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How do I measure the weight of my keel


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#1 Alcatraz5768

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Posted 13 December 2013 - 10:14 AM

I need your ingenious ideas to measure the weight of my keel. It's still on the boat which makes it a bit harder. A lot actually.
I thought I could pull the boat out and lay up some csm and polyester around the bottom of the keel, then cut it down the centre while its green, then glue both halves together again, then measure the amount of volume with water, then calculate the same volume of lead.
The keel is an ugly semi bulb tapered fin thing with a alloy stub with electric mice problems, hence the need to weigh the lead for a new t keel.
Any good ideas will be rewarded with... Nothing really.

#2 Alcatraz5768

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Posted 13 December 2013 - 10:17 AM

Ah fuck. How do I delete the other 3 of these topics?. Why did it do this, I just hit the post button once. Thanks for any advice.

#3 Mojounwin

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Posted 13 December 2013 - 11:10 AM

How long is the bulb? You could build a box or find an old bath tub, 44 Gallon drum cut in half, etc. Put the bulb in. Measure how much water you are pouring in until you completely cover the bulb, mark the water level on the tub and then refill it to the mark without the bulb in it. The difference in the 2 volumes is the volume of your bulb.

 

Good luck.

 

Cheers

Mojo



#4 bugger

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Posted 13 December 2013 - 01:39 PM

I don't know if this will work in practice (it works in theory well) but will require a LOT of measuring.  Divide the keel into the smallest possible divisions you think you can manage.  Say, every one inch along the entire length of the keel.  At each one inch interval, using a set of calipers and ruler make every single measurement you can:  length, thickness, width, etc. at every couple of inches.  That will give you a pretty good idea of the cross section shape of the keel at that point.  Using that data, you can calculate the cross sectional area of the keel at that point.  Volume is that area times one inch. 

 

Now move to the next one-inch section. 

 

Sum up the volumes of each individual one-inch section to get the total volume. 

 

This is the basis for mathematical integration, if you are familiar with that. 

 

Oh, and I have no idea what "electric mice problems" are. 



#5 amro

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Posted 13 December 2013 - 02:33 PM

If you have to take it off because you need to replace it, take it off to weigh it. Why screw around?

#6 bugger

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Posted 13 December 2013 - 02:43 PM

Alternative methods include:

 

- assume the keel is a bunch of simple shapes all stuck together (cone, hemisphere, etc.) and calculate the volume of individual simple geometries (much less measuring).

- contact the builder and ask for their drawings.  Work it out from there. 

- contact the builder and ask if they weighed it when it was built

- find out if any other keels like yours were built.  Find out who owns one and ask them if they know what it weighs

- ask a yacht designer to create a drawing of your keel in something like YachtCAD (?).  They can then easily calculate the volume.



#7 bugger

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Posted 13 December 2013 - 02:48 PM

This reminds me of this old joke.  Sorry to be so off topic.

 

**********************************************

 

 

Some time ago I received a call from a colleague, who asked if I would be the referee on the grading of an examination question. He was about to give a student a zero for his answer to a physics question, while the student claimed he should receive a perfect score and would if the system were not set up against the student. The instructor and the student agreed to an impartial arbiter, and I was selected. I went to my colleague's office and read the examination question:

"Show how it is possible to determine the height of a tall building with the aid of a barometer."

The student had answered: "Take the barometer to the top of the building, attach a long rope to it, lower it to the street, and then bring it up, measuring the length of the rope. The length of the rope is the height of the building."

I pointed out that the student really had a strong case for full credit since he had really answered the question completely and correctly. On the other hand, if full credit were given, it could well contribute to a high grade in his physics course. A high grade is supposed to certify competence in physics, but the answer did not confirm this. I suggested that the student have another try at answering the question. I was not surprised that my colleague agreed, but I was surprised when the student did. I gave the student six minutes to answer the question with the warning that the answer should show some knowledge of physics. At the end of five minutes, he had not written anything. I asked if he wished to give up, but he said no. He had many answers to this problem; he was just thinking of the best one. I excused myself for interrupting him and asked him to please go on.

