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Author Topic: Q & A - Blue Marlin - Heavy lift semi submersible ship  (Read 71250 times)

andyn

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #175 on: April 17, 2009, 09:53:34 PM »

It will sit lower with a load on the back, the whole boat weighs more when it has load.
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boatmadman

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #176 on: April 17, 2009, 10:04:45 PM »

I think the real boat has sufficient reserve buoyancy to adjust to normal running depth whether it has a load on or not, I have seen pics of her loaded and unloaded at about the same draft.

For the model, I want to try and get the same draft loaded as unloaded, mainly because there is very little freeboard. But, if I cant then its no real problem, it just means the deck may be awash in a ripple :D
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andyn

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #177 on: April 17, 2009, 10:27:36 PM »

Then what you need to do is remove lead until it sits at a normal level with load on it, when there isn't a load onyou are going to have to leave some water in the tanks...

This is going to be the most complicated bit methinks...
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AlanP

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #178 on: April 17, 2009, 10:36:58 PM »

If all efforts fail Ian, bring it down to the pond on Sunday and I will bring some chalk and we can reposition the water line  :}

Always happy to help out with a technical question   %)

Alan
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boatmadman

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #179 on: April 17, 2009, 10:49:13 PM »

Alan,

thanks for that, I knew there would be a technical solution out there somewhere!
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Mankster

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #180 on: April 18, 2009, 12:47:46 AM »

You are going to need to increase the capacity of your bumped ballast tanks to lift that load. may be you can covert some free flodding areas.

boatmadman

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #181 on: April 18, 2009, 08:36:13 AM »

Mankster,

I suspected as much. Unfortunately, thats not too easy due to the construction, I think I will work with a lighter load for now, if I come up with a workable solution to increase the pumped ballast then I may modify later.

Ian
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Bunkerbarge

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #182 on: April 18, 2009, 09:01:06 AM »

Obviously back to the basic concepts Ian, you first need to determine just what you have available as reserve ballast.  Obviously the boat needs to be stable and ballasted without load so I would start off with her in this condition at the correct water line.  Then pump out all the ballast you can into a measured container and see just what weight you can replace with the load. 

That would indicate the weight you can replace however you must also take into consideration the stability.  Although you are simply replacing the same weight with the load the ballast is low down in the hull but the load is quite high up so you will have significantly reduced the righting moment (GM). This will have the effect of reducing the weight that you can add as load to maintain the suitable stability.

I think, bearing in mind the scale proportions, that a quite light load will be the answer to start with to maintain the required stability.  Tests in the bath will be cruicial but don't simply observe the level at which the model floats, you must also induce instability by pushing the top of the mast over and observing the speed at which it returns to upright.  If it is slow to recover then it will not be suitable to sail.  Unfortunately this is one area that scale works against our models and we need our models to return to upright dramatically quicker than you would expect in a real vessel.  This is dictated by the fact that waves you will encounter on the pond with be striking the model at a frequency of perhaps 2-3 per second whereas in the real world the ship will be experiencing wave frequencies of somewhere in the region of 10 seconds.  Consequently you need your model to return to upright substantially quicker than a real ship as your righting moment has to be proportionally greater.
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hama

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #183 on: April 18, 2009, 01:53:18 PM »

Just want to be of assistance if possible cause this is such a wonderful project. As said before, some of the fixed ballast must be switched to water ballast in some way. Perhaps one or two dedicated ballast tanks. This water ballast that gets her to correct waterline without load, will help her get to correct level with load when pumped out.   {:-{
Oh, I hope you find a solution to this. Would be great to see her perform.  GOOD LUCK!
Hama
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Martin [Admin]

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #184 on: April 19, 2009, 01:12:46 PM »

Impressive, I remember it when it was frames on a workbench..... how fast they grow up!

Is it going sideways in that first pic?   :-))


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hama

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #185 on: April 19, 2009, 01:46:02 PM »

I agree, very impressive! Looks great on the water! Thanks for showing.
Hama.
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DickyD

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #186 on: April 19, 2009, 03:40:23 PM »

Really very nice Ian, well worth the wait.  :-))
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Umi_Ryuzuki

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #187 on: April 21, 2009, 12:09:05 AM »

Ian,

It is Gorgeous out on the water. Great job!  8)
Great build up.

Aimee
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TCC

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #188 on: April 21, 2009, 11:50:21 AM »

Is that single prop enough to move the model when loaded?

Though thinking about it, I suppose slow and steady is the watchword for when the real things sail.

Good build!
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chingdevil

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #189 on: April 25, 2009, 01:03:56 PM »

She looks great on the water, Great Job :-)) :-)) :-))


Brian
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Martin [Admin]

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #190 on: April 25, 2009, 01:07:06 PM »

Will she me making her way to Mayhem at Wicksteed - May 23, 24?
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boatmadman

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #191 on: April 25, 2009, 03:11:02 PM »

Certainly hope so  :-))
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Martin [Admin]

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #192 on: April 25, 2009, 03:16:29 PM »

Excellent! I'm sure we can work out a salvaging, pirating cartel and we can split the ransom 50 / 50!  ok2
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andyn

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #193 on: April 25, 2009, 03:17:17 PM »

Excellent Stuff :-))

I will be bringing the Smit Houston, but I won't be sailing it. It's an open lake and it doesn't like waves....

If you think about it, it's 1:250th scale, and if 3 waves hit it per second, that are about an inch tall (up and down), then you've got a scale wave of 20ft hitting the boat at 750 times per second :o :o :o
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Martin [Admin]

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #194 on: April 26, 2009, 07:10:07 PM »

 :-)
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DickyD

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #195 on: May 04, 2009, 10:39:43 AM »

Ian have you tried putting your photos on using Photobox ?
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boatmadman

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #196 on: May 07, 2009, 08:54:59 AM »

Dicky,

I have managed to get them to a useable state, but just havent had time to post them yet - I have to request the thread to be unlocked to post.

Ian
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Bunkerbarge

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #197 on: May 07, 2009, 10:44:20 AM »

Let us know as soon as you are ready Ian.
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Bryan Young

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #198 on: May 07, 2009, 05:55:32 PM »

Then what you need to do is remove lead until it sits at a normal level with load on it, when there isn't a load onyou are going to have to leave some water in the tanks...

This is going to be the most complicated bit methinks...
Wouldn't leaving free water in the tanks lead to a "free-surface" effect and possibly make the vessel unstable? Just asking. BY.
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boatmadman

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Re: Q & A - Blue Marlin - Heavy lift semi submersible ship
« Reply #199 on: May 07, 2009, 07:01:37 PM »

Brian,

I was conscious of the potential for the free surface effect and fitted bulkheads drilled with vents every 75mm or so.

Ian
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