Chair tramp

Discussion about making bushwalking-related equipment.

Chair tramp

Postby bernieq » Thu 08 Jul, 2021 9:57 pm

During a recent trip into the Wyperfeld NP (lots of sand) with my Helinox chair zero, I very much had that sinking feeling.

So, had a look at the commercial solution(s) - Helinox have a chair 'ground-sheet' (I think trampoline (tramp) is a better name) but it weighs 150g so thought I'd try a diy solution.
20210708_210506.jpg
finished product

I've used some leftover tyvek. Simple construction - rectangular piece with 4 corner triangular gussets.

I cut the rectangle and ironed (very cool iron) a hem on all sides. Then cut 4 squares for the gussets. Fold each square diagonally in half (to make a double layer triangle). Not sure if necessary but I did sew a reinforcing rectangle to the top of each triangle (folded over the top edge and sewn to the triangle - making 4 layers).

Slip a triangle under the hem of a corner then sew in place. Continue sewing along the hem to near the next corner and slip the next triangle in. Continue to sew around the rectangle until all triangles are sewn in. Then sew around the rectangle a second time for reinforcement.
20210708_210703.jpg
Tramp attached to chair

The only tricky bit is getting the dimensions correct - too big and the tramp will fall off. Too small and you can't get the tramp on all 4 legs. I was successful on the second try (the 1st was too short in length so I cut it in half and sewed a length of webbing in between - it now fits but weighs 14g :)

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Re: Chair tramp

Postby Petew » Thu 08 Jul, 2021 10:13 pm

Awesome! Been thinking about making one of these myself.
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Re: Chair tramp

Postby telemarktim » Sat 10 Jul, 2021 9:41 am

bernieq wrote:During a recent trip into the Wyperfeld NP (lots of sand) with my Helinox chair zero, I very much had that sinking feeling.

So, had a look at the commercial solution(s) - Helinox have a chair 'ground-sheet' (I think trampoline (tramp) is a better name) but it weighs 150g so thought I'd try a diy solution.
20210708_210506.jpg

I've used some leftover tyvek. Simple construction - rectangular piece with 4 corner triangular gussets.

I cut the rectangle and ironed (very cool iron) a hem on all sides. Then cut 4 squares for the gussets. Fold each square diagonally in half (to make a double layer triangle). Not sure if necessary but I did sew a reinforcing rectangle to the top of each triangle (folded over the top edge and sewn to the triangle - making 4 layers).

Slip a triangle under the hem of a corner then sew in place. Continue sewing along the hem to near the next corner and slip the next triangle in. Continue to sew around the rectangle until all triangles are sewn in. Then sew around the rectangle a second time for reinforcement.
20210708_210703.jpg

The only tricky bit is getting the dimensions correct - too big and the tramp will fall off. Too small and you can't get the tramp on all 4 legs. I was successful on the second try (the 1st was too short in length so I cut it in half and sewed a length of webbing in between - it now fits but weighs 14g :)


Bernieq, What a great idea. I get a similar problem with my three stick seat in the snow. i think your trick might just work. Thanks, Tim
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Re: Chair tramp

Postby keithy » Mon 12 Jul, 2021 7:49 pm

bernieq that is some stellar work!

I also made something similar for my Aldi folding chair picked up back in 2015. But mine did not look as nice as yours.

I can't find the bits I used now, but instead of making the square like you did, I used two strips of Tyvek 1443r each going diagonally on the chair legs. I have misplaced my creation, but this quick sketch (not to scale) sort of shows what I did:
tyvek chair leg sand holder.JPG
tyvek chair leg sand holder.JPG (16.26 KiB) Viewed 2237 times

The folds at the top of the splay were to reinforce the top part where it formed the pouch for the legs. I didn't sew mine, just used glue at the ends with the dotted lines, and wrapped the ends with gorilla tape when it was done.

Initially I thought of joining the two lengths together in the middle to form an "X" but I didn't end up doing that and had two separate lengths.

How did you find the "stretch" of the Tyvek 1443r? The first one I made was a little on the long side (measured before accounting for the material stretch). The second one was a bit shorter and fit better.

After I misplaced mine (admittedly when folded it looks like used tape/rubbish) I had meant to make another set but never got around to it. As an interim until I make a new set, I've been using 4 plastic peanut butter jar lids to use in sand instead - weighs about 35g.
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Re: Chair tramp

Postby bernieq » Mon 12 Jul, 2021 9:45 pm

Keithy, I thought about a couple of strips but figured they would not be as supportive as a complete rectangle. As I estimated the weight saving would be 6g at the most, it didn't seem worth it.

No stretch to speak of in the tyvek which is why the dimensions are the critical bit - it doubles as a drum! :wink:

Once the dimensions are sorted, the sewing is pretty simple. It will have a thorough testing later this week.

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Re: Chair tramp

Postby bernieq » Tue 20 Jul, 2021 3:02 pm

Update: Fail!
After an hour or so on a sandy base, one leg poked a hole through the tyvek pocket - then a second leg poke :(

At least it felt very secure up to that point so the concept works - tyvek is quite strong under lateral tension but not so good it the force is perpendicular to the material.

So I have reinforced the corners with some rubber-backed curtain material. Weight now 20g
IMG_20072021_145142.jpg
IMG_20072021_145142.jpg (75.66 KiB) Viewed 1962 times

Given the extended covid restrictions, field testing will be delayed.

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Re: Chair tramp

Postby Moondog55 » Tue 20 Jul, 2021 3:19 pm

No backyard to play in?
Yes point pressure usually does need some sort of reinforcing, and I don't think you had a total fail, just testing to destruction being part of the experimentation.
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Re: Chair tramp

Postby bernieq » Tue 20 Jul, 2021 3:43 pm

Local area not sufficiently soft for decent testing and previous experience suggests extended sitting is required.

Still, it looks and feels pretty secure.

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