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Old Nov 11, 2008, 04:47 PM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
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Well the entire truss (without carbon fiber) weighs in at 17 Oz. She will be about 22 Oz. with CF. that is 22Oz. lighter than using the Liteply. That means that the entire fuse (less equipment) will weigh about 4.85 pounds. My target was 5.5, and the wing will be 10 pounds. Take all of that and add gear, motors, controls, and batteries, and this cow should be less than 52 pounds.

But I am kind of back to square one on my motor set-up . Just got off the phone with a guy that feels my prop pitch speed is kind of low. He suggested that I have at least 70mph prop pitch speed. But all of my calcs show my propspeed at about 58mph. This plane is going to be a slow and low kite at 26Oz. wing load, one would think having a max speed of 54mph and a stall speed of 19 would be plenty. And that's what I should get with a 58mph prop speed.

Guess I will just have to start with experimenting, I know that the AXI 4130 out-runner will turn the prop I need. May just go back to shaft driving it since it looks like I am going to be able to hit my weight.

Well attached are more pics of the fuse.

DAG
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Old Nov 11, 2008, 05:50 PM
Bi-Planes
Tim Farrar's Avatar
Houston Texas
Joined Apr 2006
1,589 Posts
Oh My Dag !!!

That is so cooool !!!!

I could look at it for a long time !!!..lol lol lol...

It is even better than I thought it would be !!!!


Seeya, Tim
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Old Nov 11, 2008, 05:58 PM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
5,822 Posts
Quote:
Originally Posted by Tim Farrar
Oh My Dag !!!

That is so cooool !!!!

I could look at it for a long time !!!..lol lol lol...

It is even better than I thought it would be !!!!


Seeya, Tim
Thanks Tim.

This is one huge project. I see now that I may have to move one of the kids out of the house and into the mini-barn to start the wing.

DAG
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Old Nov 11, 2008, 06:29 PM
Bi-Planes
Tim Farrar's Avatar
Houston Texas
Joined Apr 2006
1,589 Posts
Quote:
Originally Posted by dag214
Thanks Tim.

This is one huge project. I see now that I may have to move one of the kids out of the house and into the mini-barn to start the wing.

DAG
Thats funny but then where would the 1919 sleep ?...lol lol lol...

Seeya, Tim
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Old Nov 12, 2008, 06:32 AM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
5,822 Posts
Ok,
And now for something completely different.

I am sure I will take a beating for making some of these statements, but what the heck.

I see why so many people have such fears of getting into electrics. It seems (most) of these companies that sell the motors, ESC, and batteries know a ton about watts, amps, and their equipment, but not a lot about aerodynamics or which of their motors will fly what plane with what size prop. An example, I was told that my prop pitch speed of 59mph was just to slow to fly my B-36 and I needed a pitch speed of 70mph. Now after spend some real time crunching real numbers I see that everyone is looking for their plane to go vertical on take off. A B-36 would look kinda dumb doing that. If you take any of the pitch speed calculators that I have found on the net and inter a pitch of 14 you will see that at about 4500 rpm you have a true average speed of 59.66MPH. Now if you take the drag coefficient of my B-36 which is about .069 and inter all that into the simulator (X-plane) with a 52 pound plane you get a max speed of 53mph. Now I know X-plane is close because I have design 5 planes with it and it has been spot-on correct. With a plane that has a wing loading of 26Oz. a pitch speed of 70mph that is moving. The stall speed is 19.5mph. With using standard flight design principles 2.5 times my stall speed is 48.75MPH so my max speed should not exceed 49mph.

As I mentioned earlier I was told to have a prop speed of over 70mph, and that is not correct for this type of plane, and was told that I should us a small prop and turn a bunch of RPM this is also not correct for the plane (Should have listened to Tom Hunt the first time).

