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Old Oct 25, 2012, 10:45 AM
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dbaya's Avatar
United States, CA, Union City
Joined Mar 2004
366 Posts
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Motor Mount Angle

I'm trying to fit an motor on a old F3B glider. Wanted to know if anyone is using right thrust or any down thrust. Can you give me a estimate. Or does the folding prop help??

I know a Radian can use down thrust, or is that because the nose gets slammed into the ground. I know my aerobatic planes need a couple degrees of right thrust. Notice it on a steep climb. P-Factor? Correct?
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Old Oct 25, 2012, 12:27 PM
Paul Naton's Avatar
Lewisburg, PA
Joined Apr 2002
945 Posts
It should be happy at zero down, zero right.

Paul Naton
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Old Oct 25, 2012, 12:30 PM
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Lenny970's Avatar
Greeley, Colorado, USA
Joined Feb 2000
2,698 Posts
No right thrust is needed. A couple degrees of downthrust are beneficial, but not required.
Just install the motor mount so that the spinner fairs nicely into the fuselage and you'll be fine.

Good luck,
Lenny
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Old Oct 25, 2012, 12:51 PM
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dbaya's Avatar
United States, CA, Union City
Joined Mar 2004
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Thanks!
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Old Oct 25, 2012, 12:53 PM
Red Merle ALES
Curtis Suter's Avatar
United States, Mt, Helena
Joined Apr 2002
4,964 Posts
Remember that you're only under power for less than 30 seconds in an ALES style type of flying, but much, much longer in glide. So the question for the aerodynamicists; does a slight droop of the spinner increase, reduce or have a negligible effect?

I wonder if XFLR5 would detect the differences? The way I fly less movement of the flight controls would aid in my glide ratio.

So my vote is for zero, zero.

Curtis
Montana
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Old Oct 25, 2012, 01:41 PM
JimN8UAY
United States, OH, Medina
Joined Oct 2004
540 Posts
...and what about my Radian Pro rebuild?...I noticed a distinct down and right thrust angle in the plastic housing/ nose cone. Should I not bother with it and shim the motor to a more neutral setting? I have made a couple of mods to change the decalage and strengthen the fuse so while I'm at it I could rework the motor mount, too. I know, not an F3B ship, but maybe it's similar?

Jim
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Last edited by Jimn8uay; Oct 26, 2012 at 09:23 AM. Reason: grammar
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Old Oct 26, 2012, 12:27 AM
MrE
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United States, WA, Gig Harbor
Joined Aug 2007
1,691 Posts
The closer your model is to neutral CG/trim, the less need there will be for down thrust.

If your model is on the nose heavy side, you will have a good bit of up trim dialed in or built in, which will cause the model to pitch up - possibly severely - with power on.

You can also use a mix with elevator to correct any pitching issues if you are more concerned with the looks of the nose or if it doesnt fair in well

I wouldnt worry about right thrust. If there is an issue on climbout, either fly it out with rudder corrections or program in a bit of rudder correction with throttle.
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Old Oct 26, 2012, 11:43 AM
Registered User
Okanagan Falls. British columbia. Canada
Joined Nov 2006
366 Posts
Throttlecontrol

I have found that if the model is launched at something less than full throttle, most pitching movements are controllable allowing the throttle to be opened fully as soon as the nose is raised to start the climb.I have never noticed any problem with roll control that cannot be corrected with a little rudder.
I do not like mixing controls, or having to use a switch to change flight modes. I prefer to trust my thumbs to do the right thing.The larger the glider the more docile it seems to be. I use only a couple of degrees downthrust and no side thrust.

Ken.
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Old Oct 26, 2012, 01:55 PM
the anthropocebo effect
kcaldwel's Avatar
Joined Jan 2007
3,467 Posts
Quote:
Originally Posted by CloudyIFR View Post
Remember that you're only under power for less than 30 seconds in an ALES style type of flying, but much, much longer in glide. So the question for the aerodynamicists; does a slight droop of the spinner increase, reduce or have a negligible effect?

I wonder if XFLR5 would detect the differences? The way I fly less movement of the flight controls would aid in my glide ratio.

So my vote is for zero, zero.

Curtis
Montana
XFLR5 won't tell you anything useful about fuselage shapes.

The spinner, blades, and the transition from the spinner to the fuse (which usually isn't a fair shape, step in the contour line) will likely cause transition to turbulent flow anyway, so a few degrees of angle of the spinner from aligned to the fuse will make basically zero difference in the fuse drag.

It would be great not to have the spinner and blades up front, and just have a nice shape to keep the laminar flow back on a nice low Re shape. But does anyone really notice the performance loss from the turbulent flow from the spinner and blades compared to the pure glider versions?

I just program away any thrust issues. It is so easy to do, why wouldn't you?


Kevin
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Old Oct 28, 2012, 04:51 PM
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ozmo01's Avatar
USA, MO, Ozark
Joined Nov 2006
1,435 Posts
I would keep the angles stock on either Radian just because the cone will fair in better. Less fuss too.
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Old Oct 28, 2012, 06:11 PM
LSF303 / AMA Life Member
tkallev's Avatar
USA, IL, Wheeling
Joined Jan 2003
3,018 Posts
The foamies are designed with the idea that a large number of people will just drive them around under power so the down and rightt thrust built into the Radians makes sense.

However, if you are talking about simply using the motor as a launch method, you really won't be flying in a way that the right/down thrust makes a whole lot of difference in the way the model climbs out.

Use the TLAR approach, it That Looks About Right, then it's probably fine, don't over-think these things
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Old Oct 29, 2012, 11:43 AM
the flying is good
dephela's Avatar
USA, CT, Hamden
Joined Oct 2002
2,019 Posts
I have an old Xenath and I believe it's set at zero. The nose wants to pull up a bit under full power so I have a bit of down elevator mix in the throttle[switch] and this works great as the CAM cuts the motor and the down stays in to bring it to a nice level flight for me at the end of the climb!
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Old Oct 29, 2012, 02:41 PM
JimN8UAY
United States, OH, Medina
Joined Oct 2004
540 Posts
Quote:
Originally Posted by tkallev View Post
The foamies are designed with the idea that a large number of people will just drive them around under power so the down and rightt thrust built into the Radians makes sense.

However, if you are talking about simply using the motor as a launch method, you really won't be flying in a way that the right/down thrust makes a whole lot of difference in the way the model climbs out.

Use the TLAR approach, it That Looks About Right, then it's probably fine, don't over-think these things
Good suggestion, Tom...I do tend to overthink it sometimes!
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