Sew a 20L Simple Roll Top Backpack Base With a Pocket for Frame, Can Make a Climbing, Weatherproof, Hiking, City Bag, or a Combo of These. (climbing Mod Shown)

Here is the pack shown with the climbing set up.

This is a generally simple build made entirely of simple straight stitches and designed to be sewn on a home sewing machine (with maybe a tiny bit of hand cranking of the machine at a point or two), it takes between 4 and 7 hours and would be a great starter project for learning to sew.

It does not require a large investment of funds, coming in at just $23 (at quest outfitters) for materials (minus thread and found materials).

I am recommending quest outfitters as they have a good selection, are reasonably priced on both materials and shipping, have the foam that works well for the shoulder straps (my home machine can bartack through it easily) and med and lt webbing that is sturdy and solid but my home machine has no problem going through. They also have a good heavy duty thread (though I would recommend getting a large cone of it elsewhere, to have in general, as small spools are cost restrictive, and this project prob takes two)

Modding:

You can add or subtract any elements of this to customize as you wish, ex: if you want just a simple roll top, you would remove all the loops and the gear ladder on the face. or you could subtract the side straps and instead opt for a rope strap on the top to keep the top closed (if so, use a locking slide release like the ski one on quest)

Weatherproofing beyond the natural water resistance of the coated DWR materials:

If you want to weatherproof it (codura is pretty water resistant as is, I have had a non-lined codura roll top bag with top stitching and more exposed seams not leak, even at the seams, in a downpour), you would get a half yard of lighter material (silinylon is the most waterproof, but 2.2oz ripstop, oxford, or anything under 4oz works well, with the heavier being more durable and options allowing you to pick from the fabric remnants) line the bag after doing all the face stitching but before ribbon binding the top and sewing the main body seams. This mod will cover the front and back and put the only potential leak points at the bottom and on the sides, which are largely covered by the sides of the roll top in a water coming from the top down situation, even in a hunched over situation, the seams are not on the direct path of water. This is as much as I have seen other weatherproof bags do.

If you are concerned about it being water resistant for long periods of constant and pervasive wetness, you could use silinylon and the reminder of the silinylon as binding ribbon (cut strips that are 1-1/2" wide) for the body seams.

For even more water resistance, you may be able to glue the silinylon binding on, after double stitching the seam, with silicone seam sealent, like a dribag (findable at quest), though I just read you can laminate silinylon together with GE Silicone II, (I would do a test for either method on scrap first) which if it grabbed quickly and requred no or minimal binder clipping/clamping, would be faster and easier than sewing, though I may sew the bottom 1/2" of the silinylon binding on the side and then sew the full bottom seam, and then laminate the binding on both the bottom and side in place just so you are not sewing through the lamanated seam. You could also sew the silinylon binding on and then paint silicone seam sealent on all the stitching after sewing (gluing the overlapping edge to the first body stitch on both sides and painting it over the binding ribbon stitch on both sides). At this point, provided the sealent bonds as it says it does, it should not leak unless submerged.

If you are interested in making a heat sealable dribag insert that would fit inside the main bag and attaches to the top edge of the finished (velcro), or almost finished bag (potentially sewing into the top ribbon binding and top 2"or 3" of the bag seam), please post the industructable!

Construction:

All seams have a tolerance of 1/2" and I would recommend sewing each seam with 8-10 stitches twice (one at 1/2"and the 2nd at 3/8" to sew on the binding ribbon ) with a heavy duty thread (guterman heavy duty works well, as does tex 105 polyester or bonded nylon tex 45, it should be very hard to snap. Using a binding attachment for the 1" ribbon is very helpful. though you can fold firm grosgrain ribbon between your fingers and it will hold a crease allowing you to sew it on evenly.

Material list for climbing mod:

1/2 a yard of something you would use as the bottom of a bag and is 59-60" wide (if you used 58" wide you may have to move the shoulder straps downward), like 1000D cordura or if wanted to go lighter, maybe 840D ballistics or 500D cordura, but I highly recommend 1000D cordura as this is a single layer bottom.

1" med wt web:
-roll top straps: 18"
-top of shoulder straps 20"
-bottom of shoulder straps 24"
-sturnum straps 18"
-face/bottom ladder 24"
-hip belt 40"
-carry loop 8"

1"lt webbing, 1yd for gear loops and the roll top slide release buckle loops

1"grosgrain webbing, 3 yards for binding seams.

