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  1. #11
    GilligansWorld's Avatar
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    Legit I am not being silly I'm just trying to answer the question as best as I think I understand it - If you wanted a triangle that had sides that were 5 in long I suspect you would add a half inch to each side if you were looking for a half inch seam - So I tried my little experiment with a piece of paper and it seems to work as long as all of your sides are the same

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  2. #12
    Senior Member Cruiser51's Avatar
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    Quote Originally Posted by Bob-W View Post
    This doesn't make sense! Your second hem along the left side leaves the height the same, or should if you are doing the hem properly. There's some overlap at the corners that makes things a little awkward.

    Try taking out the peaks that form this overlap to form little triangles at each vertex. Hard to describe but you are taking a diamond shape out from each corner so that the desired apexes are exposed. Doing this will mean that each hem is basically a single edge so you aren't "reducing" the opposite dimension.
    I really appreciate you taking the time to think about this and respond ... however, I assure you it does make sense when you work your way through the math, the height does get affected on every hem (as well as the width) and I do know how to hem correctly. As you said it gets a tricky to both explain and figure in your head.

    Turning any hem on a triangle, will affect both the overall height and width of the remaining triangle, if this "doesn't make sense", then you need to cut out a paper triangle, measure the height and width, then fold a hem and measure again, once you have walked through the actual physical process I think the points will be clear.

    There is no way to get around the hemming properties of a triangle, you turn a hem, you impact 2 sides. That impact will be defined by the hem width, height and width of the triangle ... you turn 3 hems, you have 6 impacts .. it is not bad hemming, just the property of hemming a triangle.

    If you do the physical check and find a way to use a simple allowance around the triangle, I would love to know about it , as it would be a lot easier and I would learn something new ... if you find that I am right and it isn't as simple as it looks, that would be nice to know as well .... so far in this thread, the only response is that I have likely overthought the issue and a 1" allowance will work, unfortunately from physically trying that, I know a) it doesn't work and b) I figured out the math as to why it is so. It would be nice to have some one actually try what i am talking about and feed back that I have a point.


    Brian

  3. #13
    Senior Member Cruiser51's Avatar
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    Quote Originally Posted by GilligansWorld View Post
    Legit I am not being silly I'm just trying to answer the question as best as I think I understand it - If you wanted a triangle that had sides that were 5 in long I suspect you would add a half inch to each side if you were looking for a half inch seam - So I tried my little experiment with a piece of paper and it seems to work as long as all of your sides are the same

    Sent from my Pixel 4a using Tapatalk
    Maybe add a bit more process information, I drew up an equilateral triangle, with all sides equal to 5 1/2" ... cut it out, folded a 1/2" seam along each side and ended up at 3.75" on a side ... so obviously we aren't doing the same thing if yours came out at 5" a side


    Brian

  4. #14
    GilligansWorld's Avatar
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    Cool

    Quote Originally Posted by Cruiser51 View Post
    Maybe add a bit more process information, I drew up an equilateral triangle, with all sides equal to 5 1/2" ... cut it out, folded a 1/2" seam along each side and ended up at 3.75" on a side ... so obviously we aren't doing the same thing if yours came out at 5" a side. I genuinely am not good at math but I do understand the difference between equilateral and isosceles - I saw Solis would give you a 5-in height where the base would be different but the process would be identical draw your plans up first and then the dotted portion is where I would add cut out the triangle with the dotted on there and when you fold it over it should be right there.


    Brian
    Perhaps we are talking about two different things but when you say a 5-in triangle I assume you're talking about a 5-in base - and if it's equilateral all I had to use was a compass to figure out where they would cross - But you are correct It will not be 5 in in height however this is what I came up with - see pictures.....
    I'm not good at math but I know the difference between an equilateral and and isosceles triangle - If you need 5 in for height it's probably an isosceles but you would do exactly what I did in pencil first then add your half inch hem - then cut the triangle out and hem should work - Again forgive me if this comes across as snarky but I meant it - I am not good at math so I draw it out.


    Drawing works.
    End of story



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    Last edited by GilligansWorld; 08-13-2021 at 21:41. Reason: Extra info
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  5. #15
    Senior Member Cruiser51's Avatar
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    Quote Originally Posted by GilligansWorld View Post
    Perhaps we are talking about two different things but when you say a 5-in triangle I assume you're talking about a 5-in base - and if it's equilateral all I had to use was a compass to figure out where they would cross - But you are correct It will not be 5 in in height however this is what I came up with - see pictures.....
    I'm not good at math but I know the difference between an equilateral and and isosceles triangle - If you need 5 in for height it's probably an isosceles but you would do exactly what I did in pencil first then add your half inch hem - then cut the triangle out and hem should work



    Sent from my Pixel 4a using Tapatalk
    TY for the post GW, I get what you are saying now and see how that works .... but maybe we are drifting from the original question in the post. It started off trying to figure out initial panel sizes in bug mesh for end panels on a hammock ... trial and error is always an option, but I thought there must be a way to actually calculate the size. The type of triangle isn't an issue, I was trying to figure out how to calculate the initial panel size (without the trimming you describe).

