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Old Oct 09, 2012, 04:11 AM
Reap the wild wind
headlessagain's Avatar
Bristol,UK
Joined Feb 2007
4,165 Posts
Bazed,
if you are running on 4s (outside spec) then that prop will be ok but for 3S then I would think in terms of a 6x5 or 7x4. Might even stretch to a 6x5.5 or 7x5 but check with wattmeter first.
You could always see if Dr Kiwi has posted test results for this motor on RC Groups.
Andy
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Last edited by headlessagain; Oct 09, 2012 at 04:22 AM.
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Old Oct 09, 2012, 04:23 AM
Crashing in style.
Bazed's Avatar
Joined Jun 2012
123 Posts
Thanks for the advice Andy. I have had this motor on a Funder & Lightning before, and it was quite a bit overpowered... ripped the motor mount off in midflight even (was also a poor glue gun job but still..). That was on 3S... didn't even know the motor could handle 4S. As the PJ8 is smaller in wingspan I'm worried about torque roll when I maiden it, should be worse with a bigger prop as far as I understand it..? I don't mind something tame for the first flight...

I'm probably over thinking this... should just fly the darn thing.

Peter.
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Old Oct 09, 2012, 11:37 AM
Reap the wild wind
headlessagain's Avatar
Bristol,UK
Joined Feb 2007
4,165 Posts
To minimise torque roll go for a smaller diameter/coarser pitch prop such as 6x5 and launch at 70% power with the model angled slightly up and to the right. Or you could just fit one of these
http://www.hobbyking.com/hobbyking/s...tabilizer.html. It helps my brother get his Super Bandit Parkjet away with zero torque roll.
Andy
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Old Oct 10, 2012, 03:47 AM
Crashing in style.
Bazed's Avatar
Joined Jun 2012
123 Posts
Thanks again Andy, I will check how many amps the motor draws with a 6x5, should be ok I think since I ran a 7x4 for the Funder and it was below max usage.
The stabilizer looks cool, have a couple of KK boards I might try to use, never thought about using them on fixed wing planes.
Peter.
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Old Oct 14, 2012, 01:39 AM
Crashing in style.
Bazed's Avatar
Joined Jun 2012
123 Posts
Hi,

Flew the PJ8 today for the first time, went ok, no torque roll whatsoever. I did have a problem with the pitch control, at 50-60% throttle I had almost no elevator up control at all. Progressively worse when going to lower speeds. I have a feeling it's either because of the canards or my thrust line. Eyeballing the thrust line, it seems pretty dead on... perhaps I should add a few washers on the lower motor screws anyway?
If it's the canards, what's the solution? I did the cardinal sin of covering the entire fuse with cover film before first maiden flight,... which btw worked out great! Had a few "mishaps", one which involved a rugby goal post and the PJ8 at full thrust, dented the wing slightly but if I hadn't had the film on it would have been ripped clean off. Anyway, what I read in other posts with similar canard problems, is to either cut them off, or angle them slightly upwards?

Any ideas?

Peter.
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Old Dec 05, 2012, 05:32 PM
Registered User
Joined May 2005
1,113 Posts
Any motor recommendation for a 28" version. Also, whats the benefits of the FSW vs the regular wing?
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Last edited by GetterDragun; Dec 05, 2012 at 11:29 PM.
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Old Dec 09, 2012, 11:15 PM
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Ok, built the 28" regular wing version. Any recomendations on a power setup (Motor, ESC, prop)? I'd prefer to buy from heads up as they have quick shipping. I have a 2200mah 3S 25C lipo for this.
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Old Dec 10, 2012, 12:37 AM
Crashing in style.
Bazed's Avatar
Joined Jun 2012
123 Posts
Hey GetterDragun, I used a Suppo A2208/12T, 1800KV and worked fine, was a 28" span as well. Flew fast and nice with a APC 6x4 prop. Had problems with the pitch authority at lower speeds,.. so built another with working canards... not flown it yet though.

Hope it helps..

Peter.

Btw, I think that lipo might be a bit on the heavy side for this plane.. I used 1000mah / 3s.... With a 20amp esc... motor maxes out at 1round 7/8 amp, but better be safe than sorry...
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Old Dec 10, 2012, 12:46 AM
Crashing in style.
Bazed's Avatar
Joined Jun 2012
123 Posts
My memory is failing me, and after re-reading the last few posts I think I ended up using a 7x4 or 7x6 prop... I have a faint recollection that the APC 6x4 was a tad underpowered.

In any case, this plane is fast... and looks GREAT in the air... never really built a second plane of anything, but this one was worth it...

Now if I can just get those canards working proper...

Peter.
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Old Dec 10, 2012, 08:18 AM
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Thanks for the reply. I'm thinking of cutting the canards off as I've heard of similar issues with the canards.
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Old Dec 10, 2012, 11:18 AM
Crashing in style.
Bazed's Avatar
Joined Jun 2012
123 Posts
Try with them first... The lack of elevator control could be an issue only I had.
I cut the canards off too, before I added steerable ones, and to be honest it didn't really fly any better (or worse)...

Peter
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Old Dec 10, 2012, 01:56 PM
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Quote:
Originally Posted by Bazed View Post
Try with them first... The lack of elevator control could be an issue only I had.
I cut the canards off too, before I added steerable ones, and to be honest it didn't really fly any better (or worse)...

Peter
You might wnt to try more weight in the front. I saw someone having a similar issue and they needed more weight.

I'll let you know how mine flies once the motor comes in.

Oh yea, what size ESC did you use?
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Old Dec 10, 2012, 08:18 PM
Crashing in style.
Bazed's Avatar
Joined Jun 2012
123 Posts
I used a 18A for the first one, but it overheated. Probably due to being inside the casing without any airflow to cool it. This time around I'll use an oversized 30A, and place it on the outside of the fuse. As mentioned I added functioning canards on the new one, but I have a feeling they won't really do much due to the control surfaces being too small, especially in slow flight. Maybe I should have set it up with full movement of the entire canard instead... anyway, that's for No.3 I figure
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Last edited by Bazed; Dec 10, 2012 at 09:19 PM.
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Old Dec 12, 2012, 06:49 PM
Foam Newbie
Jefte's Avatar
Melbourne, FL
Joined Sep 2010
502 Posts
Just got back from the maiden of my prime jet 32" auw 13.3oz powered by an Emax cf2812 spinning a 7x4. 18a ESC, 1300mah 3s and about 5 sheets of dollar store foamboard. What a great flight! I didn't have any Velcro and eventually the battery broke loose in the fuse causing a scary roll and I was forced to land.

Other than that incident she flew beautifully, with only a touch of up stick when inverted. Thanks for the plans!

Primejet 8 maiden flight (3 min 15 sec)
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Last edited by Jefte; Dec 13, 2012 at 08:32 AM.
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Old Dec 12, 2012, 10:57 PM
Crashing in style.
Bazed's Avatar
Joined Jun 2012
123 Posts
Hi Jefte, congrats on the successful maiden!
I see you don't have any canards, did you cut them off or decide to not build them at all?
How was your ESC after the flight? Mine was hot as *#$!, even melted the glue that attached the velcro.
Another question, elevator control at slower flight.. did you have any?

Just watched your video, nice flying, but what happened in the end? (never mind, got it now... battery came loose)...

Cheers!
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Last edited by Bazed; Dec 13, 2012 at 04:59 AM. Reason: Oh, just realised it was your battery that came off in the end... disregard the "what happened in the end" question :D
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