This all started when I wanted to turn a 3 bladed 18-14 prop. Only Axi has said no problem turning that prop at the RPMís I need to fly this plane, under 55MPH so I donít hurt anything. I have sent 3 e-mails to one of the motor manufactures asking for in-put, to date all I have gotten back is that the amps I want to pull is ok. What kind of customer support is that?

I see that on the web most these manufactures have examples of what motors will fly what plane, and they show what is equal to a .90 size motor, but to get them to say what motor will turn what prop is hard, and then to try to understand how it will pull your plane is even harder. It is really strange that I was told that a motor set-up I was looking at would not work well. But on the companies website it showed a motor and gearbox that was an equal to a .90 motor, how could 6 .90 size motors not fly a 50 plane?

I feel better now; I have built both full scale and models planes and learning this electric stuff has been the hardest thing I have ever done. I am going to be spending over 3k on Motors, ESC, and batteries and all I wanted to do was know what would work so I donít waste any time or money

One last thing, my average watts per pounds will be 95 with a 5-cell, and 122 with a 6-cell. So I am back to shaft driving with AXI motors.

Rock-On DAG
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Old Nov 12, 2008, 07:11 AM
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Lynxman's Avatar
Troms, Norway
Joined Jan 2004
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First of all, a static pitch speed of 59 mph will be no problem. Second, with such a high pitch prop the pitch speed actually increases a lot when the plane starts approaching top speed and the prop finally starts to unload. With a low pitch prop the pitchh speed does not increase to the same degree when the motor unloads, even though the motor unloads a lot with a low pitch prop.

Are you going for Axi 4130/20 motors? I have used several of those motors and have also rewound a few to spin scale props on 8S lipos, from 18x12 four blade to 19x14 five blade.
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Old Nov 12, 2008, 07:21 AM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
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Quote:
Originally Posted by Lynxman
First of all, a static pitch speed of 59 mph will be no problem. Second, with such a high pitch prop the pitch speed actually increases a lot when the plane starts approaching top speed and the prop finally starts to unload. With a low pitch prop the pitchh speed does not increase to the same degree when the motor unloads, even though the motor unloads a lot with a low pitch prop.

Are you going for Axi 4130/20 motors? I have used several of those motors and have also rewound a few to spin scale props on 8S lipos, from 18x12 four blade to 19x14 five blade.
Thanks for the input, yes I am using the AXI 4130/20 I am trying to get around 4100-4600RPM from a 3 blade 18-14 prop, it will be cut down from a 20", so I know I am losing some efficiency, but this plane will cruise at about 40mph, and my calcs show that I will need about 2/3 throttle to get it in the air with a great climb rate. I bet I never see full throttle with 6 of these AXI turning.

What is the most amps I can put on the 4130/20? Do you know?

Thanks a ton.

DAG
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Old Nov 12, 2008, 08:31 AM
HAL... Open the damn doors!
jfetter's Avatar
Miramar, Florida
Joined Jul 2007
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Quote:
Originally Posted by dag214
Thanks for the input, yes I am using the AXI 4130/20 I am trying to get around 4100-4600RPM from a 3 blade 18-14 prop, it will be cut down from a 20", so I know I am losing some efficiency, but this plane will cruise at about 40mph, and my calcs show that I will need about 2/3 throttle to get it in the air with a great climb rate. I bet I never see full throttle with 6 of these AXI turning.

What is the most amps I can put on the 4130/20? Do you know?

Thanks a ton.

DAG
Axi 4130/20 - 55 Amps, 1,300 watts. My personal experience says tuning a 20" prop is too much for that motor, at least if you expect longevity. In an Axi I'd go with the 5320/28 - 50 Amps, 1,750 watts and a 56kV lower rating to turn that large prop slower...

Jack

Jack
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Old Nov 12, 2008, 08:35 AM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
5,822 Posts
Quote:
Originally Posted by jfetter
Axi 4130/20 - 55 Amps, 1,300 watts. My personal experience says tuning a 20" prop is too much for that motor, at least if you expect longevity. In an Axi I'd go with the 5320/28 - 50 Amps, 1,750 watts and a 56kV lower rating to turn that large prop slower...

