A much faster Kitfox?

[Danzer1]

I'm familiar with Oratex and have read everything I can find on it, but have never read anyone referring to such a short lifespan. Do you have the article reference? There are many, many aircraft using this system, I doubt many would if they expected 6 years. Really would like to hear more.

Greg

[Kurt.A]

Kurt,

The lightest covering system I am aware of is dope and fabric. But you can't get into wanting a deep shiny finish. Just put the paint (butyrate or nitrate dope) on heavy enough so it covers just barely, and stop. It's going to be flat finish and kinda boring looking, but its going to be lightweight.

The only other very light process is this new stuff from germany that you iron on like we used to monokote model airplanes. But expensive and limited life.

Paul

So a quick look through Aircraft Spruce online catalog came up with several options for covering and painting using fabric and dope. Can you steer me in the direction of a book or someway of doing a comparison between brands and techniques? What would be the weight savings performed the way you have described vs the shiny method? When you say fabric are you referring to Dacron, Ceconite, etc????

[SWeidemann]

How about good old Poly Fiber System? Mine has at least 11 years on it, and looks good. Of course, with any fabric plane it should live in a hangar when it's not out flying.

Skot

[av8rps]

I knew someone would be asking me that, but I honestly cannot remember where I read it . It might have been on the web? Or since I get almost every aviation magazine known to man, if it was there it was in the last 6 months somewhere? I seem to recall the info was associated with Frank Knapp's Lil Cub in the Valdez STOL/Alaska stuff.

I still find the Oratex product interesting, and believe it will become more popular in time. And for anyone considering the product I would recommend using the information from their FAQ area of their website, which does talk about lifespan. I'm sure their answer to that is more reliable than what I read.

Paul

I'm familiar with Oratex and have read everything I can find on it, but have never read anyone referring to such a short lifespan. Do you have the article reference? There are many, many aircraft using this system, I doubt many would if they expected 6 years. Really would like to hear more.

Greg

[Danzer1]

Thanks Paul,

I'll keep digging. Just to clarify though so as not to slight Oratex, they don't just say 10 years or more. They guarantee it for 10 years. I'm still weighing the cost/weight/process/paint with all the others.

So far I like the Oratex tape process better and the ability to use non pinked (straight edged) tape for a cleaner look. We'll see more longevity data as time goes on, but to me it looks good. I'd like to see the price more competitive though and that is changing with the dollar/euro exchange rate. So we'll see.

Greg

[Kurt.A]

Getting back to the original intent of this thread has anyone information regarding surface finish and how it affects drag? Does the boundary layer come into effect and negate a rough surface causing more drag? Does the boundary layer become thinner with a smooth finish and in essence provide a smaller frontal area?

[HighWing]

I think weight is the most critical component for stall speed, assuming the airframe is the same.

This makes a lot of sense. Then I have to wonder. Kitfox reports their 750 lb. Super Sport stalls at 41 mph. That is one mph. higher than my 650 lb. Model IV. The math - 15% higher empty weight 2.5% higher stall speed.

I realize the only thing that is identical on the two airframes is the Riblett wing, but there are significant differences elsewhere. Any ideas what they have done with the design that results in the extra efficiency in stall speed?

[av8rps]

Lowell,

Is the stall on your model 4 at 41 mph clean, or with flaps? Do you have the full length wing? If you do have the 32 ft wing and your are using flaps, then I'd suspect something else being wrong with your plane like an inaccurate ASI at low numbers, a forward CG etc. The heavier Super Sport should most definitely stall sooner than your Model IV. I just don't believe there is enough airframe difference between the two to make affect the stall that much.

At least that's my take on it. Maybe others have some ideas?

Paul

This makes a lot of sense. Then I have to wonder. Kitfox reports their 750 lb. Super Sport stalls at 41 mph. That is one mph. higher than my 650 lb. Model IV. The math - 15% higher empty weight 2.5% higher stall speed.

I realize the only thing that is identical on the two airframes is the Riblett wing, but there are significant differences elsewhere. Any ideas what they have done with the design that results in the extra efficiency in stall speed?

[av8rps]

If you are interested I can connect you with a friend of mine that has built a whole gaggle of airplanes, including a Kitfox and an Avid. And every one of them were super light, and all were done in dope and fabric. In fact, here is the Kitfox he built a while ago in his Barnstormers Ad (he's almost done with another plane so he's selling that one). Note the empty weight

"Kit Fox new build 11 light sport stol, n numbered, in phase 1 582, only 429lbs,521 useful,42 1/2 at shoulders,20"trunda tires, line bored Grove gear, s/s taper warpdrive prop, bagage compartment.streamline struts full electric, starter sealed battery, Maul locking tailwheel, HD I beam struts, us coastis vinly easey removeable,9core rqdiator, trailer included, turtleback cover for storage or towing with wing folded, built by a little old seaplane pilot • Contact John Knapp, Owner - located Bath, NC USA • Telephone: 252-923-5145 • Posted October 14, 2014

Now, I'm sure someone is going to say that maybe his scales are off? But if they are, then it sure is interesting to see how his airplanes perform so much better than most others. If you have a chance, look at this video of his Avid Flyer he flew on floats for years;

http://www.youtube.com/watch?v=qjDSatUSoCY

If I remember correctly, that Avid on floats in the video with a 2 stroke Rotax 532 weighed only 387 lbs ON FLOATS. So he knows how to build light. But I would attribute most of that to his dope and fabric finish. Oh, and it seems to have held up well. He built that Avid in 1984.

Paul

So a quick look through Aircraft Spruce online catalog came up with several options for covering and painting using fabric and dope. Can you steer me in the direction of a book or someway of doing a comparison between brands and techniques? What would be the weight savings performed the way you have described vs the shiny method? When you say fabric are you referring to Dacron, Ceconite, etc????

[t j]

Any ideas what they have done with the design that results in the extra efficiency in stall speed?

Just thinking out loud. Vso is indicated airspeed at maximum gross weight and max aft CG. I suspect it was loaded for an aft CG which may account for the efficient stall speed.

Just for drill, here's the stall speeds for different weights and CG I recorded for my classic 4 during phase one.

WT----CG----Stall Clean ----Stall Full Flaps Vso
765-- 12.4-----38 mph
898-- 13.68----43--------------------39
954---14.42----45--------------------40
1049-14.68-----46--------------------42