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Author Topic: Frame spacing  (Read 2978 times)

AlisterL

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Frame spacing
« on: May 20, 2009, 05:31:20 AM »

Greetings to all,

I have come up with an idea for a project and it requires me to scratch build after drawing up my own plans. So I'm sort of going to do that, but as the lines are hard to draw/calculate I thought I would create the hull shape in polystyrene foam so that it looks right. I will them slice the poly at the locations where I want the frames to make a template that I then cut out of ply. I have the hull measurements and plan and elevation views of the vessel, but no hull shape detail other than can be guessed from photos. This is a tanker, a VLCC and is rather long. In my intended scale it will be 1530mm long x 230mm wide by 99mm high. I know I will need to have a reasonable number of frames at the bow and stern to get those shapes correct and I think I can sort that out myself. My concern is the frame spacing will I need to make a rigid hull along it's overall length. I probably also need to pick a suitably sized stringer... I don't want a droopy tanker!

Thoughts and comments much appreciated.
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Alister

Umi_Ryuzuki

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Re: Frame spacing
« Reply #1 on: May 20, 2009, 08:55:41 AM »

Here's a build that went from a floaty towing accessory to powered scale model.

http://www.rcgroups.com/forums/showthread.php?t=889679

And the M@lline group about to cut one in half and make it easier to pack around...
Nary a frame to be seen...  %) The plywood sides keep the ship nicely rigid.
The two new frames they are adding allow them to bolt the model together at the pond.

http://www.zeeslepers.com/mailline/html/pagina_mail_line_02.html
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andrewh

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Re: Frame spacing
« Reply #2 on: May 20, 2009, 12:28:28 PM »

Alister,

With a question like this my first answer would always be to wait for Umi's wisdom and do that :}

How about sailing the plug?  If you have gone to the trouble of making the plug to the right shape you can sail what you carved after giving it a surface finish which will depend on the use you envisage and the dinging it will get.  Surface treatments in order of increasing robustness could be:
Nothing
Paint  - any that doesn't eat your foam
Brown paper applied with white glue
Papie mache glued with emulsion paint
Fibreglass
Plank with balsa, ply sheets as large as the hull permits, or anything else cheap and durable

Then smooth, finish as required.
As Umi says the load part of a VLCC is totally parallel, so can be made with sheets of ply, etc, and you only need to shape the pointy ends.  Carving in foam is a good plan - then you can cover/finish as above and leave all or most of the foam in place.

Strength to your arm, and pics, please, as you go
andrew

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boatmadman

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Re: Frame spacing
« Reply #3 on: May 20, 2009, 03:19:55 PM »

Why not use delft ship free?

http://www.delftship.net/

It will be quick and easy to draft up a vlcc, then export the linesplan to a dfx (autocad) file, run down to your local printshop and have them print the plans for you?

Ian
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Bryan Young

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Re: Frame spacing
« Reply #4 on: May 20, 2009, 11:04:58 PM »

From your own measurements this "supertanker" will be only 1.5m x 23cm wide.  Quite a small model really. But if you really do want to stiffen-up the hull then may I suggest you use "hairy-filler" to place in a couple of lengths of 1" angle iron. This has 2 advantages. One, it adds weight at the bottom of the ship. Two, if you place them accurately the angle irons also act as a good location for the batteries and/or other weights you may need. My larger models (2m plus) use this method of stiffening and even though the all up weight can be over 100lb the hull shows no tendency to "bend" when lifted by its ends.
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Bryan Young

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Re: Frame spacing
« Reply #5 on: May 20, 2009, 11:15:52 PM »

From your own measurements this "supertanker" will be only 1.5m x 23cm wide.  Quite a small model really. But if you really do want to stiffen-up the hull then may I suggest you use "hairy-filler" to place in a couple of lengths of 1" angle iron. This has 2 advantages. One, it adds weight at the bottom of the ship. Two, if you place them accurately the angle irons also act as a good location for the batteries and/or other weights you may need. My larger models (2m plus) use this method of stiffening and even though the all up weight can be over 100lb the hull shows no tendency to "bend" when lifted by its ends.
As a rider to the above...are you talking about "frames" or "stations"? Tankers (especially the big ones) have longitudinal framing and not the more familiar upright things normally seen in photographs. Traditional "frames" are spaced only about 2ft apart. Closer together at the "ends" of the hull. So I suspect you are talking of "stations" rather than "frames". On a model such as you are contemplating a maximum of 10 stations would suffice. About 6" apart in the middle section and 3" apart at the curvy end bits. BY.
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AlisterL

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Re: Frame spacing
« Reply #6 on: May 21, 2009, 02:04:28 AM »

Thank you all very much! There are some good ideas there. The term I should have used to describe the real ship that is the inspiration for the model is ULCC and not VLCC - although it probably doesn't matter much.

