Wright Stuff C

[coachchuckaahs]

I agree with Brian. It all depends how your warps line up.

Generally, unintended warps, even small, will impact the trim of the plane. If you correct that, say with rudder, then the plane is fighting itself, and drag is induced.

If the warps are noted in constructions, and set to compliment each other, then they can be neutral or even a positive. For example, if the warp is consistent on the LE and TE, and you made both tips go upward, then you have installed a bit of dihedral, which may be beneficial, or at least not harmful. Built, if I were doing it, I would put both warps in plane of the wing, as I noted, and either have a curved sweep of the wing or have the ribs take the warps out.

As far as removing warps, you maybe could do something with heat, but I would not recommend it. In my experience, a little heat will not impact the carbon rod. Once you get enough heat, you may be doing permanent damage to the strength of the rod, not something good for your spars. We made that mistake on Heli with a soldering iron, trying to adjust pitch of a blade with carbon outlines. We ended up getting an unintentionally variable pitch rotor! If you heat enough to change shape, I believe you have done damage to the resin that binds the carbon. Probably damage your covering as well.

Coach Chuck

[scioly2345]

So this weekend at LISO invy, plane went very bad for me. My plane ended up just diving to the floor immediately when I threw it
But I’m confused because in the gym at my school it flew for about 20 seconds, so I’m trying to figure out where I went wrong. I actually adjusted the rudder by a LOT to make my circle smaller (could’ve caused the dive?) and I also offset the stabilizer to the left a little bit (could’ve caused the dive?)
My theory is that these big angles in the rudder and stabilizer is what caused my plane to dive at LISO.
Any tips on how to fix at least just the stabilizer and rudder and if that could’ve caused the diving that happened.
I kept the rubber the same, the turns the same, the way I threw the same, etc etc.

So I adjusted the rudder and stabilizer back into their places (angles not as big as the LISO angles) and I did a test glide with the prop and it dove to the floor again (this is with NO changes after 20 second stable wound up flights prior to LISO).
I never changed my COG after my “good” 20 second flights before LISO (only major change I made was the rudder and stabilizer angles) but even after I put those back to normal it still dives.

Any theories or fixes for why my plane is doing that? My rubber size is 1/16 square and I cut it at about 1.1 m then tie it. My possible guesses are
1. I could still play around with the adjustable wing and adjustable back of the horizontal stabilizer to stop the dive
2. Front heavy? Take clay off the front? My plane is around 8.9g
3. Somethings wrong with the direction the prop is pointing in (I use a metal nose hook). Is it pointing too high?
4. ***really wondering if there’s any logic to this theory lol*** Why is my plane shaking in my hand when I wind it up as if I was going to fly it but I just let it go while I’m holding it? Shouldn’t it feel stable in my hand as opposed to the instability I’m currently feeling? Am I using the wrong size rubber? Am I cutting the rubber band too long/too short? Am I not putting enough/putting too many turns? Basically? Is my rubber what’s causing the problem?

In my head, the next step is to move the wing back even more. But I want to see if there’s any more minuscule things I can change before making a big change like that.

[xiangyu]

Interesting, thank you both coaches for your responses.

Scioly 2345,

2. Front heavy? Take clay off the front? My plane is around 8.9g

I highly suggest you take off some of the clay/weight else where to get your plane down to the minimum 8 g if possible - carrying extra weight cuts into your plane's flighttime. As for the CG, where is it currently located? Is it underneath the wing?
[/quote]

3. Somethings wrong with the direction the prop is pointing in (I use a metal nose hook). Is it pointing too high?

If it's that severe, you should be able to see it with your eyes that the prop is tilted upwards. (At least that's from my experience last year, this year's different design could be more sensitive to slight angle.

4. ***really wondering if there’s any logic to this theory lol*** Why is my plane shaking in my hand when I wind it up as if I was going to fly it but I just let it go while I’m holding it? Shouldn’t it feel stable in my hand as opposed to the instability I’m currently feeling? Am I using the wrong size rubber? Am I cutting the rubber band too long/too short? Am I not putting enough/putting too many turns? Basically? Is my rubber what’s causing the problem?

That sounds really concerning... Is the rubber smacking against the fuselage as you wind? Or another possibility is that your plane's fuselage is bending under the pressure. Does your plane shake too when it is in the air? How long are you cutting your rubber? Unless you are going super extreme I don't think it would cause much problem by itself...

Also I highly recommend using a torque meter to wind as opposed to directly winding on the plane.

[lechassin]

Shaking plane means either the prop is not balanced or the drive hook is off center, or the prop doesn't run true (wobbles), or knots are hitting the motor stick, or one blade is loose and moving under load.

Basic trim settings that will fly pretty good right off the bat:
1) Wings straight, minimal warps, 1mm tops
2) Prop dead neutral with the motor stick (I run a long wire through the drive shaft carrier and verify it's parallel to the motor stick)
3) Leading edge of wing 5mm higher than trailing edge.
4) Stabilizer parallel to motor stick
5) rudder 5mm either way
6) CG about 25 mm from the leading edge
7) 8 grams on the money if you can

That won't be perfect but it'll be a good start.

