Alessandro
are you addressing Ross Roy
or Rolls Royce?
"2 stations" in this whole discussion, 'stations' refers only to underwater profiles of a station
Alessandro is correct that there is a reference to calculus, but only a reference, (almost failed it in first year). That is the reason I moved from 10 stations to 28
What Alessandro describes in his second link is the same as my '5
STEP METHOD', the arithmetic is just laid out differently
'the mere fact of trying is a merit, in my point of view'
like this guy? (my brother did it in about 1964, it now hangs in my front hallway)
😁
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"2 stations" in this whole discussion, 'stations' refers only to underwater profiles of a station
Alessandro is correct that there is a reference to calculus, but only a reference, (almost failed it in first year). That is the reason I moved from 10 stations to 28
What Alessandro describes in his second link is the same as my '5
STEP METHOD', the arithmetic is just laid out differently
'the mere fact of trying is a merit, in my point of view'
like this guy? (my brother did it in about 1964, it now hangs in my front hallway)
Roy
Your memory is still holding well👍!
SIMPSON'S MULTIPLIERS!!
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Roy,
It appears that this vessel will have a BLOCK COEFFICIENT of 0.6.
Yes, a block of wood would be 1.0 and a sharp bow and stern with a fin keel would be approaching zero, but what does 0.6 mean for a full keeled sailboat?
Thanks for any guidance
Ross
It appears that this vessel will have a BLOCK COEFFICIENT of 0.6.
Yes, a block of wood would be 1.0 and a sharp bow and stern with a fin keel would be approaching zero, but what does 0.6 mean for a full keeled sailboat?
If you look at the hull lines, draw the limiting line under the hull before it drops at right angles to the keel. Everything above is the hull to use in calculations.
The keel is then measured almost as a trapezium in cross-section by the area.
With a hull built and ready to float and weighted correctly fore and aft. I put the hull into a bath full of water. I do not make big ones any more!
I have already put some cheap masking tape around the middle and side of the hull. With a pencil I push the hull sideways through the water.
Find the sweet spot where the hull moves evenly, not going to one side or the other, and mark it.
This is the CLR.
When the sail area calculations are done and the C of E of the sail area is worked out, it is this point that should be placed 4% ahead of the waterline length. This will give a nicely balanced sailing attitude.
The mast can then be mounted in the position already determined by where the C of E is to be. I do all this before working out where access and s/s should be.
By this I mean with sails at 30 degrees she will sail a straight course with no rudder adjustment needed.
My last 3 yachts have been set up in this way and they work fine.
With Bella there was a set mast position on the plans, I ignored this and moved the mast position back aft 2cms, which was as far as I could.
To get a better balance, i installed a bowsprit and the fore jib is moved forward until the C of E is just ahead of the CLR by 4%. The length of the bowsprit was now determined. Fittings were soldered up and she looks just right as well!
The fore jib is on a loop and fixed, but after a year sailing her I decided to have a standard servo with a small arm fitted to pull in the fore jib sheet and tighten sail.
The effect is dramatic! Careful control creates a wind slot for the jib and main sail and she speeds up.
I have been struggling with my method of volume calculation. Particularly, how to identify a certain cube in the whole collection of cubes and part cubes. I sat down quietly and thought about it, after looking at BLOCK COOEFFICIENTS, (thanks to Roy for pointing me in the right direction). The calculation for block coefficient, is based on a 3 dimensional cartesian coordinates. X axis is the LENGTH AT WATERLINE, Y axis is the KEEL TO WATERLINE, and Z axis is the WIDTH. If I use 3 coordinates, I can identify any cube.
So in my case:
0 to 28 are choices for X coordinate
0 to 4 are choices for Y coordinate &
0 to 4 are choices for Z coordinate
I will set the ORIGIN at the bottom of the keel, behind the rudder post, on centreline. From there I go up to the waterline, forward toward the bow, and out to port & starboard sides
If I want a particular cube I can identify it's position with 3 numbers
eg 23,3,2. that would give me the cube close to the bow, almost to the waterline, and halfway between the centreline and the gunwale
I have been struggling with my method of volume calculation. Particularly, how to identify a certain cube in the whole collection of cubes and part cubes. I sat down quietly and thought about it, after looking at BLOCK COOEFFICIENTS, (thanks to Roy for pointing me in the right direction). The calculation for block coefficient, is based on a 3 dimensional cartesian coordinates. X axis is the LENGTH AT WATERLINE, Y axis is the KEEL TO WATERLINE, and Z axis is the WIDTH. If I use 3 coordinates, I can identify any cube.
So in my case:
0 to 28 are choices for X coordinate
0 to 4 are choices for Y coordinate &
0 to 4 are choices for Z coordinate
I will set the ORIGIN at the bottom of the keel, behind the rudder post, on centreline. From there I go up to the waterline, forward toward the bow, and out to port & starboard sides
If I want a particular cube I can identify it's position with 3 numbers
eg 23,3,2. that would give me the cube close to the bow, almost to the waterline, and halfway between the centreline and the gunwale
Hi all, nice to do the maths but which is most important, the calculation and solution or constructing a practical model?
When scaling down from a prototype as we know, hulls and sails do not change in proportion to each other. I start from the size of the finished model, i.e. will it fit in my car and also have a place in the house.
So working out a suitable hull size comes first. Dividing the model length into the prototype length gives a scale. The cube of the scale gives a 'scale displacement', in some scales just not practical! All my models have to earn their living at the lakeside.
