SPARROW HAWK by Seagul models RESURECTED - RC Groups
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Sep 29, 2017, 07:10 AM
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SPARROW HAWK by Seagul models RESURECTED


Last week I picked up a bare airframe in good condition of an un identified scale model that looked to be from the 30's -40's. It was quickly identified by you guys as Seagull models Sparrow Hawk 180. 71" wing span. Decided to power it with a brand new in the box OS120 SURPASS 4 stroke. I purchased this beautiful engine in 1986 and never used it. Well, now it found a perfect scale 1930 era racer to power. Finally.
A couple of days to install all servos and motor which by the way fits in like a hand in a glove.
Previous power was a dle 20 side mounted so the cowl has a huge opening on the side. That has to be glassed and brought back to original shape. Once its done I plan to open it on the front to cool the joule inside. I shall fly it without the cowl for now.
Last edited by Sollym; Sep 29, 2017 at 07:31 AM.
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Sep 29, 2017, 07:24 AM
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Ended up having to balance it with a 500 gr. ballast up front to arrive at the 11.5 cm from L.E of the wing as per manual. Once the cowl will be fixed and fitted I will probably remove a good 100 gr and allow the c.g. to move aft a bit. I viewed several old videos on U tube and she seems to be a docile flier. Will Re maiden her early next week after a good Break In of the engine on the ground.
Even with the cowl off she's a beautiful plane.
Last edited by Sollym; Sep 29, 2017 at 07:33 AM.
Sep 29, 2017, 07:28 AM
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I plan on using a 16x7 prop for break in of the OS 120 Surpass. Any suggestions?
Sep 29, 2017, 07:59 AM
ARFs Are Me
TomCrump's Avatar
Quote:
Originally Posted by Sollym
I plan on using a 16x7 prop for break in of the OS 120 Surpass. Any suggestions?
My 1.20 Surpass liked a 15X8 prop.
Sep 30, 2017, 09:43 PM
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Tom,
was that just for the "Break in"? or did you continue to use it for normal flying?
Thanks
Oct 01, 2017, 07:13 AM
ARFs Are Me
TomCrump's Avatar
Quote:
Originally Posted by Sollym
Tom,
was that just for the "Break in"? or did you continue to use it for normal flying?
Thanks
I broke the engine in with a 16X6, but once the engine was in an air frame, I didn't feel that it flew the model well. The 15X8 performed better, for me.

I can't provide RPM data, this was 20 years ago, and I don't remember the details.

I have another 1.20 pumper, now, but I haven't fired it up.
Oct 01, 2017, 04:23 PM
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Gues I'm just gonna try several props and find out. Thanks for your input here.
Oct 10, 2017, 12:32 PM
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Today I continued with Breaking In the engine. I did it with the plan upside down so the engine will sit right side up. Everything went well for 5 minutes and then BANG. The motor pulled itself with the Firewall out of the fuselage frame. luckily no one got hurt.
This is the second time in a couple of months that a motor pulls itself off the frame. The first was on a Great Planes Citabria. It did it in mid flight but I saved the plane and reinforced the Firewall / Fuselage junction. I thought about reinforcing this Sparrow hawk but before I got it, it flew with a DLE 20 and I thought it must have been fabricated (Seagull models) properly so I saved my self the effort. WRONG DECISION.
From now on I will reinforce every airframe I mount a motor on and I will only Break In a motor on a Proper Stand. NOT ON THE PLANE!
Nov 01, 2017, 10:44 AM
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The plane is very steady in flight.
I think that it could use the power equivalent of a 30-35cc gas engine.
There are a lot of fans of how this airframe flies.
Nov 01, 2017, 03:29 PM
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Thanks wuest3141 and you're right. It is a very stable and calm plane.
Here is how it went for me so far:
I'd built me a stand and Broke In the engine properly. I had repaired the nose of the plane and re enforced it with fiberglass layups.
Maiden -
I took off and very quickly noticed my CG was way aft. Plane wanted to climb straight up. Got it up to altitude and tried to control it but it took reducing power completely to fly level. Pushed the stick down to keep it flying and managed to land it safely. To my surprise the Sparrow hawk can slow down to a walk without dropping a wing. This was encouraging.

