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Old Apr 19, 2010, 09:19 PM
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Build Log
Jepe Fast Foam BAE Hawk

I picked up my Jepe Fast Foam Hawk from the post office today. It shipped on April 12th and it was ready to be delivered on Friday, April 16th. Unfortunately I wasn't at home to sign for the package. The box arrived without damage. Included in the box was Jepe's 8s fan/motor combo.

Jepe's Fast Foam BAE Hawk is basically a FlyFly BAE Hawk that is not painted and has some modifications and some special parts to improve the performance and reliability of the airframe. Jepe includes a CD with photos of the modifications to be performed. Unfortunately some of the photos aren't numbered in sequence so you have to look at all of them and try to sort out the order. It's not too hard but still an inconvenience. Jepe doesn't provide his own written manual. The FlyFly instructions and his photos is what you have to work with to build this model.

I plan to glass the model with 1/2 oz fiberglass cloth and Zpoxy finishing resin. Lightweight spackle will be used to fill in the overly large and deep panel lines. I will try to draw them back in once I've finished painting the airframe.

I'm going to try to build a T-45 version of the Hawk. Everyone has the Red Arrows version.

My power system will be Jepe's 8s 90mm fan and 8s motor. On 8s this is expected to draw about 68 amps. I have two 4s 4900 Rhino 25c battery packs to provide the power and a Castle Creations ICE 100 ESC. I plan to use Spring Air 602 retracts.

Here are some photos of the unboxing.
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Old Apr 19, 2010, 09:23 PM
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United States, NE, Papillion
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sweet the bae hawk is an awesome plane to have
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Old Apr 19, 2010, 09:25 PM
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any idea's on what your going to paint it?
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Old Apr 19, 2010, 09:47 PM
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Kelvin...Subscribed and thanks for taking the time to do this build thread!!
-Dave
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Old Apr 19, 2010, 10:18 PM
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Quote:
Originally Posted by j3tman View Post
any idea's on what your going to paint it?
I'm looking at this paint scheme. I need to find some pilot figures.
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Old Apr 20, 2010, 07:00 AM
Extreme CNC Alloy EDF
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Australia
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The motor appears to be an HYK from Taiwan, same as the original 1600Kv 6s motor flyfly was supplying before the cost got too high. I spose this one would be around 1300-1400Kv, afaik all HYK are 2 pole motors and spin over freely. If you look in the back you will likely see a cardboard tube between the windings and the rotor itself.
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Old Apr 20, 2010, 10:26 AM
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United Kingdom, England, Cobham
Joined Oct 2007
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Looking forward to this build, kelvin. Mine is the normal Fly-Fly version but with similar mods for the AMT as Jepe. I also filled the cavernous panel lines, but used tissue and Poly-C for covering. Still need to do the finishing coat, after which will be around 3.8Kg. That's with 9S 3700mAh.

I'm interested to see photos of the ducting just behind the nose/canopy area. On the stock model there is a blunt curve (semi-circle) which will prolly cause some turbulence. I have already hacked some of this area to get the Lipos as far back as possible, but it looks (from 2nd shot in post #3) like Jepe has done some sort of tapering compartment which is a good idea.

Jacques
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Old Apr 20, 2010, 05:46 PM
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Hi Jacques,

The blunt curve will be inside the ducting and not in the airflow once the ducting mod is completed. I could probably remove a lot of that structure but you never know how much is needed to keep the airframe intact under the stress of flight.

It's interesting you say you have to move the batteries as far back as possible. With the motor behind the wing and the CG only 5 inches or 127mm from the leading edge I would've thought the batteries would be easy to position in the cockpit area. I'll have 34 ozs ( 963 gr ) in the nose plus the nose retract, valve, steering servos and valve servo. Maybe I'll be nose heavy too.

Their doesn't seem to be much maintenance access in this model. With the fuselage glued together I can't see how you can remove the fan without damaging the plastic thrust tube and even getting the motor/ESC wires out. I still haven't figured out where to mount the ESC.

Kelvin
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Old Apr 20, 2010, 11:04 PM
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Weigh In

I like to weight all the parts before I start a project so I can compare after the project is completed.

I've taken a series of photos showing the weights.

Adding up the weight = 111.6oz or 6.9lbs or 3164gr

I'll need to add two more servos, one for the elevator and one for the purposed rudder. Those will be 2oz including extensions.

Now the question is what will the fiberglass, primer and paint weigh? 10%? Lets add 12oz for fiberglass, paint and other items that seem to crop up when building a model.

Projected weight is 111.6oz + 2oz + 12oz =125.6 oz or 7.8lbs or 3538 gr.

Kelvin
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Old Apr 21, 2010, 06:55 AM
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thats a big plane how much power are you looking for like a 1:1 weight to thrust ratio.
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Old Apr 21, 2010, 08:05 AM
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Here are some specs I found.
FlyFly Hawk
Wingspan : 1365mm(53.5")
Length : 1465mm
Wing Area : 29dm sq.
Height : 535mm
Airfoil : RG-14
Weight : 730g (body) Mine is 776 without including the canopy.
Flying weight : 2430g (with air retract landing gear) 5.3lbs.
I don't know the size or cell count of batteries they use in their flying weight. I've seen youTube videos of this model flying 5s, 6s and 8s.

The other Hawks of this size are fiberglass and/or composite.
AMD Hawk
Wingspan: 53.50 inches
Length: 56.25 inches
This model is usually powered by a 110mm fan and 10s to 12s and weighs over 10lbs.

Fox Composites BAE Hawk
Length 62 inches
Span 53 inches
This model is powered by a 110mm fan. The Stumax powered model on youTube is about 16lbs.

Sapac has a new 100mm Hawk coming out soon. I imagine its roughly the same size and the weight will fall in between 10lbs and 16lbs.

Her is another 90mm powered Hawk.
http://www.rcgroups.com/forums/showthread.php?t=1158505
Scale.............................: 1/9
Wing Span.....................: 1110mm (43.6'')
Length...........................: 1320mm (52'')
Weight is from 7.1lbs to 8.3lbs.

If I can get mine under 8lbs it should perform adequately. We'll see. I've got a Midi with a 36-75-1 from the Mirage I can also put in this model. The motor/fan combo weighs almost 5oz more but will handle higher amps.

Kelvin
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Last edited by kelvin; Apr 21, 2010 at 01:32 PM.
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Old Apr 21, 2010, 10:14 AM
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Robert Belluomini's Avatar
United States, KY, Crestview Hills
Joined Dec 2000
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Kelvin,
Great start! I want to mention that Jepe balances the rotor and spinner assembly.
You will see scribe marks that locate the spinner to the rotor. If you remove the spinner make sure line up the marks.
Bob
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Old Apr 21, 2010, 05:50 PM
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If you remove the rotor as well then this will not work. The rotor is positioned on the shaft adapter for best running condition, then the spinner is positioned last, best not to dissasemble the fan at all unless absolutely necessary.
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Old Apr 21, 2010, 05:53 PM
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The Hawk flies fine even on 1200w/32,500rpm on the midi, the 8s setup you have looks to be around 1900-2000 watts which means around 37-38K rpm on the midi, maybe a bit more, you will have over 3kg static thrust, it will fly great.
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