Sterling P-63 King Cobra restoration
01-16-2009, 03:20 PM
#76
RE: Sterling P-63 King Cobra restoration
Thanks for the first-hand information! Unfortunately, I can't quite believe all of it. To me, the incidence angles look like a neutral setup, meaning the airplane will fly level or climb or dive regardless of the power setting, even inverted, at least with only small corrections. Would make sense because a stable trim often needs a stab force resulting in considerable more drag as well as lift and induced drag on the wing.
And I think the model is aerobatic even at 7 lb weight and with the K&B .45 as shown on the GridLeaks cover above. It would even fly OK with a .30, just not aerobatic (and only from paved runways). Level cruise flight needs quite little power compared to climb or patterns, and it also needs only small AOA (just the 'built-in' 2 degrees). BTW, the difference in level top speed would be only about 18% between the 0.61hp .45 K&B and a 0.98hp .60 engine (drag increases with 2nd power of speed, so power with 3rd).
I'm trying to imagine that because we have so powerful models today and don't realize that even decent pattern flying is possible with less. Just my thoughts...
And I think the model is aerobatic even at 7 lb weight and with the K&B .45 as shown on the GridLeaks cover above. It would even fly OK with a .30, just not aerobatic (and only from paved runways). Level cruise flight needs quite little power compared to climb or patterns, and it also needs only small AOA (just the 'built-in' 2 degrees). BTW, the difference in level top speed would be only about 18% between the 0.61hp .45 K&B and a 0.98hp .60 engine (drag increases with 2nd power of speed, so power with 3rd).
I'm trying to imagine that because we have so powerful models today and don't realize that even decent pattern flying is possible with less. Just my thoughts...
01-16-2009, 09:33 PM
#77
RE: Sterling P-63 King Cobra restoration
Although using downthrust with less wing and stab incidence isn't exactly the same thing, it has a similar effect as using no downthrust and 2° or more positive incidence. A lot of planes from the '60s - like the Sun Fli's - did use downthrust and only a small amount of positive in the wing. But, they were also flying with more power than the P-63.
I guess thrust to weight ratios of 1:1 or greater were probably impossible to imagine back then for planes of this size. I guess it really wasn't until the stronger sixties and lighter radio gear came along that 1:1 thrust to weight ratios became realistic. A typical cross-flow sixty spun an 11x7 between 12, 000 and 12,500 rpm. That's about 6 to 6 1/2lbs. of static thrust. A Kwik Fli or Kaos w/o retracts could be built that light.
David
I guess thrust to weight ratios of 1:1 or greater were probably impossible to imagine back then for planes of this size. I guess it really wasn't until the stronger sixties and lighter radio gear came along that 1:1 thrust to weight ratios became realistic. A typical cross-flow sixty spun an 11x7 between 12, 000 and 12,500 rpm. That's about 6 to 6 1/2lbs. of static thrust. A Kwik Fli or Kaos w/o retracts could be built that light.
David
01-17-2009, 06:04 AM
#78
RE: Sterling P-63 King Cobra restoration
Thanks for the advice, that helps me quite a bit! It reminds me that Ed Cregger once pointed out ([link=http://www.rcuniverse.com/forum/fb.asp?m=6866271]here[/link]) that a stable forward c/g was common. The Sun Fli could be one example. Like the Kwik-Fli, it may have a symmetrical airfoil and about 0.5 degrees wing incidence to make up for the forward c/g. Maybe now it would climb at full power, but that is prevented by the downthrust. Only drawback would be that it's neutral only upright and not inverted.
As to the thrust/weight ratio, even with a Schnürle ported .60 from the 1970s (1.27 hp) the Kwik-Fli Mk III has only 0.94 T/W at 6.5 lb weight (estimate with a 11x7" prop), but it's still quite fast (70 mph). With a crossflow .60 from the 1960s (optimistic 1 hp) it has 0.8 T/W at 6.0 lb weight (and 0.5 degrees wing incidence but no down thrust, 65 mph) and won the w/c. The Kwik-Fli Mk II (1965) was even designed for a .45 (0.65 T/W at 5.5 lb weight, 55 mph) and was boosted as "the hottest competition machine you've ever flown", even though it was often flown with a .60. The Kwik-Fli Mk I (1964) was designed for a .60 and had the exact same wing loading and T/W as the MK II. It only was bigger and maybe looked too slow but not "hot" in the air (66" wingspan instead of 60", 0.66 T/W at 7.25 lb weight, 63 mph). These figures may be somewhat incorrect, but they are comparable (estimated using the same procedure).
