Can't find fuselage structural diagram

[Luked 71]

Somewhere I saw a diagram showing the fuselage tubing that indicated where weaknesses were found. Seems like the uprights to the front spar carry through were one area that was marginal. It was a side view. Does anyone know where this diagram can be found? I think it might have been a hand sketch.

 

Thanks,

Luke D.

[EDMO 1078]

Luke,

     I am almost certain that skystar increased the diameter of those uprights by at least 1/8" - maybe 1/4" - when they went from the model 4 to model 5 - maybe you can find a 5 or later to measure.   I think the only effect this would have would be in case of a noseover?

EdMO

[Luked 71]

Hey Ed,

 

Thanks for your reply. The reason I'm interested is because I'm trying to decide if I can put the longer KF wing on my plane without introducing forces it wasn't designed to take. I actually did what you said, and went and looked at a Kitfox here on our field. I'm not sure if it's a 4 or 5, but the uprights are 1/2" square tubing. ACS only lists .035" as an option for 1/2" square. My guess would be that's what they used. This KF has the long wings, so that's encouraging.

 

Luke D.

[sioux201 84]

Weak link is the aft spar fitting

My a broke off

Call me252 923 5145

[EDMO 1078]

If it had square tubing, then I think it must have been a Kitfox 5 or later - believe the 4 tubes are round, but need to check my book.  I was thinking that they used 5/8 or 3/4 tubes on the later models.

You also need to measure the crossover tubes - mine are 1 1/8" diameter x .049 wall, but that is not standard.   I have seen a rear spar attach tube broken, and believe it was probably done when wing was folded and trailered without supports in back / front?

EdMO

Edited 30 Sep 2014 by Ed In Missouri

[Luked 71]

Hey thanks guys. Sioux201, I tried calling, but got your answering machine. You can give me a call at 541 926 7757, or just let me know the best time to call you.

 

Luke D.

[EDMO 1078]

Luke, Sioux, and others,

     Neanderthal Computer Whiz Kid talking - I don't know why, but Leni and others don't give straight phone numbers on here - although I have certainly listed my number lots of times.

They use something like One 2 Three 4 five 6 to prevent hackers or something.  Just a "heads-up" for you.

EdMO

Edited 30 Sep 2014 by Ed In Missouri

[Luked 71]

Yeah, I usually wouldn't give my personal number, but that's our business phone#, and it's all over our website anyway.

[akflyer 1427]

Ed,

 

By doing it the way I normally do, it keep the web crawlers and bot from getting your number then selling said number to advertisers who just love to email and text you crap out of the blue to try and get you to buy something   That said, I have posted my number all over the web as well and if my phone starts getting blown I just put it on silent and go about my day.

 

[EDMO 1078]

I killed mine! 

EDMO

[Av8r3400 1179]

If it had square tubing, then I think it must have been a Kitfox 5 or later - believe the 4 tubes are round, but need to check my book. 

 

 

I can confirm that Kitfox Model IV and older do NOT have any square tubes in the cabin area.

 

I would guess this to be a 5 or newer by that fact.

[Luked 71]

Hey Larry,

 

I was also wondering if your friend that put KF wings on his Avid used full length KF wings and KF struts.

 

Luke D.

[Av8r3400 1179]

He did use full length Kitfox wings, but built his own struts and fairings.

Just to complicate them further, he used the fiberglass Avid wing tip bows instead so a bolted on Kitfox tip.

His full span is near 33 feet.

(Avid C fuselage)

Edited 2 Oct 2014 by Av8r3400

[Luked 71]

That's really good information. I'd love to have that extra wing area, and it's good to know it's been done before. You wouldn't happen to know what size of tubing he used for the struts would you? I can figure out the diameter from looking at a Kitfox, but I don't know the wall thickness.

[Av8r3400 1179]

I'm pretty sure it was 1" od, but I'll have to check with him on the wall thickness.

 

He did use the .065" wall spar tubes, sourced from a local steel supplier, with the Kitfox sourced stiffener extrusions.

