Page 4 of 21

Re: Designs B/C

Posted: October 13th, 2014, 7:17 pm
by azuritemalachite
taimur18 wrote:
azuritemalachite wrote:
taimur18 wrote:What do you think the best type of wood for this event would be the best. Additionally I was gonna use super glue, but what brand or type of super glue is the best?
I'm pretty sure most people use balsa. My team uses epoxy, but I'm sure gorilla glue and super glue could work.
Ok thank you. If I do use balsa would you recommend any specific type, like high density, low density, etc?
I'm not an expert on this, but lower density will be better for competition, but since you seem new at this I would start off with higher density so you can work out your design and stuff.

Re: Designs B/C

Posted: October 13th, 2014, 7:19 pm
by taimur18
I'm not an expert on this, but lower density will be better for competition, but since you seem new at this I would start off with higher density so you can work out your design and stuff.[/quote]

Ok thanks for the advice. It helps a lot.

Re: Designs B/C

Posted: October 13th, 2014, 8:58 pm
by iwonder
Honestly the density you use varies a lot with where the member is, how its loaded, etc. It's probably best to just try a bunch of different densities, get a feel for it, then mix and match what you need to get a good outcome.

Also, if you're worried about densities you should definitely start a spreadsheet with pieces and densities for different designs (it helps to see weak points/parts that are too heavy).

(and my best designs had everything from 19 g/cm^3 (very very heavy blasa), to 4 g/cm^3 (paper light balsa) in the same designs)

Re: Designs B/C

Posted: October 14th, 2014, 6:17 am
by bearasmith
Last year I started out with some crummy grade B wood. As the year progressed, and I found my favorite design, I used better low density grade A balsa. This way you can save hundreds of dollars. :D

Bearasmith

Re: Designs B/C

Posted: October 19th, 2014, 12:37 pm
by embokim
how do you find the bent wood like I saw in some youtube videos about bridge building :?:

Re: Designs B/C

Posted: October 19th, 2014, 12:50 pm
by retired1
You do not find bent wood. You can take and soak it for a few min and then bend it around an object that is the size and shape that you want. I use hot water with a splash of ammonia in it and then give the form and stick(s) 30 seconds in the microwave-3 times and then let it cool. One site used rubbing alcohol at room temp. Some use the oven at 120F for 30 min. Be aware that there will be some spring back but you can secure it and glue it in position. A curve is a bit tricky as to the placement of support truss members.
PS, do not use styrofoam in the microwave.

Re: Designs B/C

Posted: October 19th, 2014, 1:00 pm
by bernard
I personally would not attempt to bend wood for my bridge because I would have trouble with making consistent and event bends for both sides of a bridge. Making my trusses so that they both meet at the same point at the end of the bridge is enough work for me.

Re: Designs B/C

Posted: October 19th, 2014, 1:04 pm
by iwonder
I used bent wood for towers a few years back, I just soaked the wood in room temp water for a bit and put it in a jig made with pins and foam board. Waited a few days to let it dry back out and it would more or less hold shape and weighed about the same. Just be warned, if you bend wood a lot, even with water, you're changing the grain structure from what was in the tree, which is going to weaken it. It's just down to if it weakens it too much or not.

Re: Designs B/C

Posted: October 20th, 2014, 3:27 pm
by embokim
thanks guys. also does anyone know a good site to get strong condensed balsa rather than from pitsco which sells it only in a package. :)

Re: Designs B/C

Posted: October 20th, 2014, 5:26 pm
by nxtscholar
I personally just buy everything from Specialized Balsa.

If you need a particular density, you can ask for it (at an extra cost though).

But they sell everything: sheets, sticks, dowels, etc.



(On a side note, woo! Post 150)