rainedave

My Feedback: (1)

The OS Black Head FGR I posted above weighs 17.2ozs (490grms) w/muffler and prop nut.

The ST .90 weighs 27ozs (765grms) w/muffler according to Tower.

What is the wing area of the KF III? Just for my own sake, I'd like to figure what 10ozs adds to the wing loading.

David

RFJ

660 square inches

Ray

crankpin

My Feedback: (15)

A 90 in a Kwik Fli ............ ? That's a no brainer, meaning, it doesn't make sense if you have a good OS 55 or something like that around. But, if it works, don't fix it. I had some Kwik Fli's at one time. The author sez it is going to work, so it will work.

He's right though, should be the same weight. There are some real nice OS 46's on the other channel right now, cheap.
Crank

UStik

Thanks Ray for the plan!

We had this topic in January in this [link=http://www.rcuniverse.com/forum/m_6827817/tm.htm]thread[/link]. The GSM 61 weighed 26 oz with muffler and was way too heavy. My O.S. 60F-SR from the 1970s weighs only 20.8 oz with muffler, that would be more adequate but is still too heavy. That's why rainedave recommends the Black Head. You just need a .60 from the sixties. A modern .40 would be adequate by size, weight, and power. The KF III should be around 6 lb or even less. The .90 would require tail weight in addition to its own weight, that in turn would require reinforcing the fuselage and whatnot. Isn't that what you call a lead sled?

Taurus Flyer

Gents,

Looking to the drawing every overweight of the engine you have to ad with 44 % of the extra weight in the tail to get the balance again. Not talking about how the plane will fly.

So the blackhead 490 gram and the ST 90 765 gram. Difference is 275 gram
44 % of 275 gram is 121 gram in the tail to have the right position of the CG.
Difference in total weight is 396 gram (121 + 275), nearly the fuel of the tank.
The wing area is 660 square inches is 4,58 square feet.
The weight is 6 lbs normal is 2724 gram with 396 gram total extra, makes 3120 gram
3120 gram/ 28,3 is 110 Oz

Wing loading is 110 / 4,58 = 24 oz / sqft empty plane.
Total weight is 14,5 % more with the ST.
Speed needed to fly 7 % more so no problem to fly, not talking about to compare with the original!!!.

BTW the wingloading of my Orion is 32,5 Oz/sqft, that is again 35 % heavier than the Kwik Mow Mark III, and flies with the Enya 60 4 C, see picture.
Maybe Ray can tell us the difference in power between the ST90 and the Enya 60 4C. The weight I know, see the picture of the spare engine.

I would start with making the tail feathers massive!

Cees

crankpin

My Feedback: (15)

Taurus Flyer - I have been thinking of this a long time. We set up the CG with an empty tank, dry. Now, I have 12 oz. tanks in my two Intruder's. 16 oz. is usually a pound. 'A pint's a pound, the world around', right ? Now, plane is balanced dry, add 3/4 lb. of fuel when we fill up the tank, and if it is a little touchy, it is now nose heavy. If we are doing a pattern, should the contest director have the roll maneuver's at the last of the sequence, so we are more evened out, as rolling better not being nose heavy. I am surely not an expert here, and my planes are usually nose heavy, dry. Any comments appreciated.

Crank

UStik

Crank, the fuel is not that heavy. 12 oz volume are only about 10.2 oz (0.64 lb) weight. The tank's moment arm is not long, either. You should notice the small shift of c/g only if your plane is balanced twitchy and if it rolls like on rails, anyway. But I think you're basically right with your thought.

As to the quick flying lawn mower, you'd notice a slightly different stall/snap behavior if it's heavy. More important, the added weight in nose and tail makes the plane sort of a flywheel (the English language is so to the point [8D] ) in the pitch and yaw axes. That's no longer a pattern model, that's a jet model! Of course, if you like it, go for it!

Taurus Flyer

Hello Crank, a little off topic, sorry mmattockx.

I think I cannot give one answer for that but I try.

My first question is, why are your airplanes nose heavy, so you tell us? What is the reason for that?.
< and my planes are usually nose heavy, dry.>

Most important fact for me is bring the plane back on the field with a deadstick, so the CG on the right position is better for that and I would change that first .
The CG on the right position makes the plane also manouvrable and the difference between normal and inverted flying less. Maybe that’s your reason you ask?

