Model Boat Mayhem - Forum

Please login or register.

Login with username, password and session length.

Author Topic: OTW Vanguard help  (Read 78485 times)

thegrimreaper

  • Guest
Re: OTW Vanguard help
« Reply #50 on: November 15, 2011, 11:16:13 AM »

 :o %% :o %% I like that idea even better Andy that is doable. Up to now taken 3 days to do two inner disks must concentrate more on the sub and less on work. (I wish ). Two days of after today so full tilt boogy on the WTC 

Thanks again Andy

Regards Mark
Logged

bonehead

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 38
  • Location: Cambridge
Re: OTW Vanguard help
« Reply #51 on: November 15, 2011, 05:23:11 PM »

Hi
If you get the WTC as low as possible - where can you fit any lead ballast? I only ask as my tank is currently within 5mm of the hull wall at the bottom and resulted in the lead sheet ballast having to be spread out along the bottom for 70% of the WTC - if anyone out there has a better solution I will move the lead and have a winter refit! I also had to be carefull not blocking the drain holes along the underside too so I drilled through any sheet that got in the way. I supported the tank with five supports as I thought it might flex and possibly leak? Would appreciate some better mind than mine coming up with a better idea!  :embarrassed:
Jim
Logged

Subculture

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,887
  • Location: North London
    • Dive-in to Model submarines
Re: OTW Vanguard help
« Reply #52 on: November 15, 2011, 06:06:21 PM »

You can put the drainage slots fore and aft of the wtc, like the original. You don't really need that many holes on the bottom, although it helps drainage when hooking it out of the drink, it's more important to have more holes in the top to get rid of any trapped air.

Regarding the lead, you could cast it into rods or strips, and position it either side of the cylinder, or put it inside the cylinder if you have the space. You can also position it at either end of the cylinder.

In the case of the OTW module, the larger diameter makes things a bit more tricky. Certainly with about 1.5cm sitting above the waterline, that's eating up a lot of ballast tank volume. How long is the WTC? I estimate somewhere between 80-90cm.

thegrimreaper

  • Guest
Re: OTW Vanguard help
« Reply #53 on: November 16, 2011, 06:45:29 PM »

O.K. said I would post pictures of my Build of the WTC  got a few done now after a false start now got all the end plates cut out and trimmed true have now plastic welded the inner caps to the outer caps made up three baffle plates going for the conventional vertical plates with holes in (sorry Andy not using a horizontal one as an experiment, me building a W.T.C is experiment enough  OK2 ) I am using zinc rods at the moment but will be changing them for brass rods once the build gets further along

first picture is of the 1000mm tube



Second picture is the first cut which is for the ballast tank



third picture is the end plates inner and outer




fourth picture is the end plates glued together



more to follow

Regards Mark


Logged

Subculture

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,887
  • Location: North London
    • Dive-in to Model submarines
Re: OTW Vanguard help
« Reply #54 on: November 16, 2011, 08:36:02 PM »

Good stuff. The horizontal baffle plate was a tip passed onto me by Ron Perrott. I notice a horizontal baffle was used in his little Aquabat model. The vertical baffles will do the job though if you're more comfortable with fitting those.

thegrimreaper

  • Guest
Re: OTW Vanguard help
« Reply #55 on: November 17, 2011, 04:45:20 PM »

Talking of baffle plates, I have fitted two onto the centre (what would you call it) pipe ready to seal the ballast tank



More later

Regards Mark
Logged

Subculture

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,887
  • Location: North London
    • Dive-in to Model submarines
Re: OTW Vanguard help
« Reply #56 on: November 19, 2011, 10:39:11 AM »

Looks like you're making good progress.

thegrimreaper

  • Guest
Re: OTW Vanguard help
« Reply #57 on: November 19, 2011, 06:38:46 PM »

just about to seal the ballast tank not to sure if I have the size correct now I have just looked at Turbulent build from 2008 link http://www.modelboatmayhem.co.uk/forum/index.php?topic=14501.0  and his ballast tank looks a little bit bigger than I have built




if someone  (Turbulent, Subculture ) or anybody could reassure me on the size I have made mine I would be grateful
Logged

Subculture

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,887
  • Location: North London
    • Dive-in to Model submarines
Re: OTW Vanguard help
« Reply #58 on: November 19, 2011, 07:27:41 PM »

Don't forget he used 80mm tubing for his module, so would need a longer tank to get the right volume.

