1/144 scale HMCS Snowberry

GM-

You've touched on a  few topics that I have given a lot of thought to....

Your estimate about the displacement of the Revell model is a pretty decent approximation, but a little high.  Having built the 1/72 scale kit, I know it displaced about 5.5 pounds.  Cutting the scale in half means the displacement goes down by a factor of 8, which works out to about 11 ounces.  (Using the displacement of the original and calculating the value directly will be more accurate, as it avoids the error introduced by estimating a percentage of volume.)

I have also sailed both RC and pond sailers.  The issue with scale sailing models is that while the displacement goes down by a cube factor, sail area only goes down by a square of the scale.  So this means that any scale model is carrying a lot more sail area per pound of displacement than the full size vessel did.  Then there's the factor of winds-- we often sail in what would be full scale hurricanes! The only way to compensate for this is to have a hull form that is much stiffer (lower cg).  We do that with deep, non-scale keels with a lead bulb. 

You're right about the distribution of heavy items amidships. (But fuel oil is lighter than the water it displaces.)   But that is also balanced against the displacement  of the hull sections.  The finer ends at the bow and stern don't have the bouyancy to support as much weigh as the fuller hull sections amidships.  Balancing the distribution of the weight along the length of the hull was especially critical in wooden ships-- to prevent sagging or hogging.

The goal with an RC scale boat is try for realistic looking performance on the water.  Neither water nor air (wind) scale down, so you can't scale it linearly.  For example, if a ship had a roll period of 20 seconds, a 1/100 scale model will look toylike with a 2 second roll.   

Getting weight in a model as low as possible is the key, to increase stability, in terms of roll.  But experience shows that fore-and-aft weight distribution is much less critical-- you can only move your batteries and any ballast so much- the rest of the model's weight distribuition is largely controlled by the full scale design.  

A ship's turning circle is easier to scale accurately, but no one wants it.  I find that many RC boaters have no idea how much sea room ships need to maneuver- they drive their warships like  they are speedboats. For example, a FLetcher DD had a tactical diameter of 950 yards at 30 knots.  At 1/96 scale, that is a 4 foot model, doing a 30 foot circle!   Most skippers want tighter turns than that, so they increase the size of the rudder, the max deflection, or both. 

My apologies if I've given too long-winded an answer for what you were asking.. Liek I said this is a topic that interests me. It is the intersection of many things of interest to me:  Naval Engineering, my time at sea, full scale ship handling, applied math, rc boats, and plastic scale models!

Bottom line, even a model as small as the Revell 1/144 Flower can be converted to RC  and look good and handle well on the water.... 

-Bill

Thank you Bill for that answer.

It's something I'd like to hold up against an experienced aircraft rc modeler like John Eaton or Don Stuaffer, if only besuase I like to think of the models we make as representations of dynamic machines.

I would like to get back into pond sailors.

As I've gotten old, and realized that scales I can count on a calendar mean a lot in a couple of ways, I'm happiest on a sail boat.

Your observation that sail area is a square as opposed to a model thats based on the law of cubes is priceless, yes I get that. I've had the tiller on Sunfishes and Cats enough to love speed.

The best day I've ever been sailing, or one of the best, was watching New Zealand go 45 knots in the Cup races in 2014.

Thanks again. 

I forgot to deal with the dynamics in my reply.  I was talking only about making it float stable.  Indeed the ratio of mass forces to viscous forces would be impossible to duplicate, I believe, so roll and even pitch would be much faster than prototype vessels.  In some rc vehicles they mention scale speed to deal with this.

For an operating ship model, computer video editing is so good, and cheap, you can shoot video of it and then invoke a slow motion filter that would make the video appear to look more like the prototype :-)

Don Stauffer

For an operating ship model, computer video editing is so good, and cheap, you can shoot video of it and then invoke a slow motion filter that would make the video appear to look more like the prototype :-)

Don,  you are spot on. And you don’t even need a computer!

Here’s a link to 50 second  video of my 1/16 scale USCG 36’ Lifeboat 36500 shot using the “slow motion“ setting on an iPhone:

https://youtu.be/Z9_Fum3pDXs

-Bill

Hi Matey !

 I didn't know you liked to sail . There is nothing like being on the rudder , wheel , or tiller and hearing the water shsh by the hull . Just you , the boat and the water , wind and sky! That is an awesome experience that few can experience .

 I single handed a Friendship Sloop ( restored  )from Seattle to Bar Harbor , Maine ! Whatta trip .That vessel was a flawless sailor  . That's when I met Yvgorny . He was on the freighter I had to , ( with two other small boats ) share a lock with in the " Big Ditch" 

We have remained friends all these years later . He still calls me on Easter amd wants to know if the  "Yister Bunnya " has arrived yet  . We were transiting on Easter Sunday weekend .

 He loves sailing too . He lives in Boston and has a 62 foot Hereschoff designed " Bermuda Yawl ". he and his wife and kids sail her often .

Those of us who endured Queequeg's Coffin to learn bouyancy & displacement have to quibble a bit here.

Displacement is solely a question of fluid displacement volume.  It is measured in volume units.  It is also measured in weight units, but only in correlation to the fluid displaced.

