Michaelj2k

When you lift a model by the wing tips at the recommended Cg, you are performing a static balance. When you perform the dive test, you are doing a dynamic balance test. That's the important one. The static balance is good enough to get you in the air while the dynamic balance determines where the actual Cg is. I think that you should confirm where the actual Cg is then adjust incidence angles as necessary to your liking.

rowarrior

Hi buzzard bait(Jim) and Michael,

buzzard bait: after thinking about what you mentioned a little, I got it . I had not seen it from that point of view before. Thank you, it makes a lot of sense.

Now, there is just one thing I am confused about, if you increase the incidence on the horizontal stab, YES, you decrease the angle of attack of the wing, but wouldnt the thrust line also be altered downwards?? (because I am assuming the horizontal stab flies parallel to the direction of motion of the plane going thru the air, so with an adjusted positive incidence of the stab, the wings angle of attack will be less-as the tail flies a little 'higher' but also the motor will be pointing down a little more, wouldnt it?) please let me know, because it may be this assumtption of mine that is screwing me up.

Michael, thanks, you and buzzard make a lot of sense on the dynamic test ! i guess i knew about this by intuition and common sense, but never put it to the test on a dive. thank you!

BobH

My Feedback: (2)

The Positive Upper wing incidence is correct for a WWI plane.
The Incidence for the engine should be 0. the tail plane is probably + (?)degrees too. If the engine is 0 and the wing +3 degrees you have an effective -3 degree down thrust..
By adding an additional 3 degrees of down thrust you have an effective 6 degrees down thrust!
Put the wing back to whats called out on the plans. Put the engine ad 0 degrees and the tail plane to what's called out on the plans. Balance to the CG on the plans..
WWI planes have so much lift that at full power they will climb. That's ok.. its normal. Adjust throttle for for level flight..

buzzard bait

I completely agree with BobH, however, the VK Nieuport had positive incidence in the wing AND downthrust at the firewall. The kit came out back in the day when people used a lot of downthrust combined with a considerable angular difference between the wing and the stab. But I set up mine for 0 degrees at the firewall, positive wing incidence, with the stab positive enough to get proper trim.

rowarrior, I think you've got it. The stab/elevator has to be adjusted so the trim is good, whatever that takes. As long as the wing is positive compared to the thrust line, you effectively have some downthrust.

You can't be sure how to set the stab/elevator trim until you fly it (though you can usually make a pretty good guess). The stab/elevator flies in the downwash from the wing, and depending on the plane it can be a lot or a little. That will affect the trim.

Jim

BobH

My Feedback: (2)

Jim. thank you ,

Do as Jim did and maybe adjust the stab to about 2 degrees positive. Both the wing and stab should be positive.
don't try to trim the plane to fly level at full throttle because it probably will want to climb.. thats ok.

rowarrior

Hi Bob and Jim,

thank you for the good advise,

So, i reverted the plane to what it was,/supposed to be by the plans. the day was beautiful, no wind, but of course, as soon as i took off, a 15 km/h wind appeared from nowhere...
however; i didnt see a crazy tendency to climb once i set the throttle to about 1/3 (which would be the cruising speed) as I have a big OS 61 FX on the nose. , however, the wind didnt allow me to 'feel' the plane . i landed it, and i was determined to go up again when the wind calmed down, but i noticed one of the screws that holds the wing and flying wires in place must have vibrated loose and fell off ...i didnt have such screw with me. As soon as I started packing, the wind died down ...$%^%&^&
So, I will make it out there (i hope this week) and give it another go. I have to say, despite the wind, it 'felt good' despite the windy conditions. it still has the downthrust built onto the engine mount though,

so as per BobH, i stll have a -6 degree of downthrust for the time being. I am contemplating at 'breaking the horizontal stab' , shimming it, and re-gluing in place, but since the plane felt good on my last flight, i want to fly it again on calm conditions and see how she feels, here is the video of the flight in question. Notice on my final leg during landing, the engine quits and she came down in a hurry!
https://www.youtube.com/watch?v=KGSL20akD90

TFF

VK DR1 and Camel have screws holding the stab on I figured the Neiuport did too.. You might revert back to that so shimming is not so bad. Some 2-56 screws and blind nuts a little this and that, and there you go.

rowarrior

Hi TFF,

Well, this kit was purchased in 1968, I suppose it was one of the very first ones, so mine didnt have screws, but to be honest, i only built a portion of it myself, not the entire kit, but i didnt see anything regarding the adjustable horizontal stab, it would have made things easier

BobH

My Feedback: (2)

Rather than changing the stab for now try reducing the down thrust of the engine.
I believe the full scale had 2 degrees pos on the top wing and 3 degrees pos on the bottom wing.
What reducing down thrust will do is allow the plane to fly faster with less tendency to climb.

rowarrior

Hello Bob,

the plans call for a +3 on top wing and +2 bottom wing.... and that is how i have it set up right now

should i still try the reducing the engine down thrust?

BobH

My Feedback: (2)

I would reduce the down thrust by two degrees and see how it flies. It may fly just great that way. I can't tell from your video if your cowl front is perpendicular to your crank shaft. It is on the full scale plane.

buzzard bait

Mine does have the adjustable stab, screwed on. It was built by someone else in the early 70s from an early VK kit.

