Towers B/C

[Balsa Man]

Hey Everyone,
How would you go about building a jig for a base-chimney design?
In addition, would a straight legged chimney or a base-chimney design perform better. I personally think that a Base-chimney design would be more effective, even though it is harder to build.

Thanks (yall are the best)

Welcome to the Scioly board!
A question back; don't understand what you mean/are thinking, "would a straight legged chimney or a base-chimney design perform better"?
The rules dictate/define a 'base-chimney' shape. At the bottom (of the base), the ends of the legs have to (at least) span a 20cm x 20cm square hole. That means, for a 4-leg tower, the inside edges of any two adjacent legs about 16cm apart.
If you're going for the 29cm circle bonus, which is what you really want to do, then the inside edges of the legs have to be outside a 29cm circle where they contact the testing surface. That means the inside edges of any two adjacent legs have to be a hair under 21cm apart.
At the height of the 8cm circle plane above the base plane (20cm for C, 25cm for B) everything (the tower) has to fit inside an 8cm diameter circle (and has to fit from there all the way up to the top. That means for a 4-leg tower, the outside edges of any two adjacent legs about 5.5cm apart.
At the top of the tower, the legs have to fit under (as in support) the 5cm square load block.

So, meeting the rules, you have to have a base portion; legs spread apart to span 20x20cm square or 29cnmcircle, legs leaning in so that when you get to the height of the 8cm circle plane, they fit inside the 8cm circle, and the chimney portion, from there up to the top, fitting inside the 8cm circle, very slight lean-in of the legs so at the top they're close enough to support the load block. A "straight legged chimney", as an overall tower design/configuration won't work by itself. If it fits inside an 8cm circle, won't be even close to being able to span the opening in the testing base.

I'll get some thoughts on jig construction posted in the next few days, but let me point you now to the archives of the Scioly board- all the discussion of towers from last year. Go to board index, scroll down to 2017 archives, go to Towers. There's over a hundred pages with lots of very detailed discussion of important aspects of tower building, including a lot of detailed stuff on how to build a jig. Enjoy

[Unome]

Hey Everyone,
How would you go about building a jig for a base-chimney design?
In addition, would a straight legged chimney or a base-chimney design perform better. I personally think that a Base-chimney design would be more effective, even though it is harder to build.

Thanks (yall are the best)

Straight-legged would absolutely work better, but the rules are written to allow only a base-chimney design - see rules 3.d, 4.a.ii, and 5.f.

[Balsa Man]

Hey Everyone,
How would you go about building a jig for a base-chimney design?
In addition, would a straight legged chimney or a base-chimney design perform better. I personally think that a Base-chimney design would be more effective, even though it is harder to build.

Thanks (yall are the best)

Straight-legged would absolutely work better, but the rules are written to allow only a base-chimney design - see rules 3.d, 4.a.ii, and 5.f.

When you say "straight-legged" would absolutely work best, I assume you mean tower with straight legs)- like we had last year (vs. absolutexero3's "straight-legged chimney"). While legs were straight, they were at a significant angle (vs the near vertical legs in the upper chimney section we'll be seeing this year).

The dimensions at the base (how far legs are separated), and tower minimum height, are the same this year (for both B and C). The difference, in terms of 'working' (i.e., performance-score) is a bit more leg wood, and wood in base section needing to be a bit stronger (i.e., denser/heavier). But the total length of bracing will be less (in the narrow chimney section), and with the shorter braces in that section, should be able to reduce brace piece density, too. My initial take was the two-part configuration would be heavier than last year's one-part straight leg configuration. Its very preliminary, but I'm beginning to think two-parters will be pretty darn close to last year's weights

[Unome]

Hey Everyone,
How would you go about building a jig for a base-chimney design?
In addition, would a straight legged chimney or a base-chimney design perform better. I personally think that a Base-chimney design would be more effective, even though it is harder to build.

Thanks (yall are the best)

Straight-legged would absolutely work better, but the rules are written to allow only a base-chimney design - see rules 3.d, 4.a.ii, and 5.f.

When you say "straight-legged" would absolutely work best, I assume you mean tower with straight legs)- like we had last year (vs. absolutexero3's "straight-legged chimney"). While legs were straight, they were at a significant angle (vs the near vertical legs in the upper chimney section we'll be seeing this year).