In the next minute, he dashed off his answer which read:

"Take the barometer to the top of the building and lean over the edge of the roof. Drop the barometer, timing its fall with a stopwatch. Then, using the formula S=0.5*a*t^2, calculate the height of the building."

At this point, I asked my colleague if he would give up. He conceded, and gave the student almost full credit. In leaving my colleague's office, I recalled that the student had said that he had other answers to the problem, so I asked him what they were. "Oh, yes," said the student.

"There are many ways of getting the height of a tall building with the aid of a barometer. For example, you could take the barometer out on a sunny day and measure the height of the barometer, the length of its shadow, and the length of the shadow of the building, and by the use of simple proportion, determine the height of the building."

"Fine," I said, "and others?"

"Yes," said the student. "There is a very basic measurement method you will like. In this method, you take the barometer and begin to walk up the stairs. As you climb the stairs, you mark off the length of the barometer along the wall. You then count the number of marks, and this will give you the height of the building in barometer units. "A very direct method."

"Of course, if you want a more sophisticated method, you can tie the barometer to the end of a string, swing it as a pendulum, and determine the value of g at the street level and at the top of the building. From the difference between the two values of g, the height of the building, in principle, can be calculated."

"Finally," he concluded, "there are many other ways of solving the problem. Probably the best," he said, "is to take the barometer to the basement and knock on the superintendent's door. When the superintendent answers, you speak to him as follows: 'Mr. Superintendent, here is a fine barometer. If you will tell me the height of the building, I will give you this barometer."



#8 Savage 17

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Posted 13 December 2013 - 02:53 PM

Take it off and weight it

#9 casc27

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Posted 13 December 2013 - 03:06 PM

Build a box big enough to immerse the entire keel. Measure the volume of the box. Fill teh box with water all the way to the top. Immerse the keel in the box displacing the water out of the box. (Just let the water run out.) Remove the keel from the box and measure how much the water level has dropped in the box. Caculate the volume of missing water based on teh box dimensions. This is the volume of your keel.

 

Or, like amro said, since you are replacing the keel, just remove the thing and weigh it.



#10 DRIFTW00D

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Posted 13 December 2013 - 04:06 PM

U could just unbolt it. then weigh the thing,as u are getting a new one anyway. then leave it out or throw it back on.

lazer scan it. then let a program work out the Calculus.

I like the water idea old home fuel oil tank on end could work.

Back in the day at Tarten Marine a long swimming pool was under a travel lift track to chech out many things on a finished boat including IOR tippy / add lead till it rates whatever.

#11 WarBird

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Posted 13 December 2013 - 05:29 PM

@While lifting the boat, ask the crane operator to stop while the keel/hull joint at the attachment point is still in the water. The crane will have a scale, record the weight.  Record the weight of the boat completely out of the water.  Look up the specific gravity of lead or iron and do the maths.



#12 dreaded

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Posted 13 December 2013 - 07:48 PM

in relation to the physics above..    weigh the boat, subtract the weight of everything that is not the keel, voila, you have the weight of the keel....

 

uh, how about contacting the builder?  looking up specs?   



#13 Alcatraz5768

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Posted 14 December 2013 - 03:57 AM

 , you guys are legends, all good answers however most wont work or are too hard.

 

Mojo: I thought of that however the logistics are just way too hard and the travellift operator thought i was on crack.

bugger: Too time consuming and i think id fuck it up.

Amro: middle of summer here so still using the boat. Its coming out this winter to do the job but id like to have the fin and bulb mold all done before hand.

bugger again:too weird of a shape. (ill try to attach a pic)

bugger again: i  love smart arses

Savage: middle of summer here so still using the boat. Its coming out this winter to do the job but id like to have the fin and bulb mold all done before hand.

casc: middle of summer here so still using the boat. Its coming out this winter to do the job but id like to have the fin and bulb mold all done before hand.

driftwood: middle of summer here so still using the boat. Its coming out this winter to do the job but id like to have the fin and bulb mold all done before hand. I like the laser scanner idea, but dont know how.

Warbird: You are a squaler and a genitleman. what a primo idea, as long as the scales go up in 1kg increments it doesnt even matter if its inaccurate.

Dreaded: The boat was built in 1982 as a one off, no one will have any info.

 

 

You all rock, thanks for giving it some of your precious brain power.