[Luked 71]

Thanks Larry. If you could check with him on the strut wall thickness, that would be great. I'm really leaning toward the longer wing. If I go that route, I would get the KF inserts.

[EDMO 1078]

Luke,

     I am almost certain - I think it is in the Downs book - Kitfox later models use 1" x .049 wall struts.   I used 1" x .058 because I had 7/8 diameter rod which I drilled and tapped to 7/16 - 20 for my rod ends - the 7/8 is a good fit inside my tubes for welding.

EDMO

[Luked 71]

Hey Ed, what's the Downs book?

 

Edit: I just confirmed your strut information Ed. I found it here (in the Model IV-1200 section):

 

http://www.avidfoxflyers.com/index.php?/topic/603-history-of-kitfox-structural-changes/

 

(Thanks Doug)

Edited 2 Oct 2014 by Luked

[EDMO 1078]

Luke,

       When Ed Downs was head of Skystar, the maker of Kitfox Aircraft after Denny Aircraft and before John McBean started the new Kitfox Aircraft, he wrote a small book about the evolution of the Kitfoxes from 1 to 7, and also how to fly them, and lots of specs like airspeeds and weights.   It is a very interesting and informative book - lots of good info - I think it is still available from Kitfox.

The book title is "Kitfox Pilot's Guide", by Edward S. Downs.

Ed MO

Note:  I must have gotten the strut size for the Classic 4 somewhere else, as I don't see it in my copy of the book.   I think the Avid Pilots would learn enough about flying these light planes to make the book worth reading - it also covers floats flying.

Ed

Edited 2 Oct 2014 by Ed In Missouri

[Luked 71]

I see it in the KF catalog. I might have to get it. They also have the model IV operating handbook. I wonder if that would be worth getting too.

[EDMO 1078]

I haven't seen the model 4 handbook - Ed's book is really good reading about how to fly these, no matter what kind you are flying - probably all the info you need is in his book - the rest comes with experience.

EDMO

[akflyer 1427]

I would questions ones abilities if they cant fly an avid or a kitfox.. the only thing they need to know is

1) Dont try high speed taxi.  If your gonna fly it get the damn thing off the ground or you WILL ground loop it in short order.

2) There are high drag airplanes, when you pull the power, you will come down fast.

3) if you want to loose altitude in these with a 2 stroke engine, slow the plane up and you will fall out of the sky like a rock.  I can peg the VSI at 45 MPH. 

 

Most of all, have fun and dont be scared of them.  They are pretty damn sporty feeling after flying a cub or a champ.  Lighter on the stick and you dont have to bang your thighs with the stick to keep the wings level.

 

[Av8r3400 1179]

Thanks Larry. If you could check with him on the strut wall thickness, that would be great. I'm really leaning toward the longer wing. If I go that route, I would get the KF inserts.

Checked with Dave today. He used .065" wall 1" diameter tube for the lift struts.

In building his plane anything he was unsure of he referenced the set of "Wag-abond" plans he has from when he rebuilt a Piper Vagabond PA15. Similar speed and weight envelope.

[EDMO 1078]

My "quote" feature wont work on here, otherwise I would copy what Leni said about these little birds - They are nothing to be afraid of, but if you have been flying a Cessna or something while half-asleep, then you better have a cup of coffee before pushing the throttle forward in an Avid or Kitfox.

I still think Ed's book is worth the $22 price, for it was fun and educational reading.  The history and specs in it are worth the price.   I got mine a little cheaper about 12 years ago, and still keep it handy to read.

for instance, he gives the changes between models, even the tail height and elevator changes and engines, weights and speeds for each.

EdMO

I wish someone would post or PM a photo to me of how the Avid struts are welded to the lower fitting that attaches to the fuselage.   I know they are different than the Kitfox.

EdMO

Edited 3 Oct 2014 by Ed In Missouri

[Av8r3400 1179]

I took some lift strut shots of Dave's plane this afternoon.  

 

Including one of the lower strut attachment.