Zor

Hi readers,

Just keeping readers on the progress being made in preparation for the actual buiild.
We all do things our own way and some ideas can be useful to someone.

Joining the wings as I am doing allows changing the dihedral by simply making a new joiner at a different angle. That is not easy to do with a tube or rod going through the ribs.

I have now designed the front spar joiner so I know how I am going and know the dimensions of the front joiner. Having this joiner and its similar rear spar one will allow me to make the boxes to fit on without any play ( looseness ).

If any interested fellow has any questions _ _ _ just ask in this thread for an anwer.

Zor

FlyerInOKC

My Feedback: (6)

Hey Zor will the streamline struts be load bearing? Are they K&S tubing? If so I would add something inside for added support.

Mike

FlyerInOKC

My Feedback: (6)

Hey Zor will the streamline struts be load bearing? Are they K&S tubing? If so I would add something inside for added support.

Mike

skylark-flier

Guess I'm a bit slower than most - finally figured out the mechanism/methodology of those strut attachment wires (posts 1843, 44, 48). Gotta tell ya, it's ingenious - my congrats on GREAT thinking. My only question (so far), are you planning to strengthen the center rib at all to prevent wearing as the wire passes into and out of the slot? I'd think maybe some CA around the edges to "harden" the wood to prevent wearing might be in order.

Following your build (and don't worry about monopolizing - this is what these threads are all about, what we do with our Kadets) and Tom's build with GREAT interest. You two are doing things I've never done, shoot - never even thought about trying, and I'm finding it all positively fascinating. I'm one of those guys that gets the kit, builds it in a week or so and has it at the field, flying, at the earliest possible moment. Following your (and Tom's) thinking is truly interesting.

One thing I'm still fuzzy on - and YES, I really am behind the curve here - are you planning to build the wings as one piece or 2? I see refs to changing the dihedral, so I'm kinda assuming 2.

Press on my friend, press on!!

Zor

Hello Mike,

Answering your two questions _ _ _

Yes . . . the struts are branded K&S.
Yes . . . they will contribute to load bearing. Please read ' forces analysis below '.

NOTES for the general readers ( viewers ).

The drawing in post #1851 is aimed at showing that the design of the joiners and boxes has been done. It is not aimed at showing the details and dimensions. The joiners and boxes are on different layers and the rendition is with all layers ( not dimension layers ) and showing some strange colors. In their layers the boxes are orange and the joiners are green. Each layer can be shown separately and dimensions can be removed having their own layer in the drawings. The dimension layers were not appearing in the post #1851.

FORCES ANALYSIS _ _ _ based on my understanding.

The struts are ' working struts '.
The original design does not use struts. It relies on the bending strength of the wings and spars and some bending quite obviously takes place.

With struts installed we have a triangle formed by the wing main spar, the fuselage and the strut. All three are working in tension or compression. In 'right-side-up' flight the struts are in tension avoiding bending of the spars. In inverted flight the stuts are under compression again avoiding bending of the spar.

When the struts are under tension they quite obviously will not curve; they remain straight. Under compression, I feel that this size of struts are adequate to easily stand 50 lbs without bending which would be about 6 negative Gs; based on a model weighing about 8 lbs.

Worst comes the worst _ _ _ a md-length reinforcement could be installed at the half length of the struts like we see on J3 Cubs.

The drawing in post #1851 shows the possibility of two locations ( any location is possible ).The longer struts are 25 1/4 inches long. The shorter location makes them 19 inches long. I have doubts that a mid anti-bending reinforcement is needed.

Adjustment of the struts' length upon installation has to be done properly; that is a different subject.

Zor

BigTeeEldorado

WOW....you guys got way farther along in school than I did....my eyeballs do most of this kind of work for me!!

Zor

skylark-flier,

Thanks for your nice comments in post #1854.

My Kadet Sr. wings will be built in two separable units.

Also my feathers ( tail assembly ) will be bolted, not glued, as I always do for decalage adjustment.

Editing for what I forgot ......
The mddle layer of the snap-in ribs are the hardest ( heavier ) ribs as I weighted them all. They are between 6.5 oz and 7.4 oz as my scale does not show decimals in its gram setting.

I rarely use CA glue but yes the middle rib layer will be saturated from both faces with CA hardening all around the cutouts. Note that there is no forces trying to back out the snapped-in wires and that a wire prevents any backup for the struts to fall out and the forces are in line with the struts angle; not staight down out of the slots.

Zor

FlyerInOKC

My Feedback: (6)

Zor is very good at thinking things through and doing the calculations necessary to make it work. Hats off to you Zor!

Zor

I also do lots of eyeball particulaly when precision constructiion is not a factor.
I love doing drawings which I have done since I learned it at technical school during World War II.

Then it was with a drafting board, a T along the left edge of the board and a bunch of plastic templates for vertical lines and a compass for circles and ... Oh ... some French curves guides for variable curves.