2' of polyethylene (or other hard tubing) tubing with an id of 5/16's ish to pull the lt webbing through for both the the top and bottom gear loops.

a 2" by 29" by 3/8 or 1/4" peice of stiff-ish foam for shoulder straps.

total for the climbing mod is:
-1/2" peice of chosen fabric (I used 1000D cordura)
-8 yards (may have some to play with left over) of 1" medium wt webbing.
-1 yard of 1" lt webbing
-3 yards of 1" grograin (I like stiff)
-2 - 1" heavy duty ladder locs
-2 - 1" pass through sturnum strap adjusters.
-2 - 1" slide release buckles
-2 - 1" duel ajust slide release buckles
-A 2" or 3" (depending on desired shoulder strap width) wide by 29" long peice of 1/4 or 3/8th stiff-ish foam

You could look in the fabric remnants section for a lining material at a lower cost if weatherproofing is a thing of interest.

Found materials:

-Two scrap peices of material for the human facing part of the shoulder straps that are between 18"x 3" and 18"x 4" (if stretches up to 3/4", maybe a heavy duty t shirt or knit) or 18"x 3-3/4" and 18"x 4-3/4" (if stiffer). The width of the peice is dependent on the finished width of your shoulder strap, widest being for a 3" wide shoulder strap (see top of step one for details,
you could look in the fabric reminants section of the site)
-2 - 1"x16" strips of thin-ish hdpe plastic, such as you can cut from a bleach bottle, milk jugs are also hdpe, but don't cut into as good strips as round body bottles (says on the plastic type on the bottom of the bottle, next to or within the recycling symbol)
-A peice of something rigid but flexible to serve as a frame that is aprox 17" by 4.5", I used corrugated plastic. You can also use a bent metal rod (like 1/8" aluminium) that overlaps at the bottom and is shoved into the remainder of the rigid tubing.
2' or rigid tubing with at least a .233 Id, I used polyethylene tubing with a .233 id and a 5/16" od.

Pick your shoulder strap width:

2" wide base is the best for mobility, though not the best for load carrying. It will save you a very small amount of money (55 cents at quest) and will fit a smaller peice of scrap. it is also the simplest to pattern on with a fabric with enough stretch to compensate for the thickness of the foam.

2-1/2" is around optimal if you want to keep mobility when reaching above your head, though I have seem many a good large capacity climbing pack with a 2-3/4" wide shoulder strap.

3" is a bit wide for a smaller bag, but is much better at breaking the load across your shoulders.

Cut out the pattern:

The pattern cloth pattern is basicly 5 peices, 2 of them off cuts.

First you cut two strips vertically from one end of the fabric and notch out the ends (as shown).

Then fold the fabric in half and mark center, cut two squares out that are centered on the midpoint(as shown), save for frame pockets. When laying out the shoulder strap point on the back, make sure to keep the top portion around 5-1/2" to 6" from the top of the webbing to the top edge of the roll top so the bag has room to close properly on top. If it is shorter, it would be best to just move the webbing down and shorten the back portion.

Then cut out the human facing part of the shoulder straps out of something soft and flexable but durable, (thick knit like a t shirt) will work cut to the same width that as the base of the shoulder strap (you can lay the shoulder strap cut from the body material right on top of the knit and match it), if it has some give (needs to stretch aprox 3/4"), or you can take something more rigid and add a half an inch to 3/4", depending on how tight you want the foam, at the base but start the taper at the same point and taper it to the same width at the end when you notch it (may have to play with the taper on the foam when you stuff it). Same logic applies to if you want a wider shoulder strap base, the starting point on the taper and the width on the end of the strap stay the same, but you will have to add whatever the additional foam width is.

Example for a 3" wide foam base cut from 3/8" thick foam: 3" for the width of the facing away from human part of the strap cloth (2" is the orignal strap width + 1/2"seam on either side) + 5/8" for the depth of the 3/8" thick foam on both sides (choosing the middle between 1/2" and 3/4" for some foam compression as this gives it a nice and tight look, this would not be added for stretchy material that stretched aprox 5/8" to 3/4") + 1" for the new width of the foam shoulder strap base = a 4-5/8" wide base for the human facing fabric on the shoulder strap. This also stays consistent for the foam cut out, the notch would start at 4-3/4" and be 1-1/2" wide at the end no matter the width of strap base you choose.

Cut out the foam.

Cut up a plastic container that is hdpe (should say on the bottom in the recycling part, Iots of industrial bottles fit this, Clorox bleach being one), to get two strips that are 16" long by 1" wide, you should be able to get it out of the round part in the center.

test to make sure your sewing machine can go through it, my home machine goes through it easily.

Layout the pattern:

Sketch should work, if it is missing something, let me know and I will try and fix it.

Webbing note, All cut webbing and synthetics that are uncoated need to have the cut ends singed and sealed with heat (use ventilation, fumes are bad!)