 

 

 

 



#14 bugger

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Posted 14 December 2013 - 06:24 PM

I have to think about this, but I think warbird's method will give you the buoyant force due to the keel (hence its volume)

 

Fully out of the water:  crane weight = boat including keel.

 

Just at the hull/ keel joint:  crane weight = boat including keel - buoyant force due to displaced water. 

 

The differences in crane weights will be due to the buoyant force of the keel.   It will tell you how many lbs or kgs of water are displaced by the keel.

 

Let's say the difference is 300 kg (this is so much easier in metric).  Assuming fresh water (that makes the math easy), your keel has a volume of (about) 300 litres.  Multiply that by the density of materials in your keel and you have your answer. 

 

I think. 

 

If the above is correct, for this to work your keel has to be solid and all be made of the same material. 



#15 Dead air

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Posted 15 December 2013 - 06:27 AM

Floating dock could provide the answer, you need to know the size of the cylinders, then the pressure in the air system at three points ideally,
1 just as the dock starts to take weight/touches the keel
2 just as the hull leaves the water, but keel is still submerged
3 just as the keel leaves the water


Might be able to source a load cell for you if you want to go down the crane route though

#16 Alcatraz5768

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Posted 15 December 2013 - 08:17 AM

I think I'll lift it on the travel lift and mark the keel to stub joint, then take a reading of the boat out of the water then when it is submerged to the marked joint. As bugger says the difference will be the volume of displaced water (salt 1025kg per cu meter) then multiplied by 11.73 for every litre of volume for the weight of the lead. Easy peasy, and cheap as its just lift, mark and lower it back in..

Cheers guys.

#17 WarBird

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Posted 15 December 2013 - 06:39 PM

It would be nice to have a sense of th scale sensitivity. If the hoit operator will let you, you could add weight to the hanging boat.. Have 4-5 10kilo weights to add to the boat.A 3gallon fuel jug would be abbout right. Weigh it. Add them one at a time and record the weight change. That will tell you how close or far from the nextweight up on the scale display youare.

#18 WarBird

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Posted 15 December 2013 - 07:56 PM

The scale may only read.in 20 or 100 lb increments, the weigbts give you a better idea of the actual weight of boaf and keel water displa ement.

#19 hannibal

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Posted 15 December 2013 - 08:20 PM

422.1 kg  is  your awnser



#20 Alcatraz5768

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Posted 16 December 2013 - 09:14 AM

I hope it's more than that. I like your idea warbird, I'll check how small the increments are on all the local lifts.

#21 European Bloke

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Posted 16 December 2013 - 11:45 AM

I think the problem's too hard.  Lot of ingenious solutions.

 

I'm interested to know what you manage to calculate and then what the real answer is when you cut the old keel off.  I think if you get less than a 50% error you can give yourself a pat on the back, 100% won’t be a bad effort either.

 

 , you guys are legends, all good answers however most wont work or are too hard.



#22 WarBird

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Posted 16 December 2013 - 07:58 PM

You could correct for water temp too. H2O is 1 ar 22C (?).

#23 crash

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Posted 16 December 2013 - 08:14 PM

I think the easiest way is to have a big "tub" - one large enough to include the entire keel. Fill with water, measuring how much water it took to fill. Have crane lower boat into tub until water reached hull to keel joint. Remove. Measure remaining water. Difference, converted to lbs, is displacement of keel. Might need a big crane tho....

#24 WarBird

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Posted 16 December 2013 - 08:31 PM

You could correct for water temp too. H2O is 1 ar 22C (?).

.9991 @ 15c ,  .9978 @ 22C

 

Sorry



#25 WarBird

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Posted 16 December 2013 - 08:56 PM

It would be nice to have a sense of th scale sensitivity. If the hoit operator will let you, you could add weight to the hanging boat.. Have 4-5 10kilo weights to add to the boat.A 3gallon fuel jug would be abbout right. Weigh it. Add them one at a time and record the weight change. That will tell you how close or far from the nextweight up on the scale display youare.

Play some 1 gallon milk jugs and 2 liter soda bottles to zero in your weight.



#26 WarBird

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Posted 16 December 2013 - 09:44 PM

I think the problem's too hard.  Lot of ingenious solutions.
 
