[Dutkoski]

I'm at the stage where I have all the bits and pieces assembled so must figure out what the estimated weight might be. So, got out the digital scales, here are my results,

Fuselage section, one coat of primer with Fiberglass thrust tubes ...... 18.6 oz.
Wings, stab, fins, control surfaces .................................................. 9.65 oz
Canopy & cockpit floor .................................................. .............. 1.25 oz
Spars and stab control rod with brass bushing .................................. 2.3 oz
Two 70 mm EDF units with Mega 5s EDF motors ............................... 13 oz
Two 3300 mah 4 cell batteries .................................................. ...... 20.6
Two 80 AMP ESC's .................................................. ...................... 4.2 oz
Servos .................................................. ...................................... 4.4 oz
Receiver and 1000 mah battery .................................................. .... 2.7 oz
Total .......... 75.2 oz

Which works out to 4.7 lbs roughly. So, with an estimated 2 lbs in finishing, wiring, some plywood mounts for the EDF units and one servo, some Velcro, etc, I should be under the 7 lb mark which is really not that bad, should be easy to bungee launch.

[Dutkoski]

EDF's have been mounted, tested and then removed so I can wiggle. In the structure for the two stabs. Going to lay in some carbon cloth first in the area of the control rod bushing first so the foam will have some strength. I just don't trust the bare foam as it is fairly thin.

Here is the simple mounting plates I devised.

[Dutkoski]

The 12 blade Change Sun EDF's with the Mega 5S motor work pretty good on the 4 cell setup. I got readings of mid 40 amp draw producing just over 700 watts peak and settles to 675 roughly. So together, I'll get around 1300 watts of power. Just for the hell of it, I hooked up a 5 cell battery and it was too much, 1085 watts registered but the amp draw was way beyond the motor spec's at around 68 amps.

Is there any reliable motors out there that will work on in the Change Sun 12 blade and handle the higher amp draw on a 5 cell battery?

So, for a foamie that hopefully will be under 7 pounds, I can live with the 1300 watts. The ESC and battery was only slightly warm, so nothing was really stressed.

[4stripes]

I'm thinking your plane is large enough for a 6S setup and would recommend these CS7012 fans with 2000kv outrunners.
http://www.hobby-paradise.com/en/pro...ct_detail.html
They have many flights in our LX A10 and take 6S easily in a twin configuration.
We are running a Gens Ace 6S 25C 5500mah battery and set the timer to 4:30 leaving ample reserve for a couple go-arounds.
If you want to go 5S then I believe the Turnigy L2855-2100 motors would be fine and provide close to the same watts. Just be sure to do some opening of the motor mount area and motor aft fairing to allow maximum cooling. 900watts is max power for these motors. I actually run them in our ME262 on 6S but limit the power to 900watts through the ESC. At full power they pull over 1300watts and heat up fast then burn.

[Dutkoski]

Hi Eric,

Thanks for the info. I was checking the Hobby King site, the motors under Dr Mad Thrust which are RC Lander, have a 70 mm motor that will handle 85 amps, and it is for a 4 cell setup. They are also designed for a high blade count, 3000 kg, good for 1300 watts plus they are $26.84 USD each. I just might give them a try.

I want to stay with the 4 cell, but no higher than a 5 cell, just to keep the weight down. Plus, keep the cost down. This is a foamie and expendable to a certain degree. With no landing gear, the heavier the model, more likely to get damaged on each landing. I kinda like to float them in, so I like it when they are light.

[4stripes]

Let us know how they work out. I'm concerned that your flight time will be very limited.
6S batteries are common to practically all my models which is why I tend to look for solutions using them.

[NDW]

Eric / John.... Are we talking 1 pack in total driving both motors or 1 pack per motor / Esc.... Sorry if it's a silly question..... I have he same kit as john to be built the winter..... Was looking at the dr. Madd thrust 4 and 6 cell motor / fan units. Just trying to put a list of stuff together to order....
Thanks
Dave

[4stripes]

I run one pack to power both fans in a twin.

[NDW]

Thanks Eric.... I was actually thinking you were to run 2 packs...... That just simplifies a whole lot for me...... Still trying to find time to finish the 70mm composite viperjet.

Thanks again guys...... John keep up the great build thread.... You are giving me a whole lot of good ideas....
D.

[Dutkoski]

Designed and fabricated a fixture to imbed in the stab so I can slip the stab onto the pivot rod and lock it into position. So for transport, I can remove them to prevent damage.

I think I can do something very similar for the wings as well.