[lechassin]

We got our first formally scheduled Sunday morning in the gym today and the first big change to note since our last session is that the HVAC is on full bore. Our 1'45" flights with the tried-and-true plane with centered wings that banks, are now 1'30". We didn't bother with video. The plane flies fine, it just gets blown down a few feet every time it goes under the numerous vents so we didn't make any changes.

The plane with the offset wings that doesn't bank still climbs much too efficiently even with the smaller 0.060" rubber. Even below 0.2 in.oz with vents blowing down it hits several times. Cruise power is predictably reduced so we had many knots remaining after shorter times, until we shortened the motor so much that it held less knots than the 0.0625" rubber.

One option at this point is to run less pitch and more flare, so I think we'll try a new prop with reduced tip pitch to 4" and reduce blade thickness to 0.010", but it'll wind down faster in cruise with less powerful rubber, plus we'll need more (longer) rubber to hold more knots and I think we're turning in circles...

I'm glad we have 3 planes. We can keep two ready for meets and try to beat them with the third, but I'm starting to think that we've maxed out with our skill set.

[scioly2345]

Interesting, thank you both coaches for your responses.

Scioly 2345,

2. Front heavy? Take clay off the front? My plane is around 8.9g

I highly suggest you take off some of the clay/weight else where to get your plane down to the minimum 8 g if possible - carrying extra weight cuts into your plane's flighttime. As for the CG, where is it currently located? Is it underneath the wing?

3. Somethings wrong with the direction the prop is pointing in (I use a metal nose hook). Is it pointing too high?

If it's that severe, you should be able to see it with your eyes that the prop is tilted upwards. (At least that's from my experience last year, this year's different design could be more sensitive to slight angle.

4. ***really wondering if there’s any logic to this theory lol*** Why is my plane shaking in my hand when I wind it up as if I was going to fly it but I just let it go while I’m holding it? Shouldn’t it feel stable in my hand as opposed to the instability I’m currently feeling? Am I using the wrong size rubber? Am I cutting the rubber band too long/too short? Am I not putting enough/putting too many turns? Basically? Is my rubber what’s causing the problem?

That sounds really concerning... Is the rubber smacking against the fuselage as you wind? Or another possibility is that your plane's fuselage is bending under the pressure. Does your plane shake too when it is in the air? How long are you cutting your rubber? Unless you are going super extreme I don't think it would cause much problem by itself...

Also I highly recommend using a torque meter to wind as opposed to directly winding on the plane.
[/quote]

I'm cutting my rubber at a little longer than 1 meter then cutting it. Is that too long/too short? And in theory if the fuselage is getting smacked by the rubber and it's bending, any tips on how to fix the problem?

[lechassin]

I'm cutting my rubber at a little longer than 1 meter then cutting it. Is that too long/too short? And in theory if the fuselage is getting smacked by the rubber and it's bending, any tips on how to fix the problem?

If your hooks are too close to the motor stick and the knots are hitting, that will make an obvious sound, and if the motor stick is bending under load, that will be easy to see by sighting down its length with a wound up motor on it.

The way you phrased your post, I assume you mean you're cutting off any excess rubber after tying the knot? I also assume you're using 0.0625" rubber"? In any event your motors are about half the length (and therefore weight) of ours. However, that would only affect the max altitude and the total flight time. The quality of the flight should be unaffected. I don't know if you have a monoplane or a biplane, but I can say from experience that our 8 gram biplane easily carries 3 grams of rubber, total flying weight 11 grams. Your plane is heavier than most but your motor is lighter than most, so overall about the same flying weight, ergo, your problem lies in the basic setup of the airframe, not the motor.

For a plane that just crashes after a few seconds, I really recommend you do an initial setup as per my post above. From our own trials and tribulations I can almost guarantee it'll be a good start. If not, it'll at least point to other things (construction errors or communication mis-understandings). Along those lines, it wouldn't hurt for you to post some pics of the plane so we can get an overall assessment.

[lechassin]

(deleted, duplicate post)

[Hartman]

Is there a weight at which the rubber is too heavy and not worth the extra winds?

I'm thinking of making 4 gram rubbers, but it sounds a bit heavy to me and I don't want to waste rubber. Thoughts?

[CrayolaCrayon]

Is there a weight at which the rubber is too heavy and not worth the extra winds?

I'm thinking of making 4 gram rubbers, but it sounds a bit heavy to me and I don't want to waste rubber. Thoughts?

Yes; when you're left with an excesssive amount of turns at the end of the flight; 4g sounds rather excessive. I'd suggest starting with 2, evaluating, then working your way up if the data says to, but of course you can always go to a longer, thinner motor, to reduce flying weight.

You want to be flying with the lightest plane possible usually.