    For the bug netting application the hem is also a re enforcement and if I trim as shown, there is next to nothing at each apex. If the hems are left long, then the apex(s) will have several layers sewn together and create a much stronger area on each point. Trimming the actual hem material eliminates the fold over problem, but also creates some issues at the corners with strength/fray resistance.

    I appreciate this post because it gives me a different view on the issue or at least a way around, but I am not sure I am willing to compromise the corners, so i will think on it some more.


    Brian

  6. #16
    GilligansWorld's Avatar
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    Quote Originally Posted by jcksparow View Post
    I'm not sure I understand your question. Is it possible to see an example of what you mean?

    If the panel is something you only need to do once or twice, just outline the shape you need on the fabric and mark a 1" border around it to get your cut dimensions. If every line is hemmed in the same amount, the original shape should be preserved. If you're doing a triangle, you'll end up snipping some excess material at the corners created by the hems, but this won't affect the dimensions of the finished shape.
    Quote Originally Posted by Cruiser51 View Post
    TY for the post GW, I get what you are saying now and see how that works .... but maybe we are drifting from the original question in the post. It started off trying to figure out initial panel sizes in bug mesh for end panels on a hammock ... trial and error is always an option, but I thought there must be a way to actually calculate the size. The type of triangle isn't an issue, I was trying to figure out how to calculate the initial panel size (without the trimming you describe).

    For the bug netting application the hem is also a re enforcement and if I trim as shown, there is next to nothing at each apex. If the hems are left long, then the apex(s) will have several layers sewn together and create a much stronger area on each point. Trimming the actual hem material eliminates the fold over problem, but also creates some issues at the corners with strength/fray resistance.

    I appreciate this post because it gives me a different view on the issue or at least a way around, but I am not sure I am willing to compromise the corners, so i will think on it some more.


    Brian
    I understand a bit better now but the hem IMHO isn't the issue then your Finished size appears to be. I would suggest you investigate as best as possible what the finished length needs to be and then draw it out on paper and play I guess? or perhaps you can add material as you reinforcement. Another thought would be to have extra material in the area you are sewing to? Either way math and sewing never work out 100% for me which is why I draw and practice first. I have ripped too many seams and lost too many projects now that I don't trust the mathing when I am the "engineer" I have to K.I.S.S. and draw it and play.


    ******EDIT*******

    A quick suggestion just occurred to me - If you can find a very narrow gauge cordage and roll the hem over the top of the cordage, then using a zipper foot Sew as close to the cordage as you can. This does two things It creates stability and also creates reinforcement around the edges. If you used my method and you were nipping the edges just leave yourself a little tab long enough to roll over and sew around the cordage. I know I've seen something similar if I can find a picture I'll post it.
    Last edited by GilligansWorld; 08-13-2021 at 22:24.
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  7. #17
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    Quote Originally Posted by Cruiser51 View Post
    I really appreciate you taking the time to think about this and respond ... however, I assure you it does make sense when you work your way through the math, the height does get affected on every hem (as well as the width) and I do know how to hem correctly. As you said it gets a tricky to both explain and figure in your head.

    Turning any hem on a triangle, will affect both the overall height and width of the remaining triangle, if this "doesn't make sense", then you need to cut out a paper triangle, measure the height and width, then fold a hem and measure again, once you have walked through the actual physical process I think the points will be clear.

    There is no way to get around the hemming properties of a triangle, you turn a hem, you impact 2 sides. That impact will be defined by the hem width, height and width of the triangle ... you turn 3 hems, you have 6 impacts .. it is not bad hemming, just the property of hemming a triangle.

    If you do the physical check and find a way to use a simple allowance around the triangle, I would love to know about it , as it would be a lot easier and I would learn something new ... if you find that I am right and it isn't as simple as it looks, that would be nice to know as well .... so far in this thread, the only response is that I have likely overthought the issue and a 1" allowance will work, unfortunately from physically trying that, I know a) it doesn't work and b) I figured out the math as to why it is so. It would be nice to have some one actually try what i am talking about and feed back that I have a point.