The dimensions at the base (how far legs are separated), and tower minimum height, are the same this year (for both B and C). The difference, in terms of 'working' (i.e., performance-score) is a bit more leg wood, and wood in base section needing to be a bit stronger (i.e., denser/heavier). But the total length of bracing will be less (in the narrow chimney section), and with the shorter braces in that section, should be able to reduce brace piece density, too. My initial take was the two-part configuration would be heavier than last year's one-part straight leg configuration. Its very preliminary, but I'm beginning to think two-parters will be pretty darn close to last year's weights

Yeah, that was what I meant - couldn't think of any other meaningful interpretation of "straight-legged chimney" where "base-chimney design" also made sense. Unfortunately we don't have much data from 2011-2012 to compare to since the scoring was so different. It would be very interesting if two-piece towers come close to straight towers, since the latter pretty much universally favored last year.

[Balsa Man]

I think the challenge (and hence the opportunity) for a "two parter" to approach last year's one parter performance will be in the degree of precision/symmetry of construction.

The...correct basis of comparison will be load carried divided by tower weight, for one parter (last year) and two parter (thus year) towers meeting the 29cm circle bonus (not factoring in the bonus, because the jump from 2kg load credit to 5kg credit would massively skew things if you just compared scores).

It's on that basis I think it will be close. The precision challenge/opportunity lies in the...8cm circle plane. Even with a lot of care/time/effort, getting a (separately built) base section to precisely line up with a chimney section is (from 2011/12 experience) a real bear.... Multiple alignment issues
-centerline matching on all 4 legs, so upper segment is precisely aligned w/ lower,
-cut angles right on the bottom of chimney legs, and top of base section legs (so the actual cross sections at the cut match), and
-vertical alignment of the chimney, so it's not leaning even slightly in any direction.

All three of these factors are going to have to be...very tightly managed and 'nailed' in terms of precision (for maximum performance). There's also the the issue of getting the buckling strength of the ladder at the top of base section/bottom of chimney section...just right; just enough. That ladder will definitely be needed (even with an otherwise 'all Xs' bracing approach)- the upper ends of the legs in the base section will be pushing in toward each other putting a significant force on the ladders at that level- around 2kg on a C tower (a bit less on a B tower). Control all those factors right; precisely, that's what it'll take to "beat" last year's tower weight v load carried.

[absolutezerok3]

Straight-legged would absolutely work better, but the rules are written to allow only a base-chimney design - see rules 3.d, 4.a.ii, and 5.f.

When you say "straight-legged" would absolutely work best, I assume you mean tower with straight legs)- like we had last year (vs. absolutexero3's "straight-legged chimney"). While legs were straight, they were at a significant angle (vs the near vertical legs in the upper chimney section we'll be seeing this year).

The dimensions at the base (how far legs are separated), and tower minimum height, are the same this year (for both B and C). The difference, in terms of 'working' (i.e., performance-score) is a bit more leg wood, and wood in base section needing to be a bit stronger (i.e., denser/heavier). But the total length of bracing will be less (in the narrow chimney section), and with the shorter braces in that section, should be able to reduce brace piece density, too. My initial take was the two-part configuration would be heavier than last year's one-part straight leg configuration. Its very preliminary, but I'm beginning to think two-parters will be pretty darn close to last year's weights

Yeah, that was what I meant - couldn't think of any other meaningful interpretation of "straight-legged chimney" where "base-chimney design" also made sense. Unfortunately we don't have much data from 2011-2012 to compare to since the scoring was so different. It would be very interesting if two-piece towers come close to straight towers, since the latter pretty much universally favored last year.

Sorry for the confusion and a stupid question .
My first design is probably going to be a 2 part base-chimney with X truss, aiming for around 8-8.5g.
Thx for all your help.

[Balsa Man]

Hey, when you're learning, nothing is a stupid question; no need for 'sorry.'
You've gotten to the place where the most detailed info on how to design and build a good S.O tower is available, and just waiting for you to study and digest it. Dig in, enjoy, and learn, and as you run into specific questions, ask.

[musicalwhang]

Hello!
It's been a good summer and now science olympiad season is starting up again! This time I'm in Division C. To start off, as I begin to design my tower, what's are biggest differences going from last year's Division B Towers to this year's Division C Towers? What should I pay attention to?

[Balsa Man]

Hello!
It's been a good summer and now science olympiad season is starting up again! This time I'm in Division C. To start off, as I begin to design my tower, what's are biggest differences going from last year's Division B Towers to this year's Division C Towers? What should I pay attention to?

Given your question, may I respectfully suggest the first page of this thread? Your exact question answered in some detail.....

[musicalwhang]

Hello!
It's been a good summer and now science olympiad season is starting up again! This time I'm in Division C. To start off, as I begin to design my tower, what's are biggest differences going from last year's Division B Towers to this year's Division C Towers? What should I pay attention to?

Given your question, may I respectfully suggest the first page of this thread? Your exact question answered in some detail.....

Lol whoops ROOKIE MISTAKE
Sorry