I did stuff today!
After a small amount of thinking, I came up with an idea for a test tank. perhaps not the greatest, but it worked. Cinder blocks and plastic sheeting... easy. Only issue is it's only about a foot deep, which should be all I need. I took a guess at what kind of ballast I would need. Judging from the 4 or 5 lbs I had to put in the tugboat to get it to sit at the waterline, I put all the lead I had on hand in the keel, and dropped the boat in the water without the top hatch.
Sank right to the bottom. Ok then.
I put a more reasonable amount of weight in and dropped it in. Got this, and if it's not obvious from the picture, there is zero roll stability, as expected:
That's not a bad waterline, though... but once I put the hatch on, it was a whole new ballgame.. that additional weight didnt' work in my favor, again, as expected. If you look at the bottom of the picture, you can see the weight I've removed. Just for ****s and grins I submerged the boat to see, and not surprisingly it went right to the bottom of the tank and sat there. Hard. I blew ballast, and it came right up, in fact, it didn't take more than a few seconds for it to get positively buoyant and broach. I kept blowing, expecting to see air bubbles, but apparently the escaping air filled the hull and it got really buoyant:
It also didn't help that the weight slid around, and went aft when it took the up angle. Let's get some roll stability... so I cut some pink foam and worked it around a bit..
And that's where I am right now with the waterline. it's got the good LA lean going, prop is entirely underwater. Roll stability is very good on the surface, it's a little more tender under the water but that's expected. Submerged it's just barely positively buoyant... it does sit on the bottom of the tank but it's very light there. I wish the tank were a little deeper. it does seem to submerge stern first and rise bow first. I'm going to hold what I have here for now, I'm certain some trimming is in order but I have other things to do and I am going to add another layer of cinder blocks to make the tank deeper. One thing that really surprised me, this is all the ballast I used:
I thought it would take a lot more.
After a small amount of thinking, I came up with an idea for a test tank. perhaps not the greatest, but it worked. Cinder blocks and plastic sheeting... easy. Only issue is it's only about a foot deep, which should be all I need. I took a guess at what kind of ballast I would need. Judging from the 4 or 5 lbs I had to put in the tugboat to get it to sit at the waterline, I put all the lead I had on hand in the keel, and dropped the boat in the water without the top hatch.
Sank right to the bottom. Ok then.
I put a more reasonable amount of weight in and dropped it in. Got this, and if it's not obvious from the picture, there is zero roll stability, as expected:
That's not a bad waterline, though... but once I put the hatch on, it was a whole new ballgame.. that additional weight didnt' work in my favor, again, as expected. If you look at the bottom of the picture, you can see the weight I've removed. Just for ****s and grins I submerged the boat to see, and not surprisingly it went right to the bottom of the tank and sat there. Hard. I blew ballast, and it came right up, in fact, it didn't take more than a few seconds for it to get positively buoyant and broach. I kept blowing, expecting to see air bubbles, but apparently the escaping air filled the hull and it got really buoyant:
It also didn't help that the weight slid around, and went aft when it took the up angle. Let's get some roll stability... so I cut some pink foam and worked it around a bit..
And that's where I am right now with the waterline. it's got the good LA lean going, prop is entirely underwater. Roll stability is very good on the surface, it's a little more tender under the water but that's expected. Submerged it's just barely positively buoyant... it does sit on the bottom of the tank but it's very light there. I wish the tank were a little deeper. it does seem to submerge stern first and rise bow first. I'm going to hold what I have here for now, I'm certain some trimming is in order but I have other things to do and I am going to add another layer of cinder blocks to make the tank deeper. One thing that really surprised me, this is all the ballast I used:
I thought it would take a lot more.
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