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Trailering a Kitfox
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n85ae

Joined: 14 Mar 2007
Posts: 403

Posted: Fri Jan 09, 2009 2:36 pm Post subject: Re: Trailering a Kitfox

All of which, in addition to the obvious are darned good reason to

not tow with the wings spread. 



I was only talking about the comment about the Skystar trailer towing

G-Meter readings. Engineering calculations are boring, by the way, that

sounds too much like my job. 



Realistically, the average bumpy landing is more harmfull to your plane 

than towing. Not to mention landing and taxiing in a bumpy field. My

honest opinion is that the most likely damage you'll sustain from towing, 

is if the wings get banging around. I have taxied mine across bumpy

grassy fields, and those worry me a lot more. if you are on main roads

you'll likely not have any sort of bumpy enough ride to damage your plane on a trailer. UNLESS it is loose, or the wings aren't supported

or somebody runs into you. Or it gets hit by a rock.



Half the toys I've had I've towed, from dirt bikes, to cars, and planes,

boats and my camper, and the only damage has been from stuff getting hit by road debris.



I worried a lot about the effects of towing mine, until I actually did it.

The experience of hauling it behind my truck, changed everything I

really worry about. I only worry about two things now - Some jerk hitting

it, or my tiedowns coming loose. 



Jeff

msm_9949(at)yahoo.com
Guest

Posted: Fri Jan 09, 2009 2:48 pm Post subject: Trailering a Kitfox

Man, and I thought we lawyers liked to argue! I had no idea engineers were so much like lawyers . . . but with math!! How's this:

  

 Lots of trailering = 1 reportedly damaged airplane. Can we move on now?

  

 Marco Menezes N99KX

 Model 2 582-90 C-Box 3:1 w/clutch

  

 do not archive



--- On Fri, 1/9/09, Bob Brennan <matronics(at)bob.brennan.name> wrote:



 [quote]From: Bob Brennan <matronics(at)bob.brennan.name>

Subject: RE: Re: Trailering a Kitfox

To: kitfox-list(at)matronics.com

Date: Friday, January 9, 2009, 3:52 PM



[quote]--> Kitfox-List message posted by: "Bob Brennan" <matronics(at)bob.brennan.name>  The Kitfox airframe, which is fabric covered metal tube, does not have a posted MTBF that I know of, probably because the airframe is designed not to flex under load. Sorry, I should have been more clear in stating that aircraft whose frames are made of metal (rather than "metal airframes" have an MTBF of parts according to the stress they are subjected to. To be even more clear - I meant airframes of almost all airline aircraft and most standard type GA aircraft such as Piper and Cessna, which rely on stressed metal monocoque skins to form the "airframe". And all such MTBF numbers are based on the metal flexing under "momentary spikes", not constant loads.  My reply is to this subject: "This is completely flawed, because these momentary spikes mean nothing."  And this although I think "Rexinator" already replied better than me: "They completely lacked the engineering brainpower to realize that load is related to force over time."  The 3 wing attach points on the Kitfox seem to be designed well for the published maximum plus and minus loads in flight, but the designers seem to have failed to design for the stresses of the unsupported wings in the trailering position, or failed to publish limits or recommendations on how to rig the wings for trailering. I'd be happy to be proved wrong on that last point and get some real numbers, but in the meantime it seems it is left to us to hash it out here and hopefully provide some rigging recommendations that work.  I know I personally have learned a lot from these discussions, but don't want to discuss "hogwash" really. I'll leave that to farmers.  Bob Brennan - N717GB ELSA Repairman, inspection rated 1991 UK Model 2 ELSA Kitfox Rotax 582 with 3 blade prop Wrightsville Pa   --

matronics(at)bob.brennan.
Guest

Posted: Fri Jan 09, 2009 2:49 pm Post subject: Trailering a Kitfox

just hoping for one of those awards someday from the pre-eminent "hander

outer of humorless darwin awards"... albeit without actually removing my

genes from the gene pool. Too late anyway - already got 5 grandchildren 



do not archive



--

n85ae

Joined: 14 Mar 2007
Posts: 403

Posted: Fri Jan 09, 2009 2:52 pm Post subject: Re: Trailering a Kitfox

 	  Quote: 	
		  I don't have a trailer so for me this is all really theoritical, but Denney

built trailers that towed tail first with the tailwheel elevated, Skystar

did the same. 	




