scale models

[spieszak]

OK guys, this may be a bit of a strange one. I'm considering a large build, on the size of about 48x48x30. Prety handy but haven't ever done a tank build,
so, I want to work in a scale model first so that I can get some experience, and probably use the scale as a refugem. (Or I'll find out that I should just have someone do my build) My intent is to use 3/4 inch on the "real tank", with Momentive RTV103 or IS803 along with some bracing and such...
Here's my question
The plan would be to scale to a 24x24x15, and drop to 1/2 glass... Basically just cutting all my measurements in half.
How do I scale the silicone? I mean, to really judge the strength of what I'm doing and to scale correctly, I'd like lower the strength of the slicone too...

Hope that makes sense, and I look forward to hearing suggestions/opinions.

[uncleof6]

OK guys, this may be a bit of a strange one. I'm considering a large build, on the size of about 48x48x30. Prety handy but haven't ever done a tank build,
so, I want to work in a scale model first so that I can get some experience, and probably use the scale as a refugem. (Or I'll find out that I should just have someone do my build) My intent is to use 3/4 inch on the "real tank", with Momentive RTV103 or IS803 along with some bracing and such...
Here's my question
The plan would be to scale to a 24x24x15, and drop to 1/2 glass... Basically just cutting all my measurements in half.
How do I scale the silicone? I mean, to really judge the strength of what I'm doing and to scale correctly, I'd like lower the strength of the slicone too...

Hope that makes sense, and I look forward to hearing suggestions/opinions.

Don't bother scaling the strength of the silicone. Use the same silicone on both projects. If you use a "junk" silicone with the smaller project, you will be in no way prepared for using the RTV103. The materials have very different physical properties, and you have little time with the RTV (~5 min or so) to work with it. You want the maximum strength possible for BOTH projects. You need experience with the actual materials that will be used.

I would do an even smaller project first-- like with 6mm glass, then move up, if you master the techniques.

IS800 silicone is a good silicone, but RTV100 series is stronger, and this is what you should use


http://www.plantedtank.net/forums/diy/27814-building-75g-all-glass-tank.html

[spieszak]

i'm afraid if i go too small what i'll end up with is not enough knowledge of what i'm doing.. i agree with your point on the silicone, but shouldn't that apply equally to the gllass? i mean the weight and stability of smaller pieces are going to be pretty far off of the weight and stability of the large...

if i start smaller, would you suggest an intermediate project then before the large?

[chimmike]

Jim, the only thing that concerns me about that method is adding a pane after 2 days. What about the old adage that new silicone doesn't like to mate with "old" silicone?

Is 2-3 day old silicone still considered new?

[uncleof6]

Jim, the only thing that concerns me about that method is adding a pane after 2 days. What about the old adage that new silicone doesn't like to mate with "old" silicone?

Is 2-3 day old silicone still considered new?


The skin time is so short for the RTV silicone, that no matter if you do it all at once, or spread it out, the end result will be the same. Well if you can get the tank together start to finish (save the inner seal) in 5 - 7 min (can vary a little bit) the result could be different, but not necessarily better strength wise.

The inner seal on the other hand, should be done in one shot, and be a "continuous bead" as this needs to be water tight to protect the "structural" seams. Layering, or 'overlapping' skinned silicone, could leave a water leak point-- sooner rather than later.

[spieszak]

thanks for the link. i'm afraid i'm not quite brave enough to go rimless with no frame.. right now i'm considering an extruded aluminum, or 3/4 ply either with epoxy or boat coat (can't remember the real name for boat coat right now)..
Does anyone have advice or suggestions given those tow options?

[chimmike]

The skin time is so short for the RTV silicone, that no matter if you do it all at once, or spread it out, the end result will be the same. Well if you can get the tank together start to finish (save the inner seal) in 5 - 7 min (can vary a little bit) the result could be different, but not necessarily better strength wise.

The inner seal on the other hand, should be done in one shot, and be a "continuous bead" as this needs to be water tight to protect the "structural" seams. Layering, or 'overlapping' skinned silicone, could leave a water leak point-- sooner rather than later.

good to know.

Thanks Jim!