If it were me, today, I'd use a laser level. Set the hull upside down, check it is vertical and measure the WL heights above the ground at the bow and at the stern, adjust with shims until even. When painting you can then set up the laser level so it projects a line through those two exact points, the rest will be projected by the laser, make sure the laser is at the same height as the WL, ie: the light is not shining down from a huge tripod, particularly if set up close by!
Or you could measure and then use an aquarium air tube or regular hose (transparent) partially filled with water to set the line. Hold (tie it off or put a brick on it) one end above the bow and the other end up in the air. Fill until the water level is at the measured height. Use the loose end to mark the new water line wherever you please.
i bought a Reynolds 21
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Posted: Nov 25, 2011 - 05:38 AM
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Posted: Dec 12, 2011 - 06:47 AM
yeap trying to make room in garage this cold air is killing my energy level! i got to do this before the snow hits
:)
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1980 Reynolds 21 Catamaran #38
1988 Farrier 27 # 31
2002 Hobie Getaway
Pennsylvania, PA.
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Posted: Dec 19, 2011 - 01:06 PM
Edited by klozhald on Dec 19, 2011 - 12:07 PM.
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Posted: Dec 20, 2011 - 03:52 AM
Says it all really :) -
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Posted: Dec 20, 2011 - 05:34 AM
yes pretty much the same concept here, I am currently working on getting my hull in my garage! It is not to heavy but light enough and unbalanced for 2 people to walk it in of trailer so i have to figure out something else!
So i had to go get the trailer weighed before i can get it inspected to get it registered in PA. my truck weighs 6650, i took trailer with boat on it to get weighed they weighed truck and trailer,, that came to 7500 so 7500-6650 and that = 850 so boat from an ad i have said displacement is 690 for boat
so 850-690 is 160 so my trailer only weighs 160 lbs? WOW that just doesn't seem right, do you guys think that is correct?
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Posted: Dec 20, 2011 - 06:11 AM
No, use common sense. Displacement is not weight. If your anal about the trailer weight take the boat off and drive it to the scales. If you just want to get it registered, just give them a number. They will be happy with what ever weight you give them.
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Philip
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Posted: Dec 20, 2011 - 06:15 AM
SO then explain it then!
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1980 Reynolds 21 Catamaran #38
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2002 Hobie Getaway
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Posted: Dec 20, 2011 - 08:21 AM
Well displacment is the amount of water that your hulls move when it is in the water. Your boat does not sit on top of the water so the amount of water that is displaced or moved is displacement. So obviously weight of the hulls and displacement would not be related.
I know that is simple but that is how I explain it to my ninth graders.
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Posted: Dec 20, 2011 - 08:43 AM
So how would you find out how much BOAT weighs?
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1980 Reynolds 21 Catamaran #38
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2002 Hobie Getaway
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Posted: Dec 20, 2011 - 09:11 AM
Soul, that question has already been answered. See my reply above. Take the boat off the trailer and get the trailer weighed. Once you know the weight of the trailer you will know the weight of the boat. (Clarification: Boat weight includes sails, running rigging, standing rigging, tillers, cross beams, spins, boards, rudders, etc. --EVERYHING) Another route is to completely set up the boat, put it on 4 scales and sum the 4 weights (must be no wind). That will get you darn close. There are other ways to weigh it (ie. load cell) but this process is the simplest most direct cost effective route.
. . .anyway, who really cares what it weighs, you're gonna have iced down beer, fried chicken and chicks on it aren't you?
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Philip
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Posted: Dec 20, 2011 - 09:29 AM
Hahaha I hope so hell yes! Ok then that will not be done then with weighing her I am just trying to figure out how much ONE hull weighs... I have to get it in my garage and flip it over so i can do the bottom!
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1980 Reynolds 21 Catamaran #38
1988 Farrier 27 # 31
2002 Hobie Getaway
Pennsylvania, PA.
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Posted: Dec 20, 2011 - 08:11 PM
I really think your numbers are all wrong, but who cares. Sail it and have fun.
