Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Yachts and Sail => Topic started by: Richard M on February 01, 2011, 06:53:49 pm
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Hi All
I will soon be finished a Robbe Atlantis and am thinking of my next project.
I want to scratch build an East Coast working sailing vessel of some kind to about 1:24 scale, probably not Master Hand (too long) but something similar.
I intend to use line drawings (probably by Edgar J March) and would like to keep as close as possible to the original. Do I need to provide a false keel and if not how can I be confident she will be stiff enough? If a false keel is needed, are there guidelines on how to design it. I suppose if all the ballast is on the bottom of a deep fal;se keel the boat would be too stiff and not look realistic in a good breeze.
I will stay away from flat bottom designs like Thames Barges but would apprecxiate any pointers anyone can give me.
RichardM
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You could start by reading 'Inshore Craft of Britain: In the Days of Sail and Oar' by Edgar J March volume 1 and volume 2
Sadly like most of his books they have slipped in to the realms of collectors books but this and his other works are available through the public libraries.
Should you want to own a copy it will set you back somewhere in the region of £30.00to £60.00 each but inside are details and line drawings of most if not all of the long gone inshore sailing craft of the UK. :-))
For your model to sail to scale you would have to build to a fairly large scale if you don't want it sailing on it's ears in anything less than a light breeze and you would probably want to use a false keel with a lead build at the bottom.
In the resarch and design section here under Yachts and Sail R&D there are many inputs on how to achieve a realistic sailing model presented by some of our learned colleagues. :-)
Altough our models are to scale, the water we sail on isn't, so compromises have to be reached but it can be done.
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I made a 3 foot 5 sail french cutter model and a friend of mine made the same boat. On his he fitted lead to the bottom of the keel
as stated on the plan. It heeled over quite badly and was very difficult to control.
After witnessing this I made a false keel for mine 1 foot deep with a 1 mtr yacht type bulb on it that I molded myself and it sails
like a dream. It is detachable as it sits in a fin box and is held in by a threaded bar and wing nut.
If building from plans you may also have to increase the size of the rudder or control may be difficult and also if you can
fit a small motor and prop (just in case)
Hope this helped
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If I might suggest the best possible source of info for you at this moment in time is the book
Introduction to Radio Controlled Scale Sailing Models (The modeller's world series) [Paperback]
by Phillip Vaughan Williams
Published by Traplets, available on Amazon £13 to £8.
http://www.amazon.co.uk/Introduction-Controlled-Sailing-Models-modellers/dp/1900371200/ref=sr_1_1?ie=UTF8&qid=1296597042&sr=8-1
Chapters cover :- Planning a scale project. Scale sailing problems & solutions. Control systems. Modelling basics. The hull. The deck. Masts and spars. Sails & rigging. Sailing techniques. Then goes on to discuss the merits of square riggers, Luggers, Cutters & sloops, Barges, Ketch, Yawl and schooner rigged vessels.
I'm sure you will find this very helpful
Regards
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On a 1/24 Thames hoy I used a full length keel of about 2" deep 3/8" thick mild steel bar. You don't have to use lead! The long keel helped her to sail consistently with a weighted rudder and even now with r/c rudder she handles well. Yacht keels (a lead torpedo at the end of a steel foot rule) work fine but can give somewhat un-scale handling characteristics - and of course give a deep draught, which can limit your sailing water and launching spot choices.
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I can also recommend the Philip Vaughan Williams book.
I would suggest you read it before you begin the model. Because, one key bit of advice is that if you are going to fit a keel, it needs to be part of the design. Retro-design and fit is not a good idea.
A lot also depends on your prototype. If it is a fishing boat over about one meter, then these can be made without additional keel. I think there are a few around the Portishead lake with about 20+ lbs of lead in them. Yes they may be a bit stiff.
Some less beamy boats, or those less than 1m will magnify any problems with balance. One way around this is to stretch the vertical scale, so that the boat is deeper in relative scale. This is not to scale, but it will not detract from the general appearance of the boat; especially in the water.
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If you need to add a fin to a long keel boat and don't have a clue where it should go:
1/ Find a large scale elevation diagram of the sails that'll be set.
2/ Work out the area of each sail.
(This is "half base times height" for all triangles. Four-sided sails can be turned into two triangles and treated the same way.)
3/ Add the areas together to get the total sail area.
4/ Find the incentre of every triangle.
(This is the point where three lines drawn from the triangle apexes to the halfway point on the opposite edge cross.
5/ Drop the incentres vertically down to the waterline, and forget about the ones on the sail plan.
6/ Mark a datum point on the waterline - it's easiest if this is abaft or forwards of any of the incentres.
7/ For every incentre now marked on the waterline, multiply the area of that incentre's triangle with the distance of that incentre to the datum. (We're calculating moment arms, here.)
8/ Add together all the numbers produced in 7/.
