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Old Nov 14, 2011, 06:35 PM
Drifting off the reservation..
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I took the ESC out of the Ventus to change the plug. Had to wedge it out from the bilge, underneath a plywood floor plate. It did not have plugs connecting to the motor, was hard wired so I had to snip it out. It's a HobbyKing #20 linear BEC, 12v/3s lipo, and it says it's 2 amp max. The one in the RP says 30 amp max.

Is this BEC way below spec for a sailplane with 7 servos? With the stiff hinges and the retract which surely consumes lots of juice, I'm afraid of a brownout on my AR7010. It would probably happen about when I flip the retract to land.

I'm not an electric expert, so does anyone know what sort of BEC I might need for this plane? Will be using my 3S stock 1300ma parkzone batteries from the RP. Hope the RP does not mind sharing.

It's a beautiful plane, would hate to wreck her.
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Old Nov 14, 2011, 07:20 PM
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How many of the servos are digital?
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Old Nov 14, 2011, 09:03 PM
VOLTS > AMPS
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Originally Posted by Raften View Post
How many of the servos are digital?
Just the flaps.





1) Where are you guys running your control horns at for flaps and ailerons?

2) NTM 35-30 with 11x8 carbon props and a stock ESC, is that too much for it(esc) to handle?
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Old Nov 14, 2011, 10:37 PM
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United States, CA, Baywood-Los Osos
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Quote:
Originally Posted by JumpySticks View Post
I took the ESC out of the Ventus to change the plug. Had to wedge it out from the bilge, underneath a plywood floor plate. It did not have plugs connecting to the motor, was hard wired so I had to snip it out. It's a HobbyKing #20 linear BEC, 12v/3s lipo, and it says it's 2 amp max. The one in the RP says 30 amp max.

Is this BEC way below spec for a sailplane with 7 servos? With the stiff hinges and the retract which surely consumes lots of juice, I'm afraid of a brownout on my AR7010. It would probably happen about when I flip the retract to land.

I'm not an electric expert, so does anyone know what sort of BEC I might need for this plane? Will be using my 3S stock 1300ma parkzone batteries from the RP. Hope the RP does not mind sharing.

It's a beautiful plane, would hate to wreck her.
I think they were referring to the bec output, not the rating of the esc current, (30A on the RP, but the bec is only listed at 5.5V, the amperage of the bec isn't listed...probably 3A I imagine). 2A is a little slim for 7 servos if you ask me, I would want at least a 3A, or better yet a 5A switching bec, not linear. A good switching external bec, (or UBEC), isn't that expensive, here's a 3A: http://www.headsuprc.com/servlet/the...p-3-Amp/Detail, and here's a 5A: http://www.headsuprc.com/servlet/the...p-5-Amp/Detail. All you have to do is cut or remove the red wire from your esc to disable the internal bec, and plug the external bec into an extra channel of your rx, (you'll have to buy or make an adapter to plug both the esc and the UBEC into your lipo, or just splice the wires of the UBEC into the esc power leads; a "Y" cable works too if the internal bec is disabled.). I've used them on several full-house sport planes just to make sure all those servos keep humming and the rx has enough power to get the plane home; cheap insurance.

Sonny
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Old Nov 15, 2011, 08:29 AM
Zor
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Ontario,Canada
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Tail reinforcement

Hi guys,

I have been thinking for quite a while about this foam tail weakness.

At this time I came out with the following specifications.

1- Reduce the fuselage twist.
2- Reduce the fin bending mainly due to the stabilizer slot.
3- Minimize the work needed.
4- Avoid fuselage break just in front of the fin.
5- Reinforce the fin-stab 90 degrees with working flying wires.

I am attaching a drawing illustrating a possible solution for above (except flying wires which would be a strong sewing thread glued where it goes through),

I am not looking for opinions but your evaluation would be well appreciated.

Any helpers out there ?

Zor
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Old Nov 15, 2011, 11:17 AM
Bye Bye VP Aug 2010 - Aug 2012
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Originally Posted by Zor View Post
I am not looking for opinions but your evaluation would be well appreciated.
What's the difference between an evaluation and an opinion?
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Old Nov 15, 2011, 11:30 AM
Drifting off the reservation..
JumpySticks's Avatar
USA, LA, Broussard
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Quote:
Originally Posted by Zor View Post
Hi guys,

I have been thinking for quite a while about this foam tail weakness.

At this time I came out with the following specifications.

1- Reduce the fuselage twist.
2- Reduce the fin bending mainly due to the stabilizer slot.
3- Minimize the work needed.
4- Avoid fuselage break just in front of the fin.
5- Reinforce the fin-stab 90 degrees with working flying wires.

I am attaching a drawing illustrating a possible solution for above (except flying wires which would be a strong sewing thread glued where it goes through),

I am not looking for opinions but your evaluation would be well appreciated.

Any helpers out there ?

Zor
Won't the reinforcement blade(s) in the fuselage interefere with that? Also, wires have a lot of drag, might catch on weeds and stuff. I wouldn't want wires on a plane unless I had a scale WWI biplane or something.
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Old Nov 15, 2011, 02:16 PM
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I did some research and I cannot seem to find an answer. I am wondering if digital servos are needed on the flaps of the RP or any other plane. I know the difference between the analog and digital servos but what is the advantage of having digital servos on the flaps?
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Old Nov 15, 2011, 02:55 PM
Zor
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Quote:
Originally Posted by Gerry__ View Post
What's the difference between an evaluation and an opinion?
Gerry,

I like you because you are acting like one who really wishes to know.