I'm interested to know what you manage to calculate and then what the real answer is when you cut the old keel off.  I think if you get less than a 50% error you can give yourself a pat on the back, 100% won’t be a bad effort either.
 

 , you guys are legends, all good answers however most wont work or are too hard.

The process is ripe for error. The key is getting accurate weights due to the density difference of lead and water. You are multiplying an error by 11 point something! The tub is a good way to go if the yard will allow it and the hoist/travel lift can get bigh enough. And the $/hour isnt too steep. However, while the boat is up quick measurement of the keel bulb allow you to approximate the volume.. The keel in cross section is two triangular shapes. The leading edge to max thickness and max thickness to trailing edge. Measure top middle and bottom and you can closely approximate fin volume. Bulb the same though.maybe a few more diameter measurement s. Wings on the bulb treated like a fin.

#27 Raked aft \\

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Posted 16 December 2013 - 09:48 PM

I don't know why your bothering weighing the old keel anyway...

 

 why don't you work with a naval architect and design a keel (weight & shape) that will best improve

the performance of the boat given its size, shape and sail plan.

 

 

  Your welcome,

 

  Uncle Bob...



#28 DFL1010

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Posted 16 December 2013 - 10:55 PM

If you don't want to remove the keel, how about weighing boat with keel, then remove the hull from the keel and weight the hull.

#29 amro

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Posted 16 December 2013 - 11:18 PM

 , you guys are legends, all good answers however most wont work or are too hard.

 


Amro: middle of summer here so still using the boat. Its coming out this winter to do the job but id like to have the fin and bulb mold all done before hand.

bugger again:too weird of a shape. (ill try to attach a pic)

 

You all rock, thanks for giving it some of your precious brain power.

 

 

you do realize this method would take about a day, or at best, a weekend to do, cut the keel loose from the sump and pull the nuts friday nite, hoist the hull up off the keel friday nite or saturday morning, start weighing process. put hull back down on keel, with new bedding set up. retorque nuts, fair and paint keel joint. let it sit sunday, drop boat back in the soup monday afternoon. do it on an off race weekend and you don't miss a leg. every other method you are pondering is overthinking the problem tenfold, and a waste of said precious brain power,

 

i've been involved in doing this on a 44 footer, so don't tell me it can't be done. we dropped the keel, rebuilt the bottom of the hull and keel grid from what seemed like a single layer of glass, reattached the keel, faired and painted in about two weeks. literally between races.



#30 wristwister

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Posted 16 December 2013 - 11:35 PM

Find out the distance from the top of your mast to the waterline (Dm) , and from the center of the keel bulb to the waterline (Dk).

 

Add some line to a masthead halyard to make it approximately 1.5 X the mast height. Get an accurate measurement of that overall length (Dh).

 

Attach a scale to the end of that line. From the dock, pull on that halyard to heel the boat over. Pull to a specific point on the dock that gives you, say, 100 lb on the scale (F1).

 

Mark that point on the dock, and measure it’s height above the water (Dd)

 

With another halyard, pull a weight to the top of the mast (W). 100 lb should do it. 12 or so gallons of water in jugs should do the trick.

 

Pull the same halyard line/scale to the same point of the dock and record the scale reading (F2). Should be less than before.

 

Now you should have all the variables defined (Dm, Dk, Dh, Dd, F1, F2, W) to determine that keel bulb weight through a bunch of fancy math and trig. I’m pretty sure this will work, not sure how accurate it would be. I could probably even noodle out the math, but that will take a little time.



#31 Salted

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Posted 17 December 2013 - 12:57 AM

I don't know why your bothering weighing the old keel anyway...

 

 why don't you work with a naval architect and design a keel (weight & shape) that will best improve

the performance of the boat given its size, shape and sail plan.

 

 

  Your welcome,

 

  Uncle Bob...

 

Exactly what I was thinking.  Why replace like for like when you have a prime opportunity to get a better performing keel?



