/15/4 5.5x4.3 on 4s!!!! (the 6x4 APC is close but draws more amps and has more torque roll effect).
Jun 08, 2007, 09:55 AM
Registered User
Jurgen Heilig's Avatar
Quote:
Originally Posted by TreeDiver
...
See pictures of my FunJet and the "washers" I used to set the prop a bit more backwards, so that it grabs more air.
...
Wow, you are using a very bulky prop adapter (and it looks like you are using Nylon screws for the motor ). Have a look what I am using - which moves the prop even further back without any mods.

Jürgen
Jun 08, 2007, 10:04 AM
Registered User
Jurgen Heilig's Avatar
Quote:
Originally Posted by Smartarse88
https://www.rcgroups.com/forums/show...postcount=2856

Try this and see if it improves the performance of the 5.2x5.2 for you too. I agree with TreeDriver that the 16/15/4 and 4s is a very good setup, I wont stop trying a few more though....!
The cutouts in the motor shroud could actually make things worse. At least with the original mount, you have a fairly clean airflow to the prop without additional turbulence. You also have better "forced cooling" inside the fuselage with the original mount.

I would only do the mod, if I wanted to save some weight.

Jürgen
Jun 08, 2007, 10:56 AM
Registered User
Quote:
Originally Posted by Jurgen Heilig
The cutouts in the motor shroud could actually make things worse. At least with the original mount, you have a fairly clean airflow to the prop without additional turbulence. You also have better "forced cooling" inside the fuselage with the original mount.

I would only do the mod, if I wanted to save some weight.

Jürgen
In actual testing it seems to improve things, you can make a 5.2 x 5.2 cavitate at low speed easily with a powerful motor, with the cut outs it accellerates better. The plane is a little faster but the current draw is higher -indicating to me that there is more prop area being used. (I have tried it both ways, and there is actually a better through fuselage flow with these mods!)

I will try to get some proper facts when the e-logger is working again. The turbulence from the rear of the motor mount is not going to be any 'better' when it is not modified, it would need to be tear drop shaped for that! My aim was originally to make a new tapering mount that effectively matched the rear of the spinner, may still do it sometime however chasing outright speed with this airframe is a waste of the fun it can be with a lighter loading. Its just nice to know that you can!

Anyway try it before dismissing it, I am sure you will be able to get another if it decreases performance.

Regards
Scott


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