How long have you made the tank, and also what's the diameter of that conduit running through the middle?

thegrimreaper

  • Guest
Re: OTW Vanguard help
« Reply #59 on: November 19, 2011, 07:53:51 PM »

length of tank is 20cm and the conduit is 3/4 inch I now know that I miss understood earlier post by yourself Andy. Jims is 22cm X 11cm I now think mine needs to be longer about 28 cm X 10 cm  maybe even longer due to the conduit running down the centre

Regards Mark
Logged

Subculture

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,887
  • Location: North London
    • Dive-in to Model submarines
Re: OTW Vanguard help
« Reply #60 on: November 19, 2011, 09:10:26 PM »

Assuming you can fill 70% of your tank, subtracting the conduit and baffle discs gives you about 860ml volume. Provided the wtc sits below the waterline, you'll be fine.

Jim's tank has to be a lot bigger because of the 11cm diameter tubing, quite a bit of which sits above the waterline, so I wouldn't go by that, else you'll end up with a much bigger tank than you actually require.

thegrimreaper

  • Guest
Re: OTW Vanguard help
« Reply #61 on: November 19, 2011, 09:33:21 PM »

Right thanks for clearing that up Andy will bond the end caps to the tube in the morning if its the wrong size when I get the hull then I will just have to remake the ballast tank thanks again Andy

Regards Mark
Logged

thegrimreaper

  • Guest
Re: OTW Vanguard help
« Reply #62 on: November 20, 2011, 08:44:17 AM »

O.K. corrections to be made now must remember to measure twice cut once,  :embarrassed:  ballast tank is only 18cm long I was measuring from the outside of the end caps, instead of the internal size I was measuring the external size so I am going to re cut a piece of tube to 27cm that should give me an internal size of 25.8cm  O0  which is probably a little larger than is required but I would rather have the ballast tank  a little bit bigger than too small, hopefully that size of tank will be enough to get a Vanguard to submerge
Logged

Subculture

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,887
  • Location: North London
    • Dive-in to Model submarines
Re: OTW Vanguard help
« Reply #63 on: November 20, 2011, 11:07:13 AM »

I'd try it out in the hull first. Even with the smaller volume I think you will be okay.  At 70% full, you have over 750ml of volume, and provided that the cylinder sits below the waterline, you need to displace about 700ml. How did I come up with that figure?

The upper half the of the Vanguard hull, moulded from polyester GRP weighs in at about 825 grams. The polyurethane resin parts- sail, front hydrovanes and rudder weigh about 120 grams. Now we know that 1000ml of water weighs 1000grams, metric makes it easy. But some materials are lighter than water, and some are heavier, so be careful when using weight alone to determine the size of a ballast tank.

Many plastics like ABS, polyurethane and polystyrene are the same density as water, so we can use weight to determine displacement. But composites like GRP are denser- the glass content is what makes the difference. Then we need to adjust our figures a little

In the case of the upper hull, we don't have all of it above the waterline, and a rough calculation removes about 120 grams and I'm erring on the conservative side. GRP laminate is about 25% denser than water, so when converting to displacement we reduce the volume still further.

825-120= 705  then  705x75%= 529 ml displacement for the upper hull

The polyurethane parts are equal in density to water, so in that case we can directly convert the weight to displacement, so 529+120= 649 ml displacement

That leaves another 51 grams-  I haven't accounted for periscopes and paint, so that allows for that.




 

Subculture

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,887
  • Location: North London
    • Dive-in to Model submarines
Re: OTW Vanguard help
« Reply #64 on: November 20, 2011, 02:09:25 PM »

If you're indifferent to the pocket calculator method (which still has a margin of error) then here's an empirical and very accurate method of working out ballast tank volume, explained by Skip Asay.

Build your boat to the extent that everything is done except the ballast tank itself. Put it in your test tank and you'll almost certainly discover that it's light. Add whatever weight is necessary wherever necessary to get it to JUST submerge - not sink like a rock - and sit as level as possible. Something like just enough weight to have it float with just the top of the conning tower out of the water and then add just enough to get it to completely submerge. At that point, a couple of quarters would probably suffice.

