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Author Topic: OTW Vanguard help  (Read 78500 times)

thegrimreaper

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Re: OTW Vanguard help
« Reply #300 on: March 05, 2012, 09:09:47 PM »

I need to recalculate now thought I would re weigh everything which was lucky because I have discovered my WTC weighs in at just under 3Kg don't know weather I can just take of a Kilo of lead from my calcs or is that to simple if I have to recalculate then it can wait till the morning

Regards Mark
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Re: OTW Vanguard help
« Reply #301 on: March 05, 2012, 09:28:43 PM »

Yep, just remove a kilo.

thegrimreaper

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Re: OTW Vanguard help
« Reply #302 on: March 05, 2012, 10:03:30 PM »

Thanks for the quick reply Andy you will have to sort out a dive in this summer mate I owe you a load of drink  O0

Regards Mark
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bonehead

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Re: OTW Vanguard help
« Reply #303 on: March 06, 2012, 08:28:27 AM »

Andy  - Yes, trapped wind is a strong possibilty!! I have been approaching the drilling of strategic holes with reservation as I don't want it to look like a sieve and unrealistic... I add a few and try it again to see any improvement. May bring a drill with me at the next dive session!! I have had some success with spraying the inside with a weak soap solution and the better with shower glass cleaner - much better!! The long deck doesn't help much - which I've added holes to the silo details scribed in their lids/covers. I'll get there in the end!!!
Jim
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thegrimreaper

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Re: OTW Vanguard help
« Reply #304 on: March 06, 2012, 08:56:30 AM »

I think that when I fit the top of the hull to the rest of the hull I am going to have a similar problem to yours Jim not enough holes drilled for the trapped air to escape will just have to see should know later on today once the test tank is inflated and filled

Regards Mark
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Re: OTW Vanguard help
« Reply #305 on: March 06, 2012, 09:38:32 AM »

Candidates for ventilation include about two dozen holes scribed in to the deck for the retractible bollards, the silo hatch doors have vents as already mentioned, and you really could do with a larger hole or two at the stern, as air bubbles tend to get chased back there and trapped.

If you open up that little lot, I can't see you getting any problems with air bubbles under the deck, but you can't ever have too many really, it's a compromise between what looks right and what works right. Earlier boats are a good teacher, especially those of WWII, their decks were full of holes or slots to enable good ventilation and improve dive times.

Patrick Henry

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Re: OTW Vanguard help
« Reply #306 on: March 06, 2012, 10:25:07 AM »

Do you have air release holes in the sail, Mark? I would hazard a guess that any trapped air would end up in the highest point on the boat?


Rich
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Re: OTW Vanguard help
« Reply #307 on: March 06, 2012, 11:37:11 AM »

Have a look at post 263.


thegrimreaper

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Re: OTW Vanguard help
« Reply #308 on: March 06, 2012, 01:09:48 PM »

Why whats wrong with post 263 ?? top vent holes not yet drilled into deck area.

Have just put sub into test pool and got the water line spot on I think according to the plans the water line runs along the same line as the side sensor array (very star trek that) got the sub to dive but guess what Andy was right need a little bit of foam in the rear just to stop her dropping her tail first, used a bit of expanded polystyrene as a trial and that seemed to correct the dive here is a video without any foam at all in the tail. Hope you enjoy

http://youtu.be/Dkd2uqVSn5c

Regards Mark
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thegrimreaper

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Re: OTW Vanguard help
« Reply #309 on: March 06, 2012, 01:16:53 PM »

Sail is hollow Rich and their is a large hole under the sail so air can escape that way 15 holes in the deck as suggested seems to let all the trapped air out from under the deck

Regards Mark
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Patrick Henry

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Re: OTW Vanguard help
« Reply #310 on: March 06, 2012, 01:32:32 PM »

Sail is hollow Rich and their is a large hole under the sail so air can escape that way 15 holes in the deck as suggested seems to let all the trapped air out from under the deck

Regards Mark

Excellent Mark, glad it all seems to be operational...well done that man, pleased for you. Now I guess it's my turn...mine should be here tomorrow with a bit of luck.
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Re: OTW Vanguard help
« Reply #311 on: March 06, 2012, 01:35:44 PM »

No nothing wrong with post 263, Mark. Just pointed Richard towards it, as it the picture at the top showed you had already filed out all the slots in the top of the sail.

Video looks good. Takes a while to dive, but that's to be expected for a tank that size with a small geared pump. Do you have to fill the tank completely to get it under?

Spotted a little bit of torque roll from the prop, but the boat recovers quickly, suggesting things are stable. Quite a bit of ventilation from the propulsor which is to be expected with the boat surfaced. If you look at Ramesh's Typhoon you'll notice he trims it stern down so that the propulsors get a bit more bite. The 1:1 Typhoon captains do this, not sure if they do likewise with the Vanguard, all the pictures and video I've seen show them trimmed level, so perhaps not. 

merriman

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Re: OTW Vanguard help
« Reply #312 on: March 06, 2012, 04:39:04 PM »

Yeah, I note that a pre-swirl stator (and If I had to do it again, I would put less pitch on those blades), when you're going a-stern exacerbates the torque of the rotor, rolling the boat excessively.