Ian - I have been there and tried that and even found an existing free delftship model of a tanker to use/modify. DelftShip and I don't work well together it seems - I got horribly lost trying to get it to do what I wanted. I think the fault is all to do with me as I have no real idea about what the process of hull design should be. I worked my way through the demo, but what I was doing was following instructions not learning how to design a hull.

Andrew - I'm not keen on the idea of retaining the poly - if for no other reason that it floats too well - I'll get to why that might be a problem in a mo - but I was planning on covering whatever I did with fibreglass for strength and protection.

Umi and Bryan - I think that my way forward is to build a suitable tub for the rectangular section in the middle and then use a more traditional keel and frame approach for the bow and stern. That would also make it easier to do some internal ballasting with pumps. My thoughts were that when going sailing with this model that it would be launched with no ballast whatsoever and would float with more or less zero draft. Then I would flick a switch and pumps would flood some ballast tanks bringing the hull down to a suitable draft. At the end of the sailing, flick the switch he other way and pump out the ballast. Light (ish) to transport, adjustable as required for venue and appearance plus fun and challenging to build!

It did occur to me to have a keel that ran most of the length of the hull that was the full depth of the hull as well.

Thank you all again for your help.




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Alister

derekwarner

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Re: Frame spacing
« Reply #7 on: May 21, 2009, 07:34:38 AM »

quote....' I thought I would create the hull shape in polystyrene foam so that it looks right. I will them slice the poly at the locations where I want the frames to make a template that I then cut out of ply'

Alisteri....if you do go down this part....only make a half hull........it is then much easier to make a mirror reversed image of each hull frame section ...also the will be totally symetrical .....Derek
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Umi_Ryuzuki

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Re: Frame spacing
« Reply #8 on: May 21, 2009, 08:02:39 AM »

I will often build up the hull, and then shape just the bow and stern from solid.
That used to be pine, then balsa, now it's pink or blue styrene foam.

 :-)
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AlisterL

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Re: Frame spacing
« Reply #9 on: May 21, 2009, 08:49:51 AM »

Hi Derek - good idea!

Umi - what's the significance of the pink or blue WRT the styrene foam? Density maybe?
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Alister

Bryan Young

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Re: Frame spacing
« Reply #10 on: May 21, 2009, 05:33:07 PM »

Alisteri, have you considered that foam may be just a bit too buoyant? Putting a large(ish) but very light model into the water might seem to be a "good idea", but then you need more ballast! At Tynemouth we have a very large model of a tanker (12'+) that is in sections and is ballasted using water pumps as you envisage. Very effective, but the empty hull is still very heavy, so at "empty" draught the thing still sits nicely in the water. I fear that yours may be so light as to be unstable when placed in the water. If you can launch it at say 1/3rd laden draught you should be OK. My usual method is to make the whole top deck (more or less) detachable. Lifting the hull in and out is then quite easy, and when the empty hull is in the water it's a simple matter to drop the batteries and ballast blocks into their assigned positions. BY.
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Ghost in the shell

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Re: Frame spacing
« Reply #11 on: May 21, 2009, 05:37:54 PM »

using styrene foam also has a second advantage, especially when with tugs.  you have a softer front end that won't damage another model when engaged in tug towing
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Umi_Ryuzuki

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Re: Frame spacing
« Reply #12 on: May 21, 2009, 09:39:37 PM »

Hi Derek - good idea!

Umi - what's the significance of the pink or blue WRT the styrene foam? Density maybe?

Pink comes from Owens Corning,

Blue come from Dow....

Ghost, once the boat is fiberglassed, the bow is as hard as any other part of the boat, or any
other fiberglassed boat... Plus the wood keel is in there also.  ok2


If you look at how Toesupwa built his "self ballasting" barge, it could give you some ideas on how to
build up the hull. ... S false bottom perforated to allow water in, and a sealed bottom at the waterline.
This would allow the ship to weigh properly for sailing, or towing, and once drained, light enough to
move to and from the pond.

http://www.rcgroups.com/forums/attachment.php?attachmentid=2214971
http://www.rcgroups.com/forums/attachment.php?attachmentid=2282226
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AlisterL

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Re: Frame spacing
« Reply #13 on: May 22, 2009, 10:44:57 AM »

Bryan - the foam is just to allow me to get the shape right - I am not intending to make the hull out of it at all - for exactly the reason of boyancy!

Umi - There was I think you were being all scientific with various foam densities :) I shall investigate the self-flooding idea. I guess the self unflooding is done by lifting...
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Alister
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