#32 Alcatraz5768

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Posted 17 December 2013 - 08:32 AM

why wont the original idea work? if we know that the keel displaces 100 litres by there being about 103kgs of difference in weight, then multiply that by 11.73 to give an approx weight of 1170kgs. I dont want to take the keel off to weight it then put it back on then take it off again in six months to fit the new one. Neither do i want to take the boat out over winter then start the whole job. I want to have the keel designed and the steel fin built and the mold all ready for the bulb. I also can then have the internal strengthening all sorted out and ready to go.I have also dropped many keels off (about 20 as that was my job as an apprentice boat builder) and its not a weekend job. I could wrap the keel and lay up a rough mold out of csm in about 2 hrs, however i still dont think i have to using the displacement technique.

 

Attached File  Alcatraz 100.jpg   117.05K   50 downloads



#33 Alcatraz5768

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Posted 17 December 2013 - 08:35 AM

BTW i am happy with the current weight as the boat sits where i want it to, i just hate the current dog of a keel. I want to gain some righting moment with a lower cog and i may go a little deeper although it is already 2.8m.



#34 Gutterblack

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Posted 17 December 2013 - 11:46 AM

Summer sailing season is here so just sail the boat, as you well know when you begin to work on "bring on another thousand" things get out of hand and timeframes multiply as you discover surprises.

 

Not liking a keel is not the same it not working well, you could easily spend a lot of time and money and get nil improvement, given the boats radical wings and the effect on form stability you SHOULD seek the advice of bakewell-white or gray dixon. All this measuring stuff is dicking around to get inaccurate information that will only be marginally useful, but if you insist the most accurate way if you are lifting it, is the immersion into a box method and measure the displaced volume and hope the bulb is lead and not an alloy..

 

Cheers and good luck



#35 Raked aft \\

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Posted 17 December 2013 - 12:51 PM

BTW i am happy with the current weight as the boat sits where i want it to, i just hate the current dog of a keel. I want to gain some righting moment with a lower cog and i may go a little deeper although it is already 2.8m.

 

 

  So now you want more RM and a deeper keel?  Don't bother weighing your old dog, totally useless data.



#36 Alcatraz5768

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Posted 17 December 2013 - 05:40 PM

The bottom of the keel is lead and the stub is alluminium. The problem with just pulling the boat out and then doing the whole job is the time involved will blow out and I'm not prepared to just take it to a yard and ask for a new keel please as this has been estimated at approx $20 k.

The keel does need to be replaced as the stub has electrolisis corrosion all over it and a t keel has to be more efficient.

I am getting A well known designer to design it however we need an idea of the existing weight of the ballast and a whole lot of other info about the boat construction etc before he can start the drawings.

If I can get the fin and bulb mold made before the boat comes out of the water, it will save thousands of dollars in hard stand fees etc and we are on a budget with this old girl.

#37 Gutterblack

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Posted 17 December 2013 - 05:41 PM

Here's another thought, why not get the skilsaw out and trim those wings off and build yourself a canter, the boat would be a perfect candidate for it.



#38 Gutterblack

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Posted 17 December 2013 - 05:47 PM

I am getting A well known designer to design it however we need an idea of the existing weight of the ballast and a whole lot of other info about the boat construction etc before he can start the drawings.

 

you should be able to estimate it reasonably well by measuring it, its two cones yes? So get some calipers and measure the diameter, you wont be too far wrong. The beam, displacement and sail area you can also measure accurately, that and your keel info should give the designer enough to go on. An unknown is whats in the keel above the bulb.



#39 Raked aft \\

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Posted 17 December 2013 - 05:57 PM

The bottom of the keel is lead and the stub is alluminium. The problem with just pulling the boat out and then doing the whole job is the time involved will blow out and I'm not prepared to just take it to a yard and ask for a new keel please as this has been estimated at approx $20 k.

The keel does need to be replaced as the stub has electrolisis corrosion all over it and a t keel has to be more efficient.

I am getting A well known designer to design it however we need an idea of the existing weight of the ballast and a whole lot of other info about the boat construction etc before he can start the drawings.

If I can get the fin and bulb mold made before the boat comes out of the water, it will save thousands of dollars in hard stand fees etc and we are on a budget with this old girl.

 

  This is somewhat confusing,  on one hand you can't afford a yard to just wip off a $20k R&R on the keel. Yet on the other, your gonna have some well known NA draw up the latest and greatest go fast kit, factoring in the current weight of the bulb and the boat's construction?? 