Ideally net torque in the ahead direction will be zero if the pump-jet is designed and constructed correctly. However, as I designed and built this pump-jet, I introduced too much angle on the stator blades. The result is that the OTW VANGUARD propulsor stator produces a bit more torque than the rotor. Not much, but enough to notice if the metacentric height built into the boat is not terribly high.

Sorry about that.

David











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Re: OTW Vanguard help
« Reply #313 on: March 06, 2012, 05:21:48 PM »

The original propulsor supplied with this kit had the fixed stator blades as a much more shallow angle of attack, just a few degrees, four or five at most, but it still provides a lot of counter torque.

One day we may get to see what the real ones look like!

merriman

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Re: OTW Vanguard help
« Reply #314 on: March 06, 2012, 05:45:47 PM »

Indeed, Andy.

.... some day.

David
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thegrimreaper

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Re: OTW Vanguard help
« Reply #315 on: March 06, 2012, 06:11:14 PM »

Very nearly had a second video this evening BUT I couldn`t for the life of me get the foam to stay in position no matter how I tryed to stick it I think it might be over the top to use no nails so I will purchase some more bath sealent in the morning ready to restart ballancing on Saturday.
 Dave the stator looks fantastic think its just the case of learning not to increase speed from a dead stop to quick. It looks better than just a prop on their and it do`s the job thanks

Regards Mark
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Re: OTW Vanguard help
« Reply #316 on: March 06, 2012, 06:20:16 PM »

Is 'No nails' waterproof? Silicone is though.

Blu tack sometime works for temporary fixing.

Propulsors look very jet-set, but you'll discover the fixed shroud doesn't help the turning circle.

thegrimreaper

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Re: OTW Vanguard help
« Reply #317 on: March 06, 2012, 07:20:39 PM »

maybe just maybe I dont want to go round in circles  %% %% {-) silicon it is then

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thegrimreaper

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Re: OTW Vanguard help
« Reply #318 on: March 10, 2012, 07:29:37 PM »

Will be finding out about that turning circle on the morrow Andy off to new brighton to launch the Vanguard got the ballance pretty much where I want it to be I think waterline is very good submerges level and will sit level in my pool so...............HAPPY DAYS  Thanks to everyone who contributed while the build was on going. The Trafalgar is next  :D :D :D

Regards Mark
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merriman

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Re: OTW Vanguard help
« Reply #319 on: March 10, 2012, 07:40:37 PM »

Take pictures!

And take note of torque roll -- which direction, how much; any 'walking propeller' effects, so-on-and-so-forth. I want a full report.

David
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thegrimreaper

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Re: OTW Vanguard help
« Reply #320 on: March 10, 2012, 08:29:54 PM »

Pictures not a problem David, wife will be doing them with video as well but this is only my second sub David so please forgive me  but "walking propeller" effect ????

Regards Mark
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Re: OTW Vanguard help
« Reply #321 on: March 10, 2012, 08:40:20 PM »

Good explanation on wiki- http://en.wikipedia.org/wiki/Propeller_walk

Affects targets too.

bijou

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Re: OTW Vanguard help
« Reply #322 on: March 10, 2012, 08:46:17 PM »

HI,
@merriman-
I don't know anyting about these complicated propulsion sistem and I am a litle lost heare!  <:(
Yeah, I note that a pre-swirl stator (and If I had to do it again, I would put less pitch on those blades), when you're going a-stern exacerbates the torque of the rotor, rolling the boat excessively.

Ideally net torque in the ahead direction will be zero if the pump-jet is designed and constructed correctly. However, as I designed and built this pump-jet, I introduced too much angle on the stator blades....




can You make some light heare?   PLEASE?
MARIUS
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bijou

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Re: OTW Vanguard help
« Reply #323 on: March 10, 2012, 08:50:46 PM »

I mean each propeller is mouving in oposite direction but with diffrent speed?  {:-{
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merriman

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Re: OTW Vanguard help
« Reply #324 on: March 10, 2012, 08:59:07 PM »

A phenomena that is attendant to the rotation of a screw-type propeller in a fluid: Propeller Walking is a force, perpendicular, and along the horizontal plane, to the propellers axle. The direction of that yawing force in the direction of motion if the bottom tips of the blades were to enjoy the same type traction as those of a road wheel. For example: looking forward, a right-hand (clock-wise) turning propeller will 'walk' to the right; if left-handed (anti-clock-wise), the propeller would 'walk' to the left.

A single-screwed submarine with a right-hand turning propeller will (at the propeller disc) produce a yaw to the right when going ahead -- that force, working through the vessels c.g. will produce a swing of the vessel to the left and vice versa.

The walking effect is mitigated a bit by a shroud (Kort nozzle for example), and entirely by a properly designed pump-jet.

I'm asking you if you see much walking effect on your VANGUARD, as that is an indication of improper stator-rotor matching. I'm trying to gather some empirical data on the design as it stands today. I have dope on the prototype I built, but additional observation, from disinterested parties such as yourself, would help me refine cause and effect of the current arrangement.

David
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