Scaling Question

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Scaling Question

Post by bateau-webmaster »

A Customer wrote: Greetings,

I was wondering is there any way to scale a CS23 down to a 19' or a 21' ?

Thanks in advance for your time!
Shouldn't be terribly difficult. I would say keep it within 10%.
Please read the following article for all scaling-related questions:
http://bateau2.com/howto/scaling.php



TomW1
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Re: Scaling Question

Post by TomW1 »

10% would take it down to 20.7'
Restored Mirror Dinghy, Bought OD18 built by CL, Westlawn School of Yacht Design courses. LT US Navy 1970-1978

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Re: Scaling Question

Post by jacquesmm »

Scaling her down to 21' would work well. There is enough safety margin in the sole height to guarantee proper cockpit drainage when scaled down to about 21'.
For a small fee, I would provide scaled stations and panels dimensions.
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Marshall Moser
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Re: Scaling Question

Post by Marshall Moser »

Would scaling a CS23 in the height dimension only work? Say 70-80% of full sized to produce a "carolina bay" style boat? (See Tidewater Carolina Bay 2300)

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Re: Scaling Question

Post by TomW1 »

Marshall Moser wrote: Thu Apr 08, 2021 4:44 pm Would scaling a CS23 in the height dimension only work? Say 70-80% of full sized to produce a "carolina bay" style boat? (See Tidewater Carolina Bay 2300)
Your talking of reducing side panels. You can certainly do that by simply marking the frames and side panels down by the amount you want to reduce them by. Just remember by reducing the height the boat is less safe as it has less freeboard. If you don't want a true Carolina Fisherman it makes sense. Get the plans and I would leave at least 21-23" at the mid-deck from the deck to the side deck for safety. Sounds like a good idea to me.
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Re: Scaling Question

Post by Browndog »

The problem with scaling the CS 23 down and reducing the sheer line height to make an offshore boat into a bay boat is that you still have the offshore boat bottom with 17 degrees of dead rise at the transom and more draft than you might want or need.

The FS19 already has a bay boat vibe to it. It might be possible that you could add some Carolina flare and tumble home to it by modifying the transom, mid and bow frames. Adding slits to the side panels to accommodate the tumblehome and flare would be required too,

The FS19 that I built is in my opinion a fine looking boat, and based on the number of people that stop my brother every time he uses it to ask about the boat confirms my opinion.

Because of the lack of an interior liner the FS19 has as much interior room as my fishing buddy’s 22 Bay boat, is lighter, more fuel efficient and achieves the same speeds with a lot less HP.

Lots of good designs for bay boats to choose from here.

I love the lines and look of Carolina style boats myself, but your intended use and the design requirements to meet those needs should take priority over the lines of the boat.

Of course there are many versions of production built boats that have been adapted to include Carolina flare styling applied to everything from flats skiffs, bay boats, center console and express offshore boats. A used version of one of these will be your quickest, easiest and probably cheapest route to achieving what you want.

I however would love to see someone adapt one of the BBC designs to achieve a Carolina style bay boat and do not want to dissuade you from your boat building project.

If you don’t do it, perhaps I will. ;)

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Re: Scaling Question

Post by Marshall Moser »

Browndog, if I did scale the CS23, I’d scale it completely in the vertical orientation and lower the 15° deadrise. I own the FS19 plans as well. I like the FS19 program, but I think it would be easier to scale the CS23 down than to try to modify the FS19 to have flare and tumblehome. I’d probably take some of the tumblehome out if I did it though. Also, I’d want to respect the scantlings of the CS23. My only concern is how the scaling would affect the projection of the panels and how to calculate that.

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Re: Scaling Question

Post by BarraMan »

The problem with scaling the CS 23 down and reducing the sheer line height to make an offshore boat into a bay boat is that you still have the offshore boat bottom with 17 degrees of dead rise at the transom and more draft than you might want or need.
I don't know what you guys are looking for in an 'off shore' boat versus a 'bay boat', but for what its worth I don't think a 15, 16, 17 or 18 degree dead rise at the transom makes much difference. For a off-shore boat I would be looking for at least 21 degrees of dead rise.

My boat has 18 degrees of dead rise at the transom. Its spends 90% of its time in rivers and estuaries and only about 10% of its time in what might be called 'off shore', where its certainly nice to have a bit more dead rise. I was told it would 'rock and roll' at rest because of the 18 degree dead rise - it doesn't. Its just as stable as my almost flat bottomed 14' 'tinnie' - probably because its (1) wide, (2) has some reverse chine and (3) all of the fuel is in tanks set centre-line under the soul - resulting in a low C of G.

If you look through some of my fishing videos you will probably see my son and a mate walking around on the gunwales - the boat barely moves.

Hulls with dead rise need more water? True! How shallow do you need to go? I regularly run in about 3 feet of water at 28 kts! At idle I can do about 18" - maybe a bit less.

28 kts in a 22' boat in 3' of water takes a bit of getting used to - but we do. Having a hydraulic jack plate helps - particularly for getting on the plane in shallow water.

If the CS23 design appealed to me for what I wanted to do, I would have no hesitation in scaling it down by 10% to need my needs.

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Re: Scaling Question

Post by TomW1 »

If you go ahead with scaling down, get te Metric plans and a metric ruler, they have them at Lowes, they will be combined womith a US scale. It makes it much easier to scale down as all the numbers are whole and not in 1/2" etc. Makes it much easier to scale down. :D

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Re: Scaling Question

Post by OneWayTraffic »

Some of us would say that metric is just easier full stop. :P

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