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Posted: Dec 20, 2011 - 10:39 PM
I've always felt that the advertised weight for the 21 was low, mine was near 1000 lbs all up. When I pulled a hull off the trailer we were 4 guys, and that was managable. Have your cradles built and in place. When the hull comes off the trailer you can set it on the keel, and gently lay it over on its side. With the nacelle secured in the closed position and some blankets on the ground, begin to roll it onto the nacelle, and lift the hull up in the inverted position, and walk it to the cradles. -
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Posted: Dec 21, 2011 - 03:10 AM
They certainly are related. The displaced water has exactly the same mass as the object that displaced it, Archimedes Principle.
You must remember that it is not just the hull, but the entire mass of what you threw into the water.
Example: 2 hulls have a total mass of exactly 200 kilograms (440lbs, I'm using metric because the math is so much simpler than that archaic system you continue to use, in fact so simple a caveman...) If you throw them in the lake, they will displace exactly 200 litres of water,(1 litre weighs 1 kg). You are correct in saying they don't sit on top of the water. Archimedes Principle says they sink, & displace water. They contnue to sink, & displace water,until the amount of water displaced exactly equals the mass of the boat.
In the example above, we have displaced 200 litres, which has a mass of 200kg. Now, a rather rotund friend, with a mass of 150kg comes down, & jumps onto the boat. What happens? The boat sinks further, & displaces more water. How much more? Another 150 litres, which again has a mass of 150kg.
So, when you launch your Cat, it is not just the hulls mass that counts. It is the entire mass of the boat,ie, hulls, beer, mast ,sails,people etc. The boat sinks until the mass of water displaced exactly equals the mass of the loaded boat.
This is not Grade Nine, this principle was used by Archimedes & demonstrated when i was in Grade 5 science.
You take a container & place a toy boat hull in it.Set this apparatus inside a larger container. Completely fill the container containg the toy boat, right to the brim. Gently drop an object into the toy boat. The boat will sink & diplace water, that will run over the edge into the second container. Take this container, with the displaced water, & pour the displaced water into a graduated cylinder. Lets say the cylinder shows 454 milli litres of water. Again the metric system makes it simple. An ml of water has a mass of 1 gram, so 454ml has a mass of 454 grams. We know that 454 grams = 1 lb, so the object you dropped into the toy boat weighs exactly 1 lb.
The only cause for confusion will be in how the manufacturer defined displacement. Did they mean the max displacement legally allowed, that is with a max load of people/gear?
Or did they mean the displacement of the boat rigged for sailing? If the boat rigged for sailing displaces 200 litres, then it weighs 200kg.
And you guys thought physics was boring, or useless?
Edited by Edchris177 on Dec 21, 2011 - 03:21 AM.
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Posted: Dec 21, 2011 - 03:18 AM
You don't even need 4 scales, two, or even one will be pretty close. When hiway stations weigh big trucks they rarely are able to place the entire truck on the scale. They drive up & weigh part of the truck, then pull forward & weigh the next axle & so on.
You can do the same. You need your boat on a level surface. Lift the stern & place scale under both stern points, sum the two readings. Do it again for the bow points, add that sum to the stern sum & you will be very close. You can even do it with one scale, & take a reading at each corner.
Try it with a 16' 4x4. Place a scale under one end, then the other end. The sum of the two readings will be the same as if you stood the beam on end on the scale. On a cheap scale they won't agree exactly, because of scale error & your inabilty to exactly read each measurement, but it will be close.
Edited by Edchris177 on Dec 21, 2011 - 03:23 AM.
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Posted: Dec 21, 2011 - 05:18 AM
the z-21 is basically an r21 afaik
so 300-400lbs per hull?, say 350...
specs
LOA: 21' 0"
LWL: 20' 2"
Beam: 11' 0"
Beam (On Trailer): 8' 6"
Deck (Trampoline) Area: 120 s.f.
Displacement: 925 lbs.
Draft (Boards Down): 3' 0"
Draft (Boards Up): 0' 8"
Mast Height: 29' 0"
Mainsail: 190 s.f.
