Matronics Email Lists :: View topic

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Trailering a Kitfox
Goto page Previous 1, 2, 3, 4, 5 Next

Matronics Email Lists Forum Index -> Kitfox-List

View previous topic :: View next topic

Author Message

Vic Baker

Joined: 11 Jan 2006
Posts: 71
Location: Carson City, Nevada

Posted: Wed Jan 07, 2009 2:13 pm Post subject: Trailering a Kitfox

Prop tips,  rags and clamps,  softens the blow when I run my head into the 

prop.  (tight fit in garage)

Vic Baker

S7 912S Warp

Phase 1 flight testing

Carson City, Nv

---

_________________
Vic Baker
Series 7
Carson City, Nevada

wannafly

Joined: 13 Oct 2006
Posts: 53

Posted: Wed Jan 07, 2009 2:22 pm Post subject: Trailering a Kitfox

I just posted my kitfox for sale and I have some pictures with it on the trailer. Towed it more than 3000 miles home at 50-60 mph with no effect on the kitfox. have used it for the past 4 years with no issues.

 mic



[quote] From: noelloveys(at)yahoo.ca

 To: kitfox-list(at)matronics.com

 Subject: RE: Re: Trailering a Kitfox

 Date: Wed C 7 Jan 2009 18:38:35 -0330

 

 --> Kitfox-List message posted by: "Noel Loveys" <noelloveys(at)yahoo.ca>

 

 I did see a hitch for towing a 'Fox that had a screw that made the hitch

 adjustable up and down several inches. I was part of the arm not the hitch.

 

 Another idea would be to cut the arms and plate them back together like a

 roof truss. I'd only bother with that if you are consistently 0towing long

 distances at highway speeds. 

 

 Noel

 

 --

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Wed Jan 07, 2009 2:27 pm Post subject: Trailering a Kitfox

My trailer is a similar idea except it has a platform around 8'X10'.  That

makes my trailer higher and wider.  The double snowmobile trailer is

designed to carry under 1800 lb.  I extended the tow arm to take the tail of

the plane and built a stand to lift the tail.



One of the things I noticed about this unit is the weight is still on the

tail wheel when the wings are folded.  I think I'd build a small support for

the fuselage just forward of the tail spring.



Noel 



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

matronics(at)bob.brennan.
Guest

Posted: Wed Jan 07, 2009 2:34 pm Post subject: Trailering a Kitfox

Head protection...  I wouldn't have guessed!



Do not archive

bob



--

matronics(at)bob.brennan.
Guest

Posted: Wed Jan 07, 2009 2:48 pm Post subject: Trailering a Kitfox

I don't know if your model has it but my model 2 has a tube for the tow bar

right where you are thinking of adding support - already designed to take

the weight.



bob 



--

kirkhull(at)kc.rr.com
Guest

Posted: Wed Jan 07, 2009 4:03 pm Post subject: Trailering a Kitfox

I could be wrong but other aircraft has the grove gear which is taller then

the stock gear which may be adding to the 5 to 10 deg down



--

earnestj0

Joined: 04 Jan 2009
Posts: 13
Location: McCall, Idaho

Posted: Thu Jan 08, 2009 8:21 am Post subject: Re: Trailering a Kitfox

Hi All,  Good discussion of trailering.  I modified a boat trailer also to tow my Vixen.  I live about 2 miles from the airport and keep the plane mostly in my garage.  I also have towed it from California and to North Idaho several times at 60-65 mpg with no problems at all.  It is of course braced with the towing kit from Kitfox and is supported just in front of the makeshift tail wheel (homemade) at the tube going into the fuse.  I can get the fox off and on the trailer by myself and ready to fly in about 30 minutes.   The wings are at about a 10-15 degree angle, but I do tow with a pickup with a cap, so not much wind hits the wing tips.  Sorry I don't have any pictures at this time, but will post some later (Plane trapped in a hangar with snow presently).  Thanks for all the good discussions. 

Ted

n85ae

Joined: 14 Mar 2007
Posts: 403

Posted: Fri Jan 09, 2009 9:00 am Post subject: Re: Trailering a Kitfox

 	  Quote: 	
		  Way back when -- Skystar was queried at either Osh or at the flyinn? about trailering an possible damage to the plane. At that time Skystar was using an enclosed locally built trailer. They had instrumented the trailer & plane and the result were acceleration spikes that exceeded the calculated plane design limits. The conclusion was that any trailer must be designed with a very soft ride and driven at a very slow speed. They left it up to the builder to go from there. Paul 	




This is completely flawed, because these momentary spikes mean nothing. 

They completely lacked the engineering brainpower to realize that load is

related to force over time. A 10-20G spike because you hit a speed bump

on the road, is not like a 10-20 G sustained load. 