When we read the history of many planes it is clear they were designed for the program of that moment.
Read a part of an article about the way Ed Kazmirski did design the Taurus. See the picture.

Doing it this way the plane and your own skill will do the job, win from the other members of the contest.
Changing the program is not the way to win. Every plane is a compromise so everyone would like to fly his own optimum program. For example I would like to do the spin on the end.
Most important is try to fly the part of the program your plane is designed for as good as possible.
When flying classic pattern, we are all too late to become a hero so, enjoy. and keep the costs low.

Cees

8178

My Feedback: (17)

An Enya 60 with an open exhaust would be the most correct but a Webra Black Head 61 would be OK too!

mmattockx

I was looking at this again and realized the K-F is a lot smaller than I was envisioning. If it builds to around 6lbs, a 45 would be fine. I happen to have two ST 45ABC's also sitting on the shelf, so that will be a better choice.

Thanks,
Mark

Taurus Flyer

That is oké Mark,

But we all waiting for the thread you build the plane.
I want to help you.
Starting from grass hè?

Each wheel from the undercarriage his own mower.
Kwik Fly and Mow Mark III

Cees

NM2K

My Feedback: (14)

I know how you feel, RFJ. But some of those warts are pretty big and ugly!

Then there enters the factor of being competitive. Folks that fly pattern are amongst the most competitive folks on the planet, I suspect. Me included. I've been trying to keep my competitive urges under control. Frankly, that's what ruined pattern for me several times before. My own personality, that is. My talent did not match the size of my ego. Neither did my wallet.

Now I realize that I never stood a chance at being a champ, but I was good enough to bring back a trophy once in a while. I also realize that it was the interaction amongst the other competitors that I enjoyed the most and that the rest has faded into the past and mostly beyond my memory's ability to recall these days. But the friendships remain.

I sold off my hi-tech engines for classic pattern (OS FS-91 Surpass II/Pump) and returned to two-strokes. I even have three 10cc Rossi two-strokes complete with high performance mufflers (2 new AXE and 1 old R60), but I'm going to save them for BPA models and not fly them in SPA. For SPA, I'm going to stay with the older engines that folks flew back then. I'll probably never fly in an SPA contest anyway, so whether the model is competitive or not is irrelevant. However when I'm sport flying at the field, I can always point to my model and say that it is "authentic". Well, except for the 2.4 GHz R/C system. Oh, and the coreless servos. Did I mention the NIMH battery pack? Jeez...!


Ed Cregger

crankpin

My Feedback: (15)

Enough said.

NM2K

My Feedback: (14)

I have a NIB Enya .61CX just waiting for a nice model. The Kwik Fli III just might be it.

Now, where did I put those Kwik-Fli plans?


Ed Cregger

tweedy

My Feedback: (1)

I think finding room in the nose of a Kwik Fli for a ST 90 might be more of an issue than the power, not a lot of room between the firewall and spinner. Kraft mounted the Enya 60 radially to the fire wall with a 1/4" thick plate. I used a Dave Brown mount for the Enya 61-CX-TN (a very small light 61) that I used in mine and had to do some surgery to the mount to get the engine close enough to the firewall and still the back of the spinner is about 1/4" forward of the position on the plans. I drew up cad plans for the MK III a few years ago and posted them on line at the first site I have listed below, they are in DXF format. they have made their way around the world to many other sites, even a guy selling them in Brazil. The links below (one in dutch but lots of photos) that are of build threads from a fellow in Holland building his first Scratch build, and only his second model using the plans I posted he’s doing an amasing job considering he is so new at this(thus some unortadox construction techniques).He has mounted an OS-55 the way Phil did way back when and I think it looks a lot cleaner than My mount with all the grinding I had to do to it.

Richard


http://images.google.com/imgres?imgu...US274%26sa%3DN

http://www.modelbouwforum.nl/forums/...tml#post737651

http://www.rcuniverse.com/forum/m_71...page_1/key_/tm.


ENYA 61 CX TN Specs.
Displacement 9.85 cc
Bore x Stroke 24.8 x 20.4mm
Max. Power 1.7HP
Revolution range 2,500~16,000rpm
Weight 378g(without muffler

Dean Pappas

Hello Mark,
Gosh we've read an awful lot of philosophy about dropping more ponies into your Kwik-Fli but relatively little about this airplane and more power.

