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Author Topic: Help with Morecambe Bay prawner build.  (Read 3578 times)

BJH

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Help with Morecambe Bay prawner build.
« on: June 26, 2007, 12:50:35 PM »

Hi   Ladies  and  Gentlemen,

I have just started on my first project, a Morcambe Bay Prawner (Nobby) using the Waverley Models GRP hull (44” Loa, 12” beam) and  am in need of  some advise to give me a bit more confidence. This is my first posting so please be gentle with me!

I have a number of  modelling books, and the plans and notes supplied with the hull. I have a copy of L.J .Lloyds book  “The Lancashire Nobby” and  have  found various web site’s  that have  been helpful ( www.newson.co.uk  , www.nobbyownersassociation.co.uk ).

However the photos in the notes supplied with the hull have not copied very well and a bit more detail would  help me. I am at the stage where I have fitted the deck supports  and deck beams.
     
Has anyone here built one of these or a similar single masted  Gaff Cutter and have any build sequence photos that may help me.

Particular points that I need to clarify are

1). What overall weight am I working towards for the finished model and the amount of lead ballast that I will need to add.

2). I would like to fit a folding mast,  some suggestions on  how other people do this would help. Do I need to step this into the keel as  was done on the  original boats for example because if so I will need to fit a block on the inside of the keel  before I proceed much further.

3). I intend to use a 6V 4Ahr SLA, a Hitec HS785HB sail winch and a Hitec HS325HD rudder servo. I have not worked out the internal arrangement of these yet and how to mount them so any photos of  fairly similar  models would be really helpful.

 4.) I would like to fit polystyrene foam inside the hull in order to try to make the model “unsinkable”. I know this may cause long term problems with hampering the evaporation of  any moisture that gets inside the model and am making sure that the internal timber is well treated with wood preserver as I build the model. Once I get some idea of the  mass of  heavier than water ( lead ballast, battery, electronics, etc) components inside the model, I should I hope be able to calculate if  I can get enough foam into the model to keep enough water out to stop it sinking if the worst happens! Is this a sensible  train of thought.

Thanks in advance.

BJH.    

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tonyH

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Re: Help with Morecambe Bay prawner build.
« Reply #1 on: June 26, 2007, 01:31:09 PM »

Hi BJH and welcome,

As far as the weight is concerned, there are a few options.

1. If you have the displacement of the real vessel, then the theoretical displacement should be the actual weight divided by the cube of the scale.
If you're building at 1/12th scale, for example and the real boat weighs 100 tons, the theoretical displacement would be 100x2240 lbs = 2240 lbs, divided by 1728 (12x12x12) equals 12.96 lbs.

or

2. Mark the waterline from the plans on the hull, float it in the bath and add weight until it floats on the waterline.

As far as the foam is concerned, all you're interested in is the volume where water doesn't get if the hull is full of the wet stuff.
Using the same example and the boat weighs 13lbs approx, a gallon of water weighs about 10lbs so you need about 1.3 gallons worth of flotation space to carry the weight.

Hope that this helps

Tony
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boatmadman

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Re: Help with Morecambe Bay prawner build.
« Reply #2 on: June 26, 2007, 01:57:59 PM »

Hi,

I use bubblewrap for bouyancy, easy to cram into tight spaces and can be removed if required.

Ian
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cbr900

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Re: Help with Morecambe Bay prawner build.
« Reply #3 on: June 26, 2007, 02:56:10 PM »

BJH,

Welcome to the forum, for really great info on all types of fishing and trawling boats contact, Dave Lieshman on the forum he is a wealth of information....


Roy
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BJH

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Re: Help with Morecambe Bay prawner build.
« Reply #4 on: July 04, 2007, 01:29:17 PM »

Hi   Ladies  and  Gentlemen,

OK,  I have  employed the standard method of waiting till the wife is out and  then using the domestic test tank. Using a collection of  SLA batteries, jars of jam and tins of baked beans, to ballast the hull down to the required waterline  I have arrived at a target weight of  approximately 10.8kg  (24 lbs).  Does this seem about right ?

I am at present trying to fit the rudder, and have decided that I would like to fit a removable heel block so that it will be possible to remove the  rudder in the future for  maintenance/ repairs.  Do other modellers do this and is it worth the additional effort required ?  Having finished  the rudder assembly   I will work out  how to mount the rudder servo.  Anybody have any photos of this area of there own builds that would give me any pointers.

I have also checked the dimensions of the back of my car, so I know I will have to retract the bowsprit and  fold down or unstep the mast. Does anybody have any advise about methods for either folding or unstepping masts that  could help me please?  Again any photos would help me and  other modellers in future.

Thanks in advance.

BJH.
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-KEMO-

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Re: Help with Morecambe Bay prawner build.
« Reply #5 on: July 04, 2007, 03:46:04 PM »

Hi,
     this site,    www.mastman.co.uk       was mentioned in MMI this month, I do'nt know if you      know of it but they may have some advice.

Keith.
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