Great Planes P6 Curtiss Hawk - RC Groups
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Sep 06, 2006, 09:07 PM
Use the 4S Luke
feathermerchant's Avatar
Build Log

Great Planes P6 Curtiss Hawk

Well sort of a build log. It's built and should maiden Sat. I read the instructions and they mounted a 32oz glow engine and then added 16oz of lead for balance!! It even comes with a box you build to house the lead.
Anyway I set out to build it as tail light as possible. For starters, I used only one elevator pushrod and a joiner. Then I used the Sullivan rods which say they are OK for this size plane but are some kind of black composite and very light. I also made ply control horns all around. I holed out the stab platform. It is quite thick ~3/16 and hard. I installed a light DuBro tailwheel but after prelim balance I went back to the original.

I also detested the aileron servo mounting. I thought they stuck out way too far. If I was building a kit, I would probably use a rotary drive system so no linkage would show at all. Anyway the pictures show the aileron servo details. GP mounted the servos like I did here on the DR1. I know cause I have one.

The motor is a 5330/18 with a HV-45 on 8S. AUW 14lb 8oz! Can you say Porker?
Last edited by feathermerchant; Sep 07, 2006 at 12:25 AM.
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Sep 06, 2006, 10:45 PM
Registered User
Caddguy6's Avatar

Pushrod concerns

Feathermerchant, your P-6E looks, and sounds great! But I really have a big concern about the elevator pushrod and the curve that it takes leaving the fuselage going to the elev. horn. Is there that much of a bend in the wire as it appears in the photo?

The rule of thumb is keep the pushrod as straight as possible, especially in that unsupported area between fuse. exit and horn.

That's a whole lotta airplane there and the very last thing you want is not having elevator control when pulling out of a dive.

Can the pushrod run in a more direct (straighter) path?

Just my $.02
Sep 06, 2006, 11:04 PM
Use the 4S Luke
feathermerchant's Avatar
Great observation. The pushrod exits in the stock place. It would be real difficult to move. I really should have made the control horn longer. That would have straightened it out. Anyway it seems stiff enough. The wire extends several inches into the pushrod and that helps.
Sep 06, 2006, 11:04 PM
Old School E-Flyer turned FVP
mcharles13's Avatar
nice work feather merchant. There is a guy out here where i live who has already electrified this plane, though his lacks the sound box.

on RCG his name is "Bob Snedegar" (which happens to be his real name too)

It flies beautifully.
Sep 06, 2006, 11:08 PM
Registered User
Bob Snedegar's Avatar
Feathermerchant, Awesome sound system in your Hawk!! Really sounds like a V-12 Conqueror under that cowl! Please tell us more ... Does it operate off of the main motor battery? Commercially available?

Welcome to the "Electric Hawk" club - your P-6E will have plenty of power on the big Axi. I'm flying mine with a 5320-28 on 9S, 8 Ah LiPo, turning an 18X10X3 Mejzlik prop. AUW is 15 3/4 lb and she's a joy to fly!

Last edited by Bob Snedegar; Sep 06, 2006 at 11:33 PM.
Sep 06, 2006, 11:08 PM
Old School E-Flyer turned FVP
mcharles13's Avatar
Is your sound system the benedini one also? how much did the sound system cost?
Sep 06, 2006, 11:37 PM
Use the 4S Luke
feathermerchant's Avatar
Yup Benedini. See his website for costs. ~330 as I recall. The system is 3 parts.
A sound module y'd into the throttle channel or connected to a separate channel and mixed, it runs off 5V from the BEC.
An amplifier. I have the 12V variety running off of a TP 3S 1320. Draws about 17W so should be good for 2 10 min flights easy.
A speaker. I am using the 4" that he offers. It works well.
I am looking into some lighter components and will post if anything comes of it.
Bob I am really interested in that prop. I identified it as the ony one that's about scale.
Have you got a good pic of it from the front? How many watts do you draw?
Did you find a better price than me? (~$70)
Where is your CG compared to GP recommendations?
Sep 06, 2006, 11:46 PM
Registered User
What is your power system? Thanks...
Sep 07, 2006, 10:07 PM
Registered User
Bob Snedegar's Avatar
Feathermerchant, the Mejzlik seems to be a perfect match for this plane-motor-battery combo. Close to scale diameter and a pitch-speed just right to cruise at half-throttle. The P-6E really needs a 3-blader to look right, so I bit the bullet and paid about your quoted amount for the Mejzlik. Well worth it - IMO. With some silver-leaf paint applied, it really adds to the scale appearance.