Jib: 66 s.f.
Screacher: 178 s.f.
Berths: 4
Auxiliary: 5 h.p. Outboard
Estimated PHRF Rating: Low 80's -
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Posted: Dec 21, 2011 - 05:59 AM
WOW thats some nice math there, well i was just wanting a estimate to go on and if they weighed my intire load i subtract the number of my truck from my door! You know they have the weight of the vehicle there?
And yes they weighed my truck and trailer at the same time! it was a huge SCALE! it was like 2 min. form home. ALL is good well this boat must be less then the Z21 becasue i was left with 1500 bls with boat and trailer so you subtract 1500 from what ever number u want that is a Light boat ! for 21 ft. if u ask me!
Just to dam heavy for 1 or 2 people!
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1980 Reynolds 21 Catamaran #38
1988 Farrier 27 # 31
2002 Hobie Getaway
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Posted: Dec 21, 2011 - 10:21 AM
Why is it that whenever you post you want to help but sound so condescending. That archaic system by the way developed the most powerful country on Earth.
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Posted: Dec 21, 2011 - 12:13 PM
........up to their eyeballs in debt to the Chinese?????.........
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Posted: Dec 21, 2011 - 12:30 PM
Sorry Golf, no offence was intended.
I do stand by the old British system as being archaic. Had the British not won the war when America was still a colony,you too would be using metric (SI), as does nearly the entire world.
The US exports lots of stuff, all of which has to be converted for international trade. If people knew the true cost of using the Imperial system, they would bite the bullet & make the change. Short term pain for long term gain. England used to be the de facto world power, boasting an Empire on which the sun never set. They continue to cling to remnants of the old system, 'nuff said.
Think back to how much time was wasted in grade school memorizing things like 12"=1ft, 5280'=1 mile,(how many yards was that).
16.5' equals a rod, I think 3 rods,(maybe 4) equals a chain, & 1 chain pulled over 1/2 a mile,(can't remember offhand how many feet are in 1/2 mile) will give you an acre.
2 pints to a quart, I can't remember how many of those equals a peck, but I think 4 pecks = a bushel. Now a few teaspoons equal an ounce, but depending if you use the Imperial or US gallon, the number of ounces varies, & just how much mass is in a cup, pint,gallon or cubic yard of water?
You need to cut some threads for a Nacra mast ball. The DS is 9/16", so you need to drill a hole of 33/64ths,(WTF I don't have that bit in my toolbox) then cut national fine threads,which are how many to an inch?
When I go to do up those fittings, through experience i know that if 1/2" is to small it might be 9/16, but what if that is to big? What are the 32nds or 64ths wrenches in between...much easier to grab a 10 mm,too small, get the 11m or 12mm, there is never any mental gymnastics involved.
Just how tall is a horse that stands 17 hands? My hands, yours, Jethroes?
The system is so complex that most people constantly get it wrong. How many times do you hear folks referring to "weight" as lbs? As in my boat weights 375 lbs. when lbs is actually a unit of force. The measure of mass in that system is "stone".
The system was developed when all people had to measure with were their feet, hands, field rocks, & other implements of the bronze age. We don't build roads the way the Romans did. There is no reason not to progress, otherwise we would all be pulling our Hobie 14s to the lake with ox carts.
Many might argue that it doesn't matter, but it does, big time. The mixing/confusion of improper units is akin to mixing concrete. Mixing improper ingredients, or the wrong values of ingredients does not yield concrete, it yields disaster.
You already use the metric system for money, 10 pennies gives you another unit,(dime). Ten of those gives the next unit,($), & 10 A. Hamiltons gets you a Franklin.
The entire metric system is that easy, kids learn it in 10 minutes, & never forget as there are no multitudes of archane values to memorize. The proof is in the pudding, I showed a method to get a very accurate value for the mass of an object that requires no pencils, calculators, or math. The project could be easily & cheaply scaled to weigh large objects with a simple dunk tank.
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