Jack

Jack
Hi Jack,
I am not trying to turn a 20" prop, I am cutting a 20" down to a 18" to get the preformance I need.

Attached is what I will be putting on the motor.
Am am at about 52 amps, and that's at 100 power. I will be running at about 2/3 throttle.


Thanks, DAG
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Old Nov 12, 2008, 11:15 AM
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Troms, Norway
Joined Jan 2004
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I have used the 4130/20 with up to 18x8 in direct drive. I normally don't load the motor more than 48 A static draw myself as they get pretty hot at that current draw, but I think you'll be fine even with 55 static in your plane, but I think the current draw will be lower at just 6S.

I have a 4130/20 that I'm not using at the moment. I could slap on an 18" soloprop, set the pitch to 14" and give it a whirl on 6S. It won't be an accurate comparison to the prop you'll run but it will at least let you now the ballpark rpm figure at that voltage. I won't be able to do it today though as I need to borrow a battery from a friend, I only fly 4S, 8S and 12S.
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Old Nov 12, 2008, 11:27 AM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
5,822 Posts
Quote:
Originally Posted by Lynxman
I have used the 4130/20 with up to 18x8 in direct drive. I normally don't load the motor more than 48 A static draw myself as they get pretty hot at that current draw, but I think you'll be fine even with 55 static in your plane, but I think the current draw will be lower at just 6S.

I have a 4130/20 that I'm not using at the moment. I could slap on an 18" soloprop, set the pitch to 14" and give it a whirl on 6S. It won't be an accurate comparison to the prop you'll run but it will at least let you now the ballpark rpm figure at that voltage. I won't be able to do it today though as I need to borrow a battery from a friend, I only fly 4S, 8S and 12S.
Lynxman,
That would be great, I think the reason I might pull over 50 amps is I have 3 blades, but I really think this plane is going to have so much power that I may never have it at full. SR battiers has a 17 pound Eindecker with the 4130/20 and I believe they have a 18-8 prop with a prop pitch speed of around 45mph, and it flies great.

When you got time I would love to know what you turn that prop at.

Thanks, DAG
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Old Nov 12, 2008, 11:37 AM
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Lynxman's Avatar
Troms, Norway
Joined Jan 2004
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I will set it up and make some readings when I get a chance. I use one to spin a 21.5x14.5" home made three blade scale propeller via a home made belt drive in a 16 lbs 1/6 scale P-40, so even one motor is able to fly relatively big planes when set up right:
Electric CMP P-40 (2 min 56 sec)
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Old Nov 12, 2008, 12:20 PM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
5,822 Posts
Quote:
Originally Posted by Lynxman
I will set it up and make some readings when I get a chance. I use one to spin a 21.5x14.5" home made three blade scale propeller via a home made belt drive in a 16 lbs 1/6 scale P-40, so even one motor is able to fly relatively big planes when set up right: http://www.youtube.com/watch?v=YQ95gR9yQM4
Lynxman
That is way cool, why didn't you shoot down that darn 3D plane?
Any pics of your set-up in the P-40??? Post away if you do.

I just found the prop calcs for a Biela 18-10 3 blade and it is close to the APC calcs. It looks like a great preforming prop. Might have to test it and see what I get.

DAG
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Old Nov 12, 2008, 12:30 PM
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Troms, Norway
Joined Jan 2004
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I just tested on a partially charged 4S to see what it gave.

18x14 Soloprop
4S battery

14.0 V
38 A
3570 rpm

From this I can tell that the most likely will try to run faster than 4460 rpm at 6S. the Soloprop is very fat though, much heavier to run than an APCE.
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Old Nov 12, 2008, 12:33 PM
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Troms, Norway
Joined Jan 2004
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Here are a few pics. I'm going to make a new reduction system with a more advanced propeller soon. I'm mostly into jets at the moment though.
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