It is fortunate that to make a model sail, the invisible part under the water can be doctored in many ways.
The models by Glynn Guest have relatively crude hulls and what used to be called 'stand off scale' appearance. I have built several and they look good on the water. I also enjoyed the construction.
So we have to decide where your interest lies? Doing exact calculations for hull displacement is conditioned by sailing in water (and waves) that have obstinately remained at full size.
Hull displacement calculations could have a 10% error but it would not be noticeable when on the water. Bearing in mind that all the mentioned calculations have an end in practical sailing.
If only constructing a display model the numbers are irrelevant!
It reminds me of the radio control of the 1950s where the boat was the least important aspect of the model!
Just my two pennorth!
Roy
Thank you Roy for you further thoughts. Actually I enjoy the planning part, the solving of a puzzle, (check some of the discussions between Alessandro and me). As you suggest the goal is stand-off scale sailing. If you go back a few entries you see my transport vehicle, my wife's truck. (yea, it's in her name and she is its driver). The basement here is empty and it's display spot is already picked out. My fear is that I will put it in the water and it will simply turn upside down. (another member here did that with an old carved boat, he caught it before it went under.) You mention earlier that one of your CE:LCP is 4%. Mine is currently calculated at 14%. A full schooner is supposed to be 7% The mast steps haven't been set yet, so that is definitely being shifted. Yes, I can do the calculations, but I need the modellers, like you, to add their personal input. As a wise nanny once said, IN EVERY JOB THAT MUST BE DONE THERE IS AN ELEMENT OF FUN. YOU FIND THE FUN AND SNAP, THE JOB'S A GAME! The puzzle solving is my therapy😁
Thank you Roy for you further thoughts. Actually I enjoy the planning part, the solving of a puzzle, (check some of the discussions between Alessandro and me). As you suggest the goal is stand-off scale sailing. If you go back a few entries you see my transport vehicle, my wife's truck. (yea, it's in her name and she is its driver). The basement here is empty and it's display spot is already picked out. My fear is that I will put it in the water and it will simply turn upside down. (another member here did that with an old carved boat, he caught it before it went under.) You mention earlier that one of your CE:LCP is 4%. Mine is currently calculated at 14%. A full schooner is supposed to be 7% The mast steps haven't been set yet, so that is definitely being shifted. Yes, I can do the calculations, but I need the modellers, like you, to add their personal input. As a wise nanny once said, IN EVERY JOB THAT MUST BE DONE THERE IS AN ELEMENT OF FUN. YOU FIND THE FUN AND SNAP, THE JOB'S A GAME! The puzzle solving is my therapy😁
Aren't these beautiful underwater lines? (WHAT?? it's just a bunch of numbers. Is he smoking that wacki tabaki again?)
The underwater coordinates in a 3D matrix. I now have to finish the formulas to make it work. I have an advantage of knowing how it SHOULD be. Each correction of a formula gets a little closer (as usual click the box in the corner and follow the prompts to open)
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Aren't these beautiful underwater lines? (WHAT?? it's just a bunch of numbers. Is he smoking that wacki tabaki again?)
The underwater coordinates in a 3D matrix. I now have to finish the formulas to make it work. I have an advantage of knowing how it SHOULD be. Each correction of a formula gets a little closer (as usual click the box in the corner and follow the prompts to open)
Sorry Ross, I only replied to the private message now. I read it some time ago, with the intention of replying as soon as possible and then I forgot.
In my haste I may have made some mistakes, bear with me.
I finally got around to weighing the component parts of the boat. I am 2.6% overweight, from calculations. I consider that a great relief.
Without ballast yet
calculated:10.65kg
actual :10.92kg
CONTENTS: 1 SCHOONER, some assembly required
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Re: ...while the hull and INCREASED number of winches were heavier than estimates. coming out almost even, loss for gain in weight. This will assist in lowering the center of gravity and rolling moment...
Depends.
It depends on the position of the winches.
If they are very low it is better that their overall weight has increased, otherwise not. It's a good thing that the sails are lighter logically.
However, to be safe I would consider them wet.
The sails could always get wet or damp (unless you use waterproof fabric; then you are safe).
WINCHES:
Given the scale of the vessel and the size of the winches, they can be placed at or below the waterline. More important could be the position fore and aft for balance.
SAILS:
The plan is that the polyester-cotton sails will be only short term. As they pass the test, they will be upgraded to RIPSTOP, MORE WATER RESISTANT. High up weight, like any sailboat can be critical. I am hoping the Ripstop will help with that.
BALLAST:
The ballast, at this stage, is is set for 8 kg.
Given the scale of the vessel and the size of the winches, they can be placed at or below the waterline. More important could be the position fore and aft for balance.
SAILS:
The plan is that the polyester-cotton sails will be only short term. As they pass the test, they will be upgraded to RIPSTOP, MORE WATER RESISTANT. High up weight, like any sailboat can be critical. I am hoping the Ripstop will help with that.
Be honest with me, is the mast in the right ways? The instructions said to insert tube into hole in keel. (the main spar of the ballast fin)
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Hi Ross, I want to answer you honestly, but I can't focus the image.
Can you take a better photo?
You mean the keel?
Take several photos, including one on-axis.
11 months ago you posted this photo. Is this the same model you are asking about today? Come on fellow model builders let’s help Ross with this project.
