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Very Hot Topic (More than 25 Replies) Miles Sparrowhawk Dimer (Read 761 times)
MKelly
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Re: Miles Sparrowhawk Dimer
Reply #28 - Sep 9th, 2020 at 9:04pm
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Thanks Pete.  I've got a pretty aggressive prop on the model (1.4 P/D), and I've seen that same sag with left roll/slip at launch on other scale models with similar high-pitch props.  I was thinking a bit more right thrust and a bit less down thrust would help - I also think I'll likely have to go to 1 loop 1/16" plus 1 loop 3/32" to get the model to carry the weight of a longer motor.  Regardless, I'm pleased with how it's shaping up.

Mike
  
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staubkorb
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Re: Miles Sparrowhawk Dimer
Reply #27 - Sep 9th, 2020 at 1:47pm
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Looks really nice, Mike!  That last flight has it almost nailed, but I think you could take out a teensy bit of down thrust.  The model seems to want to sink at the burst, as if the prop was pulling the plane down.  Once the burst is spent, she has a nice but rather shallow (albeit, SCALE) climb.
  

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MKelly
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Re: Miles Sparrowhawk Dimer
Reply #26 - Sep 9th, 2020 at 8:07am
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Did a bit more trim flying on Monday - I'm pleased with how things are progressing.  Video at:

https://www.youtube.com/watch?v=v071qtSKtUk

Mike
  
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Re: Miles Sparrowhawk Dimer
Reply #25 - Aug 15th, 2020 at 10:08pm
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Glads to hear she's trimming out.  Sorry to hear about your regular field! Cry
  

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MKelly
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Re: Miles Sparrowhawk Dimer
Reply #24 - Aug 15th, 2020 at 11:59am
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Did some test glides and hand-wound flights this morning at our small alternate field - the Sparrowhawk is much happier with the c.g. a bit more forward. A touch less downthrust and she was doing nice circles for 20-30 seconds on ~450 turns.  Will probably need a bit more right thrust as torque goes up, but much steadier than last time out.

Our old field has been completely scraped over, with excavations ongoing for roads, utilities and drainage.

Mike
  
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MKelly
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Re: Miles Sparrowhawk Dimer
Reply #23 - Aug 10th, 2020 at 9:41pm
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Thanks Tom and Neal - it was great to build something straightforward for a change.  Now, if the wind would quit blowing, I'd like to give it some more air time.

Mike
  
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Kerak
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Re: Miles Sparrowhawk Dimer
Reply #22 - Aug 10th, 2020 at 7:43am
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That's the word, Mike...pure inspiration!  Great build, great model...the essence of inspiration in the air.

Neal
  
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Re: Miles Sparrowhawk Dimer
Reply #21 - Aug 8th, 2020 at 10:40pm
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I really appreciate your trimming details.  I also love the pics you post.  They're all inspiring and challenging to better my skills.  Gotta get over this bronchitis and get out to try to get something in the air!  Well Done! Smiley
  

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And ye shall know the truth, and the truth shall set you free. Jn 8:32
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MKelly
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Re: Miles Sparrowhawk Dimer
Reply #20 - Aug 8th, 2020 at 6:20pm
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Thanks for posting the plans link Tom - it's a well-drawn plan and built up with really no drama at any point.

Monday's initial trimming session went fairly well.  Based on the recommendations from my spreadsheet I took two motors, 1x18" loops of 3/32" and the same with 1/8" rubber.  After a bit of glide trimming I started out with the 3/32" rubber.  Flights were steady but anemic and typically landed with a lot of turns still wound.  I swapped to the 1/8" motor and things were better, but the model was easily upset in pitch and very sensitive to thrust adjustments.  Working up to 1000 turns I was able to get some 40-50 second flights, but the model didn't seem happy or steady.  The last flight popped into a robust thermal and got quite a bit of altitude, had me worried for a bit.  Fortunately it spiraled down fairly steeply after the power went out and landed on the field after 1:06 duration.

After returning home I checked the model over and found that delta incidence between the wing and tail was down to about 1.75 deg, and the cg with the larger motor was right at the aftmost position calculated using the McCombs formula (~45%).  I've added about 3/4g of clay up front and moved the cg forward about 1/8" to ~40% MAC, we'll see if that steadies things out.

Got some nice pictures and screen captures during the session.

Mike
  

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Re: Miles Sparrowhawk Dimer
Reply #19 - Aug 4th, 2020 at 6:32pm
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For those interested in the plan for the Miles Sparrowhawk from the FAC newsletter here's the link: Miles Sparrowhawk around page #26.
Sky9pilot
  

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Your attitude will determine your altitude!- John Maxwell
And ye shall know the truth, and the truth shall set you free. Jn 8:32
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MKelly
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Re: Miles Sparrowhawk Dimer
Reply #18 - Aug 3rd, 2020 at 12:41pm
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New Builder wrote on Aug 3rd, 2020 at 7:19am:
Gotta ask tho, how did the thinner work to fasten the tissue, what's under it?
Mike


Thanks Mike and Tom.  Mike, I sealed the tissue on this one with Krylon Satin Clear spray.  I've used this on my last several models and have been quite happy with it.  I made a quick test frame with the silver tissue, shrank and sealed the test panel, then tried Home Depot lacquer thinner to stick down some trial markings.  After the thinner dried I brush-painted over the marking with Tamiya gloss clear acrylic to seal them.  The test panel worked fine so I used that approach to complete the markings on the model.  The only caution is that if you drip thinner on the sealed tissue it'll leave a mark like a waterspot (Below the "G" in the attached picture).  I saw this on the test panel, so I was careful not to do it on the model...

Got a chance to trim fly it a bit this morning - went well overall, still a few things to fine-tune.  Will post details after I take care of a few other things here at home.

Mike
  

( 286 KB | 24 Downloads )
0803_Markings_Test_Panel.JPG
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Re: Miles Sparrowhawk Dimer
Reply #17 - Aug 3rd, 2020 at 10:27am
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Once again an amazing model.  And so fast!  Well Done! Smiley
  

If God is your Co-pilot...switch seats...
Your attitude will determine your altitude!- John Maxwell
And ye shall know the truth, and the truth shall set you free. Jn 8:32
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Re: Miles Sparrowhawk Dimer
Reply #16 - Aug 3rd, 2020 at 7:19am
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Quote:
Glue-stick the end of the tissue strip near the stab, gently pull it tight and align along the longeron, then hit it with thinners

Absolutely superb. I'm amazed at your finishing details, truly a work of art. Gotta ask tho, how did the thinner work to fasten the tissue, what's under it?
Mike
  

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MKelly
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Re: Miles Sparrowhawk Dimer
Reply #15 - Aug 2nd, 2020 at 9:09pm
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Chopped poplar 1x2s.  Got it all wrapped up today, except maybe a pilot.  Very pleased with the airframe weight, just under 14g balanced (without rubber).  I foresee more Miles aircraft in my future - they have such beautiful shapes.

Mike
  

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0802_Completed_Outside_Right_Rear.JPG
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Re: Miles Sparrowhawk Dimer
Reply #14 - Aug 2nd, 2020 at 4:39pm
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Looking great Mike.  Are those blocks balsa or chopped 2X4's?
  

If God is your Co-pilot...switch seats...
Your attitude will determine your altitude!- John Maxwell
And ye shall know the truth, and the truth shall set you free. Jn 8:32
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