    Brian
    Forget about height and width for a moment.

    What you are doing when you hem is folding to a line. It doesn't matter what the shape is or the allowance, fold to the line and you will end up with the intended dimensions. Gilligan's photos show this.

    Now ...
    Maybe add a bit more process information, I drew up an equilateral triangle, with all sides equal to 5 1/2" ... cut it out, folded a 1/2" seam along each side and ended up at 3.75" on a side ... so obviously we aren't doing the same thing if yours came out at 5" a side
    Here's where you are going wrong! A 1/2" seam does not increase the length of each side by 1/2"!!!! Draw out an isosceles triangle with sides of 5" now draw three lines parallel to each edge 1/2" on the outside of the triangle and make sure they intersect. Now measure between the vertices of this new triangle and you'll have a length of close to 7" not 5 1/2.

    Because of this your starting conditions are wrong. Look at Gilligansworld's last shot. See those dashed lines? Extend those outward until they intersect then measure the length of the edges. I'm sure there's some maths to calculate this but drawing it out will work for any type of triangle or pentagon or hexagon or whatever.

    Edit: to prove the above, cut out a triangle with 5" sides, one with 5.5" sides and one with 7" sides. Lay them on top of one another - 7" on the bottom then 5.5" then 5" and centre and align them. Now measure the distances between the edges. You'll find that the difference between the 5 & 5.5 is minimal, maybe 1/4", but the distance between the 5" & 7" triangles is 1/2".
    Last edited by Bob-W; 08-14-2021 at 07:08. Reason: better explanation
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  8. #18
    Senior Member Cruiser51's Avatar
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    GW ... it never occurred to me that there were options, for camp gear, other than lapping the hemmed corners. looking around the web I found a couple of places that explained how to use a mitered hem and get the re enforcement

    https://www.hammockforums.net/forum/...ners-for-Tarps

    and a more detailed video

    https://www.youtube.com/watch?v=I0BUBNSB-ig

    Sort of a modified version of your cut outs ... this neatly side steps the sizing requirements that exist with using a simple lap corner ...



    BW ... the real issue here was that it appears you and GW are both using/suggesting a form of mitered corners and all of my posts are using a simple lapped corner. Your observations on lines is basically what I was posting earlier in the thread and are still valid for lapped corners. The sizing considerations between the two do not appear to be compatible. That is why the 5" cut out trial didn't work, if you don't make the mitered corner, the second hem reduces the vertical a second time ... we were so busy trying to prove/explain our views, the fact that we weren't using the same initial method was lost.



    The feed back and time is appreciated, I will add the re enforced miter corner to the sewing "tool box" ... this wasn't the expected out come, but anytime I can learn something new it's a good day

    Thanks
    Brian

  9. #19
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    Actually what I'm saying in my last post is that the corners are irrelevant whether you lap or mitre them. If you mitre the fabric you'll get one double rolled hem all the way round. If you don't then the corners will have two double rolled hems.

    Do the experiment as I described and you'll see that simply adding 1/2" to the length of the side is not the same as adding 1/2" to the width, you need to account for the increased length of the adjoining sides as well. This isn't restricted to triangles but any corner in any shape, it's just that once the internal angle of any corner drops below 90deg then the effect is more pronounced.

    Take the last image in Gilligan's post - he's got mitred corners. Extend the dashed lines so they all meet. You've now your original 5" isosceles triangle superimposed on a 7" isosceles triangle. If you now hemmed that 7" triangle you'd end up back at your original 5" model. Again, doesn't matter if you mitre the corners or not, that's a distraction.
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  10. #20
    Senior Member Cruiser51's Avatar
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    Quote Originally Posted by Bob-W View Post
    Actually what I'm saying in my last post is that the corners are irrelevant whether you lap or mitre them. If you mitre the fabric you'll get one double rolled hem all the way round. If you don't then the corners will have two double rolled hems.

    Do the experiment as I described and you'll see that simply adding 1/2" to the length of the side is not the same as adding 1/2" to the width, you need to account for the increased length of the adjoining sides as well. This isn't restricted to triangles but any corner in any shape, it's just that once the internal angle of any corner drops below 90deg then the effect is more pronounced.

    Take the last image in Gilligan's post - he's got mitred corners. Extend the dashed lines so they all meet. You've now your original 5" isosceles triangle superimposed on a 7" isosceles triangle. If you now hemmed that 7" triangle you'd end up back at your original 5" model. Again, doesn't matter if you mitre the corners or not, that's a distraction.

    Thank you .... you are quite correct. Did the experiment and am still shaking my head.


    Brian

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