Unfortunately, I don't have a pattern model with semi-symmetrical airfoil in the simulator yet (not even the Taurus), but I tried with the Kwik-Fli Mk II: At 7 lb weight (instead of 5.5 lb!) with a .45 (0.51 T/W) it's still aerobatic, despite the symmetrical airfoil, and needs only 0.8 degrees wing incidence and a suitable balance to be trimmed neutral (upright, needing substantial down elevator inverted). It takes off from grass, looks quite right in the air (a tiny bit nose-up), and still has 25 m/s (55 mph) top speed.
The P-63 should be even better and nicer! Unfortunately, we won't know that because Chris will make his a modern stunter, like an old car with a modern engine turned into a dragster.
(Sorry Chris, couldn't resist, and I'm helplessly nostalgic.)
As to the thrust/weight ratio, even with a Schnürle ported .60 from the 1970s (1.27 hp) the Kwik-Fli Mk III has only 0.94 T/W at 6.5 lb weight (estimate with a 11x7" prop), but it's still quite fast (70 mph). With a crossflow .60 from the 1960s (optimistic 1 hp) it has 0.8 T/W at 6.0 lb weight (and 0.5 degrees wing incidence but no down thrust, 65 mph) and won the w/c. The Kwik-Fli Mk II (1965) was even designed for a .45 (0.65 T/W at 5.5 lb weight, 55 mph) and was boosted as "the hottest competition machine you've ever flown", even though it was often flown with a .60. The Kwik-Fli Mk I (1964) was designed for a .60 and had the exact same wing loading and T/W as the MK II. It only was bigger and maybe looked too slow but not "hot" in the air (66" wingspan instead of 60", 0.66 T/W at 7.25 lb weight, 63 mph). These figures may be somewhat incorrect, but they are comparable (estimated using the same procedure).
Unfortunately, I don't have a pattern model with semi-symmetrical airfoil in the simulator yet (not even the Taurus), but I tried with the Kwik-Fli Mk II: At 7 lb weight (instead of 5.5 lb!) with a .45 (0.51 T/W) it's still aerobatic, despite the symmetrical airfoil, and needs only 0.8 degrees wing incidence and a suitable balance to be trimmed neutral (upright, needing substantial down elevator inverted). It takes off from grass, looks quite right in the air (a tiny bit nose-up), and still has 25 m/s (55 mph) top speed.
The P-63 should be even better and nicer! Unfortunately, we won't know that because Chris will make his a modern stunter, like an old car with a modern engine turned into a dragster.
(Sorry Chris, couldn't resist, and I'm helplessly nostalgic.)
01-18-2009, 02:25 AM
#79
Thread Starter
RE: Sterling P-63 King Cobra restoration
That's OK US,
I don't actually fly very fast right now so there may be some time period in which it will be flown quite slowly.
I actually have a new Torp 45 C/L! Perhaps if I had had an R/C version i would've gone for it...
I'm going to use right thrust as designed, and the incidence difference as designed. The question is whether to use the 2.2 or so wing incidence or reduce it some small amount. If the incidence meters show the fuselage to be accurate to the plans I'll be inclined to use all of the stock numbers as the model is already built and is stock.
I have really gone around the subject full circle as originally I wanted to change everything!
David,
Thanks for your thoughts. I mulled over adding downthrust and removing incidence. The airfoil question is the big unknown for my limited knowledge, though.
Chris...
I don't actually fly very fast right now so there may be some time period in which it will be flown quite slowly.
I actually have a new Torp 45 C/L! Perhaps if I had had an R/C version i would've gone for it...
I'm going to use right thrust as designed, and the incidence difference as designed. The question is whether to use the 2.2 or so wing incidence or reduce it some small amount. If the incidence meters show the fuselage to be accurate to the plans I'll be inclined to use all of the stock numbers as the model is already built and is stock.