  And somehow do it cheaper??



#40 Alcatraz5768

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Posted 18 December 2013 - 09:33 AM

Not confusing at all. I have the skills to do the job but need the plans and calculations done. I don't want to take the keel off and weigh it then put it back on for the next 6 months before it comes off for the new one. I want to have some prep done (ie fin made, bulb mold ready to go) so the boats not out of the water for ever.

#41 Gutterblack

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Posted 18 December 2013 - 06:40 PM

Its not that hard to make a keel. Any competent designer can estimate the weight from the dimensions and images you supply, moreover the sail area, mast height, c/e, beam etc will give a lot more of the required design info. plus your sailing experience of the boat in various wind/sea/sail combos.

 

You are making this too hard for yourself by overcomplicating it.

 

Plan for the boat out of the water for two to three weeks,

Assuming you are a competent builder, haul and remove keel on day one or two. Truck to foundry to get it weighed and stored until further notice.

Designer already has keel bolt pattern, desired draft, and shape of keel in cad format based on the other relevant data. That should give you the fin part, I presume you will use a steel fin keel with a bulb. so you already have the fin part rolled and fabricated so all you have to do is wait for the casting to arrive, bolt it all together and launch.You then supply the exact weight, he presses the button and you should have an exact keel weight for the design within a few days of hauling. You then make the pattern which you should be able to do over a weekend, get it cast that week if youre lucky, spend the next week fairing and fitting etc..

 

The above is assuming you're organised and there are no surprises but I cannot see why you could not do it if you planned it well.

 

But I am not sure what problem you're trying to solve here, is it a design issue? Electrolysis may be sorted with welding new material in, but a new keel may be a nice idea that ultimately gives very little improvement in performance without the corresponding rudder and rig modifications.You may be better off sailing the boat, and then getting a different one, possibly a class boat like young 11, 1020, stewart etc to spend money on, as this one looks like a bit of an oddball that easily eat lots of $$ and be worth nothing at the end.



#42 DRIFTW00D

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Posted 18 December 2013 - 07:02 PM

3d laser scanner rental "Auckland New Zealand"

 

 
07 544 3942 (8:30am - 5:00pm)
 
022 657 3634
 
 


192 Welcome Bay Road, Welcome Bay, Tauranga, New Zealand
Survey Solutions provide land surveys, sales & rental of survey equipment and 3D laser scanning services.
 
 


#43 Alcatraz5768

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Posted 19 December 2013 - 08:41 AM

Its not that hard to make a keel. Any competent designer can estimate the weight from the dimensions and images you supply, moreover the sail area, mast height, c/e, beam etc will give a lot more of the required design info. plus your sailing experience of the boat in various wind/sea/sail combos.
 
You are making this too hard for yourself by overcomplicating it.
 
Plan for the boat out of the water for two to three weeks,
Assuming you are a competent builder, haul and remove keel on day one or two. Truck to foundry to get it weighed and stored until further notice.
Designer already has keel bolt pattern, desired draft, and shape of keel in cad format based on the other relevant data. That should give you the fin part, I presume you will use a steel fin keel with a bulb. so you already have the fin part rolled and fabricated so all you have to do is wait for the casting to arrive, bolt it all together and launch.You then supply the exact weight, he presses the button and you should have an exact keel weight for the design within a few days of hauling. You then make the pattern which you should be able to do over a weekend, get it cast that week if youre lucky, spend the next week fairing and fitting etc..
 
The above is assuming you're organised and there are no surprises but I cannot see why you could not do it if you planned it well.
 
But I am not sure what problem you're trying to solve here, is it a design issue? Electrolysis may be sorted with welding new material in, but a new keel may be a nice idea that ultimately gives very little improvement in performance without the corresponding rudder and rig modifications.You may be better off sailing the boat, and then getting a different one, possibly a class boat like young 11, 1020, stewart etc to spend money on, as this one looks like a bit of an oddball that easily eat lots of $$ and be worth nothing at the end.


