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Old Dec 05, 2012, 04:10 PM
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4stripes's Avatar
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Regarding the pitch up with throttle, mine had the same tendency. My Cg was tested farther back from stock to the point of tail heavy but the fix for the throttle pitch was simple. Just glue come thin plastic card at the top of the exit tube to straighten out the upward curve that is only at the top. This makes the plane track level power on or off.
Cheers
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Old Dec 05, 2012, 04:23 PM
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Originally Posted by 4stripes View Post
Regarding the pitch up with throttle, mine had the same tendency. My Cg was tested farther back from stock to the point of tail heavy but the fix for the throttle pitch was simple. Just glue come thin plastic card at the top of the exit tube to straighten out the upward curve that is only at the top. This makes the plane track level power on or off.
Cheers
well thats kind of odd, but I am running a thrust tube so that would be why mine never did that
install a thrust tube with a 70mm exit, I think this is a better solution. you will also gain some performance
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Old Dec 05, 2012, 04:26 PM
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Ha... I was just about to calculate the thrust tube exit diameter myself, when you posted the 70mm answer... What percentage FSA is it?

Also--once you get a serious motor in there--how did you get the whole unit into the fuselage? I'm thinking that the only way is to actually glue the two halves (left and right) of the fuselage AFTER the fan is in place... Is that the only way?

Finally--I'm thinking about buying the TamJets HET 700 heatsink and tailcone combo before I bury the fan system there (http://www.tamjets.com/original/prod...roducts_id=714). Any thoughts about that?
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Old Dec 05, 2012, 04:39 PM
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My exit was 75mm with just the foam. wemo sells thrust tubes for 90mm fans and I believe their exit is also 75mm. Seems to work well.
Cheers
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Old Dec 05, 2012, 04:41 PM
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The fan will fit through the opening if you cut some extra foam away from the front. Simply glue those pieces to your hatch.
Cheers
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Old Dec 05, 2012, 04:44 PM
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Quote:
Originally Posted by ysolomon View Post
Ha... I was just about to calculate the thrust tube exit diameter myself, when you posted the 70mm answer... What percentage FSA is it?

Also--once you get a serious motor in there--how did you get the whole unit into the fuselage? I'm thinking that the only way is to actually glue the two halves (left and right) of the fuselage AFTER the fan is in place... Is that the only way?

Finally--I'm thinking about buying the TamJets HET 700 heatsink and tailcone combo before I bury the fan system there (http://www.tamjets.com/original/prod...roducts_id=714). Any thoughts about that?

Yoram
here is the fsa's for a wemo
Exhaust Diameter (single outlet)
100% FSA 81.34955439
95% FSA 79.28973767
90% FSA 77.17496356
85% FSA 75.00058333
80% FSA 72.76125343
75% FSA 70.45078069
70% FSA 68.06192034

as far as getting the thrust tube in there I made it easy for myself knowing that I was going to do a thrust tube and also wanted the ability to install my TJ90 so I extended the motor hatch two more inches back this mod makes these things a lot easier I also separated the motor hatch from the wing. I can post pics later if interested. I need to go and run some errands right now. will be back later
oh I prefere esc in the tailcone but be carefull of the cg issue, I would have had a serious problem had I done that with mine others may not have the issue
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Old Dec 05, 2012, 06:03 PM
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Spain
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Originally Posted by jcdfrd View Post
Jandro
a couple of things for you to try out
your pitch up when under power is cg you are still nose heavy, move the batt back a little at a time untill that goes away also add some crow to your ailerons for take off and landings, start at 2mm. this will decrease the tip stalling and these two things together will allow for even slower more stable performance
Thanks for the help, but I already know I'm tail heavy. The thing is I can't move the battery further back, and I'm not adding weight, so a gyro will have to be enough.
And it will get worse with the FPV equipment...

As for the ailerons, I need the spare channels for pan-tilt... hahahahaha!
But thanks again, anyway!

