General Discussion

[Balsa Man]

Couple quick thoughts, Illazar,
As you know, the answer probably depends on what kind of joint.
Joints under compression are cake- they act to hold themselves together; it's high tension load joints that are the challenge; assume that's what you're dealing with.
The strength of the joint is limited/constrained by the strength of the lightest piece in the joint; the glued surface will hold under load, but at some point the wood into the piece from the glued surface will fail. Higher density wood will support higher strength joints. Larger glue area =lower load/unit area.
What we've found to work best for high tension load joints (end points of main tension members in bridge, outer ends on boomilever tension members) is Gorilla glue - good penetration. To be able to use it, though, you need to be able to apply good tight clamping pressure.
There may well be some fancy/special/industrial epoxies out there with...better strength specs than what you'll get off the shelf from, say Home Depot - maybe worth researching. As you probably know, epoxy strength generally goes up ad the hardening time goes up; 30-minute epoxy is significantly stronger than 5-min epoxy.

[Faustina]

Has anyone built any towers yet? I've built 3, with scores of 59, 79, and 81. While these scores aren't terrible, I see a lot of room for improvement. Anyone else have scores yet?

[mrsteven]

Has anyone built any towers yet? I've built 3, with scores of 59, 79, and 81. While these scores aren't terrible, I see a lot of room for improvement. Anyone else have scores yet?

I have not yet, but by the end of the week I should have a dozen or so tested. I'll post my high and low scores then . . .

[hogger]

Has anyone built any towers yet? I've built 3, with scores of 59, 79, and 81. While these scores aren't terrible, I see a lot of room for improvement. Anyone else have scores yet?

Which formula are you using? Regional, State, or National?

[Faustina]

Has anyone built any towers yet? I've built 3, with scores of 59, 79, and 81. While these scores aren't terrible, I see a lot of room for improvement. Anyone else have scores yet?

Which formula are you using? Regional, State, or National?

Regional formula

[jma]

We built our first tower last Friday. We couldn't test it because the chimney leg was not straight. We made our jig based on the info we learned on Youtube. Since it was made from cardstock, it wasn't sturdy enough, therefore the base top of the tower was not perfectly square which caused the chimney leg to lean a little.

We decided to build another jig based on the info given by Mr.Joeris on November 4 last year (we read it at least 10 times before we could understand). We bought a piece of plexiglass and a cutter from Home Depot today and tried to cut out some shapes, but we couldn't do it.

Mr. Joeris, can you give us some advice on how to cut the plexiglass? Thank you very much.

[LKN]

jma,

If for whatever reason plexi glass doesn't quite work, head over to the image gallery to see a foam board jig --> http://gallery.scioly.org/details.php?image_id=3633
I recently posted this jig made out of foam board for a square base and plan on posting a jig for my lean-in rectangular base soon. I think plexi glass would definitely be the most preferable to use as a building jig, but working with foam poster board is very convenient. Just make sure that you account for the thickness of the board in the 3D dimensions, otherwise you may end up with a rectangular base that you meant to be square. Make your cuts with a new sharp blade about .5cm away from your drawn design, and sand away to make up the difference. I used 60 grade sandpaper. The nice thing about poster board is that it is very easy to manipulate with sandpaper to get it just right. It might also be faster/easier to construct with poster board than plexi glass? I am not sure just a thought. The big downside is that the foam is porous and can be difficult to glue with CA, clamping somehow while keeping the structure at 90 degree angles when connecting the sides to make perfect corners would be preferable. I still got away with just holding the structure together on a metal straight-edged right ange piece and the jig came out great. I would still like to hear the plexi glass technique and give it a try as well.

[Balsa Man]

We built our first tower last Friday. We couldn't test it because the chimney leg was not straight. We made our jig based on the info we learned on Youtube. Since it was made from cardstock, it wasn't sturdy enough, therefore the base top of the tower was not perfectly square which caused the chimney leg to lean a little.

We decided to build another jig based on the info given by Mr.Joeris on November 4 last year (we read it at least 10 times before we could understand). We bought a piece of plexiglass and a cutter from Home Depot today and tried to cut out some shapes, but we couldn't do it.

Mr. Joeris, can you give us some advice on how to cut the plexiglass? Thank you very much.

Cutting-
Two ways- first is the cutter. Without more info, I don't know why you had problems with it. You need a good steel straight edge. Scribe (as in scratch in) your line(s). Carefully line up your straight edge. Then make repeated passes with the cutter. Each pass will cut/scrape away a little more material. Depending on how hard you press down, it may take....20 or 30 passes. (that's for 3/32nds/0.090" plexi). You don't have to cut all the way through Once you're decently past half way, you can snap-break. Move the piece to the edge of a table/counter/workbench. Get a piece of wood as long as your straighe edge. Line the cut up just barely (like a mm or two) past the edge of the table (or whatever). Put the straight edge on top of it so it is aligned with the cut. Put the wood on top- it gives you a way to press down good and hard. Holding down on the side of the cut on the table, pull up on the overhanging side. The cut will snap along the line. Try the technique on some scrap till you get it right.
The other way is a table saw. Cut your jig plate shape in some styrene sheet (you can get at Hobbytown 0.040 works well), or you could also use posterboard. That piece will act as a guide for setting the saw up to cut the plexi. The advantage of the table saw is when you have it set up, you can stack 4 pieces of plexi and cut them all at once- and they all come out the same shape.

[jma]

Thanks Mr. Joeris and LKN.
I used the first way when I tried to cut a 5x5 from a sheet of plexiglass last time. I think the problems were 1. I didn't scribe deep enough ( too hard for me, will ask my dad for help next time), 2. My cut wasn't the whole length of the sheet. Instead, I had to break my small square (both length and width) at the same time.

[SONinjaGuy]

Anyone have tips for making a square-base tower jig. Last year, I wasn't the senior tower builder so it didn't matter if I was good or not, but now I am and I don't want to be making towers without a jig anymore, as they are never very successful.