Some of you young fellows may not know what I am talking about.
Now my drawings are done with computer software. We have to keep up with modern technology L O L

Zor

BigTeeEldorado

See I knew there was some technical training in there somewhere. By the way, I hope you or any reader ever take my flipp comments as offensive. You and all the contributions at this site are a wealth of support for the technical training I unfortunately missed.

Which brings me to this question; I believe it was You who just gave me an idea on a completely scratch built (no plans) P38 I am currently struggling with when you mentioned that you leave the tail as bolt on in order to have access to the incidence. I am currently set at 0-0 in my design which is supported by other twin kits I have built but I am using a different semi-symmetrical wing which should produce more lift. I like the idea of being able to adjust the Incidence of the tail after trial flights in case the plane "hunts". The question is where would you begin with the wing tail relationship on a powered aircraft using a high lift semi-symmetrical wing? I am reading some posts that advise at least 1 percent positive.

FlyerInOKC

My Feedback: (6)

I picked up my technical drawing in Junior High back in the early 70s, still like doing it over CAD!

Zor

Hello BigTeeEldorado and all readers,

I prefer posting what or how I do certain things. I always have a reason to do things a certain way.

Cooncerning the bolted tail instead of being glued has the following reasons.

First let me explain that a fully aerobatic model that is never flown straight and level but in constant control of aerobatic maneuvers should ( usually have ) a symmetrical airfoil and zero incidence on both wings and stabilizer. That is to say that the decalage is zero.

Then we have the intermediate models. Sport flying, pattern models, racers, and non-specialized models.
We also have of course "so called trainers" and we have pilots of different experience and abilities.

Here is my thinking _ _ _

The airfoil in use is not of high importance since they all produce positive or negative lift at some angle of attack. In the purely aerobatic models the symmetrical airfoil and zero decalage is aimed at having similar responses whether the fuselage is right side up or inverted. We have, if we may so so, a symmetrical model above and below a horizontal geometrical plane. Such a model is not designed for stability as helpful in a trainer. An aerobatic model is designed for quick and similar response whether it is right side up or inverted or at any angle of rolled attitude.

I enjoy some aerobatic at times but I also enjoy just flying around in a relaxed frame of mind.
For such models I aim as much as possible to have realistic behavior which means that _ _ _
- I have reasonable stability in straight and level flight stretches ....
- I can cruse hands off the transmitter for many seconds meaning from one end of the field to the other ( within view of the model attitude ) ....
- I have a cruise speed at least twice the stalling speed at no more than half power .... ( that DOES NOT mean the Tx stick is half way. The Tx stick half way is much more than half power.
- I DO NOT wish the flight to stay level with changes in power setting .... ( down angled thrust settings ) ....
- I wish a level cruise setting with neutral elevator ( in line with the stabilizer ) ....
- I wish a rate of climb with power above cruise or trim for higher speed ....
- I wish a rate of descent with reduced power below cruise and trim for descent ....

The conclusion is that in strqaight and level flight at cruise speed the angle of attack of the main wings should just produce a lift equal to the flying weight while the horizontal tail IS NOT counteracting for a CG location which is not correct. The CG location should allow the tail to have zero angle of attack while maintaining the correct main wings angle of attack to have a lift equal to the weight.

These are my aims in settng a general flying model _ _ _ anyone can of course do whatever is their preferences.

So I do not glue the tail assembly so I can change the decalage by shimming the stabilizer.
Note that most airliners have an adjustable stab incidence while in flight.

Zor

FlyerInOKC

My Feedback: (6)

The old J-3 Cub and an adjustable tail as well.

spaceworm

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TomCrump

Sometimes that's the best way to design !

If it looks right, it is right, often works in model design. The work that you do is outstanding, and you have fun dong it !

I have no formal engineering education. The modifications to my Kadet are based on experience, not schooling.

I see no need to make this stuff complicated. For me, there is no need to carry things to the 10th decimal.LOL

Some enjoy these facts and figures. There's nothing wrong with that.

They put me to sleep, however. I just need to know that something works, not why it works.

We all derive different pleasures from our hobby. There's room for all schools of thought.

flyingagin

Checking back in Dave. I have been away from the web for a bit. No internet. Went to the local library, got a card and finally got on for a bit.
We spent from Sunday morning to Thursday noon traveling (moving). We made it right on schedule to my mother's. Thursday at noon. Got the truck off loaded Friday. Getting the lay of the land again.
Should have internet Monday or Tuesday, I hope. So will resume following then.
Just wanted to tell Dave and all we had a safe and uneventful trip. Uneventful being the best kind.

But when I can I am following Tom And Zor's builds.

Hoping to at least glue a couple of sticks or stack sand some ribs or anything , just anything airplane building next month.

Ken

Zor

I understand that what is free is an evaluation edition that works for 30 days.

It could be fun to play with this for that period of time.

I do not see any relation to kit building a Kadet Sig product.

Zor

BigTeeEldorado

That's the word I was looking for "decalage".