A good reason for this is axle location and tongue weight, when you 

design a trailer, you need to locate the axle, and this affects the tongue

weight. To keep the tongue weight reasonable you end up with the

axle location of the trailer pretty close to the planes cg. Considering 

you need to be able to turn as  well when towing you pretty much end 

up sketching and calculating to the point where you have a backwards

towing rig. Which is exactly what I did. Somewhere I have an excel

spreadsheet with all the calculations I did for the trailer in the

previous picture.

 



Jeff

matronics(at)bob.brennan.
Guest

Posted: Fri Jan 09, 2009 2:59 pm Post subject: Trailering a Kitfox

All good points Jeff, except for one. You *knew* I'd find at least one

didn't you?<g>



With the wings out all the forces along the wings are perpendicular to the

fuselage and concentrated on 3 connect points, which is well documented and

presumably designed for and tested to the stated maximum loads.



But it seems that with the wings folded and only supported by 2 of the

attach points, now with the force-moments *parallel* to the center line of

the fuselage - stuff can break. And worse yet it can be damaged via metal

fatigue rather than wings snapping off during transit. These are things I

try to do my best to understand, and avoid. 



bob



--

matronics(at)bob.brennan.
Guest

Posted: Fri Jan 09, 2009 3:02 pm Post subject: Trailering a Kitfox

2 reported damaged airplanes Marco, so far. 1+1=2 with  math<g> 

  

 I don't want to be number 3

  

 tedious bob

  

 do not archive



   From: owner-kitfox-list-server(at)matronics.com  [mailto:owner-kitfox-list-server(at)matronics.com] On Behalf Of Marco  Menezes

Sent: 09 January 2009 5:47 pm

To:  kitfox-list(at)matronics.com

Subject: RE: Re: Trailering a  Kitfox

 

                   Man, and I thought we lawyers liked to argue! I had no idea engineers        were so much like lawyers . . . but with math!! How's this:

        

       Lots of trailering = 1 reportedly damaged airplane. Can we move on        now?

        

       Marco Menezes N99KX

       Model 2 582-90 C-Box 3:1 w/clutch

        

       do not archive



--- On Fri, 1/9/09, Bob Brennan        <matronics(at)bob.brennan.name> wrote:



       [quote]From:          Bob Brennan <matronics(at)bob.brennan.name>

Subject: RE:          Re: Trailering a Kitfox

To:          kitfox-list(at)matronics.com

Date: Friday, January 9, 2009, 3:52          PM



[quote]--> Kitfox-List message posted by: "Bob Brennan" <matronics(at)bob.brennan.name>  The Kitfox airframe, which is fabric covered metal tube, does not have a posted MTBF that I know of, probably because the airframe is designed not to flex under load. Sorry, I should have been more clear in stating that aircraft whose frames are made of metal (rather than "metal airframes" have an MTBF of parts according to the stress they are subjected to. To be even more clear - I meant airframes of almost all airline aircraft and most standard type GA aircraft such as Piper and Cessna, which rely on stressed metal monocoque skins to form the "airframe". And all such MTBF numbers are based on the metal flexing under "momentary spikes", not constant loads.  My reply is to this subject: "This is completely flawed, because these momentary spikes mean nothing."  And this although I think "Rexinator" already replied better than me: "They completely lacked the engineering brainpower to realize that load is related to force over time."  The 3 wing attach points on the Kitfox seem to be designed well for the published maximum plus and minus loads in flight, but the designers seem to have failed to design for the stresses of the unsupported wings in the trailering position, or failed to publish limits or recommendations on how to rig the wings for trailering. I'd be happy to be proved wrong on that last point and get some real numbers, but in the meantime it seems it is left to us to hash it out here and hopefully provide some rigging recommendations that work.  I know I personally have learned a lot from these discussions, but don't want to discuss "hogwash" really. I'll leave that to farmers.  Bob Brennan - N717GB ELSA Repairman, inspection rated 1991 UK Model 2 ELSA Kitfox Rotax 582 with 3 blade prop Wrightsville Pa   --

n85ae

Joined: 14 Mar 2007
Posts: 403

Posted: Fri Jan 09, 2009 3:07 pm Post subject: Re: Trailering a Kitfox

ok, ok, ok. I Have the solution. 



A really BIG box, and styrofoam peanuts!



Those packaging engineers aren't dummies, they invented that stuff

for a good reason.



Have a nice weekend. 



Regards,

Jeff

gary-n-dorothy(at)tctwest
Guest

Posted: Fri Jan 09, 2009 4:09 pm Post subject: Trailering a Kitfox

So --it seems that we need a structural engineer to design a  3 rd attachment  point/ brace to be used for transport , locating it  to the outboard end of the wing, and attaching somewhere near the rear of  the airframe, the wing forming a triangle / or a truss,  better spreading  the load to the airframe and eliminating  the "lever action" the wing  imparts to its two attach points when folded.

