Padding for rucksac hip belt???

[Moondog55]

I am going to have a go at making my own replacement hip belt for the old Macpac external frame.
Blacksheep has made a very generous offer but I want to have a go.

I have heavy nylon duck and cotton duck for the carcass; I like the cotton against my skin and I tend to walk almost naked in the hot weather. I have an old Karrimat that will give me some padding but as the new hipbelt is much bigger than the old one I can't re-use the existing grey foam.
Looking for the various options on padding as the state of the art has moved and I have not kept up.

What foam is readily available and what is the best to use in peoples opinions??
Pix of the replacement parts so far

[Macca81]

I would look at using a stiffer version of CCF for the main part of the belt, to help giv it some structure, then a piece of lighter CCF for the padding right against your body... i know this doesnt help much, but i dont really know a lot about foams i just know i would use a lot of stiffer stuff and then some softer stuff against your body, and i know that CCF is light

[andrewa]

Have a look in Ray's Outdoos - I got some ?15mm foam from them years ago that was soft on one side, and harder on the other, that I think was designed for tent flooring, and came off the roll. Otherwise use contact cement to stick some softer open cell foam over a closed cell foam base, or................

........go to Kathmandu seconds shop, and they often just sell separate hip belts and shoulder straps for $5-$20. Although I've made a variety of shoulder straps and hip belts over the years, it is SOOOOOOOOOOOOOO much easier just to buy one of these, modify your pack if possible, and use them instead. May not work if trying to "replace" something, but perfect if trying to make or modify one.

A

[Moondog55]

What you say is true in many regards Andrew, but I enjoy the challenge and I have almost all the required fabric and webbing.
Also I have some idea of what is needed to make a substantial improvement for this particular frame based on my experience with an almost identical Karrimor hipbelt many years ago.
Bunnings sell a very soft foam that is used to make expansion joints in concrete, it looks and feels just like the foam that was in the existing hipbelt, I may just use that in combination with the piece of Karrimat.

[Moondog55]

I just went to Bunnings.
Interestingly they had two lots of expansion strip on the shelf, one very soft ,open foam and another with dual density and three layers; I bought a roll of the 3-layer stuff and at 100mm wide and 10mm thick it is almost exactly the right size.

At this stage I'm not sure if I need to use any additional open cell foam, I'm going to think about that for a couple of days, in the mean time I'm having a think about the shoulder harness.
I am wondering if there is any great advantage in having the straps go down the back of the frame to the horizontal bar in the middle of the frame and adding shoulder lift straps and a sternum strap

[awells]

Don't bother with open cell foam. High density closed cell foam (usually grey in colour) is fine on its own. Old ccf sleeping mats are OK but tend to compress fairly quickly when used in shoulder straps and hip belts. The best foam I've used (white and very lightweight but nice density) was purchased from Ray Jardine (Google for his website) but I don't know where he sources it from.

[Moondog55]

I had sort of come to that conclusion myself, although the old style REAL Karrimat is far superior they stopped making them, the piece you see is my last remaining bit.
If I want more cushioning I have some bonded polyester fibre that I will use.
I have a roll of 68mm stuff here which I will be using in the shoulder straps, it fits nicely in the 80mm tubular strapping ( the blue in the picture )

[clarence]

Most of the foam mats are arond the 35-40kg per cubic metre denisty (closed cell). You will probably want something around the 45 to 70kg per cubic metre density, preferably in high quality closed cell "zote" type foam. Between 8 and 10mm is probably best. Some wholesale suppliers will cut to whatever thickness you want off their blocks (which are usually 2000x1000mm), but you would have to buy a whole sheet at that thickness. Only some of them will sell direct to the public. I got a whole bundle of different densities and thicknesses years ago from a place in Syndey. I even got a 2mm sheet 2mx1m which covered my whole tent floor for snow camping.

Most foams you will find in retail outlets like clark rubber,bunnings etc will probably not be up to it. I think if you are going to spend all that time making the gear, make sure you get the good stuff to do it.

Part of the issue is support, the other is creating enough stiffeness around the entire waist area so the belt is sufficiently stiff. The 60 plus kg per cubic metre in 10mm denisty will do this provided you dont carry greater than say 20kg in the pack.

Most sleeping mats will not be sufficienlty stiff or have enough "memory". The old yellow karrimats are probably the only exception.

I personally think the dual density foam (with high density closed cell foam bonded to lighter open cell foam on the comfort side) is not required and is more of a selling point for packs in shops than a performance requirement. It adds to weight too and is hard to acheive in home-made components.

Some manufacturers use a sheet of high density polyethylene (or similar) either sewn or glued to the outer part of the closed cell foam to create the required stiffness, and this too adds other complexities to manufacture, especially depending on what sewing machine you have.

The other big issue if the way the actual webbing (ideally 38mm minimum) attaches to the front of the belt. If it is not sewn in through the foam the webbing will just pull excessively on the outer layer of the fabric and be ineffective. The design of that junction is critical to the function of the hipbelt. Webbing which goes right around the hipbelt defeats the purpose of wide padded hipbelt. That front webbing junction must spread the load from the buckle into the foam and fabric around the rest of the waist to acheive the correct effect.

The pattern of the hipbelt is better if it has some circularity in it. This means a very slight crescent shape, with the low point at the back and the high point in the front buckle. This means when the belt is closed it forms a slight "cone" around the hips therefore distributing weight more evenly.

The other option is to get something from Dave and Brett at Summit Gear in Katoomba. They do know their stuff.
If I ever can't be bothered making a pack I'll get it from Summit Gear. Their quality of manufacture and product knowledge are exceptional.

Clarence