Towers B/C

[hearthstone224]

Ah Balsa Man I'm in C-Div, doesn't that change the numbers?

[Balsa Man]

Ah Balsa Man I'm in C-Div, doesn't that change the numbers?

Yeah.
The numbers for C (the multipliers for 1/2 thru 1/7- the bold, underlined ones in the post above are:
8.92
20.07
35.68
55.74
80.27
109.26

So, I see where your 8.91 20.11 came from. Do you understand how to use them now, from the examples in my post above?

[hearthstone224]

Yes, I was just trying to make sure. That way I can calculate the BS that the 36'' balsa must have to be braced at a certain interval and work.

For example, if I braced at 1/2 interval, it has to have at least 518g or more to be safe. I got this by doing 4608/8.91. So when I'm testing, if the stick doesn't make greater than 518, then I know it isn't going to work at 1/2 interval bracing.

And our goal is to brace at the least interval possible (least meaning I favor 1/4 over 1/5) so then I would use the most powerful sticks to brace at the least interval.

So to make clear, when you say "shelf board" you just mean like a flat surface? Could I use like a table surface?

[hearthstone224]

Can you explain this part to me:

Then scribe (as in scratch into the plastic) the top line, at 90 degrees to the inside vertical line. Then scribe the point along the top line the correct distance out from the vertical back edge, then scribe the point along the bottom edge that is the correct distance out from the vertical back edge. Then scribe the angled line connecting the top and bottom marks. Figure the first time you try, you’re gonna mess something up, so figure 5 starting rectangles. 15 min/panel, then 15-20 min each doing the cutting (repeatedly running the cutting tool along the cut lines till you can snap off the scrap side. A couple hours at least till you have 4 good panels cut; let’s say 2 1/2. Then taping them together, and sanding the leg and top sides till they’re perfectly matched. Another ½ hr, so 3 hrs. Up to 7hr…

What does it mean? So I take this 3/32 panel that I have, and sand it down. Next, I don't know what the directions mean.

What is the inside vertical line? And how big should our panels be that we cut?

[Balsa Man]

Can you explain this part to me:

Then scribe (as in scratch into the plastic) the top line, at 90 degrees to the inside vertical line. Then scribe the point along the top line the correct distance out from the vertical back edge, then scribe the point along the bottom edge that is the correct distance out from the vertical back edge. Then scribe the angled line connecting the top and bottom marks. Figure the first time you try, you’re gonna mess something up, so figure 5 starting rectangles. 15 min/panel, then 15-20 min each doing the cutting (repeatedly running the cutting tool along the cut lines till you can snap off the scrap side. A couple hours at least till you have 4 good panels cut; let’s say 2 1/2. Then taping them together, and sanding the leg and top sides till they’re perfectly matched. Another ½ hr, so 3 hrs. Up to 7hr…

What does it mean? So I take this 3/32 panel that I have, and sand it down. Next, I don't know what the directions mean.

What is the inside vertical line? And how big should our panels be that we cut?

I believe the attached should make it clear; pictures and words

Jig Plate shape-dimensions 2016-17.xlsx

(28.11 KiB) Downloaded 152 times

Yes, I was just trying to make sure. That way I can calculate the BS that the 36'' balsa must have to be braced at a certain interval and work.

For example, if I braced at 1/2 interval, it has to have at least 518g or more to be safe. I got this by doing 4608/8.91. So when I'm testing, if the stick doesn't make greater than 518, then I know it isn't going to work at 1/2 interval bracing.

And our goal is to brace at the least interval possible (least meaning I favor 1/4 over 1/5) so then I would use the most powerful sticks to brace at the least interval.

So to make clear, when you say "shelf board" you just mean like a flat surface? Could I use like a table surface?

Yes, any flat surface
Yes, bracing at 1/2 interval, a 36" stick would need to test >518gr. That is, btw, way higher than you'll find in 1/8" balsa. Don't know what size you're thinking. I can tell you that 1/8 balsa will work.... at a reasonable number of bracing intervals. But you get to figure that out. You correctly understand how to do that now..
Have fun

[hearthstone224]

You were so right when you say they vary in BS...

Some were 30, some were 150

You could kind of tell while holding the stick.

[Balsa Man]

You were so right when you say they vary in BS...

Some were 30, some were 150

You could kind of tell while holding the stick.

Yup.
And, of course they vary in density- higher density (higher stick weight), stiffer, lower density, floppier. With a range of ~30 to 150, for 1/8th", you're probably looking at stick weights from oh.....1gr to about 2.5gr- that about right?

The key is finding 'a few good sticks' at what you settle on as your design basis. Let's say for discussion, you settle on 85gr BS at 36", which if braced to 1/5 interval will get you a bit over the needed target leg strength 4738. Now, if you had ....a hundred sticks that all tested at 85gr, you'd find their average weight would be.....oh, probably around 1.6gr. You'd probably have a few that might weigh as little as around 1.3gr, and a few that might weigh as much as 2gr (+/-~20%). Ideally, what you'd like is 4 that test at 85gr, and weigh 1.3gr. Unless you buy a lot of wood to find a few really sweet sticks, you'll not get to that level of.....perfection, but what you want to be doing is finding the lightest sticks that test with sufficient BS.

And you're right, you can feel the differences in stiffness. The pushdown BS testing gives you a way to.....quantify the differences.

[hearthstone224]

When I read your article on bracing, I understood most of it but I do have a question-

Is it ok if we don't use a bow? Maybe our performance might not be amazing but I'm not sure if that's my top priority right now since I kind of want to focus on making a jig first.

Thanks!

[Balsa Man]

When I read your article on bracing, I understood most of it but I do have a question-

Is it ok if we don't use a bow? Maybe our performance might not be amazing but I'm not sure if that's my top priority right now since I kind of want to focus on making a jig first.

Thanks!

Who am I to say what's ok for you? Seriously, that, and priorities are your call entirely.......
Yes, jig is the first step, in terms of things to be .... built.
When that's done, then it'll be time to build. One step at a time.

You said when you first came to this board you wanted information on how to "do well." You have gotten such information. Whether and how you use it is totally up to you.
The bracing system I've described depends on the X pieces being put on under a bit of tension. If they have any slack, they won't work. Bows are the easiest way to do that tensioning that I know of. You don't have to cut them out of plastic, btw, you could glue together pieces of, oh 1/2 x 1/8 basswood.

[hearthstone224]

It says in the excel sheet:

"See Tab "Overview Figures" for a 3-D view and See Tab "JigPlates Tops-Bottoms" how we get the dimensions seen above"

Where is this referring to? There were no tabs on the excel sheet.

Thanks!