My master piece

[evantica]

Hi. I'm building my Master piece right now! A heavydeplacement -kind of- C.Archer, It's going to be a globetrotter, safe and strong! I'm on a tight budget, so tips and clever solutions will be appariciated. I need your help to figure out the "Waterline". I know there's a Matematic calculation on this subject! But I dont know it! Maybe someone of you do??? It messures : 8 Meters x 3 meters wide and draft is about 1,6 Meters, not quite sure on the decplacement yet.

[AdriftAtSea]

without knowing how much it weighs or what the hull form shape is, it is hard to say where the waterline will end up. 

[evantica]

 Yes thats right... about the weight and so... I have to consult a "Pro boat designer" to get all the parameters right!

I was just curious about the "Matematic/ calculation".

[evantica]

Adriftatsea... Do you know the formula for this subject?

[AdriftAtSea]

sea water weighs 64 lbs per cubic foot.  If you know the displacement of the vessel, you can roughly calculate the waterline, but you don't know the displacement yet...so there's no way to calculate the waterline position.  You simple don't have enough information.

[Captain Smollett]

Adriftatsea... Do you know the formula for this subject?

There is no "formula" for computing the waterline.  It (such a formula) is different for each hull shape.  It requires numerical calculation of the true hull shape in three dimensions to get the submerged volume as a function of waterline (whether the calculation is done with modern CAD tools or the old fashioned way using graph paper and the plan drawings is immaterial).  To see this in practice, go to the Sail Calculator Page, look up half a dozen or so similar boats, and look at how different the lbs per inch metric are.

Depending on the hull shape, you MAY be able to roughly estimate it using a triangular prism or some such simple geometric figure as the volume 'generator.'

Here's a free volume of a submerged sphere simulator I wrote a few years ago.  Even for a simple sphere (like a ball buoy), the function is a cubic.

Finally, you can try FreeShip, especially if you have or can find a ready plan file for your hull.

In short, there's a good reason why boat designers spend a lot of time in school and get paid decent money to calculate such design parameters as waterline and lbs per inch of submersion.

Lastly, perhaps the EASIEST way is to simply put the boat in calm water, trim her properly and mark the waterline. Haul the boat back out and paint it on.  If you do this, mark it about every foot or so, so you can accurately spline the line.

[AdriftAtSea]

In short, there's a good reason why boat designers spend a lot of time in school and get paid decent money to calculate such design parameters as waterline and lbs per inch of submersion.

Lastly, perhaps the EASIEST way is to simply put the boat in calm water, trim her properly and mark the waterline. Haul the boat back out and paint it on.  If you do this, mark it about every foot or so, so you can accurately spline the line.

Of course, this is much easier if the boat is nearly finished....

[tomwatt]

In short, there's a good reason why boat designers spend a lot of time in school and get paid decent money to calculate such design parameters as waterline and lbs per inch of submersion.

Lastly, perhaps the EASIEST way is to simply put the boat in calm water, trim her properly and mark the waterline. Haul the boat back out and paint it on.  If you do this, mark it about every foot or so, so you can accurately spline the line.

Of course, this is much easier if the boat is nearly finished....

If it's not finished, then it's really easy... the waterline will be up there somewhere above the masthead!
 

[evantica]

Thanks for -complex- answers! I realize this is complex stuff. Good I contacted a boat designer for all the important parameters! But I think it's kind of interesting also and I will try to learn more about this Boatdesign suject.
Another facinating thing is: How "they" messure/ calculate what sailing area nessecery for a vessel. To  consider stabillity, Weight, and more... to get this right, sound like a whole lot of work... "It scares me" when the "bill" comes from the "boat designer" for my boat...
Have any of you used the "Gunther rigg"

[maxiSwede]

In short, there's a good reason why boat designers spend a lot of time in school and get paid decent money to calculate such design parameters as waterline and lbs per inch of submersion.

Isn't that SO true.  I've always been kinda amazed with all these sailors who buy a boat and then start doing alterations to it (adding bow sprit -changing the foretriangle for example). Boat design is a VERY complex process and why buy a specific design in the first place if it's so crappy (?) designed that an amateur could improve it?

don't get me wrong here, I am certainly not against amateur design in itself, what bemuse me is all the 'good old' boat designs you see in every marina that are 'modified' the most weird ways.... rarely making them better....

just my 2 cents

[newt]

You know what is funny, but as I am getting into building sails, I am realizing that each boat on the water is a little different. I mean so much different that the best way to make sails is to measure the boat- because those measurements differ in the same model! Boats are still very much like their owners- each with personality. The modification process is almost endless.

