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Author Topic: Scratch building advice  (Read 2847 times)

Bill Harris

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Scratch building advice
« on: January 04, 2010, 05:28:51 PM »

Long-time aeroplane builder, neophyte boat builder.

I'm planning a steam launch based on this scratch-built hull.  Rather than transfer a number of photos over from another site, let me simply send you over for a look:

http://www.rcgroups.com/forums/showthread.php?t=1163423

http://www.rcgroups.com/forums/showthread.php?t=1159829

For the initial design layout,  the sides of the hull will prove to be the interesting challenge.  At the mid-point former, the side is vertical. Towards the bow, it leans outward (positive); towards the stern, it leans inward (negative).  Probably what needs to be done is to make the keel (with the bow and stern hull side attachment points) and the middle and (temporary) intermediate hull formers.   Temporarily install the top (deck) longeron and the lower (chine) longeron and use those to define the width of the intermediate formers.   I don't think it is all that critical, but it will need to have nice, smooth transitions to look good.  This does not look that difficult, except that it could easily become a topological nightmare...

Do you know of any Build-Logs here of a similar hull that I could get guidance from?  At best, this will be trial-and-error, but I'd like to try to reduce the number of iterations of the trys.

Thanks,

--Bill


 
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andrewh

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Re: Scratch building advice
« Reply #1 on: January 05, 2010, 10:52:22 AM »

Hi, Bill

Happy New Year to you

I have not seen this hull before, but it is well within the capabilities of balsa, or Bass or plywood to do this twist.

Do you have plans?  if so you will have the shapes for the hull skins.  The ones in the threads seem to be "formerless" so they are joined by some form of stitch-and-glue process, i think

If you don't have plans you can develop the shape of the hull skins by three ways that I know of:
1) Use delftship or other free ship design program to draw the hull and print off the panel shapes
2) do a Ricky Webb - carve half of the hull in foam and trace off the panel shapes
3) You are an areomodeller!  Get hold of lots of scrap card (I get the boxes from a florist) and use trial, error and masking tape to create the hull

Hope these help
andrew
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Bill Harris

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Re: Scratch building advice
« Reply #2 on: January 06, 2010, 01:47:17 AM »

No plans-- this is a scratch-built copy of a scratch-built boat.   I have photos from several angles from the construction threads on RCGroups and a good idea of the dimensions I'll want.  I can make the keel and key formers and I can fill in the rest.  On the hull skins, I'll get
"poster board" (2'x3' cardboard 0.015" thick) and, as you say, trial-and-error the hull skin shapes.  It's not going to be easy, but it's not an
 impossible build.

Eventually I want to make this boat steam-powered, so some of the interior layout I can get from "Peconic Steam's" boat.  Since the steam plant will be 2-3 years down the road, I can electric-power it for a while.

It might be easier to carve and shape the hull from a piece of foam and make a fiberglas hull from that, but a steam boat like this somehow needs a built-up hull of wood.

I'll start a build-log when I get far enough along.


--Bill
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andrewh

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Re: Scratch building advice
« Reply #3 on: January 06, 2010, 12:55:50 PM »

Bill

You have got it sorted in your mind, so best of luck with it!

One thing which might help is when you have your keel and formers assembled  - presumably on a strongback -  you could notch the formers (if they are not already notched) for gunwales and a chine stringer.  these can be shaped in place before gluing without distorting the framework if they are soaked and softened first and allowed to dry while pinned in place.  You can also laminate them from several strips of thinner wood.

The gunwale and chine stringer will strengthen the whole enchilada and give better gluing area to the skins once they are made.

I'm sure you would anyway but:
1) do keep a copy of the shape of the skins somewhere
2) pictures pplease as you go :}
andrew
 

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Bill Harris

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Re: Scratch building advice
« Reply #4 on: January 06, 2010, 11:13:13 PM »

I've been reading in the "Build Masterclasses" section and have been picking up a lot of ideas. 

I'll be sure to take notes and plenty of photos, and share them.

--Bill

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Greggy1964

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Re: Scratch building advice
« Reply #5 on: March 12, 2010, 12:22:06 PM »

Hello Bill,

Might I suggest you start your quest by learning how to use freeship, it is the original version of the current Delftship but the older version allowed you to develop compound shapes of hull panels from your own designs which you can the plot and build a model from.

Take a look here and do some digging, you want the original version of the program

http://freeship-plus.pisem.su/downloadsE.html

With this set up you can form your own hull shape, (there are turorials on this forum for model boat builders to guide you.

The shape of boat shown in your photos was formed into a hull from flat sheets of plywood by the practice called the 'Tortured Plywood technique'

Paper/Card/Plywood can only be bent into one curve at a time, it will not accept compound curves but it can be fooled into two dimentions by forming it into a cone, try this experiment with a sheet of paper.

With practice you can create planked hulls also and of course develop their flat plank shapes too.





And get your plank developments like this



Of course you hull will be much simpler as it has only four panels to worry about instead of 20 in my exaple.

But once you get your head around the program your hull can have as many panels as you like.

By playing about with freeship you are allowed to form these shapes, the program will plot a 3D image of your hull and any areas trying to form compound curves will show up as red areas, by changing the hull lines these areas can be removed.

The resultant plotted developed panels can then be formed into a hull shape.

Below are photos of a model I built back in the 80's of a 16ft sailing dinghy that I plan to build one day, back then I built this hull out of 1mm birch plywood skins over balaswood frames and keel.

I have taken the liberty of taking lots of shots from different angles so you may study its attractive shape (to my eyes anyways!  :-))  )











Photo 6 below shows how the side panels blend into the bottom and I have outlined the shape of the side panel in pencil for you.













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Greggy1964

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Re: Scratch building advice
« Reply #6 on: March 12, 2010, 01:07:27 PM »

I forgot to mention, there is an active Yahoo Group

http://groups.yahoo.com/group/Freeship_HTandT_Group/

This lot are quite passionate about this little program and there is tons of advice as well as images of peoples efforts.

If you want to learn how to use freeship, signing up here would be a good start.

The DelftShip website also has a forum but it's geared more towards naval architects who buy the full program than to us lowly model builders, but still useful info can be gleaned.
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