Quote:
Originally Posted by 4stripes View Post
Regarding the pitch up with throttle, mine had the same tendency. My Cg was tested farther back from stock to the point of tail heavy but the fix for the throttle pitch was simple. Just glue come thin plastic card at the top of the exit tube to straighten out the upward curve that is only at the top. This makes the plane track level power on or off.
Cheers
That seems worth considering. Actually my plane is pitching up more with throttle than with speed so it probably has more to do with ducting than CG centering, although nose heavyness will also contribute greatly.
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Old Dec 05, 2012, 07:02 PM
Another one on the way...
ysolomon's Avatar
Plano, Texas
Joined Feb 2009
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Quote:
Originally Posted by jcdfrd View Post
Yoram
here is the fsa's for a wemo
Exhaust Diameter (single outlet)
100% FSA 81.34955439
95% FSA 79.28973767
90% FSA 77.17496356
85% FSA 75.00058333
80% FSA 72.76125343
75% FSA 70.45078069
70% FSA 68.06192034

as far as getting the thrust tube in there I made it easy for myself knowing that I was going to do a thrust tube and also wanted the ability to install my TJ90 so I extended the motor hatch two more inches back this mod makes these things a lot easier I also separated the motor hatch from the wing. I can post pics later if interested. I need to go and run some errands right now. will be back later
oh I prefere esc in the tailcone but be carefull of the cg issue, I would have had a serious problem had I done that with mine others may not have the issue
So, 75%... (and it appears others stayed with 85%). I may go in between. 72mm for 80%. We'll see.

Yes, if you could post pictures--it would be very helpful. I'm trying to envision what you've done. I wasn't crazy about the wing having part of the hatch anyway... I'd love to see what you've done. I will likely not put the ESC in that cone. Will have too long of battery wires as a result. I will likely put it in the battery compartment "extension".

Glassing it taking its time. Although I used 20min finishing epoxy (with 33% in volume alcohol), I am using EZE Kote (from Horizon) for the finish. We'll see what it looks like at the end.
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Old Dec 05, 2012, 07:58 PM
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ok here ya go take note of the angle cut and tonge left on the hatch so that when the wing is bolted down it secures the front of the hatch, then the just extended the cuts back 2in further and moved the attachment hardware, pretty simple really
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Old Dec 05, 2012, 08:11 PM
Another one on the way...
ysolomon's Avatar
Plano, Texas
Joined Feb 2009
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Got you. This makes so much more sense!!! I'll do the same. Will take some carving, but will end up so much better. Thanks for the pictures!!!
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Old Dec 10, 2012, 06:03 PM
Another one on the way...
ysolomon's Avatar
Plano, Texas
Joined Feb 2009
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Has anyone heard of an issue with the HET 700-68-1680 being slightly "fatter" than other 700-68 motors? I just got the heatsink and tail cone from TamJets, and it would not go on the 700-68-1680, although it fits just nicely on the 700-68-2250. I'm not going to change from 8S/1680kV to 6S/2250kV just because the motor is too fat... Anyone heard anything? Any idea?
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Old Dec 10, 2012, 06:50 PM
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ya thats pretty normal Yoram Tams centerbody cones are sized to fit the Neu brushless motors that he uses and custom fits each one, some go on properly and some have to be turned down on the lathe(motor can that is). if it seems like its really close then 220 sand paper by hand will get it.
here is Tam showing some of his procedures in this shop tour vid
Mini Interview Video Part ll With TamJets "How A TJ70MM - 120MM Fans Made" (9 min 59 sec)
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Old Dec 10, 2012, 08:16 PM
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Crazy... Sand the motor??? I thought you will tell me to sand the inside of the heatsink...
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Old Dec 10, 2012, 08:17 PM
deltas are cool
AIR SALLY's Avatar
Tehachapi ,CA.
Joined Apr 2006
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nice work John i like any idea that allows easier maintance ...just make really good sense....plus when you do it for a living a easier way is always better
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Old Dec 10, 2012, 11:30 PM
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Originally Posted by AIR SALLY View Post
nice work John i like any idea that allows easier maintance ...just make really good sense....plus when you do it for a living a easier way is always better
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