I understand that I want lift to match weight for a given configuration.....configuration to include type of airfoil, airspeed, incidence and attitude. Attitude is the factor that decalage effects for a given airspeed. So I guess the real question is how to calculate lift? Or more accurately in my case quesstimate.

A couple of the variables are kind of elusive and/or just too complicated to apply in a small scale (that being my brain as well) but decalage is something I can test fly adjust and test fly again.

I know I wasn't real clear with the question but my question is asking if your experience would suggest a starting point for wing incidence along the thrust line. I'm currently configured at 0 decalage and 0 incidence on the wing. The problem is I have no idea how much lift the wing will produce at 0 incidence for a given airspeed. I feel like I would be safer to hedge against my evil adversary, gravity, with a little positive wing incidence and adjust out too much lift with the tail once I can test fly and establish what wide open throttle produces for airspeed and thereby lift. Or should I start at 0-0 and plan on using only tail incidence to adjust attitude for a given airspeed and thereby lift.

I would think the perfect world is 0-0 and the wing produces just enough lift to match the weight at wide open throttle. Unfortunately that is not my world!!

Which would you consider the best chance for success? Would one configuration be inherently more stable than the other (positive or negative tail incidence)?

acdii

I did make a mold off my P-51 cowl, but nothing like what you are doing.

Zor

BigTeeEldorado,

I regret not being allowed in this thread to help your understanding.
It is not my lack of knowledge but the fact that this thread is dedicated to building Kadets from a Sig kit.
Consequently I cannot start talking about aerodynamics and related matters.

Hopefully I can be tolerated with a few comments.
An airplane is aimed at travel speed with minimum energy consumption ( cost of fuel ).
This is attained by cruising at the best lift to drag ratio obtained for most airfoils at an angle of attack of 3 to 4 degrees.

While flyng the angle of attack of the wings is self adjusting.
The idea is to have a decalage ( difference of angle between the main wings and the tail ) so that at cruising the main wings have their best lift to drag ratio. At a lower speed the wing angle of attack will increase and result in a descent. That has to be trimmed to become steady. At a higher speed the angle of attack will derease and result in a climb. That is normal unless compensated by a downthrust setting.

The adjustment of the decalage angle, the angle of thrust ( down usually or up ) and the CG location all enter into the adjustment. Thus keeping the facility of settings. Most fliers do not bother as they are constantly maneuvering while flying.

I hope this post will not ban me from this forum. The word "trolling" is very convenient for convenience if a fellow divert from the main topic.

Just trying to help you if you wish to setup your model for hands off straight and level flight.
Stability has three settings; degrees of stable, neutral and unstable. Another subject I will not cover having already gone out of the main topic of this thread. Sorry for that with my apologies.

I really wish to talk only about my Kadet build in this thread.

Zor

skylark-flier

No doubt about that!!! He's so far beyond me and my capabilities - to say I'm impressed wouldn't even scratch the surface. I can follow most of his work, but to ever come up with it myself - not a chance.

But even so, I follow his ideas and make notes, then I go to Tom's thread and make more notes - and eventually, when I get my own Sr. kit (and I'm 100% sure that'll happen) I'll have all these good ideas to work with.

Zor

Hi folks,

First thanks for the nice comments.

I have now fabricated one of the dural pieces for the laminated wing joiner at the main spar.

This piece is so strong in the lift direction that I may revise having two at the main spar.
I was considereing of having only one at the rear spar joiner; that still stands.

Using only one dural lamination at the main spar may now use two 1/8 inch birch 3 ply; one on each side for a thickness of 0.282 inch.

The height of the joiner is 1 5/16" which would give the wing a positive and negative lift capability well over 10 Gs. Consideration of the wings breaking up or down at high G loads is a matter of the moment arm. The outer half of the wings produce the same amount of lift as the inner section being the same airfoil and area. There is spar webs from wing roots to 26 inches outward on the main spar and to 19 1/4 inches on the rear spar. I do not think these wings are weakly built..
Plus the addition of struts would make those wings absolutely solid as far as lift is involved.

A word about those spar webs. The specs are asking for the grain to be vertical parallel to the ribs. I disagree with that. The forces of lift are trying to form parallelogram between the ribs so the grain being max in tension, the grain should be at an angle.typically 45 degrees and if webs are also used on both faces of the spar then the webs are better have 90 degrees to eah other.

I am having trouble witht writing this text in this editor.

Of course a drawing is helpful in making the pieces; see attached.
The dihedal is 2 degress on each side.


Zor

spaceworm

The relationship is YOUR comment about using CAD in the development of the Kadet project!

Perhaps someone else wants to become as technologically smart as you are.

BigTeeEldorado

Thank you for the consideration. I will apologize also, I'm still learning the etiquette. You gave me a better thought process and a couple really good ideas, so Thank you

FlyerInOKC

My Feedback: (6)

Threads like this are the closest you will ever come to getting an education at R/C University and it's free!