First you want to take the two peices of 20" long med wt webbing and mark an inch off the end of them after cutting and burning the ends.

line the bottom end (part that gets the ladder loc) of the shoulder strap you layed out (the part made from the material the bottom is also made from) up with the 1" line on the webbing, make sure the webbing lands on the center of the bar tack point you layed out previously, and sew it down on the edge.

Now lay the scrap you cut for the human facing side of the shoulder straps on top of the webbing, which should be on top of the top side of the material (uncoated side), and sew it 3/4 of the way around, leaving the backside open to stuff the foam in after you turn it right side out, stitch back and fouth at the ends so the stitching doesn't pull out when stuffing foam. If your going with a 3" base or even adding for a less stretchy material, you may have to clean up the edges a little between the human facing material and the body material, make, this is normal, try and only cut the human facing material. You can also clip the excess material in corners (without cutting into the finished seam) on the bottom of the strap next to where you are going to put the buckle to make for a cleaner bottom corner and to make for easier turning.

Turn them right side out by starting the end with your finger or a wooden ruler and then slowly pull on the webbing to finish the turn, then put the buckle on, pull buckle tight to shoulder strap material and bartack (either sew back and fourth 5 times with a 5mm long stitch or zig zag over it with a tight/button hole stitch) twice, once as close as you can to the buckle and then around 1/4" away from the first, making sure to hit the webbing tail that is inside the shoulder strap material with both.

Stuff with foam (it helps to use baby powder to get it in with less friction) till foam is about 1-1/4" from the open end, slide the sternum adjuster on and bartack at the bartack point at the top of the strap, edge stitch the end of the strap togeather and cut off and sear excess webbing.

Wrap the webbing around the strap and through the sturnum strap ajuster, sew together and fold over end of strap so it does not come out of buckle.

Now you are just going to sew everything you layed out (including the roll top closure straps on the sides, noted in the 2nd picture), starting with the frame pockets, which you are sewing the bottom seam then turning and top stitching an 1/8th inch from the edge, after turning three sides, though you can ribbon bind the open edge (you may need another yard of grosgrain to do that) if you prefer. The bottom frame pocket gets special treatment as you want to leave a gap across to allow for a 1" or 1-1/2" webbing belt to slide through and behind the frame (last picture, the vertical stitching that runs upwards is not actually through the body of the bag, it just holds the fold on the cloth)

When sewing in the lower shoulder strap anchors, I tacked them upwards into the material as well as along the seam, forming an L shape, you could close the L and just make a triangle.

When pulling the lt web through the plastic tubing, you can use a cut up coat hanger with a tight hook bent over on one end and the point sharpened, kind of like a really small fish hook. the lt webbing lengths are aprox 9"-9.5" for the lower gear loops and 6" to 6.5" for the uppers. You want to pull the webbing through and then leave about an 1.5" on either end of the tube.

When sewing on the shoulder straps, carry loop and whatever else is under the webbing, line it up so about 7/8" is between the webbing layout lines and bartack it roughly center with it leaning closer to where it is coming out from under the webbing, bartack it again on top of the webbing on the edge where it is coming out from under the webbing, which you should sew on aprox 1/8" from the edge on both sides.

Sew the plastic in and ribbon bind last, if you are adding a silinylon or 2.2oz ripstop liner, try and sew it the plastic on the non-edge side first then sew the liner in catching the edge side of the plastic and liner in one shot.

add the two clip points for the roll top leaving enough room to sew past the buckle, this is not shown.

Also, I added in a lt webbing loop between the carry loop to lash rope down between the ladder and the back.

Sew and ribbon bind the side seams, bartack any loops or straps you have in them, then even up the bottom of the sides, pinch the bottom so the seam lines up cleanly all the way from corner to corner and sew closed.

This is the step where you would laminate the silinylon over the stitching (more info in intro), to do the test swatch, I took GE silcone 2 and put a thick enough layer to make up the gaps in the stitching on the strip of cut silinylon and just folded it over and stuck it on, pressing it on well enough to stick it but not so hard that you squeeze the silcone out of the sides too much, though you want it to come out enough that it seals the edge of the binding so it can't get stuff under the lip and lift it off.

The picture is before the bottom seams are sewn. The bottom seams almost close themselves.

I like corrugated plastic a large amount. it is sort of like a frame sheet but is also sort of padded. You can also slide bars into the corrigan, which I did with bailing (though wire hangers probably would work better) wire to allow it to be shaped but still flex, I bent the bailing wire into three with all the ends folded over so it does not damage the material. You also may want to tape around the edge of the frame or finish it with something to reduce abrasion.

The hip belt is just a 40" long peice of 1" webbing with both ends folded and sewn over it, it slides in behind the frame in the gap you left in the stitching on the lower frame pocket.