I have really gone around the subject full circle as originally I wanted to change everything!
David,
Thanks for your thoughts. I mulled over adding downthrust and removing incidence. The airfoil question is the big unknown for my limited knowledge, though.
Chris...
01-18-2009, 05:00 AM
#80
RE: Sterling P-63 King Cobra restoration
Yeah, I'm as well trying to figure that out. I think what makes the semi-symmetrical airfoil special are two things: It can deliver more lift (even if only upright) so patterns can be flown with less speed and we can get by with minor power (of the old engines). And it has a down pitching moment, which is constant, though, as long as the lift stays the same. It does in level (unaccelerated) flight so the moment simply can be balanced by a more rearward c/g. Hope that's correct. [
]
Of course, more lift (higher lift coefficients) means more induced drag. I think that's why the old pattern planes had a higher aspect ratio and why the patterns were smaller in the old times. The incidence angles were chosen to let it look good in patterns flown upright.
]Of course, more lift (higher lift coefficients) means more induced drag. I think that's why the old pattern planes had a higher aspect ratio and why the patterns were smaller in the old times. The incidence angles were chosen to let it look good in patterns flown upright.
01-26-2009, 10:34 PM
#81
RE: Sterling P-63 King Cobra restoration
The plans published in American Modeler and later made into the Sterling kit are available from AMA.
BELL P 63 KINGCOBRA 70" AMERICAN MODELER 3/62, HESTER $23.00 plan #23838
BELL P 63 KINGCOBRA 70" AMERICAN MODELER 3/62, HESTER $23.00 plan #23838
02-02-2009, 04:42 PM
#82
Join Date: Jul 2007
Location: Elm Grove,
WI
Posts: 486
Likes: 0
Received 0 Likes
on
0 Posts
RE: Sterling P-63 King Cobra restoration
The UPS man just delivered the Sterling P-63 kit I won on ebay. Talk about a trip down memory lane. The plans look just like those of the Sterling Ringmaster U-Control kit I built 100 years ago as a kid. There are text instructions and isometrics filling about every inch of space on the two side plans.
The parts look as though they have never been out of the box. On the top is a die cut ply sheet with little brass eyelets installed for all the control horns. There must be a million little parts, and huge precarved balsa blocks with carving both inside and outside. For a Sterling kit the wood seems quite good. I took a crack at a Sterling Flying Fool kit about ten years ago. The wood on that one was so bad (hard, heavy) that I gave up on it. This kit is certainly buildable with the original wood.
In summary, worth every penny.
Jim
The parts look as though they have never been out of the box. On the top is a die cut ply sheet with little brass eyelets installed for all the control horns. There must be a million little parts, and huge precarved balsa blocks with carving both inside and outside. For a Sterling kit the wood seems quite good. I took a crack at a Sterling Flying Fool kit about ten years ago. The wood on that one was so bad (hard, heavy) that I gave up on it. This kit is certainly buildable with the original wood.
In summary, worth every penny.
Jim
02-03-2009, 01:17 PM
#83
Join Date: Jul 2007
Location: Elm Grove,
WI
Posts: 486
Likes: 0
Received 0 Likes
on
0 Posts
RE: Sterling P-63 King Cobra restoration
Here are some details of the aileron hinging as mentioned early in this thread. The ply die cut sheet has preinstalled brass eyelets for the control horns and for the hinge pins. The back view shows how they are riveted in place. Imagine a kit manufacturer doing that today. The die cutting quality and ply condition may also show up in the photo. One end of one die cut sheet has the ply delaminated and those parts will have to be replaced. Luckily it's not the sheet with the eyelets.
The ailerons are hinged on the end ribs only. The pushrod from the bellcranks comes out the top of the wing. It appears that the Cobra shown in the link (post 11) was built with the original aileron setup, because the pushrod can be seen exiting the tops of the wings. The plan shots also give an idea of the level of construction detail on the plans.
Jim
The ailerons are hinged on the end ribs only. The pushrod from the bellcranks comes out the top of the wing. It appears that the Cobra shown in the link (post 11) was built with the original aileron setup, because the pushrod can be seen exiting the tops of the wings. The plan shots also give an idea of the level of construction detail on the plans.