Now add square or rectangular polystyrene foam blocks under the hull until the boat sits at its proper waterline. Since it's a round bottomed boat, you'll have to start by building a cradle (use foam) so the foam blocks won't just roll out from under. Make that cradle and the foam blocks you put under it approximately 4" - 6" long. When the boat is at its proper waterline, determine the cubic volume of all the foam (including the cradle) by multiplying length X width X thickness. Then convert that to the volume of a cylinder (3.14 X radius squared X length).

Another benefit to this method is that by sliding the foam fore and aft, you can determine the EXACT location for the tank.

Yes, when all is said and done, you'll have to remove weight equal to the weight of the ballast tank itself but that's a small price to pay. Plan ahead when you're adding the weight to begin with - don't make it all permanent.

Skip Asay

thegrimreaper

  • Guest
Re: OTW Vanguard help
« Reply #65 on: November 20, 2011, 05:37:12 PM »

 :o :o Wow er thanks Andy I think  :} problem that I have is that I cant even order the hull until December so trying it in the hull is a no no at the moment. I can still continue with the build though and alter the size of the ballast tank as and when the time comes. I can put it all together using the zinc rods that I have test the WTC for leaks and then when the hull arrives change out the ballast tank if needed after testing in the test tank and also change the zink rods for brass. Cant thank you enough though Andy for the tips and explanations that you have given on here and the tips from the other members aswell.

Regards Mark
Logged

Subculture

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,887
  • Location: North London
    • Dive-in to Model submarines
Re: OTW Vanguard help
« Reply #66 on: November 20, 2011, 06:36:17 PM »

Good stuff. Hope I didn't confuse you, just trying to explain how I arrived at the figure I did.

thegrimreaper

  • Guest
Re: OTW Vanguard help
« Reply #67 on: November 20, 2011, 08:03:35 PM »

not at all well not a lot anyway much just truly greatful for your help on the matter Andy I want to get it right at the end of the day

Regards Mark
Logged

thegrimreaper

  • Guest
Re: OTW Vanguard help
« Reply #68 on: November 21, 2011, 09:36:21 PM »

Put a full day in today working on the WTC also started on the front tek rack




the overall length of my WTC is 68cm





I have built in 2 baffles into the ballast tank

Regards Mark
Logged

thegrimreaper

  • Guest
Re: OTW Vanguard help
« Reply #69 on: November 22, 2011, 02:37:32 PM »

More done today but not as much been working on the pinch valve quite a simple device to make and fit but it holds the sub under and lets her surface can also be made to have a leak past as a built in fail safe a slow acting fail safe but free

the two main components



and how they fit together




I think we all know the principle of the pinch valve

Regards Mark
Logged

Subculture

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,887
  • Location: North London
    • Dive-in to Model submarines
Re: OTW Vanguard help
« Reply #70 on: November 22, 2011, 04:18:29 PM »

Coming along. If you want some stainless steel studding to replace the zinc plated stuff, these chaps are pretty good-

http://stores.ebay.co.uk/stainlessbolts/Stainless-Allthread-Studding-/_i.html?_fsub=5429090&_sid=268924222&_trksid=p4634.c0.m322

thegrimreaper

  • Guest
Re: OTW Vanguard help
« Reply #71 on: November 22, 2011, 05:29:20 PM »

Thanks for the link Andy will probably be going the brass way just attempted to fill the ballast tank and sprung a leak at the inter-connection pipe so a re-seal is in order now

Regards Mark
Logged

Subculture

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,887
  • Location: North London
    • Dive-in to Model submarines
Re: OTW Vanguard help
« Reply #72 on: November 22, 2011, 05:44:23 PM »

Oaky. Are you able to get brass studding cheaply? I've always found it a bit tricky to source- brass rod is easy though.

thegrimreaper

  • Guest
Re: OTW Vanguard help
« Reply #73 on: November 22, 2011, 06:33:33 PM »

Brass rod available from B & Q 5.odd for a 3 foot length, I have a tap & die? set for threading so not a problem. Will retest ballast tank tomorrow evening

Regards Mark
Logged

Subculture

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,887
  • Location: North London
    • Dive-in to Model submarines
Re: OTW Vanguard help
« Reply #74 on: November 22, 2011, 07:23:09 PM »

Ah okay. Agreed, rod is easy enough to source and cheap(ish). Brass studding is more difficult though. The only alternative to purchase, is screw cutting your own. Running a die beyond an inch or two of thread isn't practical, you end up with a wonky thread.
Pages: 1 2 [3] 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18   Go Up