I took it home and added (apparently) too much weight. Took off the next day and it wanted to nose dive when I dropped a wing for a turn. Other than that it was very stable and took min. trim. I flue around for five minutes and set up for landing. Our flying field is actually a huge commercial grass field with rows of sprinklers and it's imperative that you land in the 8 meter wide strip between the rows of sprinklers, or else.
Well, I concentrated so much on the hot landing because of a forward cg that I did not pay close attention to keep the plane centered and clipped a sprinkler with my outboard wing. Damage is repairable but I was so Pi....d off. I was really looking to enjoy this beautiful plane once removing 100 grams of weight from the front. I felt that it will be a great flier once I nail down the cg. The OS 120 Surpass was a concert music to my ears. Lots of power and great response.

back to the working table.
Last edited by Sollym; Nov 01, 2017 at 03:40 PM.
Nov 11, 2017, 12:43 AM
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I reviewed this plane with a OS 120 P with a 16 x 6. this is the last bit of the test flight.
As I pulled back on the elevator the Sparrow lifted its nose and climbed out on a very steep angle. Putting in some down elevator saw the Sparrow dive at the ground like its’ namesake! Pulling back on the stick slightly, the Sparrow Hawk would widely pitch up. Easing back the throttle helped a lot by slowing things down, as I fought against the laws of physics for control of this tail- heavy plane. After what seemed to be forever, I managed to get the Sparrow back on the ground and in one peace! Re-checking the CG measurement showed it to be a little bit nose-heavy as it was setup according to the instructions. Enlisting help from a fellow club member, it was calculated that the CG point should be 21mm further forward. 300 grams of lead was added under the flight pack and it was back out to the club for hopefully a more successful test flight.
in the instructions they give the CG at the wing tips not the std leading edge
Nov 12, 2017, 02:02 PM
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propwas1,
Thanks for the input. Hope to repair the wing next week and get back to flying it. How did it fly with the corrected C.G? and where is the sweet spot for it. cm from the LE?
Thanks
Nov 14, 2017, 04:27 AM
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on the instruction diagram, where do they show the CG point? if its at the wing tip there is the problem. use the measurement they give at the wing tip but measure it at the leading edge. it flies like a trainer. it is very very stable and the 120 is spot on
Nov 14, 2017, 04:36 AM
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Very cautiously, I eased back on the elevator and the Sparrow was airborne. With the elevator now giving a positive feedback, my confidence in the plane quickly grew. As I started to come to grips with the high speed of the Sparrow Hawk Racer, I could feel a smile starting to grow on my face, as at full throttle, the 16x6 propeller puts out a very scale-like racing howl. A quick test for the stall speed: what stall! It just loses height and the control surfaces become softer to my inputs, while still retaining good response. Back up to warp speed and it was time to put the Sparrow through its’ paces, to see if it is more than just a Racer.

Inside or outside loops could be as large as you liked, with no sign of snapping out. Rolls show just a touch of being a barrel roll, but I think if I mix in a little rudder to the ailerons, that should fix this. Stall turns took a bit of practice to get right, but once mastered they look great. The call came from the an observer,
‘What about an inverted pass or two?’
Rolling to inverted showed that only a small amount of down elevator was needed for level flight. This is a very good indication that the new CG point is on the money. In fact, the Sparrow flies almost as good inverted as it does the right way up, with no surprises. I thought, just for fun, I would see if it would knife edge, and to the surprise of all bystanders, it would knife-edge out of sight, with a slight pull to the wheels. I thought,
Nov 14, 2017, 07:17 AM
Registered User
Great Information. looking forward to flying once I get the wing all fixed up.
Thanks.


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