I hear you, however I will need to modify the bottom of the hull considerably and want a head start. I used to own a stewart34 and sunk heaps into it over about 6 years. The reason I bought this boat is the fact that its an oddball, with the OD Stewart, in order to win championships th boat has to be fully stripped over summer and therefore essentially can't be cruised. We have 4 kids who love going away on the boat so we bought this freakshow so we could race it with the squabs etc on board as its handicapped to that.

It's hard to design the fin without knowing how heavy the bulb is going to be.

#44 Caca Cabeza

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Posted 19 December 2013 - 08:22 PM

weigh the boat with the keel. Remove the keel. Weigh the hull again. The difference between the two is the weight of the keel left next to the scale.



#45 Gutterblack

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Posted 19 December 2013 - 09:54 PM

I hear you, however I will need to modify the bottom of the hull considerably and want a head start. I used to own a stewart34 and sunk heaps into it over about 6 years. The reason I bought this boat is the fact that its an oddball, with the OD Stewart, in order to win championships th boat has to be fully stripped over summer and therefore essentially can't be cruised. We have 4 kids who love going away on the boat so we bought this freakshow so we could race it with the squabs etc on board as its handicapped to that.

It's hard to design the fin without knowing how heavy the bulb is going to be.

 

Good luck with the mods, but every boat is a hole in the water and it would be so easy to pour cash into this one to get about 1/3rd of it back when you sell.

If I were you, I would sail over summer and pull the boat in winter and remove the keel. Fix all the crap you're definitely going to find and aim to be afloat in november.

A lift and a truck ride home both ways will be cheaper than westpark or pier 21 for 4 months.

 



#46 Alcatraz5768

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Posted 20 December 2013 - 06:05 AM

Thats the plan anyway. Wifey is stoked to have the boat on the front lawn. Even more stoked that my mates one tonner is going to be there as well. Crashed the boat on Wed night and tore a 1m hole anyway so i have to have that fixed by the 27th. 



#47 sherpa

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Posted 20 December 2013 - 11:21 AM

The rule of thumb that I've been told is 0.25 ballast to displacement ratio for older race boats and closer to 0.35 for older racer cruisers. Hope that helps a little with an estimate.

 

I worked on a project on an old J/N that did what you are proposing without removing the keel. An architect designed a shape and we hired a guy with a lead plane to rough it in. The shavings were weighed and cast into a bulb that was bolted onto the bottom of the keel. It required minimal grid work. This technique accomplished the designer's goal of adding a bulb, reshaping the keel and maintaining the original weight.

 

FWIW



#48 Zonker

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Posted 20 December 2013 - 01:53 PM

While ingenious, the ocean displacement method relies on travelift scales which are notoriously off.  I like the 3D laser scan idea.  They're getting cheaper by the day it seems.  You just need the volume, don't have to have a perfect surface or anything.

 

I think the easiest way is to have a big "tub" - one large enough to include the entire keel. Fill with water, measuring how much water it took to fill. Have crane lower boat into tub until water reached hull to keel joint. Remove. Measure remaining water. Difference, converted to lbs, is displacement of keel. Might need a big crane tho....

 

We did this at a party once.  The conversation turned to bra cup sizes and what they really represented (pre Google).  I, being a clever NA, figured the Archimedes principal would solve this easily.  Convince the girls to take turns going into the bathroom and immersing a tit into a brim full mixing bowl of water.  Spillage goes into the sink.  Measure the resulting volume with a measuring cup.  Very simple.  What could go wrong? And lot of fun when I got to help. All was going so well... until girl #3. She declined my assistance.  Her very loud shrieks from the bathroom had us all wondering what had happened....

 

 

Oh.  Forget to mention to use warm water to her.



#49 Gutterblack

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Posted 20 December 2013 - 09:41 PM

The problem is cold water alters the volume, nipples erect more volume vs warm water which would tend to make the whole tit a big bigger but smaller nipple. Nice problem to solve, it could take a while to work out by the time you had a statistically useful sample.



#50 Alcatraz5768

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Posted 21 December 2013 - 05:36 AM

i didnt know there was an option of measuring tits instead of keels. i choose tits. i will try to measure my wives tits, however they are quite big, if fact small tits want to orbit them.