I am drawing about 57 Amps static WOT from the 35 Volt, 8 AH, 10C LiPos. Power measured at the battery terminals is close to 2 KW. Assuming ~80% motor efficiency, that's about 1.6 KW turning the prop - definately over 100 watts / lb. My flying style with this and my other scale planes is conservative, but I do like to have some extra "get out of trouble" power available. Actually, I started out with an 8S battery and it flew very well with that, but needed a little more weight in the nose so upgraded to 9S. Now I actually need 1 1/2 oz of lead in the tail!

It's not easy to check balance on a bipe of this size and weight, but I suspect my Hawk is still slightly nose-heavy. No problem in flight, but she does like to nose over on grass landings! I have just switched to larger wheels, which will hopefully help out there.

Sep 07, 2006, 10:16 PM
Use the 4S Luke
feathermerchant's Avatar
Man I was thinking of a 19X10 on my 8S setup. I am flying the same motor and batteries on a different plane and have tried 20X8 or 20X10 on that plane. What do you think?

Do you have any video?
Last edited by feathermerchant; Sep 07, 2006 at 10:55 PM.
Sep 07, 2006, 11:05 PM
Registered User
Bob Snedegar's Avatar
If you are using the Axi 5330-18 that you mentioned on the RCU P-6E thread, an APC-E 20X10 should be well within the motor's capabilitys on 8S. Check the prop range recomendations for the Axi motors on the manufacturer's web site: . When I was running my 5320-28 on 8S with the Mejzlik 18X10X3, it only drew ~45 Amps max.

Sorry, no video yet. Maybe someone will shoot it at this year's NEAT, which I am attending next week.
Last edited by Bob Snedegar; Sep 07, 2006 at 11:29 PM.
Sep 08, 2006, 08:04 AM
Use the 4S Luke
feathermerchant's Avatar
Yes I listed the power system in the first post above. Mine does dray about 45A. I missed that you were using the 5320. So both motors have almost the same kV.

Regarding the noseheavy issue, is the elevator trimmed 'up' for level flight? You can look at it from the side and tell. Does it require a lot of down elevator to maintain level flight inverted?

I tried to figure out how many volts per cell you are running and at 2,000W I get:
2,000 / 57 / 9 = 3.9V
That seems high. M,aybe the current is higher.
I would have expected more like 16-1700W

I have this same system in a 9.5lb Edge and it preforms like a 3D plane should.
At 55A it is about 1600W but my batteries hold their voltage like a 9S pack.
Sep 08, 2006, 11:12 PM
Registered User
Bob Snedegar's Avatar
Actually, I took the measurement on a fully charged battery, and 57 Amps is just over a 7C load on my 8 Ah LiPo pack, so the voltage drop would be minimal. As the battery is drawn down toward nominal voltage during flight, the maximum power output would certainly drop somewhat. I should at least have the 2 KW to start my takeoff roll with, though.
Last edited by Bob Snedegar; Sep 08, 2006 at 11:38 PM.
Sep 09, 2006, 06:46 PM
Flys with Thumbs
Danal Estes's Avatar

Very realistic flight with this power system!

I witnessed the maiden of this aircraft earlier today. First flight without sound; second flight with. The is the single most "scale like" flight I've ever seen from any model. Very smooth, powerful; you can hear the airflow over the wings and cabane struts on the downlines. Turns, rolls, loops, are majestic and "happen at the right speed". This airplane is just really, really great in the air with or without the sound.

Startup/shutdown with the sound module is cute as can be. But I have to go back to the way it flies. Just fantastic.

Good job Bruce!

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