This is just somebody looking at the G-meter after towing their plane

and seeing it pegged, and thinking WOW, it pulled 30G's on the trailer!



If this were such a problem, I'd be more worried about breaking the

trailer than the plane, honestly.



You can trailer a kitfox on any kind of trailer, and if you built the plane

well, and properly brace the wings you'll have absolutely no problems.



Regards,

Jeff

matronics(at)bob.brennan.
Guest

Posted: Fri Jan 09, 2009 9:26 am Post subject: Trailering a Kitfox

Sorry Jeff - large momentary spikes cause metal fatigue, not sustained

loads. Metal airframes have a TBF (Time Between Failures) based on flexing

due to spikes, not sustained loads. All metals can only flex a certain

number of times before breaking. And yes, I are a engineer... 



Bob Brennan - N717GB

ELSA Repairman, inspection rated

1991 UK Model 2 ELSA Kitfox

Rotax 582 with 3 blade prop

Wrightsville Pa  



--

rexinator(at)gmail.com
Guest

Posted: Fri Jan 09, 2009 9:53 am Post subject: Trailering a Kitfox

This is an interesting exchange. One post claiming the (ex)manufacturer 

determined you should be concerned about shock loads while trailering 

and another states they lacked the engineering acumen to puzzle through 

such a basic problem.

 Oh where can the truth be?

Rex Hefferan

SE Colorado, Model 2, 582-C

n85ae wrote:

 	  Quote: 	

> Way back when -- Skystar was queried at either Osh or at the flyinn? about trailering an possible damage to the plane. At that time Skystar was using an enclosed locally built trailer. They had instrumented the trailer & plane and the result were acceleration spikes that exceeded the calculated plane design limits. The conclusion was that any trailer must be designed with a very soft ride and driven at a very slow speed. They left it up to the builder to go from there. Paul

>     

 This is completely flawed, because these momentary spikes mean nothing. 

 They completely lacked the engineering brainpower to realize that load is

 related to force over time. A 10-20G spike because you hit a speed bump

 on the road, is not like a 10-20 G sustained load. 

 This is just somebody looking at the G-meter after towing their plane

 and seeing it pegged, and thinking WOW, it pulled 30G's on the trailer!

 If this were such a problem, I'd be more worried about breaking the

 trailer than the plane, honestly.

 You can trailer a kitfox on any kind of trailer, and if you built the plane

 well, and properly brace the wings you'll have absolutely no problems.

 Regards,

 Jeff

akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Fri Jan 09, 2009 12:16 pm Post subject: Re: Trailering a Kitfox

 	  matronics(at)bob.brennan. wrote: 	
		  Sorry Jeff - large momentary spikes cause metal fatigue, not sustained

loads. Metal airframes have a TBF (Time Between Failures) based on flexing

due to spikes, not sustained loads. All metals can only flex a certain

number of times before breaking. And yes, I are a engineer... 



Bob Brennan - N717GB

ELSA Repairman, inspection rated

1991 UK Model 2 ELSA Kitfox

Rotax 582 with 3 blade prop

Wrightsville Pa  



-- 	


well the bold part certainly explains alot lol.



On the rest, if momentary loads mean nothing then why do wings fold up in severe turbulence or sudden high G maneuvers?

_________________
DO NOT ARCHIVE
Leonard Perry aka SNAKE
Soldotna AK
Avid "C" / Mk IV
582 (147 hrs and counting on the rebuild)
IVO IFA
Full Lotus 1450
#1 snake oil salesman since 1-22-2009

I would rather die trying to live, than to live trying not to die....

n85ae

Joined: 14 Mar 2007
Posts: 403

Posted: Fri Jan 09, 2009 12:25 pm Post subject: Re: Trailering a Kitfox

 	  Quote: 	
		  Sorry Jeff - large momentary spikes cause metal fatigue, not sustained

loads. Metal airframes have a TBF (Time Between Failures) based on flexing

due to spikes, not sustained loads. All metals can only flex a certain

number of times before breaking. And yes, I are a engineer... Wink

	




Uh-huh or hogwash? which reply, and to what subject?



I don't agree. Find me the MTBF number of a Kitfox airframe,  and I'll

be happy to bow every time you walk by  In fact if you can find ANY real

engineering numbers from Skystar not only will I bow, but I'll do it

in amazement.



Cheerfully,

Jeff

matronics(at)bob.brennan.
Guest

Posted: Fri Jan 09, 2009 12:53 pm Post subject: Trailering a Kitfox

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 12:59 pm Post subject: Trailering a Kitfox

 	  Quote: 	
		   if momentary loads mean nothing then why do wings fold up in severe

turbulence or sudden high G maneuvers?
	




