Topic: Q & A - Blue Marlin - Heavy lift semi submersible ship (Read 119658 times)

boatmadman · « **Reply #75 on:** July 16, 2008, 08:11:15 pm »

Mankster,

Thanks, great stuff and more for me to think about.

Questions:
1: if the foam is inside the free flooding tanks, wont it reduce the ballasting effect of the water?
2:If the deck isnt watertight wouldnt the pumped ballast tanks need to be watertight, otherwise the pumps would never be able to empy the tanks?

Ian

Mankster · « **Reply #76 on:** July 16, 2008, 08:24:31 pm »

1) foam outside the ballst tanks, but inside the free flooding part of the hull - yes the foam is to counter act the water, you are aiming to make the boat a little too haevy so she sinks, then add foam till she floats. The foam added to the sides high up has great stabliziing effect as you are raising the metacentric height (vertical distance between the centre of gravity and the centre of bouyancy) - thats why you want lead at the bottom, foam as high up (just below the water line). The more foam you end up adding the more stable the boat (as well as more heavy unfortunatly as you will need to add more lead to cancel the buoyancy of the foam. Thats why in my initial post I said that if you find that your boat is tender when carrying a heavy load it is easy to correct with more foam and lead.

2) yes you need a sealled ballast tank: water in via a pump through the bottom, air out through a tube to somewhere above the water line (hidden in the upper part of the superstructure will do) - Think off a plastic fuel tank in a rc plane or boat, same principle. Once agian this how the ballast tanks in the 1:1 boat work.

roycv · « **Reply #77 on:** July 16, 2008, 08:27:57 pm »

Hi all I was watching a documentary about a similar ship and the captain said that they sink down stern first to preserve stability and then level up when at required depth.
regards Roy

boatmadman · « **Reply #78 on:** July 16, 2008, 09:04:10 pm »

Great, thanks. Its coming clear now.

Before cutting through the hull, I think I will use a plastic bag in each of the outer sections of the 4 ballast tanks, fill with water, add lead to heavy water line, then pump into the pumped ballast tanks. If I have the idea right this should help me work out just how much extra weight I need?

Ian

Umi_Ryuzuki · « **Reply #79 on:** July 16, 2008, 09:32:24 pm »

Good posts,..

I was already thinking about free flood hulls and "sub driver" WTC.

This is the first time I thought about Lateral balance, and loaded vs unloaded.

:)

Mankster · « **Reply #80 on:** July 16, 2008, 10:38:03 pm »

Quote from: boatmadman on July 16, 2008, 09:04:10 pm

Great, thanks. Its coming clear now.

Before cutting through the hull, I think I will use a plastic bag in each of the outer sections of the 4 ballast tanks, fill with water, add lead to heavy water line, then pump into the pumped ballast tanks. If I have the idea right this should help me work out just how much extra weight I need?

Ian

There's an easier way. The ballast tank only has to lift the volume of the the hull between the high and low waterline + the weight of your load. So you only need to estimate the water displaced by this section of the boat, which is esentially the volume of the materials in this part of the boat. If you have any watertight/sealed off areas in this section, then you need to add the volume of of this area as well. The weight of the area between the high and low lines is immaterial. As the load is not permanently attached to the hull (floats off when submerged and and is carried high and dry surfaced), you need to add its weight .
Divide it between your 4 tanks and then make it say 30% larger to compensate for the triming requirements.

boatmadman · « **Reply #81 on:** July 17, 2008, 04:37:39 pm »

Thanks again Mankster - all becomes clear now. By these calculations I think I will have a lift capacity of 4kg, leaving an extra 1,2 kg for trim.

These pics show the conduit installed to allow wiring to run for/aft....looks a bit messy, but all this will be hidden from view!

The second shows the forward watertight bulkhead dry fitted. This is made from 6mm marine ply - why? cos i had some! Also, I reckon that some extra stiffness at this point will be useful, also, if/when she gets knocked whilst loading, this is a prime target.

