Yacht design the hard way. learning from Kav800 (most beautiful boat EVER...etc LOL!)

I don't think so.

 

oopse! thats supposed to be 60.5 cm

 

So 60.5cm = 605mm.

Therefore 7930/605= 13.11. So your model scale is 1/13.11.


I don't think you have mentioned what you are trying to accomplish with your modelmaking. I think you have wasted more money on the two methods you have tried than you would have spent doing a proper plank-on-frame construction.

 

I admit I do not know at all what I am doing. I bought most of the stuff I have used a long time ago because I always wanted to make an actually decent RC sailboat or airplane. All the other ones I just kinda threw together from this plan or that plan, but none of them really made me go "WOW! this flies really good, or floats nicely. (If they even floated or flew.)

My intention in building models is to learn about the processes of the design aspect of naval architecture. I have learned from home on my computer everything I know about drawing 3d models and after deciding that RC modeling shouldn't be scary and should instead be FUN I decided that 3d models were no longer fun and that I want to go to the next logical step of building one and seeing what I can learn.

I don't have a lot of anything except a lot of understanding about 3 dimensional objects. I can sketch sketches on paper which look 3d to the mind's eye and have had that ability since before high school.

I don't know anything about RC modeling from scratch, but I have built thousands of plastic models of cars, planes, aircraft carriers, etc. I don't have a car and live way out in the boonies so I can't just go to the local hobby store and buy wood. I live near a hardware store though, so I get most of my supplies from there.

I am not good with numbers. I have a form of autism called Auspergers. I am disabled and live in a travel trailer. I don't have a job or a car, but I want to learn a trade and right now I want to learn yacht design. I am splitting up my days between learning Free!Ship, watching how to sail videos, shopping for a sailboat, learning math, and working on the model. Altogether, I spend about 17-20 hours a day learning about designing boats and why I shouldn't buy this one, and why that one costs more, etc.

I also realized a few months ago that yacht design might just use every single thing I'm good at, and several that I'm needing to work on. I don't have any idea why, but I look at something and go 'humm, what if this were made a different dimension so that it sat on top of the water when swamped instead of sinking like a ferro concrete hull with the keel torn out of it?' and then sometimes I try and work out the math to see if it would probably sink anyways.

Aside from all that, I'm having lots of FUN.

 

Having fun is the thing that will keep you going past the mistakes and problems. Keep at it!

Here are a couple of suggestions that might be useful;

When you are doing math, keep the same units throughout the calculation. You tried to mix mm and cm in the same calculation and got the wrong answer; Paul was careful not to do that, he divided mm by mm and got the right answer first time.

When you scale down a boat into a model not everything changes at the same rate. The wind will cause a scale boat to tip, or heel, more than a full-size boat. Model boat designers make the sail and mast smaller, and put as much ballast as the boat will bear. The ballast is also mounted as low as possible on an extra-deep keel. If you click on these links and compare the model sail boat with the full-size ones you will notice these differences; compare the keel on the model (first link) with the keel on the J-Boat (second link) . . . and the model's sail with the sails on the 12 meter yacht (third link) and the huge J class boat (last link)

http://sailrc.com/Images/JudySteveBoat.jpg
http://www.cupinfo.com/images/ranger5e.gif
http://www.trivia.de/SaintTropez/Trivia/Trivia08small.jpg
http://www.cupinfo.com/images/ende-lee-2-102.jpg

 

Thanks, I know that having fun is a great driving force in my model building. I also have a strong will to finish stuff unless it has become totally hopeless.

I realize my mistake now. Please understand that this is the first time I've worked with metric. I want to work in metric because I feel like it will eventually be much faster and more efficient working with that than trying to figure out 7/32 plus 9/16ths.

I can't have that long of a keel in this pond!!! It won't work at all.

Let me draw a little picture of what I think might work instead.



Uploaded with ImageShack.us

 

I think maybe I can make multiple keels and make them thread into the hull somehow so that I can play with different ones and see what works and what does not.

EDIT:: Okay, so what if I simply add weight to the ballast by wrapping copper wire around a bulb until the model sits right at the correct water line once the mast and rigging are onboard?

I want lots more than 0.115 kgs ballast

 

The keel odd in shape, and ballast WAY out of proper position.
DO NOT change anything in so radical way -you will create a pile of disappointments.
_______________

As to "not fair enough" hull you got out of foam, f**** the accuracy, finish it and assemble all the keels and rigs go to your lake!
Unfair, ugly, banana shaped, whatever, but floating and functioning model is much more fun than 1X-th time starting the new one, this time "fair enough".
The next model will be better as the first one, but if the first one will not see the water quick enough, the fun will be over all to soon.
Believe me, I did it.

 

Right now, the water is frozen so kinda hard to sail on.

I wish Alik would send me the plans for the keel bulb.

Should I just drop the ballast for the centerboard design straight down? I kinda want to make a simple centerboard anyways and see if I can make it work somehow.

 

Just make the oversized "centreboard" ~2.0 times the dimensions of original, and hang a bulb on bottom of it.
Top of board could be trimmed to suit the centreboard case if you do not vant to weaken the hull with cut-out so big .

 

Okay, I could do that =0)

 

I have yet another question related to hull speed. The curvature calculations on a hull I'm trying to make in Free!Ship has 0.38 at the top of the curve. This is a good number right? It started at over 0.79, but I messed around with it till I got it lots lower.

The center of flotation however is at 5.90 and I have no idea where to look to find out what that means, or what to do next to check the center of flotation when heeled.

 

"....I'm trying to make in Free!Ship has 0.38 at the top of the curve. ..."
You probably talk here about resistance value, which is possible to do in Free!Ship.
To have the correct numbers, it is necessary to enter the correct values for hull geometry and displacement.

Hull speed (even if it is not a "sound barrier" for a boat of this shape and lightness) is v[kn]=2.43*SQRT(LWL[m])
in this case :
v[kn]=2.43*SQRT(0.6)=1.88[kn]
If you will manage to keep the weight in scale, in right conditions and properly handled, she will be able to move faster.


There is no point to worry about center of floatation for other than educational purposes. The number 5.9 you mention is probably the distance between CF and midlength of LWL in % of LWL (make sure in Project-> Project settings-> Hydrostatics the "actual dimensions of submerged body" is selected).

 

Okay, I think I understand now. Once I closed the transom and therefore was able to put the stern in the water I have a new top of curve at .27 I made some really slight changes and can get that number as low as .19 but it has to be wider than a trailer to get that low a number. I think that when heeled over it would not be as good because it would probably put the bow lower in the water, but if you could stay upright it would move really easily.

 

What is this number .27, .19, ....?