Jim
02-09-2009, 12:26 PM
#84
Thread Starter
RE: Sterling P-63 King Cobra restoration
Thanks for the post on your kit, Jim.
I have the kit plans but had never seen the kit unbuilt. Neat prefabrication on the ply parts there! I guess when I get to the wing I'll find those nifty eyelets in the ailerons...
I'm back to work now after 7 monyhs off, so my mdeling will be a little slower but I should add to the thread a bit this month with more fuselage work.
Thanks for all of the input guys,
Chris...
I have the kit plans but had never seen the kit unbuilt. Neat prefabrication on the ply parts there! I guess when I get to the wing I'll find those nifty eyelets in the ailerons...
I'm back to work now after 7 monyhs off, so my mdeling will be a little slower but I should add to the thread a bit this month with more fuselage work.
Thanks for all of the input guys,
Chris...
04-28-2009, 03:04 PM
#85
Thread Starter
RE: Sterling P-63 King Cobra restoration
ORIGINAL: RFJ
Save yourself a lot of hassle and just use center hinged ailerons. Much easier to build, less prone to flutter and any adverse yaw can be trimmed out with differential set up using TX mixing.
Ray
Save yourself a lot of hassle and just use center hinged ailerons. Much easier to build, less prone to flutter and any adverse yaw can be trimmed out with differential set up using TX mixing.
Ray
Hi Ray,
I'm back on the King Cobra and wondered how you modified your aileron coves to center hinge this type of aileron. I'm going to use a servo per aileron, and have some ideas about how to go about it but wanted a second opinion.
Thanks,
Chris...
08-02-2009, 08:33 PM
#86
Thread Starter
RE: Sterling P-63 King Cobra restoration
I decided to fill the aileron cove and use Robart hinges at about 20% of the aileron chord. Using a rounded aileron leading edge. Typical horn on the bottom with "a servo per wing" type set-up. I'm cleaning up all of the construction and with the dings and water spots about all sanded off it looks OK. I'll probably use Stix-It to make sure the cover stays stuck in case something creeps out of the wood's fibres.
Pix later, I promise.
Chris...
Pix later, I promise.
Chris...
10-07-2009, 05:22 PM
#87
Thread Starter
RE: Sterling P-63 King Cobra restoration
Thrashing on projects other than the King Cobra. Kaos ARF, (it's done). Son's birthday present Spitfire ARF (back burner). Flying electrics with dear old Dad. Son has a C/L Scale contest this weekend, I'm sick until today, first day out of bed. Working too much.
King Cobra model is bare, wing is kinda finalized, fuse is shaped with cockpit and canopy to go on then I'll c/f the body. I'll cut the tail off and rebuild the stab and fin and rudder.
Quick, all-white paint scheme (Lustrekote spray cans) with famous racer markings (Charlie Tucker #28 with red pegasus on nose). Wing and tail Monokote. Williams Bros. racing wheels with hub caps and hopefully a test and trim day before a Scale contest (Fun Fly really) on the first weekend of November.
Chris...
King Cobra model is bare, wing is kinda finalized, fuse is shaped with cockpit and canopy to go on then I'll c/f the body. I'll cut the tail off and rebuild the stab and fin and rudder.
Quick, all-white paint scheme (Lustrekote spray cans) with famous racer markings (Charlie Tucker #28 with red pegasus on nose). Wing and tail Monokote. Williams Bros. racing wheels with hub caps and hopefully a test and trim day before a Scale contest (Fun Fly really) on the first weekend of November.
Chris...
10-09-2009, 06:32 PM
#88
RE: Sterling P-63 King Cobra restoration
Thanks for the update, Chris. We're all still out here waiting for a pilot report !
I was admiring the picture of Maxey holding his P-63 (Post #61) just now and noticed that particular model doesn't have an upright engine. Looks like it might be side mounted with the head on the left side. This is one more indication, as we speculated before, that Maxey may have built a whole new airplane at some point.
Dick
I was admiring the picture of Maxey holding his P-63 (Post #61) just now and noticed that particular model doesn't have an upright engine. Looks like it might be side mounted with the head on the left side. This is one more indication, as we speculated before, that Maxey may have built a whole new airplane at some point.