9/ Divide the result found in 8/ by the total sail area to find the centre of lateral effort.
10/ The centre of lateral effort is the distance from the datum to the effective centre of the sails' sideways force.
The centre of any fin wants to be situated on or - preferably - slightly forward of this point. (Weather helm being better than lee helm).
...I should point out that it's almost quicker to calculate this point than to type up the instructions on how to find it.
Andy
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Richard,
While NOWHERE is anywhere as good as Mayhem :} there is a very good hotbed od information on scale sailing at
http://www.rcgroups.com/scale-sailboats-653/
Many of the people who contribute there also scan mayhem, so they may (and often do) join in here
Among our local experts John Dowd makes SUPERB Schooners (and is a good person, too) His website carries a wealth of information about making, controlling and sailing large scale sailing vessels (sorry - havn't got the URL to hand, google "John Dowd" +schooners)
And whats wrong with flat bottom boats like TSBs :}
andrew
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Hi All
Thanks for all the useful comments, given me lots to think about. I had better provide for a false keel, I can always omit it at a later stage, better than trying to retrofit unobrusive attachments.
Re the 2 Edgar March books, an early birthday present (I wont say which one) is already on its way via the internet. I had better start dropping hints for the other recommended book.
As far as Thames barges are concerned, I love them. I was brought up near Maldon and my sailing club on the Blackwater used Mamgu(ex Cawana) as a cubhouse and I have sailed on barges Centaur and Dawn. I just did not think I could make a good sailing model with an accurate scale hull,often they seem to be deepened? Perhaps I should rethink this?
RichardM
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Hi again
I have just ordered the recommended book, the Edgar March ones I have plus (courtesy of the library) his book on sailing trawlers.
I am about to start scaling the drawings to 1:24 but am not sure how to incorporate a removable keel case into the design. Splitting the keel in the middle will make a rebated garboard a problem. I am sure others have solved this, any thoughts please? I am sure there are more elegant solutions than I can think of a present.
Richard M
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Hello :-)
On my Master Hand build I've deliberately scaled her big to try and avoid a false keel, but should I need one I plan to drill holes up through the keel to accept brass tubes that will run up to under the deck supported by internal frames within in the hull, they will be boned into the keel and the tops will be well above the load water line so no water will enter the hull. O0
A ballasted fin keel of design yet to be pinned down will have 3 or 4 - 4mm diameter piano wire rods threaded at their top end and bonded to the false keel to fit up these tubes and bolt it in place at their tops.
There will be a series of these tubes spaced along the keel so the false keel rods will fit into any adjacent tubes so that I may shift the whole keel forwards or backwards for trim.
When the ship is on display the fin will be removed and the holes will not show as they will be on the underside of the keel :-))
Thats's my grand plan :-))
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If you'll pardon this Yank sticking his nose in...
The 1:24 scale SC&H models run in the 5 foot on deck range and run about 100 pounds (7+ stone) sailing weight. Half of that, or nearly so, is in the form of a removable ballast keel attached to the very bottom of the model, adding 3 or 4 inches to the model's draft of 6 to 8 inches.
This lead bar is attached to the model by a pair of threaded rods that pass through the hull from keel to deck in tubes for water-tightness, and bolted on deck.
The nice thing about this set up is it allows you to detach half or more of the model's weight making it easier to handle out of the water. The mounting for the ballast can also double as a sturdy "invisible" display stand mount. It also get a lot of the weight as low as possible making your model stiffer in the wind. The lower the ballast, the less you need beyond just getting the hull down to the waterline.
There are, of course, variations on the theme. For my 1:36 Constellation I'm using a 2 inch I.D. PVC pipe filled with lead bird shot. It weighs in at 42 pounds (3 stone). Using iron pipe instead of PVC would gain some extra weight without a gain in size. There was no casting involved; lead or resin - just PVC glue and some hand-sawing. I'll still have 10 or so pounds internal to bring the model to proper trim.
My set-up in cross-section:
(http://todd.mainecav.org/model/constellation/pics/cross_section.gif)
HMS Killingsworth uses basically, the same idea:
(http://www.modelboatmayhem.co.uk/Modellers/Brian/images/P9290721%20B%20lrg.jpg)
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Hi Jerry
Thanks for the detail, really helpful to this scratchbuild novice. I think I will try something similar as it will be easy to maintain hull integrity.
By the way, love your launching trolley but how do you transport that? Big American Pickup I guess.
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Killingsworth isn't mine, she's over on that side of the pond.
I haven't gotten to the launching cart stage for mine yet - but It'll go into a big American Chevrolet Tahoe (derigged and folded up) or into a Brenderup horse trailer towed by that Tahoe (rully rigged).
I have a horse, so the trailer is already in hand and available. It has the space, nice suspension, and a loading ramp. It's not meant to be submersible - so I will have to devise a cart for launching and moving the model.
My Models (http://todd.mainecav.org/model)