How To Find Gusset Length On Bag.

[DavidL]

I read through a few general leather working books and haven't come across any instructions on how to find the gusset length on bags with emphasized rounded corners. Most bags don't have too much of a rounded corners, on some bags the corners round off more and cause the gusset to become longer. Both the curve of the corner and thickness of the leather make it difficult to find out the correct length of the gusset for a proper fit.

The way I find works is to figure out the length and height of the bag first. In a 90 degree corner bag with a gusset, you would calculate the gusset by length + double the height. With the emphasized curved gusset bag the length would be a little bit shorter.

In a square corner bag with height of 20 cm and length of 30 cm the gusset will be

Length + Height + Height = 70cm gusset length. Give or take a few mm for thicker leather

A corner radius of 5 cm diameter for the curved corner bag with the same dimensions height 20cm, length 30cm. To find the length of the gusset:

Length - double the diameter of the corner radius + height + height + (diameter X 3.14 then divided the total by 2) = length of gusset.

30cm - 10cm + 17.5cm + 17.5cm + (5 X 3.14 divided by 2) = 67.85 cm

To take it a step further to include the added length to the gusset by using 9 ounce leather:

Thickness of leather X 3.14 divided by 2

3.6mm X 3.14 divided by 2 = .6cm

If you choose to keep using the same radius curve but different lengths: 10 cm diameter:

subtract double the diameter + (3.14 X diameter divide by 2)

-10 - 10 + (3.14 X 10 divided by 2) = -4.3cm off the length

Gusset length.pdf

[whipstitchwallets]

good lord

[AndyL1]

good lord

Lol!

Seriously man... enough with the math. It's not complicated... just make it double height+width, attach and cut off the excess.

[DavidL]

I get what your saying. Its a bit complex, however I'm pretty positive a 5th grader can do it. If you do the calculations wrong the bag would be scrapped. When your dealing with something that isn't a square gusset its not as easy as length + double height. You also have to account for thickness of leather and the curve (could be 10cm diameter radius curve or 2 cm diam. radius curve, both will have different lengths)

One calculation with math then one more time by physically doing it by hand. It shouldn't take more than 30 seconds to do a calculation, for a pattern you can use as long as you like. In my opinion leather working is an all around effort of designing, pattern making and actually making the product as close to the design as possible.

[AndyL1]

I get what your saying. Its a bit complex, however I'm pretty positive a 5th grader can do it. If you do the calculations wrong the bag would be scrapped. When your dealing with something that isn't a square gusset its not as easy as length + double height. You also have to account for thickness of leather and the curve (could be 10cm diameter radius curve or 2 cm diam. radius curve, both will have different lengths)

One calculation with math then one more time by physically doing it by hand. It shouldn't take more than 30 seconds to do a calculation, for a pattern you can use as long as you like. In my opinion leather working is an all around effort of designing, pattern making and actually making the product as close to the design as possible.

Aw man... you're really over-thinking it. I make all my bags with a rounded corner as it's easier to sew up. I just do the even simpler 2nd grade math of doubling the height and adding the width, then add an inch or so for a slight bit at the end. Attach, cut off the extra, sew.

EDIT: If you really want to know the exact length you need, use a tailor's tape. This isn't rocket surgery here. ;-)

Edited October 24, 2014 by AndyL1

[Tinkerton]

I second the tailor's tape. Easy and inexpensive solution.

[billybopp]

Provided that the sides and bottom are perpendicular, the rounded portion will always be 90deg (1/4 of a circle ) hence the length around it will always be 1/4 of the circumference of said circle.

Where h = Side height

w = width of bottom

r = radius of curve

total length of the perimeter will be:

2(h-r) + (w-2r) + 2(pi*r*2*0.25) = total length

Simplified: 2(h-r) + (w-2r) + (pi*r) = total length

In your example: 2(20-2.5)+(30-2*2.5)+(3.15*2.5) = 67.85

That said, in my experience even the best measured gusset is never exactly right after cutting, dying, shrinking, stretching, stitching .. Any and all of which can cause the dimensions to change slightly. According to Murphy's law, this change will ALWAYS be on the side of too damned short rather than a little long. So just cut the thing a little longer than you need and trim it in place for best results.

Bill

[Hi Im Joe]

I think this is what you are after?

[BAD HIDE]

That said, in my experience even the best measured gusset is never exactly right after cutting, dying, shrinking, stretching, stitching .. Any and all of which can cause the dimensions to change slightly.

Bingo. A little dampness and minor adjustments can alter a messenger bag seam as much as 1/4" each direction depending on the leather you're using. If you can't use that to your advantage, all the math in the world isn't going to help you. If you know and can use that, 10th grade math is unneeded.

I make a paper prototype and take rough measurements to get the gusset length. I then make a full leather prototype carefully noting how short or long I was off, 9 times out of 10 - the prototype is fixable or close enough anyway. Keep notes, and by the 3rd bag, the length is close to perfect.

How do you fix a gusset at the wrong length?

• line up center lines and mold into place.
• If too long, either cut off the ends evenly and re-burnish, or adjust the gusset so it sits proud of the surface all around. 1/8" can net you over 1/4"at each end.
• if too short, line up the ends and cut the corners increasing the radius, or set the gusset back from the face.
• Glue into place, trim, and sew together.

Edited October 26, 2014 by BAD HIDE

[paramedic192]

On 10/21/2014 at 7:36 AM, DavidL said:

I read through a few general leather working books and haven't come across any instructions on how to find the gusset length on bags with emphasized rounded corners. Most bags don't have too much of a rounded corners, on some bags the corners round off more and cause the gusset to become longer. Both the curve of the corner and thickness of the leather make it difficult to find out the correct length of the gusset for a proper fit.

The way I find works is to figure out the length and height of the bag first. In a 90 degree corner bag with a gusset, you would calculate the gusset by length + double the height. With the emphasized curved gusset bag the length would be a little bit shorter.

In a square corner bag with height of 20 cm and length of 30 cm the gusset will be

Length + Height + Height = 70cm gusset length. Give or take a few mm for thicker leather

A corner radius of 5 cm diameter for the curved corner bag with the same dimensions height 20cm, length 30cm. To find the length of the gusset:

Length - double the diameter of the corner radius + height + height + (diameter X 3.14 then divided the total by 2) = length of gusset.

30cm - 10cm + 17.5cm + 17.5cm + (5 X 3.14 divided by 2) = 67.85 cm

To take it a step further to include the added length to the gusset by using 9 ounce leather:

Thickness of leather X 3.14 divided by 2

3.6mm X 3.14 divided by 2 = .6cm

If you choose to keep using the same radius curve but different lengths: 10 cm diameter:

subtract double the diameter + (3.14 X diameter divide by 2)

-10 - 10 + (3.14 X 10 divided by 2) = -4.3cm off the length

Gusset length.pdf

This was very helpful. I sew my pockets onto the gusset before I sew the sides and this calculation helped me get an initial length that was nearly perfect. I used the calculation, cut the piece, and then fit it to assure all was right.  Fit perfect. The method of cutting the gusset long and cutting off the extra after sewing works fine if you aren't attaching something like a pocket to each side that need to be in the same place on each side. 

 

Thanks,

 

Kyle