Dick
11-05-2009, 02:32 AM
#89
Thread Starter
RE: Sterling P-63 King Cobra restoration
Hi Dick,
Still trying to get this model finished, this weekend is not going to happen but then there will be others.
Maxey sure had some good looking P-63's. That one looks more scale than the others, for sure. Either a rebuild or (probably) a totally different model altogether.
I have been shaping the sides on mine to get a bit of curvature into those slab sides, and added a wing intersection fairing. The bottom I made thicker so I can round it off too. 100 grit moves it along pretty quickly, but I just cannot find the time to get the stuff done like I used to. No follow through!
Hope your projects are going well.
Chris...
Still trying to get this model finished, this weekend is not going to happen but then there will be others.
Maxey sure had some good looking P-63's. That one looks more scale than the others, for sure. Either a rebuild or (probably) a totally different model altogether.
I have been shaping the sides on mine to get a bit of curvature into those slab sides, and added a wing intersection fairing. The bottom I made thicker so I can round it off too. 100 grit moves it along pretty quickly, but I just cannot find the time to get the stuff done like I used to. No follow through!
Hope your projects are going well.
Chris...
12-18-2009, 10:34 PM
#90
Thread Starter
RE: Sterling P-63 King Cobra restoration
Do any of you 91 four stroke guys have a good, middle of the road fuel capacity preference? I would like as small of a tank as is practical. 8 oz enough?
Chris...
Chris...
02-01-2010, 10:30 AM
#91
Senior Member
Join Date: Oct 2009
Location: mills river,
NC
Posts: 232
Likes: 0
Received 0 Likes
on
0 Posts
RE: Sterling P-63 King Cobra restoration
I'm glad Ifound this thread. I just purchased a Sterling P-63 kit off of ebay and will be building this plane this summer. Very interesting to read about all the unique features of this plane &kit, and the history lesson is awesome!
Mark
Mark
02-24-2010, 12:59 AM
#92
Thread Starter
RE: Sterling P-63 King Cobra restoration
Great Mark! Glad to know another is going together.
Here are some pics from a while back. I'll post some more next week.
Chris...
Here are some pics from a while back. I'll post some more next week.
Chris...
02-24-2010, 01:01 AM
#93
Thread Starter
RE: Sterling P-63 King Cobra restoration
Great Mark! Glad to know another is going together.
Here are some pics from a while back. I'll post some more next week.
Chris...
Here are some pics from a while back. I'll post some more next week.
Chris...
03-02-2010, 10:48 PM
#94
Senior Member
Join Date: Oct 2009
Location: mills river,
NC
Posts: 232
Likes: 0
Received 0 Likes
on
0 Posts
RE: Sterling P-63 King Cobra restoration
Found this on Ebay today:
http://cgi.ebay.com/ws/eBayISAPI.dll...%3DI%26otn%3D2
Just in case someone else wants to do one too!!
Mark
http://cgi.ebay.com/ws/eBayISAPI.dll...%3DI%26otn%3D2
Just in case someone else wants to do one too!!
Mark
12-18-2010, 11:10 AM
#95
Join Date: Jan 2005
Location: riverside, CA
Posts: 97
Likes: 0
Received 0 Likes
on
0 Posts
RE: Sterling P-63 King Cobra restoration
I'll add my two cents to the subject. I plan built this one about 3 years ago with retracts and a K&B .61 for power. Only mod was adding about 4" to the nose to get the nose gear to fit. All other parts were built to the original plans. I built the original kit about 40 years ago and powered it with a Fox .36 believe it or not. The kit was covered with olive drab coverite with the kit decals. The plan built one was covered with silk and dope with Klass Kote two part epoxy for the finish. I still have the plans and may put one of these together again. I lost one to battery failure and the other to high power lines that sucked the model in when the radios were AM sets. Both flew great. If I build again I would forgo the bellcranks for the ailerons and go to servo per aileron. I couldn't get the bounce out of the ailerons on either ship when it was on takeoff run. One other thing I would do is reshape the fuse to a rounder shape aft and at the cockpit sides. Have the real thing about 1 hour from home at the Palm Springs Air Museum. Saw it do a run up and mag test on the 16th of Dec. for a flying demo on Sat. Quite a bird and quite rare! Resto looking good!
