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Old Nov 12, 2010, 12:06 PM
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Originally Posted by CryHavoc View Post
... Would a Hacker B50-10xl in a Midi-pro on 6cells be enough to fly this thing? Would 8 cells be too much? Mike
I think that big Hacker should handle 8S no problem. It will pull 2400W on 8S 3000's :

http://www.s4a.ch/eflight/fancalc.htm

The $19 TGY B36-56 motors are too small for this plane, they max out at ca. 1500-1700W. But they are as good & efficient as the Hacker B50's

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Old Nov 12, 2010, 12:08 PM
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Originally Posted by chalmrast View Post
When you get a chance, could you measure the depth at the retract mounts? What is the deapest retract housing that will fit?
Not very deep unless you re-do the mounts. See pics below ...
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Old Nov 12, 2010, 12:17 PM
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Servo wells accept HS-81/85 or similar.

225's sized servos are too big (and too heavy) although you can always butcher the wing to fit some oversized servo.

I am using a pair of JR's for the ailerons and two HS-85MG for the flaps.

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Old Nov 12, 2010, 12:22 PM
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Quality Springair 602 retracts don't leak, are sturdy, always dependable and fit nicely.

http://www.retracts.com/Retrax_600.htm

Some situably sized lightweight struts would be nice if they hold up to a 7 lb plane (HK $28 in the picture).

Note that part of the retract mount (the rear part not visible in the pictures below) sits on a balsa rib ...

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Old Nov 12, 2010, 12:28 PM
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Lightweight electric retracts with plastic mounts fit but will be kind of marginal on a 7+ lb plane

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Old Nov 12, 2010, 12:32 PM
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CMPro intends to sell a set of air retracts (air up, spring down for reliability, like the Springairs) & struts.

They look very nice, it would be interesting to know what the weight is (and the price). My guess is the whole setup is $200+.

Edit: they have a price now : $75 + $69 = $144, not bad at all if they work reliably :

http://www.nitroplanes.com/oppaforedft.html

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Old Nov 12, 2010, 12:35 PM
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Fit of the Springair air retract for the nosegear.

"Do not paint" ... I get it

Need to ensure that the nosegear strut & wheel disappears nicely into the fuse when retracted.

The servo opening for the pull pull steering seems designed for a smaller servo than the one I am using (HS-85 MG).


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Old Nov 12, 2010, 01:08 PM
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The main gear location is just barely (a few mm's) behind the stated CG ...

But at least they did not do the colossal design mistake of the lead sled (9.8 lbs, http://www.rcgroups.com/forums/showp...&postcount=346) JetTeng Hawk/T-45 (which has a shorter wingspan than the CMP T-45, namely 43.6 inches)

http://www.rcgroups.com/forums/showp...&postcount=315

which put the wheel wells & mains ahead of the CG - thus making the model possibly unflyable with gear.


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Old Nov 12, 2010, 02:45 PM
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Herb,
Thanks for the motor info. I guess trying to fly this thin on 6 cells is not gonna be "enjoyable"?

What are the dimensions of those spring-airs? I.e. LxW of the mounting tabs and depth if you don't mind. There is not alot of info on the website.

These retracts look really similar to the pic on the NP website- http://www.hobbyking.com/hobbyking/s...idProduct=7998

Thanks,
Mike
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Old Nov 12, 2010, 03:53 PM
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Nice work Herb! Those HK struts look good. Do you have a link for them?
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Old Nov 12, 2010, 03:54 PM
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Quote:
Originally Posted by Steph280
Herb, Are you sure about the B50-15L running 8S? Can it handle 80+ amps and 2400 watts? Seems the recommended setup is on 6S, which is only 1200 watts. ...
Steph,

I know the B50-18S (or any B50-xxS) can handle 1300-1500 W in an EDF no problem ... Mine are like 5yrs+ old . They weigh 198 grams.

http://www.aircraft-world.com/prod_d...ets/hm-B50.htm

Your motor (B50-15L) is 255 g, so the max power in an edf is around (255/198) = 1.29 * 1300-1500W or around 1700-1900 Watts. That's not a whole lot for the T-45 unless you keep it real LIGHT.

Have you looked at the HYK (Taiwan) and ARC (China) motors as an alternative to the Neu 15xx ?

http://www.jettechmodels.com/servlet...-KV1600/Detail

For > 2000W you need an inrunner motor that's > 300g . Play around a bit with that impeller calculator I suggested ... It's quite accurate.

http://www.s4a.ch/eflight/fancalc_e.htm
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Old Nov 12, 2010, 04:01 PM
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Originally Posted by rvincent View Post
Nice work Herb! Those HK struts look good. Do you have a link for them?
http://www.hobbycity.com/hobbyking/s...dProduct=11300

Have not used mine yet ... well made but not ultrastrong.

I have these as well, they seem a bit stronger but that could be an illusion :

http://www.sonicelectric.com/Merchan...roduct_Count=3
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Old Nov 12, 2010, 04:05 PM
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Originally Posted by CryHavoc View Post
... What are the dimensions of those spring-airs? ...
Same as the Behotec C-21's ?

http://www.altecare.com/retracts.htm

Yes the Hawk on 6S could turn out to be a bit overweight & underpowered ... I think I can lighten it up a bit by taking out all of that un-needed wood inside

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Old Nov 12, 2010, 04:09 PM
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We could always change the springs I like the looks of the HK struts better, but Danny is just up the road
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Old Nov 12, 2010, 05:22 PM
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Two low profile 9g quality microservos for the the two elevators should be plenty ...

The computed torque even with 15 degree deflection is rather small (~9oz in); anything bigger will just add weight & weaken the stabs.

Either the servos are mounted in opposite ways, or a servo reverser is used.

I have a similar twin elevator servo setup in three other large edf jets.

.
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