I thought yours flew quite well in the video. Congratulations! I don't think I would change it, though of course it's hard to tell from a video. Reducing downthrust should cause it to climb more, not less, so even if what you have is not scale, I would probably leave it alone. I gather from your comments that you are flying at pretty low throttle, which is the way it should be. A modern 60 is an extremely powerful motor for that plane, way beyond any resemblance to scale, so keeping it throttled back is good.

Nice job!

Jim

TFF

It does fly well in the first video. Many dont survive because many dont expect it not to fly like a sport plane. Heck it did not even flip on landing; its already a mutant.

BobH

My Feedback: (2)

Reducing down thrust won't increase climb. The delta of down thrust and wing incidence = lift. If you had zero down thrust and zero incidence you would have less lift. So increasing each increases effective lift.

Michaelj2k

You might try experimenting with larger diameter props, say a 14-4, 14-6, 15-4 or 15-6. Maybe even a 16-4. Since you have so much power available on a light weight airframe, I think you can afford to lower the rpm's which might help with the speed issues. We had one years ago with a light case ST .60 swinging a 14-6 which was a good flyer with that combination. Your OS .60 has so much more power than the old ST I think it could work.

Think of the perspective that the original aircraft only had 80 to 110hp swinging a large prop at around 1500 rpm. What the rotary engine lacks in rpm is the amount of torque available and it took a large prop to absorb all that effort.

CafeenMan

I didn't see anyone mention this but the only way to actually test wood is to destroy it and then you can't really use it.

Most wood in a model doesn't have to be that strong - it's more for shaping than for strength.

But if it were me I would replace all the wood for spars and longerons. That's some really old wood in the kit and there's no telling how many extremes in climate it's endured even if you know it's been "climate controlled" all along. Old wood tends to get too dry and become brittle.

I've built that exact kit and it's a lot of work. And I didn't do anything extra to it. I'd hate to lose it because a spar snapped when an extra ten bucks could have replaced all the spars and longerons with fresh wood.

Good luck with the build!

rowarrior

Hello Guys!!

well,

FIRST OF ALL, thank you all for your help and great advise, buzzard bait, BobH, TFF, et all.

I brought the incidence of the top wing down to spec, moved the horizontal stab a little(what i could without breaking it) and flew the plane yesterday on calm winds and flew it 3 times with that set up. it flew good. Felt good, landed good.. so I am very tempted to leave it like that!!!! and yes, it may be a mutant because she did not want to nose over or nothing!

but maybe in few months I will bring that down thrust closer to zero, but we will see! thanks for all your help. I will take more video and show you guys.

Maybe a bigger prop is next i think a wooden 14X6 may do!? not too big for the OS 60 FX?

Again, thank you all !!!

BobH

My Feedback: (2)

Leave it!! The proof is in the pudding aka flight. I think you are fine now Congrats.

rowarrior

thanks BobH !!!! I think I will !!!
gotta love WWI planes hey ? i have been flying for 25 years, and for a while my love for RC decreased significantly, but WWI planes re kindled it as they are a challenge every time you take them out... the keep you on your toes, you are actually flying it...love it!

leojzamboni

Hello guys. After seeing Rowarrior´s videos I decided to buy an old VK Kit that was stored for decades An old and experienced builder is helping me to build this beauty, here in Brazil. It will be powered by an OS 55 AX. We believe the maiden will take place in december or january. Following are some pics of the construction. Any piece of advice will be great!! Regards!!

rowarrior

Hi Leo!!

I am very glad to hear i could provide some inspiration. These VK kits are a work of art. if i can be of help in the future, let me know.
only 2 things that i can suggest right now that may make your plane more convenient to fly:

1)i moved the firewall 1.5 inches forward (otherwise you will need too much weigh on the nose to balance it)
2) the aileron servos, instead of putting them in the fuselage with bell cranks as per the kit, I embedded them in the wings, very thin glider servos

hope this helps you!!

leojzamboni

Rowarrior,
Thank you for your tips. We´ve already moved the engine a little forward, but I´m afraid we won´t escape adding lots of weigh to that nose. We are still trying to figure out about the servos instalation. If it is not na abuse, could you, if possible, post a picture of your servos inside the fuselage?
Thanks again!
Leonardo

buzzard bait

Here's my installation, with the battery in a box under the cowl next to the engine, and servos all mounted in back of the firewall. I moved the firewall back just a bit; I didn't want the engine sticking out past the cowl except for the prop shaft. No nose weight needed at all. Total weight, 5 lbs 6 oz. Jim

leojzamboni

Thanks Jim,
It helped a lot. Just bought a micro servo for the throttle. By the way... nice engine this of yours!
Leonardo

buzzard bait

You're welcome, Leonardo. The engine was a PAW 40. It was great for that model, but I had to put a sheet of cardboard under it every time I started it or else leave a pool of black goop on the grass on our club field. I loved the sound and it's ability to swing a large prop, plus it started easily and provided the perfect power for the plane, so it was with mixed feelings that I finally sold the engine. I am now substituting an old Enya 45 that swings a 13 inch prop well enough on the test stand that I think it will make a good substitute. The sound is not as nice as the diesel, but with the large prop I like it well enough. I hope it will do well in the air.

Another thing I want to try is to put a gyro on the rudder for take off. Ground looping really drove me nuts with this plane, and I've been flying mostly tail-draggers for at least 20 years so I know the techniques. Good luck with your N.17!

Jim