I ought to get you a good dictionary but for you it is easier to simply write the question. Why bother researching?

An OPINION is a belief or conclusion held with confidence but not substantiated by positive knowledge or proof.

An EVALUATION is to examine and judge, appraise, estimate in order to have some backup for the results.

Hope this reply helps you.

Zor

Editing spelling ... confidnce became confidence
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Old Nov 15, 2011, 03:20 PM
Zor
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Quote:
Originally Posted by JumpySticks View Post
Won't the reinforcement blade(s) in the fuselage interefere with that? Also, wires have a lot of drag, might catch on weeds and stuff. I wouldn't want wires on a plane unless I had a scale WWI biplane or something.
Hello JumpySticks,

Please spend a quick moment to look at the drawing I posted.
There is no blades involved.

A #10 thread is pretty strong and I believe offers very small air resistance while providing a good mechanical force to prevent any resonance of the vertical and horizontal tail surfaces. Such resonance is quite possible particularly for the horizontal surfaces that are quite thin.
Such resonance could quickly break the stabilizer.

We can compare to so called "flutter" due to slop in a control surface.
There is only three hinges for the elevators and they are foam. If the middle hinge would fail due to fatigue the flying wies may prevent the stab from also breaking. Some fellows have replaced the complete tail assembly with balsa built empanage.

Resonance was the main reason for propeller blades breaking and falling off the original props. That is my opinion and not an evaluation.

Nice reading you JumpySticks.

Zor
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Old Nov 15, 2011, 03:46 PM
Zor
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Quote:
Originally Posted by Flux Cobalt View Post
I did some research and I cannot seem to find an answer. I am wondering if digital servos are needed on the flaps of the RP or any other plane. I know the difference between the analog and digital servos but what is the advantage of having digital servos on the flaps?
Flux Cobalt,

Just submitting my thinking and trying to evaluate as compared to just write an opinion.

If we compare the work being done by the flap servos compared to the aileron servos _ _ _
First, the aileron servos have a less critical usage in the sense that if there is dissimilarity it would not affect the rolling motion in any noticeable way. They are also subjected to less force being further out and only providing a force that rolls the mass concentrated at or near the fuselage.
Second, the flap servos are subjected to a steady force contributing to the lift and thus work harder than the aileron servos. A more important factor is that most of the time they receive a signal that is identical for both. So they need better locating precision because if the flaps are not deployed the same it would result in a rolling motion of the model. That rolling motion would vary with any variation in the approach speed.

This is my abbreviated analysis and it is costing you 1/2 a penny .

Zor
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Last edited by Zor; Nov 15, 2011 at 03:53 PM.
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Old Nov 15, 2011, 03:52 PM
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Thanks Zor that information was helpful.
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Old Nov 15, 2011, 03:56 PM
Zor
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Quote:
Originally Posted by Flux Cobalt View Post
Thanks Zor that information was helpful.
You are very welcome.
I did not want to elaborate too long. We have to consider the servos differences and characteristics and ratings as well as their duty.

Zor
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Old Nov 15, 2011, 06:45 PM
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United States, WI, Appleton
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Zor

Your tail reinforcement will probably help some with bending of the fin, but probably won't do very much to stop the fuselage from twisting. You might consider laminating a piece of light fiberglass cloth onto each side of the fuse, maybe starting an inch or so in front of the vertical and going back to around half the stab chord. You could put it right over the top of the control rod tubes (although obviously, not on the control rods themselves.) You'd want to put it on with the warp/weave of the glass at about a 45 deg. angle from vertical.

Or, you could even try adding some strapping tape (the stuff with fiberglass strands in it) but you'd have to put two layers on (one at +45 deg and the other at -45 deg) to get full strength. Might be a little heavy.

As far as stiffening the actual fin and/or stab, I's suggest cutting a shallow groove in the foam and then glue a small carbon fiber rod where you see worrisome deflection. Make sure to put the rods near the front of the surface though (around a quarter chord), or you could actually increase the chances of flutter.

Good luck with the mods!
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Old Nov 15, 2011, 06:46 PM
Drifting off the reservation..
JumpySticks's Avatar
USA, LA, Broussard
Joined Jan 2011
2,293 Posts
Quote:
Originally Posted by Zor View Post
Hello JumpySticks,

Please spend a quick moment to look at the drawing I posted.
There is no blades involved.

A #10 thread is pretty strong and I believe offers very small air resistance while providing a good mechanical force to prevent any resonance of the vertical and horizontal tail surfaces. Such resonance is quite possible particularly for the horizontal surfaces that are quite thin.
Such resonance could quickly break the stabilizer.

We can compare to so called "flutter" due to slop in a control surface.
There is only three hinges for the elevators and they are foam. If the middle hinge would fail due to fatigue the flying wies may prevent the stab from also breaking. Some fellows have replaced the complete tail assembly with balsa built empanage.

Resonance was the main reason for propeller blades breaking and falling off the original props. That is my opinion and not an evaluation.

Nice reading you JumpySticks.

Zor
Zor,
There is a blade of plasic reinforcement running down the fuse. It's horizontal, embedded in the fuse even with the pushrod tubes. It may be that your reinforcement would not go deep enough to hit it. Maybe you could butt it up against that reinforcing blade for extra strength.

Personally I don't think the tail wobble is a serious issue with the RP. It looks funny but the plane controls fine IMHO. Only control issue is with the high speed dive, which I have not had a problem with lately.
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