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edit to post #13
I forgot the bow dive plane guards.
Here they are...
Dan
I forgot the bow dive plane guards.
Here they are...
Dan
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Born in Detroit - where the weak are killed and eaten. -
Pretty fair shipping box, but bubble-wrap does not an inner box make! should have been double-boxed with at least a 2" annular space.
The glass layup (chop-gun) is way, way, way, way waaaaayyyyy overdone! the upper hull half must weight a ton.
Love the engineering that went into the bow and skeg pieces -- good work.
DavidWho is John Galt?Comment
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DIY cam - the ballast system "brain"
Sheerline uses a very simple ballast system. Basically, water is pumped into a closed tank which a) adds weight to the sub - causes it to dive, and b) pressurizes the trapped air inside the tank. As the pump is not the sealed type a pinch valve in needed to hold the air and ballast water in the tank.
here is the pinch valve...
here is the switch controlling the pump motor...
Sheerline recommends using a ball raced servo. I chose this one...
here is the servo mounted on the equipment tray...
there are three states to the cam:
here is the cam...
1) pinch valve open - air and water flow in or out of the tank + pump is off...
2) pinch valve closed - pump motor off...and
3) pinch valve open - pump motor on - ballast water is being pumped into the tank...
the cam was made from a medium sized servo wheel.
DanBorn in Detroit - where the weak are killed and eaten.Comment
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A beautifully simple and effective method of getting the water in and out of the ballast tank. Problem is the free water in the tank in submerged trim -- will its shifting around adversely affect pitch stability?
David,Who is John Galt?Comment
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Fair enough - I'm hoping there's baffles in the tank.
What you can't see from my pictures is the built-in failsafe. If I make the cam so that the pinch valve is never truly totally closed then there will be a slow but steady leak of water from the tank. Not enough to greatly disrupt the diving trim but enough so that, over time (the time is determined by the amount of leak) the sub will return to positive buoyancy and surface. Personally, I'd like to see a more positive/active failsafe like a gas system blowing out the water but that's not the case here.
DanBorn in Detroit - where the weak are killed and eaten.Comment
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more..........
more parts...
DanBorn in Detroit - where the weak are killed and eaten.Comment
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Who is John Galt?Comment
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yes, more parts...
we're almost done with parts.
DanBorn in Detroit - where the weak are killed and eaten.Comment
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the tower
the tower...Born in Detroit - where the weak are killed and eaten.Comment
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Stability is good with these models. If they were poor performers, they wouldn't still be selling 20 years after they first appeared on the market.
Most of the models are now supplied with NiMH batteries configured into a long stick that's slung underneath the cylinder. The Type II is one such model, alongside the Trafalgar and Ohio class models.
The latter two originally used Pb batteries mounted in the bow, and in fact the Akula still uses this method. Twenty years ago, the only way to get a high capacity battery for reasonable cost was a lead acid brick. But the stability of the Trafalgar and Ohio was considerably compromised with this set-up, as both boats have larger tanks to deal with the large freeboard of these boats. Chris modified the designs by switching to underslung NiMH batteries, and thinning out the top half laminate- the boats handling improved instantly. I believe the tanks are baffled inside, although the Akula may not as the tank is very small on that boat.
One thing to be mindful of, is that after a few ballast cycles a little residual water remains in the tank, not very much, but enough to lower the boats trim a little- clearly a little compressed air escapes with the ballast each time the system is cycled. I've seen some people use a bicycle pump to empty the tank completely after a run.
I see a lot of Sheerline boats at the Dive-ins, they're proved themselves to be exceedingly reliable and tough, the laminates are rather beefy (hand laid CSM I believe as opposed to a chop gun), but it does have the advantage of making these boats very resiliant to the bangs and scratches that go hand in hand with working models.
Chris tends to recommend the slow leak mechanical failsafe, as it's as close as you can get to a 100% failsafe. An electronic system can only work if you have power available to move the servo, and indeed run the microcontroller on the failsafe! If the pond you sail in is wadeable, or a pool, you can adjust the pinch valve to shut off completely.
One last thing, always make sure the the pinch valve is unpinched when the boat is stored between runs, if you leave it pinched up the tubing will lose its springyness. Some people use a small ball valve available from Festo in place of a pinch valve. These work very well, but you can't set them up for the 'slow leak' failsafe, also you need to modify a servo to operate over 180 degrees (or use a servo extender) to actuate them.Comment
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fore and aft equipment trays
I've reached a point where I can't continue without the ballast tank which is, hopefully, on its way to Sheerline. Here is as far as I can go on the equipment trays until I get the tank back:
ballast control tray...
drive motor tray...
Might as well start on the dreaded drain holes while I'm waiting.
DanBorn in Detroit - where the weak are killed and eaten.Comment
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I started today opening up the flood holes on the solid bow casting. All I can say is that I'm so bad at this. I'm not even going to show the initial results as they're that bad. Methinks I have to find someone with a milling machine to do this job correctly. I can't even imagine doing the several hundred holes in the deck without some sort of machine aid. This puts my end of July deadline in serious question but I'd much rather do it right than show up with a total "butcher" job.
DanBorn in Detroit - where the weak are killed and eaten.Comment
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