type 214 "ΠΑΠΑΝΙΚΟΛΗΣ"

[redboat219]

I was wondering if it would be possible to use in this set up a centrifugal (dynamic type) pump instead of a gear or peristaltic (positive displacement type) pump? Dynamic pumps have the ability to operate under closed valve conditions, as oppose to positive displacement pump which result in a continual build up in pressure resulting in mechanical failure of either pipeline or pump ( in this case rupture of the bag ) hence no danger of overfilling.

Since they're no designed to run reversible I would need to install 2 pumps, 1 to fill and another to empty the bag.

[He Who Shall Not Be Named]

I was wondering if it would be possible to use in this set up a centrifugal (dynamic type) pump instead of a gear or peristaltic (positive displacement type) pump? Dynamic pumps have the ability to operate under closed valve conditions, as oppose to positive displacement pump which result in a continual build up in pressure resulting in mechanical failure of either pipeline or pump ( in this case rupture of the bag ) hence no danger of overfilling.

Since they're no designed to run reversible I would need to install 2 pumps, 1 to fill and another to empty the bag.

Good point and a practical, simple solution to the over-pressurization-of-the-bag problem. Yes, the centrifugal pump is self-limiting as to maximum system pressure, but that very same 'leak-by' characteristic that makes the centrifugal pump useful in this application also necessitates the inclusion in the system of a valve to isolate the pump from the filled bag. No big deal, a simple pinch-tube type valve will work here. The same cam that toggles the pump switch 'on' can, in the other direction, pinch the supply tube from pump to the bag 'shut'.

And yes, you can use a second centrifugal pump to empty the bag. You could also use the one centrifugal pump with four isolation valves (arranging the pump and valves in a 'balanced bridge' type circuit -- though hydraulic, not electronic) to fill, isolate, and empty the bag.

David,

[redboat219]

You could also use the one centrifugal pump with four isolation valves (arranging the pump and valves in a 'balanced bridge' type circuit -- though hydraulic, not electronic) to fill, isolate, and empty the bag.

Can you provide an illustration (even a hand sketch will do)

Thank you.

[bassplayer1]

Very usefull advise indeed, I still have a lot to learn from you people! Thank you all! Something I forgot to mention on my previus post is that I do have instaled a fail-safe and also a "pinch" valve on the way to the bag. Here is a photo.

[He Who Shall Not Be Named]

Very usefull advise indeed, I still have a lot to learn from you people! Thank you all! Something I forgot to mention on my previus post is that I do have instaled a fail-safe and also a "pinch" valve on the way to the bag. Here is a photo.

Ah! The picture tells it all. You are almost completely covered.

But, one last casualty scenario for you to consider and protect against: Partial loss of system power; the receiver and fail-safe and hence the servo loose power, but the pump-motor does not -- a blown BEC could cause this situation -- while inflating the bag.

That would necessitate a relief valve somewhere between the pump discharge nipple and the bag. That relieve valve either dumping overboard or into the suction side of the pump. May I suggest a modified Schrader valve?

David,

[bassplayer1]

That's something I never thought off! Thanks a lot again David!

[He Who Shall Not Be Named]

Geared water pump, not a peristaltic.

Oh! I stand corrected, Andy. Good catch. Thanks.

That explains the pinch-valve in the discharge line. Duh!

David,

[Outrider]

Nice to see the Wizard engaged again on the Type 214. Now maybe we can get him to start talking about his own Type 214 work again. Though it's "merely" a 1:144 Revell kit, it's still nice work. If only we knew more about it... It's an interesting topic in any scale. If only we could receive some wisdom on the subject. If only...

[Albion]

Dynamic pumps have the ability to operate under closed valve conditions,

For a short period

It should also be remebered that centrif pumps run at a lower flow as the pressure increases, so getting that last drop into the bag may take some time

[bassplayer1]

Hi everyone! I had a good time today sailing my 214! Some more adjustments have to be done but generally speaking I'm quiet pleased with that! Here are some pictures and tomorrow I'll post a video!

[Slats]

A beautiful boat and I admire your set up and craftsmanship. One area of concern. About 10 years ago I applied a similar pinch valve to a line to a sealed rigid tank.
The boat ran beautifully for many many months, until the pinch valve (which in my case was a roller on the end of the servo arm), finally combined with the water pressure to fatigue the line enough to cause a crack in the flexible line I used. May I suggest as part of your preflight checks that you thoroughly inspect the line for fatigue / failure every day you use it. The boat that this happened to still sails today in the hands of a collector. But in handing it over to him, I suggested he not only regularly check the line but he replace it after every 20 hours of operation. There is nothing at all wrong with the set up, Norbert B's book even documents it, but its an area of expected fatigue and eventual part failure that needs to be respected. I apologise in advance if you are already aware of this.

Best
John

[He Who Shall Not Be Named]

Wonderful work! An inspiration.

(I've got to get this damn little 1/144, Type-214 going for Jim -- long promised and still in work).

I'm simply amazed at your fabrication expertise and ability to integrate, successfully, the sub-systems required to get this beautiful model working. You have taken us back to school with this project; this thread has been very instructive. Thank you.

Yeah, let's see that video!

David,

[bassplayer1]

Thank you guys! Here are a couple of videos but they are not very good, it's my son messing around with the camera!http://www.youtube.com/watch?v=ppYvi7E8NFE

http://www.youtube.com/watch?v=qrVQGemkaVE

[Slats]

A nimble performer - well done.
J

[bassplayer1]

Thank you John also for the advice about the pinch valve! To be honest, it does worry me a bit! Mind you I liked your thread about the semi aspirated tank and I'm thinking about making one when I get some time! That will solve the problem of the pinch valve and I won't have to worry about it any more!