Ian

bigford · « **Reply #82 on:** August 02, 2008, 07:26:53 am »

updates

cos918 · « **Reply #83 on:** August 02, 2008, 02:29:54 pm »

hi Ian found this photo of the german model.

john

boatmadman · « **Reply #84 on:** August 02, 2008, 05:39:14 pm »

Nice one thanks. Thats a bit bigger than mine!

Ian

bigford · « **Reply #85 on:** August 03, 2008, 01:04:49 am »

mines bigger then yours

only problem is i dont know how to get it out of my head

and onto the building bench :(

bigford · « **Reply #86 on:** August 08, 2008, 03:12:32 am »

waiting for this ship to sail

so i can pick your brain on all the odd's and ends ::)

boatmadman · « **Reply #87 on:** August 08, 2008, 05:36:11 pm »

Wont be much left to pick after sorting this beast out!

bigford · « **Reply #88 on:** August 26, 2008, 04:01:22 pm »

i wonder if the real ship builder have all these problems

boatmadman · « **Reply #89 on:** August 26, 2008, 06:52:50 pm »

Doubt it...they design it properly, not make it up as they go along!

Umi_Ryuzuki · « **Reply #90 on:** August 26, 2008, 07:43:16 pm »

Quote from: boatmadman

Quote from: bigford on August 26, 2008, 04:01:22 pm

i wonder if the real ship builder have all these problems

Doubt it...they design it properly, not make it up as they go along!

I take it you didn't catch the Mighty Servant 3 incident in 2006? :-\

It sank in about 60 meters of water.... I calculated that the mast is about 65 meters above the keel...
I was told (on shipspotting forum) that the port of Angola would station a boat out by the mast during the day.
But at night the boat would go home, and any evening shipping was on its own.

http://www.cargolaw.com/2006nightmare_mightyserve3.html

All crew survived this incident, and the MS-3 was refloated in May the next year.

hama · « **Reply #91 on:** August 28, 2008, 02:15:40 pm »

This thread is so fun to follow, the thing with the rudderservo is brilliant. I would never have figured that one out and I've now stored it in my memory for future use.
Thanks!
Hama

Martin (Admin) · « **Reply #92 on:** August 28, 2008, 02:28:00 pm »

Is that a hi vis (high visibility) vest in the background or a life jacket?!?!?

boatmadman · « **Reply #93 on:** August 28, 2008, 06:43:24 pm »

Thats a lifejacket - I need it cos the boat sinks!

Ian

Umi_Ryuzuki · « **Reply #94 on:** August 29, 2008, 01:30:26 am »

Quote from: hama on August 28, 2008, 02:15:40 pm

This thread is so fun to follow, the thing with the rudderservo is brilliant. I would never have figured that one out and I've now stored it in my memory for future use.
Thanks!
Hama

Taking notes also!!

Eddy Matthews · « **Reply #95 on:** September 02, 2008, 06:01:15 pm »

The two springers really help to give an idea of the size of the model, thanks.

Although I've had nothing to say on the build so far, I've been watching it with interest, as it's a vessel I've always fancied having a crack at myself one day....

Regards
Eddy

bigford · « **Reply #96 on:** September 02, 2008, 06:02:20 pm »

looking top notch

andyn · « **Reply #97 on:** September 06, 2008, 03:09:57 pm »

Looking superb

Can see this being a nuisance at mayhem next year, while someone is nattering about their boat instead of driving it, you've turned up and nicked their boat ::)

Martin (Admin) · « **Reply #98 on:** September 06, 2008, 05:16:28 pm »

I think boatmadman is going to uplift our boats to the middle of the pond and make demands with menaces!!! :'(

boatmadman · « **Reply #99 on:** September 06, 2008, 06:41:43 pm »

Who told you my top secret plans

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Author Topic: Q & A - Blue Marlin - Heavy lift semi submersible ship (Read 119658 times)

Umi_Ryuzuki

bigford

bigford

bigford

bigford

Umi_Ryuzuki

hama

Umi_Ryuzuki

Eddy Matthews

bigford

andyn