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If you were to build a tower with just x's, would you make the braces attached with butt joints or lap joints? It seems that the goal in making just x brace towers is to make them light, so would a 1/8 leg and 1/16 x brace using lap joints work?

random-username wrote:If you were to build a tower with just x's, would you make the braces attached with butt joints or lap joints? It seems that the goal in making just x brace towers is to make them light, so would a 1/8 leg and 1/16 x brace using lap joints work?

I can't comment on the rest, but since the purpose of X's is to resist tension, you would want them to be lap joints.

Unome wrote:

random-username wrote:If you were to build a tower with just x's, would you make the braces attached with butt joints or lap joints? It seems that the goal in making just x brace towers is to make them light, so would a 1/8 leg and 1/16 x brace using lap joints work?

I can't comment on the rest, but since the purpose of X's is to resist tension, you would want them to be lap joints.

Ah, but in an Xs only configuration, they have to handle both tension and compression....

I feel like the X's and ladders is a better and easier design, but X's only is the only way to make a super light tower scoring 2500+.

MIScioly wrote:I feel like the X's and ladders is a better and easier design, but X's only is the only way to make a super light tower scoring 2500+.

That's just build quality If you build a perfect tower with perfect cutting, gluing, and angles you would get a tension only tower that wouldn't bow inwards and would only require tension bracing (I think?) Every tower I've seen 2800+ or 3000+ are purely lap joints for tension members. However, do heed these people building these amazing towers are either using a well built precise jig and/or have years and years of experience choosing wood, designing, and building.

Raleway wrote:

MIScioly wrote:I feel like the X's and ladders is a better and easier design, but X's only is the only way to make a super light tower scoring 2500+.

That's just build quality If you build a perfect tower with perfect cutting, gluing, and angles you would get a tension only tower that wouldn't bow inwards and would only require tension bracing (I think?) Every tower I've seen 2800+ or 3000+ are purely lap joints for tension members. However, do heed these people building these amazing towers are either using a well built precise jig and/or have years and years of experience choosing wood, designing, and building.

So, I'm curious, how do you envision preventing inward bowing, having a 'tension only tower'? Building a slight bow into the legs?
BTW, still don't know where the limit is for ladders and Xs, but I do know its above 2500. As I've said before, I understand all the engineering for ladders and Xs, but don't, yet, for Xs only when you get above...3200/3300. Clearly, there is a way to do it.

Balsa Man wrote:

Raleway wrote:

MIScioly wrote:I feel like the X's and ladders is a better and easier design, but X's only is the only way to make a super light tower scoring 2500+.

That's just build quality If you build a perfect tower with perfect cutting, gluing, and angles you would get a tension only tower that wouldn't bow inwards and would only require tension bracing (I think?) Every tower I've seen 2800+ or 3000+ are purely lap joints for tension members. However, do heed these people building these amazing towers are either using a well built precise jig and/or have years and years of experience choosing wood, designing, and building.

So, I'm curious, how do you envision preventing inward bowing, having a 'tension only tower'? Building a slight bow into the legs?
BTW, still don't know where the limit is for ladders and Xs, but I do know its above 2500. As I've said before, I understand all the engineering for ladders and Xs, but don't, yet, for Xs only when you get above...3200/3300. Clearly, there is a way to do it.

I personally haven't done it myself but have seen the teams with towers using only tension members. I think a good example of this working (on a much easier scale) is the Double Z design for Bridges last year- it solely relied on the tension members to work and many teams did not use compression members last year. I understand this year the compression force is much more to be reckoned with but some teams have managed to surpass that threshold. I can only think that they build a slight bow that is controlled with warping equally with a warm bath and then setting for about 3 days to let it dry fully in addition to great wood selection and building technique. Again, as I have not personally built one I can only comment my ideas on the teams that have magically succeeded.

Here is a video of our tower tested at the Indiana State Competition several weeks ago:

https://www.youtube.com/watch?v=o7XudIK9qGA

As you can see, our design was X's only except for a few ladders at the very top and bottom. These may not have been necessary, but we simply ran out of time to build another tower and test it before the competition. The tower weighed 6.2 grams and carried the full load for a score of 2419. My partner and I have spent the past three years building bridges and towers and it was very satisfying to end our Science Olympiad careers with a 1st at state after previously placing 5th and 3rd. As I am from a relatively new team, part of me wishes that Science O allowed state event winners to participate in just that event at nationals, perhaps in a separate "best of the best" division, but nevertheless I wish good luck to everyone competing in May.

GhostPants_ wrote:Here is a video of our tower tested at the Indiana State Competition several weeks ago:

https://www.youtube.com/watch?v=o7XudIK9qGA

As you can see, our design was X's only except for a few ladders at the very top and bottom. These may not have been necessary, but we simply ran out of time to build another tower and test it before the competition. The tower weighed 6.2 grams and carried the full load for a score of 2419. My partner and I have spent the past three years building bridges and towers and it was very satisfying to end our Science Olympiad careers with a 1st at state after previously placing 5th and 3rd. As I am from a relatively new team, part of me wishes that Science O allowed state event winners to participate in just that event at nationals, perhaps in a separate "best of the best" division, but nevertheless I wish good luck to everyone competing in May.

Thanks for sharing... VERY nicely done, and congratulations on the gold! Now if we could only get other States (Ohio) in the 21st Century and use auto loaders, we'd be all set!

Raleway wrote:

Balsa Man wrote:

Raleway wrote:
That's just build quality If you build a perfect tower with perfect cutting, gluing, and angles you would get a tension only tower that wouldn't bow inwards and would only require tension bracing (I think?) Every tower I've seen 2800+ or 3000+ are purely lap joints for tension members. However, do heed these people building these amazing towers are either using a well built precise jig and/or have years and years of experience choosing wood, designing, and building.

So, I'm curious, how do you envision preventing inward bowing, having a 'tension only tower'? Building a slight bow into the legs?
BTW, still don't know where the limit is for ladders and Xs, but I do know its above 2500. As I've said before, I understand all the engineering for ladders and Xs, but don't, yet, for Xs only when you get above...3200/3300. Clearly, there is a way to do it.

I personally haven't done it myself but have seen the teams with towers using only tension members. I think a good example of this working (on a much easier scale) is the Double Z design for Bridges last year- it solely relied on the tension members to work and many teams did not use compression members last year. I understand this year the compression force is much more to be reckoned with but some teams have managed to surpass that threshold. I can only think that they build a slight bow that is controlled with warping equally with a warm bath and then setting for about 3 days to let it dry fully in addition to great wood selection and building technique. Again, as I have not personally built one I can only comment my ideas on the teams that have magically succeeded.

Understand.
Not related to towers, but not familiar w/ ‘double Z’ bridge approach, and how it could work with no compression members. Our bridge last year was at 7.5gr, second at State by about 20 points.
I’m with you thinking that high performance Xs only towers have got to be using bowed legs. Haven’t seen any – only have reports. Compression loading is less than in bridges last year- under 4kg vs 5-6kg.