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Author Topic: Dumas P6-E Hawk (17.5") R/C flies  (Read 1565 times)
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Konrad
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« on: April 04, 2012, 12:38:04 AM »

Guys and gals,
I took a chance and test flew the P6-E between the rain squalls.The wind was a little strong for a test flight about 3+ mph and coming in about 15° off to the right.
Well she has a lot of POWER!  I was using the GWS 3x3 prop as I thought 80+ watts/lb was more than enough power. The CoG balance point was set at 7.5mm ahead of the bottom's leading edge ( I used the edge of the table method to check balance. more on this latter). Well I'm glad I had the power and that she was (is) a little nose heavy as she went into a nose high deep stall at take off. I had pitch problems and directional control problems trimming out the ship. I'm sorry to say the ship relied of shear power more than my piloting skills during this part of the test flight. I powered out of more deep stalls than I'd like to admit.  I got the plane down OK. Realized that I needed to set the elevator with a lot more down trim. I also moved the battery back about 3mm. (With all the prop hanging she should have snapped)!
Next take off run resulted in a nose over (too much down trim) reset the trim between the two previous positions. This time she climbed nice.

Time to test the dihedral. I noticed the the ship would turn both left and right but that she yawed more than rolled  I noticed that slight rudder did not pick up a down wing at full power (she skidded more than turned).  Cutting back the power did help a lot with the turns but she still felt dead to the roll  on initial rudder command no matter what I did during all the flight test flight. I got some what comfortable with turning the ship. But if she hit a wind gust she did not respond well to the counter gust input. Again I got more yaw than roll.
I think I need more dihedral. But I am using 60% expo, this might account for the dead or slow response to rudder. (I don't think so as the ship did yaw fast enough she just didn't pick up the low wing as fast as I'd like.
I did have problems with the landing as I couldn't hold the nose up with the motor off. (The wind might have been pushing the bird down or she might really be very nose heavy) I noticed I could keep the nose up a while longer with some power. So I'll need to do some more experimenting with the CoG and/or prop diameter to help with airflow over the tail feathers.

The plane is still in great shape (a few bruised wheel pants and a scraped wing tip. I will say I like how the struts stayed on even when the wind drove the ship into the ground a few times (she is a strong gal).

So  after 2, 120 mAh batteries worth of test flight in bad weather (I had to dodge some hail, gotta love Seattle) I can say she flies well but still needs some fine tuning.  The jury is still out on the dihedral but I think if I was to do it again I'd add 1.5mm (1/16") to each of the top wing's tips. (Right now the top wing is flat along the top of the wing).

Sorry for the poor quality of the photos. The light was poor and I was keeping the speed up making it hard for my photographer.
I need to thank my brother for standing his ground taking the photos, as this ship flopped all over the place while I tried to learn how to fly her.
I'd also like to thank Henry for the doll. Some of those flight shot would have looked rather bad without  someone at the desk!

Check out this link for the build thread.
http://www.hippocketaeronautics.com/hpa_forum/index.php/topic,11737.msg79480.html#msg79480

Engineering specs:
Weight 61 grams as shown
Power to weight with GWS 3x3 prop 86watts/lb
Battery 2 cell 120 mAh (from Eflight Beast)
Electronics brick from Efight Beast
Motor 5 gram 2000Kv (HXM1400-2000)



All the best,
Konrad
Attached files Thumbnail(s):
Dumas P6-E Hawk (17.5") R/C flies
Dumas P6-E Hawk (17.5") R/C flies
Dumas P6-E Hawk (17.5") R/C flies
Dumas P6-E Hawk (17.5") R/C flies
« Last Edit: April 04, 2012, 12:54:21 AM by Konrad » Logged

Cut it twice and it's still too short!
Konrad
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« Reply #1 on: April 05, 2012, 09:01:11 AM »

More flight testing. The CoG was moved back to 2mm ahead of the lower wing's leading edge. I can now raise the nose to flair. She now can do touch and goes, not that the picture shows this  Embarrassed
She can do loops and fly inverted. She is rather neutral to speed changes (down thrust and CoG are just about right).
She won't spin and the turns still look more like skids (yaw) than I like. The elevator is showing a bit too much down trim. I will make note of this in the build thread to add some incidence to the stab.
Attached files Thumbnail(s):
Re: Dumas P6-E Hawk (17.5") R/C flies
« Last Edit: April 05, 2012, 09:36:10 AM by Konrad » Logged

