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Old Dec 03, 2012, 09:36 AM
Feeling the THRALL
Jackson Stone's Avatar
USA, CO, Parker
Joined Dec 2009
819 Posts
Peter,

I am inspired by your comments to put more flap angle in my planes. I put more flap angle in my FMS V.6 Mustang last night and will do the same for the P-47 tonight.

Thanks for this input.

Jackson
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Old Dec 03, 2012, 04:53 PM
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Australia, VIC, Melbourne
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My TX has "slow" function per channel, so I have all aircraft flaps set for a 6 second total travel time - from retracted to extended, and back.
I "slow down" first of course - but we can't tell speed really, so how slow is "slow"? hehe
I visualise physics of everything I do, so I this case see 'severe flap angle' (once down) and often worry about what stresses are on them! Just like a real plane can't deploy them above speed X and have them cope! Though I have never lost any control surface off a plane!! hehe. Flaps or others.

But of course take note that using high angle flaps would probably not be a good idea at high speeds! LOL
Though, they do seem to usually be quite strong things......
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Old Dec 03, 2012, 06:54 PM
Feeling the THRALL
Jackson Stone's Avatar
USA, CO, Parker
Joined Dec 2009
819 Posts
Peter,

My DX8 allows slow deployment of flaps as well. I believe mine are set to 2 seconds. I will increase this number and see how it works for me.

BTW, I picked up a Master Airscrew 16x8x3 prop today to try on the P-47. I think it will probably give me much more efficient power to thrust conversion than the stock 4 blade prop. I really love the looks of the stock prop, but I also want the power and performance that a well-designed sport prop will give me.

Thanks,

Jackson
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Old Dec 03, 2012, 10:49 PM
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Quote:
Originally Posted by Jackson Stone View Post
BTW, I picked up a Master Airscrew 16x8x3 prop today to try on the P-47. I think it will probably give me much more efficient power to thrust conversion than the stock 4 blade prop. I really love the looks of the stock prop, but I also want the power and performance that a well-designed sport prop will give me
Jackson, please update us after you try that prop & tell us how well it works. Current draw & watts would be great too if you have them. Thanks, Greg
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Old Dec 04, 2012, 12:39 AM
Feeling the THRALL
Jackson Stone's Avatar
USA, CO, Parker
Joined Dec 2009
819 Posts
Crashmaster,

Well I got the P-47 firewall reattached and tested four different props. I am now inclined to keep the stock prop in place as it definitely seemed to provide the best thrust.

Here are the props and the stats for watts and current draw at full power:

Master Airscrew 16x8x3 412 watts and 26 amps;
APC 17 x 8 sport prop 571 watts and 36 amps;
Master Airscrew 18x8 Classic series 501 watts and 32 amps;
Stock four blade prop 747 watts and 50 amps.

I may do some flight tests to evaluate how the different props perform in flight.

Regards,

Jackson
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Old Dec 04, 2012, 12:55 AM
Foam air frame tester
Australia, QLD, Gold Coast
Joined Nov 2012
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FWIW and another interesting variant to try, the FMS 1700mm P-47 runs an 18x8x4 prop and i did the numbers on the full scale prop and at 1:7.5 scale (starmax size) we should be running a 20x8x4

The full size plane only had 7" of ground clearance when it had rotated on takeoff!
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Old Dec 04, 2012, 01:02 AM
Feeling the THRALL
Jackson Stone's Avatar
USA, CO, Parker
Joined Dec 2009
819 Posts
Maybe I should get a FMS 18x8x4 prop and test that.

Jackson
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Old Dec 04, 2012, 04:41 AM
Foam air frame tester
Australia, QLD, Gold Coast
Joined Nov 2012
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Just remember it runs a 5060 300KV on 6S but the 18" prop definitely helps the scale look.

Im going to fit the fms landing gear legs, doors and cockpit.

I'm currently in the process of putting FMS spinners, props, guns, landing gear and servo actuated doorsin my J-Power P-38. Not super easy, but makes the cheaper model look 100% better.
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Old Dec 04, 2012, 07:15 AM
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Originally Posted by Jackson Stone View Post
Crashmaster,

Well I got the P-47 firewall reattached and tested four different props. I am now inclined to keep the stock prop in place as it definitely seemed to provide the best thrust.