      I can understand  the concerns   brought up here. But believe that Sky star  designed an airplane ---not a  trailer, and I do believe that the loads imparted to the airframe over a  period of time will damage the basic airframe attach points. Chuck holes,  speed bumps,  gravel roads and freeways, trailer spring rates, all will  bring different levels of abuse,  So  I guess each of us in our own  way will have to solve their transport  problem. 

       Personally,  I tow on a trailer  , tail propped up, wings close to level with the aircraft facing forward, and  the wing butts covered with a wind chock, removing it when unfolding the wings.  

       The box full of Styrofoam  peanuts sounds fun  !!!  you may need a lot of help tho, cleaning  runways when unpacking. :~}

  

 have a good weekend 

 GG

  N4276M

 [quote]   ---

Fox5flyer
Guest

Posted: Fri Jan 09, 2009 4:50 pm Post subject: Trailering a Kitfox

Nice trailer, Jeff.  Very nice.  Ever thought about making plans for it?

Deke Morisse

Mikado Michigan

S5/Subaru/CAP 402+ TT

"The aim of an argument or discussion should not be victory, but progress."

- Joseph Joubert



do not archive

---

dwight purdy

Joined: 10 Feb 2006
Posts: 85

Posted: Sat Jan 10, 2009 5:42 am Post subject: Trailering a Kitfox

I have never commented on this subject and am also tired of deleting them. 

That being said I must comment on this idea of fastening down tight. Who 

ever built my trailer made the tongue carry through too weak and it flexes a 

bunch. If you tie it down tight your plane becomes an integral part of the 

trailer. You do not want your longerons doing that! I need to beef up my 

trailer.



  Dwight Purdy

  Model II

---

_________________
dwight
model II

pwmac(at)sisna.com
Guest

Posted: Sat Jan 10, 2009 6:55 am Post subject: Trailering a Kitfox

Replacement of the spar steel doubler would be one option. Pretty low 

tech and it puts the plane back to what it was when built.

Examine  the  front/rear braces for any tell tale issues that would 

give a hint of plane attachment issues?

Verify the fuge lower structure is still straight as designed.

Consider some kind of ndt for the tail spring?

Paul

==========

At 05:30 AM 1/10/2009,  Dick Maddux wrote:

 	  Quote: 	
		  I know we have beat this subject to death but I really would like to 

solicit an opinion on the best way to check the rear spar pivot 

point for damage. Unfortunately I had to trailer my Kitfox from just 

south of Boston to Pensacola ,Fl due to the lousy weather enroute 

when I bought it. It was towed on a tandem wheel trailer and it was 

a rough ride on the interstate due to the light weight of the 

Kitfox. The tanks were empty and the front brace bar was installed. 

I examined the rear spar pivot point visually upon arrival as I 

thought this might be a  possible weak point. It appeared to be ok 

but now with all this discussion I think I will reexamine it. Any 

good ideas on how to check it other than visual (i.e.: dye 

penetrant,etc) Any other areas to check?

   Thanks

                     Dick Maddux

                     Fox 4-1200

                     Pensacola Fl

shinco(at)bright.net
Guest

Posted: Sat Jan 10, 2009 8:35 am Post subject: Trailering a Kitfox

n85ae wrote:

 	  Quote: 	
		   



 ok, ok, ok. I Have the solution. 



 A really BIG box, and styrofoam peanuts!



 Those packaging engineers aren't dummies, they invented that stuff

 for a good reason.



 Have a nice weekend. 



 Regards,

 Jeff





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p 23774#223774



   

 ------------------------------------------------------------------------

 Checked by AVG - http://www.avg.com 



   

NOW That is a good idea.....may be all so we could have UPS ship it for 
	


us.from home to airport..that way you all so would not need a tow truck 

to pull it..Steve Shinabery N554KF  KF2  St.Marys Ohio

shinco(at)bright.net
Guest

Posted: Sat Jan 10, 2009 8:44 am Post subject: Trailering a Kitfox

Dwight Purdy wrote:

[quote] 



 I have never commented on this subject and am also tired of deleting 

 them. That being said I must comment on this idea of fastening down 

 tight. Who ever built my trailer made the tongue carry through too 

 weak and it flexes a bunch. If you tie it down tight your plane 

 becomes an integral part of the trailer. You do not want your 

 longerons doing that! I need to beef up my trailer.



  Dwight Purdy

  Model II

 ---

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