All aircraft have clearly published plus and minus G forces that the design

can withstand under varying maneuvers, if you exceed the forces - bad things

happen. But as pilots we knew that already and I assume this statement was

directed at the original poster not me, with tongue firmly in cheek?

Possibly even butt-cheek? 



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 1:15 pm Post subject: Re: Trailering a Kitfox

It is still force over time that breaks your wings off, and makes the

fillings fall out of your teeth on a bumpy road. It's just a matter of how

much force, and how much time.



30G at .01 second, does not equal 30G at .1 second, and that's 

yet again not the same as 30G at 1 second.  



Jeff

n85ae

Joined: 14 Mar 2007
Posts: 403

Posted: Fri Jan 09, 2009 1:37 pm Post subject: Re: Trailering a Kitfox

By the way, here's one of the trailers I made. The center rail is

designed to elevate at the front to adjust aircraft attitude on the trailer.

And there is a swing open bar at the back,



Regards,

Jeff

trailer.jpg

Description:

Filesize:

272.89 KB

Viewed:

554 Time(s)

pwmac(at)sisna.com
Guest

Posted: Fri Jan 09, 2009 1:43 pm Post subject: Trailering a Kitfox

Jeff is correct.

It is true that the area under the G vs time curve is significant. 

And it is true that several short duration spikes have little 

significance to a space frame structure like our planes. When 

trailering it is logical that more than several spikes would be 

present and definitely cause harm due to the normal fatigue life of 

the metal and welds.



Trailering is a high risk activity and should be minimized. Ie short 

trips at low speeds.



Anyway don't miss the point of my post which says make sure you have 

a soft riding trailer.

Wings off will eliminate the spar/pass thru problems and certainly 

minimize the fuge loads. A soft play ball under the rear of the fuge 

would be a good addition to any setup so as to keep any vibration 

loads from the tail wheel attach and the unsupported fuge.



Soft tires would be a good help.

Paul

n85ae

Joined: 14 Mar 2007
Posts: 403

Posted: Fri Jan 09, 2009 2:00 pm Post subject: Re: Trailering a Kitfox

Actually something to consider is your tiedowns. If you make your tires 

really spongy, etc. Odds are good your planes gonna get damaged by 

banging against the tiedowns. It's better to tie it down as tight as possible,

and let the trailer suspension absorb the shock. The plane should be tight

and the trailer suspension soft. That's the best way to do it.



Jeff

matronics(at)bob.brennan.
Guest

Posted: Fri Jan 09, 2009 2:18 pm Post subject: Trailering a Kitfox

Of course the amount of time a force is applied makes a difference - but

only as regards the mass and inertia of the object being acted upon. We're

talking about fairly massive structures here (the wings) and they of course

will not respond to millisecond forces. We're talking about bumps in the

road and gusts of wind as the damaging forces. But don't forget also we are

talking about forces on a pivot point where the forces are acting along a

moment of the length of the wing. I assume you know how to do a

weight&balance using moments? 



Now fly an airplane where the critical support structures that hold the

wings on have been weakened by metal fatigue from repeated forces too small

to break the structure, you do know what metal fatigue is? The wings *will*

fall off at a much lower G stress than their rating if not damaged. You

*will* fall out of the sky due to accumulated "momentary spikes" that you

said "mean nothing".



The solution, as I see it, thanks to posters on this list, is to eliminate

the moment multiplier of the force by not allowing the strut connect points

to be pivot points = support the wings.



Bob Brennan - N717GB

ELSA Repairman, inspection rated

1991 UK Model 2 ELSA Kitfox

Rotax 582 with 3 blade prop

Wrightsville Pa 



--

akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Fri Jan 09, 2009 2:32 pm Post subject: Re: Trailering a Kitfox

 	  matronics(at)bob.brennan. wrote: 	
		   	  Quote: 	
		   if momentary loads mean nothing then why do wings fold up in severe

turbulence or sudden high G maneuvers?

	




All aircraft have clearly published plus and minus G forces that the design

can withstand under varying maneuvers, if you exceed the forces - bad things

happen. But as pilots we knew that already and I assume this statement was

directed at the original poster not me, with tongue firmly in cheek?

Possibly even butt-cheek? 



Bob Brennan - N717GB

ELSA Repairman, inspection rated

1991 UK Model 2 ELSA Kitfox

Rotax 582 with 3 blade prop

Wrightsville Pa 



-- 	




yes Einstein, it was directed at others...

Display posts from previous:

	Matronics Email Lists Forum Index -> Kitfox-List	All times are GMT - 8 Hours Goto page Previous 1, 2, 3, 4, 5 Next
Page 4 of 5

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum