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  1. #151
    Senior Member jadekayak's Avatar
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    And does it help you make a better quilt?

    I always start in a different fashion.

    I calculate the fabric area i need and buy that.

    That includes baffels.
    I cut the baffels to desired height and sew it all together.
    However many you need to prevent serious down migration.
    I have a target fill weight in mind and divide that by the number of baffels and bang-you have the weight of down per baffel.

    The overall weight can be THEORETICALLY calculated by area of fabric as follows-
    Say the finished size is 2m x 1.2 m and 10 baffels at 80mm high(including sewing allowances)
    1.2 x 2 = 2.4m².
    Weight of fabric = 15gsm
    Baffels 2m x .08m =.16m²

    Total fabric weight is (2.4 + .16) × 15
    =38.4 grams.

    If you want 700grams of down total weight is 38.4 + 700
    =738.4 grams.

    Although you use a few meters of thread(estimate of 47m) the weight is inconsequential.

    So the finished weight is somewhere between 739 grams and 745 grams.

    BUT WHY BOTHER-it will be whatever it weighs when finished-and you might even put water repelant breathable material(spray) on increasing the weight more and a compression bag for transport with a built in storrage bag for when not in use!.
    Still less than 1000grams.

  2. #152
    Senior Member Cruiser51's Avatar
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    The nice thing about DIY is that you are free to make however you like ... with or without a plan, using other peoples posted experience and help or ignoring them and striking out on your own.

    Personally, I learned a lot from this whole thread series and have used the calculator extensively ... it represents a lot of thinking by quite a few very smart folks trying to provide a tool to simplify the quilt design process.

    To answer your question "And does it help you make a better quilt?" ... no question about it, it definitely builds a better quilt

    As far as your process description goes ... it does describe a quilt, but not a differential cut underquilt, which of course is the whole reason this thread was started.


    Using the calculator you get the layout information and basic performance expectation on the differential quilt before you start. You are then building/sewing to your performance goals with a viable design, with the reasonable expectation that if you execute the design properly, you will end up with a quilt that performs close to the design.

    Given a choice of working with the calculator and understanding my design choices ... I will pick the design tool every time and this one is very good IMO




    Brian

  3. #153
    Senior Member Cruiser51's Avatar
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    I love this calculator and have used it for quite a few projects and they have all performed pretty well.

    On my bridge setup I have a heavier UQ with a design of -15C and a TQ rated at -5C ... the temp dropped to ~-1C and CBS started. I slipped my 1/2" CCF pad in place to fix the cold and that worked perfectly. The UQ has shock cord side and end suspension, I also added a clew suspension to provide the required longitudinal pull to get it snugged up tight.

    Under those conditions I really didn't expect to encounter any warmth issues and I am reasonably certain the suspension is working well, so when I got back home I did what any self respecting DIYer would do and set about figuring out why my BUTT got chilly ( it may also have been looking for an excuse to make a new UQ). I reread most of this post and came up with several theories ... daydreamed and doodled how that area could get compromised. Thought maybe since that butt area kind of gets dimpled and the UQ couldn't shape correctly, but gadgets mod of "puffies" really should be able to handle that ( the discussion on those is sooo well done).

    For TQs I have my own heavily modified workbook, that I use for that purpose, and I made up a temperature rating "guesstimator" based on loft ... I take that temp rating with a bit of caution, but it is a useful guide.

    During the hunt for a viable reason for the cold butt I started cross comparing the temp values between the two workbooks and they didn't match up at all ... a little digging and I figured out why and I think it may be a real issue and was hoping to a) get confirmation on that and b) warn folks that are using the sheet of the issue

    There are 2 flavours on the last update for "experimantal temp ratings" ... the Jardine rating seems to be hopelessly over estimated, but the second temp values look reasonable and I had taken to using that as a guide. To be clear, the temp area is labeled with a warning that it is experimental ....

    The issue I am seeing is that if you design your differential baffles, put in the down values you get two estimated temperatures for the quilt performance .... the Jardine is based on the loft and gives values which do not appear to be realistic, but the second temp values based on down quantity look reasonable until you add in any over fill.

    Since the baffle shape is already set, I don't think that "overfill" should influence the temperature rating directly. I use overfill simply to make up the difference between what the down FP has been measured at and what it will likely degrade to under field conditions. My understanding is that the cottage vendors do largely the same thing, calculate what should be needed and then add 20%-30% more to make it work and be comfortable at the rated temps.

    The work around(s) I see would be to work from a loft versus temp table, modify the workbook to just use loft for temp rating and the simplest way to just enter 0% overfill when determining the working temp for your quilt ....

    In my case, I use a 30% overfill and this inflates the temperature rating quite significantly, enough so that I feel the issue with my UQ is likely that the actual temp rating (based on loft) is quite a bit lower than I thought and that is the likely issue.

    This is getting posted (and hopefully confirmed) that when you are using the calculator tool to design, use a 0% overfill when looking at the temp rating, once you have what you want, go ahead and add the over fill for the chamber down quantities.


    Brian

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