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RE: [PSUBS-MAILIST] drive test



I enjoy following these progress reports, thanks. Good point on sensitivity of the longitudinal trim. On a K-250, just opening the hatch throws the boat off trim perceptibly, because the weight of the hatch moves a little aft when opened. 


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From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Recon1st@aol.com
Sent: Tuesday, September 01, 2009 9:45 AM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] drive test

I will get some video out. The last test my camera person did not make it.
 
I have been finding out I am not totally comfortable with the wide open MBT's
In one of my tests I dumped the air out of the aft tank. What I did not like is it
would not recover. The angle would not allow enough air to start bringing it up.
I know all I had to do was let a little out of the front to square it up, but just seems
like not the perfect situation. I will need to tow great distances on Lake Superior
and I can see the air dumping with the wave action.
 
I may consider closing them up quite a bit, and or adding another tear drop type in the
aft. Can never have enough freeboard.
 
Open water trials will start next week. My surface support boat is getting new ignition
systems, tired of fighting with those old points.
 
As a newbe I am a little surprised at how touchy the balance is. I understand much better
why a movable weight is advantages in the fine trimming. Maybe later.
 
In a message dated 9/1/2009 12:12:05 A.M. Central Daylight Time, ShellyDalg@aol.com writes:
Hi Dean. Ya, pin holes can be hard to find. You can put duct tape over the bottom holes and pump up the tanks with a small compressor. It doesn't take hardly any pressure to make bubbles at a pin hole. Just squirt soapy water all round and bubbles will form at the leak.
Hope you're having fun testing.
Some of the guys are putting poppet or mushroom valves on their tanks to let the air out quicker, so submerging doesn't take so long. I'm like you in that respect. I'm not that concerned with how long it takes to flood the tanks. I'm using 1 inch valves and the bottom holes ( 2 on each tank ) are about 3 inches in diameter. I'm putting little diverters on the holes so water won't be forced into the tanks if the sub needs to be towed at relatively high speeds.
With 2 holes on each tank I should be able to "blow ballast" and get the water out fairly quickly. The tanks are 12 gage so a little pressure build-up when dumping air into them shouldn't be too risky. Worst case scenario would be to "bulge" the tanks a little if I added air too quickly. Expensive to replace but not life threatening.
Are you going to take any video of your sea trials? That would be a real kick in the ass to see.
Be careful and have LOTS of fun. Frank D.