#51 Ishmael

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Posted 21 December 2013 - 05:42 AM

i didnt know there was an option of measuring tits instead of keels. i choose tits. i will try to measure my wives tits, however they are quite big, if fact small tits want to orbit them.

 

How many wives do you have?



#52 Gouvernail

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Posted 21 December 2013 - 05:08 PM

You could weigh the boat then remove the keel then weigh the boat without the keel and assume the difference in weight has to do with the keel.

~~~~~~~~~~~~~~,~,,,~~~

You could remove the keel and take it to acrecycling facility where they would give you $$$ per pound.
Around here, the dump will take the hull for $30 or $65 if they must use their equipment to pull the boat off your trailer

#53 Gouvernail

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Posted 21 December 2013 - 05:13 PM


i didnt know there was an option of measuring tits instead of keels. i choose tits. i will try to measure my wives tits, however they are quite big, if fact small tits want to orbit them.

 
How many wives do you have?

It may be one of his life's goals to be reincarnated and have wives in each of his lives but in this reincarnation that goal may not also be his wife's.

#54 Alcatraz5768

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Posted 21 December 2013 - 06:46 PM

Sorry team, I ment wife's. I'm not allowed more than one.

#55 Alcatraz5768

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Posted 23 December 2013 - 08:09 AM

Alright hobos, you have seen a pic of my oddball yacht above somewhere. I need to increase RM as she is very tender and then a wing hits the water and we slow down a lot, so i was looking at it the other day an thought that a foil that came down vertically from the wing then angled toward the waterline would act like a dss foil however be a permanent fixture. hard to damage as the wing would protect it i could build it with an adjustable aoa to tune it. 

 

Flame away bitches



#56 dash34

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Posted 23 December 2013 - 08:17 AM

One possibility that would be relatively inexpensive and doable would be to put a 10-12" spacer between the existing keel and the stub.  Fabricate it out of iron or something suitably strong. It needs to accept the existing keel bolts on the bottom, and have its own bolts that extend upward through the existing stub.

 

From the looks of things you just need a bit more righting moment.  I'm guessing you sail shorthanded a lot and don't have crew weight to help out on a boat that is designed to have crew weight helping at all times.

 

Or, just a bigger bulb.  Make sure you hire a NA to do the design for you to be sure you won't break the boat.

 

Hope this helps

 

dash



#57 Presuming Ed

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Posted 23 December 2013 - 08:50 AM

If you do increase RM, it might be a good idea to check with a rigger that the rig is capable of dealing with the increase? An engineer for the internal structure too?

#58 Alcatraz5768

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Posted 23 December 2013 - 05:27 PM

The rig is only a couple of years old. As dash said, the boat is designed to be sailed with a pile of body's on the rail, which makes it amazingly fast, however when is gets down to 4-5 of us it sucks arse.

#59 Dead air

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Posted 24 December 2013 - 06:27 AM

I think M1 used to have something like what you are describing when it first launched, not sure how they went with it through.

Have you conspired retrofitting water ballast bladders to add some weight during the short handed days? Weight would be in the rail when you want it, but you don,t have to drag the weight down wind. Cheaper and easier than most other options as it kinda replicates the loads from people on the rail so very little extra engineering required, just some plumbing

#60 Alcatraz5768

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Posted 24 December 2013 - 11:09 AM

From what I remember M1 had rotating sockets in each side of the hull with extendable struts that had small surface skimming foils on them. They could retract for parking and were able to change the apart by rotating the arm. Water ballast would work but suck up the harbour in a westerly.

#61 Blitz

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Posted 23 January 2014 - 03:50 AM

Somebody designed the thing get the weight there. Anything within reason you do will have a lot of error. Take it off if you want a true weight.

#62 Blitz

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Posted 23 January 2014 - 04:08 AM

Somebody designed the thing get the weight there. Anything within reason you do will have a lot of error. Take it off if you want a true weight.

#63 Alcatraz5768

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Posted 23 January 2014 - 05:27 AM

That is the conclusion I'm coming too as well. I might try the travelift idea on its way out to see how close it is. The plan has changed and grown to include a new keel, chop off the wings (with a chainsaw to start with, just cause people love hearing a chainsaw start in a boatyard), new cockpit and a full paint. Should be easy. (Cue maniacal laughter)




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