12-18-2010, 08:58 PM
#96
Thread Starter
RE: Sterling P-63 King Cobra restoration
Thanks for the comments on your P-63's, Scratchbuilder. Hope you decide to try another one.
I bought a NOS Super Tigre V60 with an uncut NOS Froom Spinner. Quite a nice find. Does anyone know of an available MACS open front muffler for this engine?
The ideas I had for mine 3 years ago all seem better suited to the models I have acquired since. It'd be better to make this one a tribute to Maxey Hester.
I kinda got the idea from the Kaos I saw at the AMA Convention last year. Period stuff is cooler for this ship.
Chris...
I bought a NOS Super Tigre V60 with an uncut NOS Froom Spinner. Quite a nice find. Does anyone know of an available MACS open front muffler for this engine?
The ideas I had for mine 3 years ago all seem better suited to the models I have acquired since. It'd be better to make this one a tribute to Maxey Hester.
I kinda got the idea from the Kaos I saw at the AMA Convention last year. Period stuff is cooler for this ship.
Chris...
12-19-2010, 04:45 AM
#98
Join Date: Jul 2007
Location: Elm Grove,
WI
Posts: 486
Likes: 0
Received 0 Likes
on
0 Posts
RE: Sterling P-63 King Cobra restoration
Chris, if you are looking for an open front muffler, and can use it where you fly, consider a Semco. The 60 size mufflers were a standard size; an adapter was used for each engine. (you probably already know that) They do show up on ebay or a wanted ad over at RCG might unearth one. The muffler should be easy to get, the adapter a little harder. ST did make strap ons for these - don't remember if in open and/or closed front.
Jim
Doh! I just actually looked at your pictures after I posted this. Your V60 has muffler lugs. The above all assumed it was the earlier engine without lugs.
Jim
Doh! I just actually looked at your pictures after I posted this. Your V60 has muffler lugs. The above all assumed it was the earlier engine without lugs.
12-19-2010, 08:12 AM
#99
Join Date: Jan 2005
Location: riverside, CA
Posts: 97
Likes: 0
Received 0 Likes
on
0 Posts
RE: Sterling P-63 King Cobra restoration
Chris, great find on the engines. I would stay with the engine mounting and attitude as it is on the plans. It just looks right and the engine is a lot easier to tune! I will think about another after the projects on the board are completed. I am working on a TF F4U .60 size right now as well as a TF P-51D for our club pres. Putting an arf together for a friend who is having surgery and getting a float plane ready for next year. I kind of am the fixit guy for the club also. The repairs keep me in fuel, as my fee is usually a can of 15 or 20% for the repair. It is just part of the hobby that I enjoy. Not too many kit or plan builders in my club. It is a shame that tissue and dope means tp and drugs to some of the younger members! I can remember when silkspan was included in the kits. Glad you are doing this P-63 over. I really enjoyed how it flew. As I said earlier just too much slop in the ailerons due to their mass. As a side note, I built the Spit that Sterling kitted from plans and it flew great. I built the Platt Spit years ago and I would say the Sterling flew better. Once upon a time there was an article about scaling out the Spit which I obtained from the author. Another project in my mind. Good luck with your P-63. I will follow this thread for a flight report.
07-27-2011, 08:39 PM
#100
Thread Starter
RE: Sterling P-63 King Cobra restoration
My good friend Tom Lay found an old open face Super Tigre/Semco/Macs/? muffler for my NIB V60 R/C and my son has just left for his mother's after a lot of flying here on summer vacation, so I've started back on this model by mocking up the cowling.
Also a challenge is that the motor mounts are too wide to catch any of the Tigre's mounting bolts. I may have to gut the front end to install a firewall motor mount. If that won't work, possibly rock maple mounts. This thing hasn't been easy from the start, but I'll get it flying no matter what.
Chris...
Also a challenge is that the motor mounts are too wide to catch any of the Tigre's mounting bolts. I may have to gut the front end to install a firewall motor mount. If that won't work, possibly rock maple mounts. This thing hasn't been easy from the start, but I'll get it flying no matter what.
Chris...