We use the weights of materials used for the displacement (and within) only to understand the bouyancy equation expressed therein.

Back in the day, we aspiring naval officers were told to cipher values for Queequeg's coffin.  Melville is under-exact in giving us dimensions, so, we are typically told to use a volume of 6x3x2, and to estimate therefrom. 

So, we have a total volume of 36 c.f., which, as a 2' draft would give a seawater displacement of 36 x 65# or 2340# all told.  If we presume the coffin is 1" mahogany, it's 72x36x24 less 70x34x22 or 15,848 c.i. or 9.17cf.  At 47#/CF that's 431#.  We will then add 150# for Queequeg.  (We will not bother with the weight of the air within the coffin as negligible at 0.0807#/cf.)

So, the (with all due aplogies) deadweight value is 431+150 or 581#.  581 ÷ 65 gives us 8.9 cf, which we can them divide by the 18sf "foot print" of the coffin, to give us  0.49 feet for the draft, or 5.958 inches.  Starbuck's 175 pounds will not much change that.

In our modern times, we could probably use these same equations to show why Jack cannot share a door with Rose after the Titanic sinks

Another misconception is that adding styrofoam internally to a given volume makes it more bouyant.

If the door was 4' x 8' x 2" thick, thats a little less than 6 cu. ft. Say the thing is walnut, 40 lb. per cu. ft. That's a 240 lb. door.

6 cu. ft. displaces 372 lb.s of water. That means Rose can weigh 132 lbs and achieve neutral bouyancy with the deck just awash. Of course she was soaking wet too.

Add Jack to the mix at 150 lb.s and that's another 2.5 cu. ft. of displacement they are going to need. Humans basically have the same unit weight as water, esp. undernourished skinny ones; it's a no-win propositon.

Don Stauffer

I forgot to deal with the dynamics in my reply.  I was talking only about making it float stable. 

What I meant was, "does scale sail?". There's been some good answers, including yours, to that.

Pfjn, It is a very nice & fun to build kit. All the newer kits have really improved. I built it a few months ago & really enjoyed it & I am 87. Still bilding. Here is mine.

 I built my own railings from brass rod & plastic rod. easy to do.

GMorrison

f the door was 4' x 8' x 2" thick

I believe the current classroom dimesnions of "Rose's Door" are 60 x 84 x 2 with a presumed deadweight of 49#/cf (teak, well oiled)

So the door is 285#; we call rose 110#, that's 395#, or a bit over 6cf.  Or, a shade over 2" (2.0835 or 52.9mm per my calculator).  So, movie magic is required.

Which is as mean as professors adding to the Queequeg problem by asserting that the coffin is leaking at 1/32 gal/hr, and woe betide the officer candidate who forgot to cipher the free surface effect along with how long poor Starbuck has before the coffin sinks.

I’m glad to see my topsider math verified. Wanted to go to USNA but not a good student.

What folks don’t realize, in particular is that once you go negative buoyant, ie add sinking Jack to the door, it doesn’t settle in as a Jack sized hole in the sea, but it goes ... down.

The Fleet boats in WW2 didn’t take on water to go neutral, they drove down in dynamic fashion and then trimmed to neutral bouyancy.

To go negative meant hitting the bottom running.

People boggle at the thought of concrete ships, but they really do work.  Controlling the metacentric height is an issue, but a typical one in naval architecture.

The Flower-class were not designed for speed or elegance; but they have seakeeping and endurance galore.  That almost semi-circular body rolled like a pig, but was copious and had reserve bouyancy by the truckload.

Well concrete weighs maybe 200 lbs/ cu. ft. for the harder stuff. And there is lightweight concrete with expanded lava type aggregates.

Compare that to steel at 500 lbs/ cu. ft.

What did in concrete on the water is that it's really labor intensive to build a ship that way. And full cure times kill you.

One remembers all of those keel sailboats that sort of got half finished with shot crete or gunite.

Where the first generation of Flowers failed was inadequate accomodations. They had a pretty good size crew, eighty or so.

Stuffing most of the ones not on watch in a forecastle 20 feet wide and 20 feet long, along with the chain locker, gun pedestal, heads and ammo storage just didn't make for a happy crew.

 The Mulberrys used in WW2 were concrete & the ones I saw at Arrowmanches are still there. The ones at Omaha sunk because they wern't anchored, or something. How do they figure in what you are discussing.

Not much, but I asked about how scale floats and sails. That then leads to naval architecture.

gene1

Pfjn, It is a very nice & fun to build kit. All the newer kits have really improved. I built it a few months ago & really enjoyed it & I am 87. Still bilding. Here is mine.

...

Hi,

That turned out great.  Thanks for posting the images.

PF

PS.  I'm not fully sure how/when this thread got resurrected, as my OP is from sometime last year, and my local hobby shop recently closed doors but I still am very interested in getting this kit, once I clean out some of my backlog of other things to build so its really nice to see other peoples builds of the kit

PF, Keep looking on ebay as they have prices from very cheap to very crazy high. Watch the shipping as some make their money on shipping. Buy used kits, I have only a few times had a part missing.