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GP Stearman to gas

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Old 03-04-2018, 07:38 PM
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katman74
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Default GP Stearman to gas

I was recently given a GP stearman. Is it best suited for a 20 or 30 cc gas
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Old 03-05-2018, 08:21 AM
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RBACONS
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At 15 lbs or so, I would definitely opt for the 30CC. 20CC would probably fly it but not have much oomph.
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Old 03-06-2018, 03:31 AM
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I had a Zenoah 23cc in mine, It performed "normal" aerobatics. I felt that it had plenty of power.
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Old 03-07-2018, 04:38 AM
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Katman be careful when considering engines especially larger gassers, please understand there were two versions of that airplane, the GP PT-17 Stearman and the Super Stearman. The PT-17 has two ailerons instead of four, an additional cockpit and a detailed scale radial engine cowl with open cylinders instead of a large townend pressure cowl, they were otherwise identical.

If you have the PT-17 version then be very carefull in engine choice if you intend to use the scale radial cowl it would be difficult to still use this cowl with physically much larger engines than the 120 four strokes this
arf was intended for. You could go bare but that radial cowl was the charm of this airplane in the first place or you could us the large pressure cowl of the Super Stearman.

Have been flying my PT'17 many years with the OS 120 SE as a hard working glider tug and it is a wonderful engine airframe combo.

John

Last edited by JohnBuckner; 03-07-2018 at 04:43 AM.
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Old 03-09-2018, 10:19 AM
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Thanks Guys,
John mine is the PT-17. But with no cowl or radial engine. As I have found it is impossible to find a replacement cowl. No one makes one.
I was considering a cowl like the super.
Keith
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Old 03-10-2018, 08:14 AM
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Cool If you have no cowl/cylinders then finding whatever pressure/round cowl to fit the engine would be fine. And make no mistake sometimes with these bipes even going 'Bare' can have its own charm.as well as the improved functionality just in operations..

Now as to engines. As I noted my PT-17, I have only flown it since the beginning with the 120 FS they recommended and have towed up to eight pound gliders many times. Conventional aerobatics are a pleasure. I have also two larger biplanes (Busa Nieuport 28) The first built from a kit many years ago I installed an OS 120 SE same as my PT-17 and this airplane is not really an aerobat where rolls are OK and loops pretty much out of the question but major fun for flybys and simply landing increditably slow.

Now just two years ago I picked up a second 28 for just fifty bucks, almost complete but never finished and no engine. For this one I choose a DLE 20 cc. and this engine flys the bigger 28 very nicely. The reason I wanted two of the 28's is to fly together with one of my former students just for the joy of it.

My point is I believe 20 cc will fly your 17 quite well. The problem with that though is to carefully consider the configuration of the gasser. Namely where is the carb? That DLE had a rear carb and that presented major problems in the 28. I had to build an engine box but not the normal protruding type but an inverse engine box to put the carb back into the cabine area of the fuselage. This was an after the fact major pain in the butt intended not to end up with the prop sticking ridiculously out the front.

My whole point in these comparisons is: First I believe 20cc or there abouts is a good match for your PT-17 (remember is is much smaller that the 28's and second consider where the carb is on whatever engine you may choose. I assembled my PT-17 long ago but if my memory is correct it has a conventional protruding engine box/weight box that will have to be delt with.

Its a great airplane, enjoy.

John

Last edited by JohnBuckner; 03-10-2018 at 08:19 AM.
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Old 03-11-2018, 02:41 AM
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I have a Stearman with a DLE 30.
It really helps with the balance. Cowling needs some cutting to fit the stock muffler. There is a muffler out that moves the can to the rear of the engine if holes in the cowl bother you.
Impressive power, use full throttle for verticals and times of trouble, otherwise 1/4-1/2 throttle cruising is a piece of cake.
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Old 03-12-2018, 08:50 PM
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I recently purcased​​​​​​​ from a friend the Navy PT-17 version with the blue tail, gray fuse and yellow wings. It has a Saito FG-30 on it. It does fly very well with this engine. It dos not have a manual so if someone could please tell me the Monokote numbers for the three colors I would very much appriciate it. I need to repair a wing tip rash. Thanks
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Old 03-21-2018, 11:23 AM
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Originally Posted by Mokulele View Post
I recently purcased from a friend the Navy PT-17 version with the blue tail, gray fuse and yellow wings. It has a Saito FG-30 on it. It does fly very well with this engine. It dos not have a manual so if someone could please tell me the Monokote numbers for the three colors I would very much appriciate it. I need to repair a wing tip rash. Thanks
lYou can find the manual on the great planes web site. I believe the colors are wings-cub yellow, fuselage-dove gray, and tail sky blue I had this plane and it flew great with a DLE 20 with smoke and a Pitts style muffler and the cowl with the fake radial.
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Old 03-21-2018, 03:07 PM
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Thanks reptureboy, I haven’t been able to fly it yet due to the miserable weather on the flying days. Thanks again for your help.
Larry
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Old 03-27-2018, 10:03 AM
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Been kicking the tires on changing my GP Super Stearman from glow to an RCGF 35cc RE. Any one know of that combination or any advice? Thanks.
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Old 03-27-2018, 10:22 AM
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A 35cc would really haul that aircraft around. Mine has a DLE 30 and it's PLENTY fast enough. Helps with the balance immensely. Zero added nose weight.
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Old 03-27-2018, 10:26 AM
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Thank you! That looks really good too. I just brought mine in to the workshop from the building it was stored in. I will strip out the glow stuff tomorrow and start planning for the 35. I have a lot of lead up front that hopefully will go away.
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Old 03-27-2018, 10:28 AM
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Just FYI Jimmy, looks like the upper starboard mounting bolts is missing.
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Old 03-27-2018, 10:37 AM
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Yeah that's an old pre-first flight still under construction pic. The only thing bad about the DLE is the side muffler mount. Had to chop up a beautiful cowling. If your motor has a rear mount muffler you be loving it.

Good luck with your project. If needed, I can send pics of the radio/fuel compartment. Had to do some engineering in there to fit everything and make it accessible and of course look nice!!
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Old 03-27-2018, 11:05 AM
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Any help and advice would be greatly appreciated.
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