Here are the props and the stats for watts and current draw at full power:

Master Airscrew 16x8x3 412 watts and 26 amps;
APC 17 x 8 sport prop 571 watts and 36 amps;
Master Airscrew 18x8 Classic series 501 watts and 32 amps;
Stock four blade prop 747 watts and 50 amps.

I may do some flight tests to evaluate how the different props perform in flight.

Regards,

Jackson
Huh,,,our motors must NOT be the same KV, because my results are SO much different than your Jackson (were your tests with the 400kv 5065?). I have a cheap tachometer coming on the slow boat from china, so in a week or two I will be able to figure more out.

I have an N5065 that is labeled 400kv from Leaderhobby.com in my P47, but it seems to be spinning more than 400kv or my stock motor may actually be less than 400kv because my new motor pulls a lot more amps than the stock with the same prop and battery. My static results are below...

Stock Motor (400kv?) & Stock 4-Blade prop:
4s 6000mAh 40 C pulls 65 amps
5s 5300mAh 40 C pulls 80-82 amps (motor got hot fast!!)

N5065 (400kv?) & Stock 4-Blade prop:
4s 6000mAh 40 C pulls 90 amps! (I flew it with this and was very disappointed, NOT noticeably faster than stock)
5s 5300mAh 40 C pulls 100++ amps (my meter stops at 99 amps)

N5065 (400kv?) & 2-Blade APC 16x12 prop:
4s 6000mAh 40 C pulls _?_ amps (It flew nice with this, a little faster than stock)
5s 5300mAh 40 C pulls 75 amps (I LOVE IT with this, WAY faster than stock, almost unlimited vertical)

So from my tests, I have determined that the stock prop that I love so much is just VERY inefficient and can not pull the plane much faster than the stock motor on 4s. Even at 90 amps on 4s it was not noticeably faster. So, unfortunately I'm now hooked on the speed of the 2 blade and will probably only put the big 4 blade on for show in the garage, or when I break the 2-blade.

But I'm still interested in any info on a well designed 4-Blade, but I can't spend more too much on a prop, no carbon fiber for me. If anybody tries any of the FMS props, let us know your results.

Greg
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Old Dec 04, 2012, 09:26 AM
Feeling the THRALL
Jackson Stone's Avatar
USA, CO, Parker
Joined Dec 2009
819 Posts
Hi Greg,

I am using the Firepower 50-65 motor with 410 kv. I agree that it is odd how our results are so different. I am also encouraged and excited about your findings with the APC 16x12 prop. I will have to get one of these and try it as I love the kind of performance you are describing.

Just ordered an APC 16x12 from Tower Hobbies. Let the fun begin!

Regards,

Jackson
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Old Dec 04, 2012, 09:27 AM
Feeling the THRALL
Jackson Stone's Avatar
USA, CO, Parker
Joined Dec 2009
819 Posts
Quote:
Originally Posted by d3c0yz3d View Post
Just remember it runs a 5060 300KV on 6S but the 18" prop definitely helps the scale look.

Im going to fit the fms landing gear legs, doors and cockpit.

I'm currently in the process of putting FMS spinners, props, guns, landing gear and servo actuated doorsin my J-Power P-38. Not super easy, but makes the cheaper model look 100% better.
Sounds like we should all be buying FMS planes. I do love my FMS 1400mm "Marie" V.6 Mustang. I probably have 100+ flights on this baby.

Jackson
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Old Dec 04, 2012, 07:23 PM
Foam air frame tester
Australia, QLD, Gold Coast
Joined Nov 2012
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Well for me living in Australia a 1700mm FMS warbird comes in just under $500 landed and i got the Starmax 1600mm delivered from the HobbyKing AU warehouse for $250.

So in my case FMS is pretty much out of the question. Unless you are prepared to pay 2x the price for FMS in Australia, HobbyKing really is the only cost effective option.

