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Author Topic: water line  (Read 5644 times)

markit

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water line
« on: February 21, 2013, 12:49:55 pm »
This may be a stupid question but I will ask any way because I don’t know.

How do you determine the water line on a model hull? How do you determine how deep it should sit in the water.
 
sorry if this is a silly question but i am new to this boat building thing!
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TailUK

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Re: water line
« Reply #1 on: February 21, 2013, 01:47:48 pm »
The waterline should be marked on the drawing of the boat your'e building.  At some point you mark it on the model and test the hull on the water and determine how much ballast it will need to float the hull to the waterline.  The weight of ballast will be decreased by the weight of the batteries, control gear and motor and of course the rest of the model, upperworks and fittings, etc.
The ballast may need to be divided into several discrete packets arranged around the inside to trim the hull so it floats level in the water. a small amount at bow and stern will stop the hull "digging in" as it moves forward and 2 portions set amidships just below the waterline will help prevent the boat from rolling unduly.
 
Obviously the testing needs to be done when the hull is waterproof and don't forget to plug the proptube if the prop isn't fitted to prevent sinking.  If it's ready to run boat like a racing boat or sailing yacht there are plenty of sites where you can find information about trimming the hull to get good performance.  HTH
 
If this is related to your Sheffield build I've got some books in PDF format I could send you if you would like them.  PM me with an e-mail address and I can e-mail to you.
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markit

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Re: water line
« Reply #2 on: February 21, 2013, 02:32:03 pm »
Thanks for the reply. Can't recall seing anything on the plan must have a closer look. Apreciate the reply and i have sent you a PM
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Tug-Kenny RIP

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Re: water line
« Reply #3 on: February 21, 2013, 04:38:51 pm »

I thought this was an interesting question.

What Does govern how deep any boat should float. I appreciate tipping over sideways is a concern but there is a formulae to calculate those markings found on larger ships dependant on salt water or fresh water. I'm afraid I don't know the details but would it apply to models ?

ken

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Neil

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Re: water line
« Reply #4 on: February 21, 2013, 04:43:05 pm »
Quote from: markit on February 21, 2013, 02:32:03 pm
Thanks for the reply. Can't recall seing anything on the plan must have a closer look. Apreciate the reply and i have sent you a PM

Mark.....it might just be marked with a short line at bow and stern with 3 letters LWL............load water line.
 
neil.
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RAAArtyGunner

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Re: water line
« Reply #5 on: February 21, 2013, 08:57:59 pm »
To follow on, let us say the line is non existant on the plan/s or you are drawing your own plans.
 Is there a definitive location for the water line or can you make it whatever, so long as it has freeboard????????????????
 
Too much freeboard andwill  it is top heavy, too little and it will it be swamped.
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markit

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Re: water line
« Reply #6 on: February 25, 2013, 09:51:39 pm »
Have looked and looked no line on the plan what do i doo now to set the water line
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Circlip

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Re: water line
« Reply #7 on: February 25, 2013, 09:57:36 pm »
Gizza clue, what is the boat?
 
  Regards  Ian
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TailUK

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Re: water line
« Reply #8 on: February 26, 2013, 10:02:51 am »
Quote from: markit on February 25, 2013, 09:51:39 pm
Have looked and looked no line on the plan what do i doo now to set the water line

Guesstimate it.  You have waterline sideview drawings and know the size of your hull. Look at the hull square on from the side and take a guess how much should stick out of the water.  The GG plan is a "semi scale" anyway and you can always tweak the ballasting later if it looks as if she's riding high or low.
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markit

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Re: water line
« Reply #9 on: February 27, 2013, 09:58:31 pm »
The GG plans of HMS Sheffield. So it'sjusta case of suck it and see put it in the water and weight it till it looks ok To me then !
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tigertiger

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Re: water line
« Reply #10 on: February 28, 2013, 12:58:23 am »
Does this picture help?
Google images has many photos.



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Circlip

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Re: water line
« Reply #11 on: February 28, 2013, 01:01:13 am »
Wrong Sheff Tiger, best put a call out to GG on this forum. Look through the members listing and send him a P/M.
 
 Regards  Ian.
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tigertiger

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Re: water line
« Reply #12 on: February 28, 2013, 05:34:07 am »
Quote from: Circlip on February 28, 2013, 01:01:13 am
Wrong Sheff Tiger, best put a call out to GG on this forum. Look through the members listing and send him a P/M.
 
 Regards  Ian.

PM sent to GG.
Also, are there any images of the right HMS Sheffield out there?
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big_bri

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Re: water line
« Reply #13 on: February 28, 2013, 09:19:07 am »
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Brian

malcolmfrary

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Re: water line
« Reply #14 on: February 28, 2013, 11:20:43 am »
A scan from Janes.  Waterline level marked fore and aft.
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markit

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Re: water line
« Reply #15 on: February 28, 2013, 01:59:11 pm »
Thanks for that
Just about where i imagined it would be
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Bryan Young

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Re: water line
« Reply #16 on: February 28, 2013, 05:52:37 pm »
Quote from: Tug---Kenny on February 21, 2013, 04:38:51 pm
I thought this was an interesting question.

What Does govern how deep any boat should float. I appreciate tipping over sideways is a concern but there is a formulae to calculate those markings found on larger ships dependant on salt water or fresh water. I'm afraid I don't know the details but would it apply to models ?

ken
Kenny.
The point you raise is called the "Fresh Water Allowance" and has many permutations. If you'd like me to explain further then I'd be happy to do so. BY.
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tigertiger

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Re: water line
« Reply #17 on: March 01, 2013, 05:00:27 am »
The answer from Glynn Guest is that with an all up weight of 10lb/4.5kg the model should draw just under 2"/50mm.





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