Fortunately, you can always throttle back or install a 60 if you have issues, as the 90 case is indeed a 60 drop-in.
The Kwik-Fli was famous for its "Kwik-Fli dance", a phugoid or oscillation in yaw under most high speed conditions.
It never harmed a thing, and the plane flew great. Some thought it was charming ... whatever.

Try it, and let us know. If it happens, you might try some tape-on wing fillets carved from wood or foam, just to settle the old argument about the cause.
Tapered wings didn't fix it, turtledecks didn't fix it, and some always did it worse (or better!) than others.


Looking forward to your test flight report,
Dean Pappas

NM2K

My Feedback: (14)

Yes, a flight report would be great, regardless of the engine used.


Ed Cregger

mmattockx

Richard,

These are the plans I have. I will lay in a drawing of the ST90 to see how it would fit and post a pic when I get to it.

Mark

Ben Lanterman

Hi Mark,

I have a Kwik-Fli Mk III, Quick Fly, whatever - that was built from the old original Graupner kit many years ago. I flew it with a Gold Head OS 60, Black Head OS 60 and in the last few years an OS 60 of some sort ( I forget the exact name of the motor). I have since sold the motor. I replaced that motor with an AXI 4160 electric motor running on 6s1p 4200mah lipoly and am basking the the luxury of no greasy clean up and my lovely wife, Bonnie, doesn't complain about being my mechanic and pit person. She always goes flying with me since we are both retired and enjoy being with each other.

Back to the KF - you could go with the .90 and do loops that will be out of sight. Certainly my KF is has good performance and is very aerobatic with the extra weight of the batteries and no doubt is close to the weight that your .90 powered airplane will be.

I haven't tried it myself but I believe the QF/KF, etc. dance could be cured by adding an airfoil section to both the horizontal tail and vertical tail. Going up to a 12% thick symmetrical section on each tail surface will make them a little more effective around the very small angles of pitch and yaw that allow the dance to occur. The control effectiveness will not be compromised. Certainly other airplanes have flat tail surfaces and don't exhibit that characteristic but let's face it, they were made flat because Phil was feeling a bit lazy that day.

Since you might need some tail weight to balance the big .90 make the tail surfaces with a 1/64 inch flat plywood center panel with soft balsa laminated on either side of that. You can use the ply sheet to help maintain the center line of the symmetrical section while you sand the surface to shape.

Good Luck with the project,

Ben Lanterman

rainedave

My Feedback: (1)

On the subject of the tail dance, I was told by Dave Geurin (we belong to the same club) that an airfoiled tail would cure the problem, as Ben suggests. I've never built a KF, but I did take his advice and added the mod to my .40 Super Kaos (the original also has a slab tail). I can tell you that it has one of the smoothest elevators of any plane I'm currently flying. I've also never noticed any wagging tendency. It's an easy mod and, IMO, looks better, too.

David

NM2K

My Feedback: (14)

Built up tail surfaces are one of the reasons that Goldberg's Falcon and Skylark series locked-in, at least in the pitch axis. A built up vertical fin and rudder would have completed the package.


Ed Cregger

mmattockx

Thanks for the tip on the airfoiled tail feathers. That will be something to incorporate no matter which engine I use.

Mark

Ben Lanterman

Mark,

I forgot to add that a couple of years after the original model was published I built a 80% scale (or thereabouts) scaled down Kwik Fli that could use a .40 sized engine. The flat tails were changed for airfoiled ones. I have worn out two fuselages along the way and the wing and tail surfaces are in the shop waiting for a new fuselage. Anyway that model was a bit overpowered with the rear valve ST .40 I put in it and it could fly at any speed with no dance evident.

My big electric Kwik Fli does have flat tails. I tell myself every winter that I should add an upper and lower spar on the tail and make a diamond section out of it. It wouldn't take much time.

One thing I like about the big Kwik Fli comes about from the fact that it was designed at a time when there were very few paved runways. The structure could handle a lot of abuse and bouncing in holes on landings, etc. It could mow through the high grasses and finally get flying. The modern flying eggshells couldn't handle the abuse very well.

Lots of fun,

Ben