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What is the best point to jack up a Cobra Trailer ?



 
 
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  #1  
Old November 7th 18, 05:36 PM posted to rec.aviation.soaring
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Default What is the best point to jack up a Cobra Trailer ?

I changed a wheel in my Cobra trailer with the glider inside. I located the Jack just under the corner between the bottom and side wall, next to the fender.
Looked flimsy, but held fine, no bending of wall or edge.
Was I lucky or is this the right place to do it ?
Dan
  #2  
Old November 7th 18, 06:13 PM posted to rec.aviation.soaring
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Default What is the best point to jack up a Cobra Trailer ?

Terrible point to jack from. Puts stress on the floor, sidewall and suspension. Jack should always be placed under the axle itself. Plus you don't have to lift more than a few inches to get the tire off the ground. Jacking up the "box" requires you to lift it high enough for the suspension to extend fully. Don't do it again!
  #3  
Old November 7th 18, 06:42 PM posted to rec.aviation.soaring
Bob Kuykendall
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Default What is the best point to jack up a Cobra Trailer ?

On Wednesday, November 7, 2018 at 9:13:20 AM UTC-8, wrote:
...Jack should always be placed under the axle itself...


The typical Cobra has a trailing-arm suspension that doesn't really have an "axle" to put a jack under, not like a car at least. The next best thing is the steel crossmember that contains the torsion springs. But even then, you have to raise it enough to extend the suspension.

--Bob K.

  #4  
Old November 7th 18, 07:56 PM posted to rec.aviation.soaring
Steve Leonard[_2_]
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Default What is the best point to jack up a Cobra Trailer ?

On Wednesday, November 7, 2018 at 10:36:19 AM UTC-6, wrote:
I changed a wheel in my Cobra trailer with the glider inside. I located the Jack just under the corner between the bottom and side wall, next to the fender.
Looked flimsy, but held fine, no bending of wall or edge.
Was I lucky or is this the right place to do it ?
Dan


You did fine. On the cross member, as Bob K suggests, can end up as an awkward lift if the tongue weight is low. That point could actually be ahead of the CG, so being tied down at the front becomes important. If the side extrusion wasn't stressed for handling the axle loads, the axle wouldn't be secured to it. And you know where the axle is attached. Just don't slip over onto the floor board section, as that is pretty thin aluminum on foam, and it will compress and fail if you put a jack on it to pick up one side of the trailer. Best stick close to the outside edge of that "corner", as the tabs that the floor sticks into are about an inch and a half or so long.. And you don't want to lift by them. You want to push straight up into the sidewall. Just like the axle attach does.

Steve Leonard
  #5  
Old November 7th 18, 09:08 PM posted to rec.aviation.soaring
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Default What is the best point to jack up a Cobra Trailer ?

After reading Steve's response, I have to say that he is right and I was wrong. However, I do suggest that the jack should be placed under one of the crossmembers behind the fender, as Cobra often has the axle positioned slightly forward of the actual mid-point of the trailer box. On my (old) Cobra, the position is quite a bit forward of the middle. If there are no crossmembers on the newer Cobra models, I would suggest using a 12 inch 2x4 between the jack and the trailer body to spread the load somewhat. And don't forget to loosen the lug nuts before jacking the wheel off the ground.

  #6  
Old November 8th 18, 12:20 AM posted to rec.aviation.soaring
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Default What is the best point to jack up a Cobra Trailer ?

Good stuff.

Off topic slightly, my old Komet trailer--steel tubing with aluminum skin and wood floor--had a doubler tube welded in alongside the lower longeron where the axle attached on each side. That weld between the doubler and the longeron eventually failed, allowing the axle mount on that side to push up, bulging the wood floor enough that the wing dolly wheel wobbled each time we brought out the wing. We initially thought it was just the wood floor warping after some years but discovered by crawling under the trailer and inspecting that the damage was more severe. Straightforward to fix: remove glider plus portions of the sidewall skin and floor, then drive it over to a welding shop to add reinforcement.

My Cobra has extruded side panels and an aluminum/foam floor. IIRC, the axle attaches via a short section of angle that acts as a doubler. Depending on the clearance, I've used a jack under that doubler and also under the pivot of the axle swing arm itself. I, too, use a short length of 2x4 to spread out the load if I'm jacking directly under the side panel where there's no crossmember.

It's important to note that if the trailer tongue is not fixed to the ball of the tow vehicle, jacking up one wheel can make the whole trailer somewhat unstable, even more so if the front dolly wheel--which is supporting the tongue--is partially extended and can swivel/roll. That's especially true if you're working on the brakes and therefore don't have the parking/emergency brake engaged. This is all hypothetical, of course; I've never had any close encounters with disaster.

Chip Bearden
  #7  
Old November 9th 18, 06:09 PM posted to rec.aviation.soaring
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Default What is the best point to jack up a Cobra Trailer ?

Am Mittwoch, 7. November 2018 17:36:19 UTC+1 schrieb :
I changed a wheel in my Cobra trailer with the glider inside. I located the Jack just under the corner between the bottom and side wall, next to the fender.
Looked flimsy, but held fine, no bending of wall or edge.
Was I lucky or is this the right place to do it ?
Dan


You should try this:

https://www.cobratrailer.com/catalog...97er1u9l1gedv2

That´s the perfect solution.

Regards
Bernd
  #8  
Old November 9th 18, 07:48 PM posted to rec.aviation.soaring
Nick Kennedy[_3_]
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Default What is the best point to jack up a Cobra Trailer ?

I think you should do a practice run on your trailer, changing the wheel, at home before heading out on the open road. On the side of the interstate, with traffic whizzing by a 80 mph is no place to find out your jack doesn't work and your lug wrench is the wrong size.
Or your spare doesn't fit anymore due to a axle change.
  #9  
Old November 9th 18, 08:22 PM posted to rec.aviation.soaring
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Default What is the best point to jack up a Cobra Trailer ?

On Friday, November 9, 2018 at 1:48:12 PM UTC-5, Nick Kennedy wrote:
I think you should do a practice run on your trailer, changing the wheel, at home before heading out on the open road. On the side of the interstate, with traffic whizzing by a 80 mph is no place to find out your jack doesn't work and your lug wrench is the wrong size.
Or your spare doesn't fit anymore due to a axle change.


Good advice. And remember that a jack that slips neatly under the trailer when the wheel is on the hub may not fit at all if the tire is flat or essentially missing (experience with both).

Chip Bearden
  #10  
Old November 9th 18, 08:49 PM posted to rec.aviation.soaring
Tim Taylor
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Default What is the best point to jack up a Cobra Trailer ?

I added stabilization jacks on my trailer about at 3/4 of the length. The advantage is that they can be used to lift a wheel off the ground to change the tire. No need for a different jack.
 




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