When you take into account the FMS advantages are all cosmetic, for me it makes it even harder to justify. All the FMS parts i want to fit do not effect the way the plane flies and as we know this is a great flier, same with the J-Power P-38 ($369 for the FMS version i got this one for $130 delivered).

The FMS also has wing spar issues (same with the FMS 1700mm P-51) and the V1 propellor hubs were known to fly appart (fixed in the V2).

I dont think the FMS prop will make it any faster as it has the same 8" pitch this is more for scale looks and really as i said before we want a 20" prop for that.

I think the solution to using the stock prop is to switch to a 6S 50mm can motor so you can crank the RPMs up. How much more RPM you need to equal 12" pitch i have no idea, maybe someone else can chime in on this. For reference the stock setup (4S) should be doing just under 6000rpm as im sure you all know.

This is my guess work:
As 12" is 50% gain in pitch would 9000rpm give a similar result (what are the chances of the relationship being linear haha)?

So 600KV on 4S (thats going to be an expensive motor and lots of Amps 120+)
Or 405KV on 6S

Something like this might work with a 120A esc?
NTM Prop Drive 50-60 Series 380KV / 2665W Max 90A
http://www.hobbyking.com/hobbyking/s...dProduct=23521
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Old Dec 04, 2012, 08:49 PM
Feeling the THRALL
Jackson Stone's Avatar
USA, CO, Parker
Joined Dec 2009
819 Posts
D3,

I see only one flaw in your analysis: the assumption that the stock prop can handle the kind of load that your power system would deliver. My concern is that the prop would fly apart under this load, posing a severe danger to all who are in proximity. I love this hobby, but am aware that it can be dangerous to myself and others if not pursue with proper diligence. I had a friend who cut his arm with a spinning prop last summer and required 16 stitches. I will never forget the sight of blood spurting out of his arm.

Accordingly, I would suggest that as we consider power systems consuming more than a kilowatt, we each find appropriate propellers from established vendors that can handle the load and stress. This morning I ordered APC 16x12, 17x12 and 15.5x12x3 props based upon Greg's findings with the 16x12. These should be in within a week or so. I plan to bench and flight test all of them and will gladly share my findings with you.

I am planning to fly my P-47 tomorrow with the stock prop and one or more of the other props I have on hand. Probably the APC 17x8 or the Classic 18x8. My prior experience with scale v. sport props tells me that the bench testing is only part of the story. A well-designed sport prop can deliver much more thrust per unit of power being consumed. This becomes evident in the flight characteristics of the plane. I am hoping to get some video so I may be able to share these flight tests with you.

Regards,

Jackson
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Old Dec 04, 2012, 09:39 PM
Foam air frame tester
Australia, QLD, Gold Coast
Joined Nov 2012
325 Posts
Yes i was thinking about the max RPM of this prop too. If it was a hub and individual blade type setup like the FMS i would be more concerned about it, but since this is a moulded one piece unit surely it would be more resillient to this?

I agree with better blade design on sports props would yield better results. I will be interested to see if the 17x8 works that should be less thrust than the stock prop by a fair bit.

I was going off this blade conversion chart:
http://www.zingerpropeller.com/_2_blade_.htm

This is one i would love to test!!
http://www.troybuiltmodels.com/items/BP2010-4BY.html

20x10x4 Carbon with scale markings
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Old Dec 04, 2012, 10:16 PM
Feeling the THRALL
Jackson Stone's Avatar
USA, CO, Parker
Joined Dec 2009
819 Posts
D3,

I agree that the molded prop is better than the individual blade design of FMS, but still think the stock prop on the P-47 is not going to have the strength and ability to handle load of a APC glass-filled nylon prop.

The blade conversion chart looks handy. I find that it is hard to generalize about props; two different props with the same diameter and pitch can yield very difference performance!

As far as the Biela prop, yes that would be the ultimate. For that I would get one of the really nice F4Us that Troy Built sells. The 74 inch ESM F4U electric conversion with that prop would be a gorgeous and expensive build. I will get there someday, in the meanwhile I am learning the craft with HobbyKing and FMS models.

Cheers,

Jackson
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