BaeHawk 90mm EDF - 1st

[RAPHAEL_CINTRA]

Hey there pilots/friends from Hobby Squawk,

I want please a piece of advice from the most experience pilots...

Some days ago i got my first one (in fact, was a exchange with some of my prop planes), a BaeHawk 90mm composite EDF (1100 wingspan + flaps+retracts) with some pretty decent electronics on it (YEP 90amp ESC + Jet Power 12 blades Al EDF+ 1750KV motor i think)...as usual, i´m very excited to put it on the air (like all our new planes), but before i want to please receive some recommendations regarding the EDF flight in general and if possible some specific characteristics related to this model. As far as i noted/can imagine, the wing loading should be high in this one.

I have some specs (this kit was originally sold by HK):

Wingspan = 114 cm = 46 ''
Length = 122 cm = 49 ''
Wing area = 24 dm^2 = 372 sq in
Est. weight rtf 7.2 - 8.0 lbs

I´m planning to use 6s 5000mah 65C pack for it. Hopefully will give me 1:1 ratio but i´m not sure.

Meanwhile i'm waiting for my freewing yak-130 to be delivered BUT as far as it goes it will take more than 45 days :-( (Registered Air Parcel from Singapore)...probably better to wait and gain experience with the foamies first...but, this bird is here and seems "ready to fly" let´s say.

Safe flights to all!

[ddsjoseph]

When you have the jet all put together, use a luggage scale to do a horizontal static thrust test on the ground. The amount of horizontal thrust in Lbs, should give you an idea how this thing will fly. Prop planes usually have more than 1:1 thrust ratio, especially ones for 3D planes can have as much as 1:2 or even as much as 1:3 thrust to flying weight ratio. Jets on the other hand can have 1:1 or even slightly less than that. Unlike prop planes, jet require a great deal more runway to pick up speed required for lift, therefore 1:1 ratio is plenty for take off.

[RAPHAEL_CINTRA]

When you have the jet all put together, use a luggage scale to do a horizontal static thrust test on the ground. The amount of horizontal thrust in Lbs, should give you an idea how this thing will fly. Prop planes usually have more than 1:1 thrust ratio, especially ones for 3D planes can have as much as 1:2 or even as much as 1:3 thrust to flying weight ratio. Jets on the other hand can have 1:1 or even slightly less than that. Unlike prop planes, jet require a great deal more runway to pick up speed required for lift, therefore 1:1 ratio is plenty for take off.

Dear ddsjoseph,
Thank you for your reply.
I agree with you, in my constructions i always use 1:1 or more of ratio...i´ll test on the ground.
For the EDF´s i have near my home a grass and a concrete runway (both with more than 180 meters length) that should do de trick :-)...let then run :)

Hopefully this electric setup will give me 8lbs of thurst despite the heavy wing loading.

I don know what to expect about BaeHawk characteristics/flight envelope/ bad-stall tendencies...i think is not a "easy bird"....hope to receive some advice about it.

Safe flights :-)

[ddsjoseph]

My experience with the BAE Hawk has been with the FLY FLY BAE Hawk. It is made of EPS Foam. The flying weight was about 8.5 LBS with a 90mm EDF 10 bladed, motor out of HSD Viper 90 with a 130A ESC. The jet flies great and has a long glide path. Since the jet weighs over 8 lbs, you need to bleed off speed before you land. Otherwise it comes in hot. Don't worry, the Air Frame design allows the jet to fly with very little bad habits.

[RAPHAEL_CINTRA]

My experience with the BAE Hawk has been with the FLY FLY BAE Hawk. It is made of EPS Foam. The flying weight was about 8.5 LBS with a 90mm EDF 10 bladed, motor out of HSD Viper 90 with a 130A ESC. The jet flies great and has a long glide path. Since the jet weighs over 8 lbs, you need to bleed off speed before you land. Otherwise it comes in hot. Don't worry, the Air Frame design allows the jet to fly with very little bad habits.

Just great ddsjoseph...almost the same weight..wow...a heavy fomie you have out there ;-)
You use 6s lipo on your´s? Do you have 1:1 ratio?
People use 8S in this model i have but my ESC (YEP 90amp) only supports 6S :-(

[EDFjetpilot]

My stock FW T-45 flew well off grass with a .73 thrust to weight ratio. I wouldn't try with anything less than that. In my experience, a .80 ratio is good, anything higher is that much better, but a 1:1 isn't required to get it off the ground.

Sean

[RAPHAEL_CINTRA]

My stock FW T-45 flew well off grass with a .73 thrust to weight ratio. I wouldn't try with anything less than that. In my experience, a .80 ratio is good, anything higher is that much better, but a 1:1 isn't required to get it off the ground.

Sean

EDFjetpilot,
Thank´s for your reply!!
Your suggestion is very nice...this weekend i´ll try do the below:
1. Put the jet nose down to a scale and measure the RTF weight (6s5000 lipo + everything)...it should be around 7Lbs.
2. I´ll go full throttle and see what i got...7 to 10 sec at full, should be enought for a good reading...
3. I looking for a total "weight" in the scale of 12-14lbs

[EDFjetpilot]

EDFjetpilot,
Thank´s for your reply!!
Your suggestion is very nice...this weekend i´ll try do the below:
1. Put the jet nose down to a scale and measure the RTF weight (6s5000 lipo + everything)...it should be around 7Lbs.
2. I´ll go full throttle and see what i got...7 to 10 sec at full, should be enought for a good reading...
3. I looking for a total "weight" in the scale of 12-14lbs

Yep, you're on the right track.

To be safe, multiply your RTF weight by .75 (desired minimum thrust to weight ratio) and add that weight back to the RTF weight to determine your minimum full throttle weight.

For example, 7 pounds times .75 is 5.25 pounds. So add the 5.25 to your 7 pound RTF weight, which is 12.25 pounds. You'll want your full throttle weight to be at least 12.25 pounds (a thrust to weight ratio of .75).

BTW...I use a digital fish scale for my tests. I hang the RTF plane carefully by the nose wheel to get the AUW. Then put the plane on the ground, loop a cord around the mains, attach it to my fish scale, tie the fish scale to an immovable object, and throttle up to get the actual horizontal thrust. Then divide the thrust by the AUW to determine the ratio. I found this easier than trying to keep the aircraft pointed nose down at full throttle, one hand balancing the plane on a scale, the other working the throttle, while looking for a stable weight reading.

Let us know how it turns out.

Good luck,

Sean

[RAPHAEL_CINTRA]

Yep, you're on the right track.

To be safe, multiply your RTF weight by .75 (desired minimum thrust to weight ratio) and add that weight back to the RTF weight to determine your minimum full throttle weight.

For example, 7 pounds times .75 is 5.25 pounds. So add the 5.25 to your 7 pound RTF weight, which is 12.25 pounds. You'll want your full throttle weight to be at least 12.25 pounds (a thrust to weight ratio of .75).

BTW...I use a digital fish scale for my tests. I hang the RTF plane carefully by the nose wheel to get the AUW. Then put the plane on the ground, loop a cord around the mains, attach it to my fish scale, tie the fish scale to an immovable object, and throttle up to get the actual horizontal thrust. Then divide the thrust by the AUW to determine the ratio. I found this easier than trying to keep the aircraft pointed nose down at full throttle, one hand balancing the plane on a scale, the other working the throttle, while looking for a stable weight reading.

Let us know how it turns out.

Good luck,

Sean

Great idea.
I'll go with your method and post the results !
Thank you very much..again :-)
Safe filghts!