[evantica]

I did a fatal mistake and asked some question on a Boatbuilding forum, and questioned if it really was that important with all the parameters... I was talking about the ol' Vikings and so, "they probably did not use any speciall parameters and so on.. went to sea anyway, and did well" (in most cases) Oh my God they went amok on the "site" and did not like me at all... I meant well but couldn't present it well so... This is a hot subject.

How about the "Gunther rigg" any of you???

[CharlieJ]

A Gunter rig is great on a small boat. Lets you stow all the spars in less than the length of the boat. Could be workable on a larger vessel I suppose, but I've never seen one so rigged.

[Captain Smollett]

A Gunter rig is great on a small boat. Lets you stow all the spars in less than the length of the boat. Could be workable on a larger vessel I suppose, but I've never seen one so rigged.

Just talked to a guy here at the marina who used to sail a Drascombe with a Gunter rig...he said he's actually seen them mentioned on boats up to 40 feet.

He liked the rig, at least on his 18 footer.

[s/v Faith]

Evantica,

  First, congratulations on your progress.  I looks like you are going to have quite the little ship there.  I personally have neither the skill, nor the inclination to undertake such an endeavor.  I sure do like seeing 'in process' pictures of the builds, and know that they are hard won photographs.  I have been building a house for just over a year now and know how frustrating it can be to work all day long and look back and not be able to see real progress.

  It looks like you have made some real progress, but it seems (to me, with the limits I expressed earlier) that you have a bit of a pickle.  I see you need a reference point (water line) to level your interior on... but you can not do a float test to find one until you have more of the interior built.

  Seems to me that you need some numbers from other Colin Archer designs that are floating on their lines.  As John says, it is going to be very difficult (if not practically impossible) to come up with the numbers you are looking for 'by formula'.  Numbers from other boats should get you close.

  If your design is modified enough that this will not work, maybe you could make a 'temporary' bulkhead, build the decks, and float the hull to get your waterline... then build your interior once you have established "level".

  Whatever you do, I wish you well.  Thanks for sharing your progress with us, and I look forward to reading about your future progress.
 

Hi. I'm building my Master piece right now! A heavydeplacement -kind of- C.Archer, It's going to be a globetrotter, safe and strong! I'm on a tight budget, so tips and clever solutions will be appariciated. I need your help to figure out the "Waterline". I know there's a Matematic calculation on this subject! But I dont know it! Maybe someone of you do??? It messures : 8 Meters x 3 meters wide and draft is about 1,6 Meters, not quite sure on the decplacement yet.

[SeaHusky]

Hello Evantica!
I like your build and your blog!
I have no real knowledge so these are just my thoughts. As you seem to be building "on the go" so to speak and may need to simply do trial and error until you get the rigging, sailarea and such right, perhaps a junk rig could be a place to start.
Just put a mast and a large battened sail up and try. this way you can shift sailarea for or aft and reef a section at a time until you find what the boat seems to like. Then take those numbers and convert them to a cutter rig or what ever you want?
As for the waterline. Is it possible to patch up the "plug" and weigh it down for a floattest and get a rough estimate?

What was the plug by the way?

[evantica]

Thanks for kind words! Yes this is a real "treat" for me... I have contacteda designer to do all the messurments and so... A job much to difficult for me! I will keep you updated along the building process.
 The plugg was a Lots kutter, a real go anywere boat! I did sail her and had confident in her, so that one og many reasons!
Fair winds friends...cpt. Hakan

[maxiSwede]

A really interesting project Hakan. Goo idea to involve a professional too I would think.  If it's a Pilot Cutter type. or Colin Archer type as you wrote somewhere, why not consider  a gaff rigg? 

Good luck with all that hard work!

[evantica]

Hi there. The reason for not use a Gaff rigg is the complexity, If short handed! In other case I would! Like those ol' fashion, nostalgic looks C. Archer boats

[Godot]

I don't think a gaff rig would be a bad idea at all.  The only place I think a marconi rig has a serious advantage is hard on the wind.  Gaff sails are much simpler.  There is a lower center of effort.  The rig and hull stresses are smaller.  Based on the tiny gaffer I used to sail, there are two halyard (throat and peak) for the main.  By playing with the peak halyard you can drastically change the shape of the sail.  If the wind suddenly picks up you can rapidly reduce sail (albeit in an ugly fashion) by releasing the peak halyard and scandalizing the main.

On an 8 meter boat I don't think you would have much difficulty handling the gaff rig, even single handed.

Besides, they look cool.

It's a matter of personal preference; but obviously I like them.  If I were to build another boat, it would most likely be a gaffer.