Cut it twice and it's still too short!
Tomcat-Tech
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« Reply #2 on: April 18, 2012, 10:56:12 AM »

Konrad you've done a nice job on that one! Is the finish dope over tissue? Back in the day we did it that way, now there are many other types of materials but whichever you chose the finish looks good. The in flight shots are great. Keep up the flight test reports... I'm curious to see if you can improve the turn response. Co-ordinated turns with rudder might hold the most promise.

 Thanks for taking the time to post.

 Craig.
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Konrad
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« Reply #3 on: April 19, 2012, 12:15:35 PM »

Craig,
Thanks.
The covering and art work are done in Solite/Nelson film. If I was to do it again I'd use a film called R.A. Microlite http://www.homefly.com/products.asp?id=31
Yes, I've done my share of dope finishes, both nitrate and buyterate.

As for coordinated turns the ship is only a three channel ship no ailerons. As I feared there isn't quite enough dihedral in the wings for good roll coupling from the rudder.

I have learned that if flown at half power that the rudder will yaw the ship enough to produce the skid needed to induce the roll from the little dihedral that she has. At high power setting she just goes in the direction of the yaw. The prop pulls the ship with such authority that there is little chance of a skid developing which is needed for the dihedral to induce a roll response.

By the way I'm now grafting in a set of ailerons on to the top wing. I'll post my progress in the build thread listed earlier.
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glewis
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« Reply #4 on: April 23, 2012, 03:21:41 PM »

Nice job Konrad! Grin
About the yaw/skid, my Skyraider does the same thing. My first flights were terrible, the model just refused to turn on rudder alone. It would just yaw and crab along while still traveling in a nearly straight line! Eventually it would turn but the turns looked terrible!
CG changes only made it worse. i was about to give up on it when I discovered that adding rudder then a quick poke of up elevator will initiate the roll and the turns look a lot better.

Glenn
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Konrad
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« Reply #5 on: April 23, 2012, 03:50:03 PM »

Glenn,
Thank you.
I too noticed that the ship would turn better with elevator input. Much to my surprise I find that unloading the wing (down elevator) helps more than up elevator. I can fly it but it really isn't what I'd consider fun. So dropping the ship on its wing tip was all the impetus I needed to open up the wing!

All the best,
Konrad
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glewis
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« Reply #6 on: April 24, 2012, 12:14:00 PM »

Hey, good idea about down elevator, I'll have to try that.
Now that I think about it, that's what's happening with the up elevator. The 'blip' of up elevator causes the nose to rise momentarily and then drop slightly. When the nose drops slightly the wing unloads and the wingtip on the inside of the turn drops.
Keep us posted on your aileron modification, it's too pretty a model to become a hangar queen.
Glenn
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danrc
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« Reply #7 on: June 07, 2012, 11:50:06 AM »

Hey Konrad,
Great work! I hadn't been following your thread for a while and just stumbled back upon it.
I dinked my Eflite Beast (still flyable) recently. Maybe your success may motivate me to dink it a little harder next time.
Good to see your work again.
Dan (Danrc)
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Konrad
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« Reply #8 on: June 07, 2012, 03:49:11 PM »

Dan,
Thanks for the kind words.
I think is is good to dink foam. I have to say the Beast flies great I just don't know how to repair them. So the guts often live on in other balsa models.

I think this weekend I'll do some work on the ailerons. See my build thread for up dates.

All the best

Konrad
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Cut it twice and it's still too short!
danrc
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« Reply #9 on: June 07, 2012, 04:46:48 PM »

Agreed. I bought the Beast on discount with one thing in mind, gear extraction. I soon realized that it was fun to fly, so my plans have been put on hold until I have a catastrophic incident with it.

You encouraged me (with a guillows dr1 that I had no business building/converting) when I was first starting out with scale building, and while I'm no master, I credit you and others from Rcgroups with helping me along. I just thought I should thank you. The plane flew and it put me on to a (hopefully) lifelong affection for scale flight/building.

Keep up the good work!
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