4 EASY TESTS TO CHECK YOUR BOAT EFFICIENCY

User avatar
matthias72
Posts: 1752
Joined: 04/07/2008, 16:33
Location: ROMA

4 EASY TESTS TO CHECK YOUR BOAT EFFICIENCY

Postby matthias72 » 01/11/2010, 13:01

I'll show you Four easy checks to test your boat efficiency:

1. Keel rigidity:

Block with a clamp (protecting well the keel before) the keel on a table, and leaving 400mm of keel could exit.
Image
Put a standard 2800 grams weight to flex the keel and measure the flexion distance. The lower is the distance and the better is the keel. If you use a bulb of 2800 grams instead the
standard weight control that the central bulb axe is at 400mm from the table.
If your bulb is heavier or light weight respect 2800 grams, increase or decrease the 400mm distance following this formula: Distance=1120000/your bulb weight in grams.
For example your bulb is 2850g the distance is 1120000/2850=393mm.

Reference values:
-More than 50mm, Not so good
-Between 40mm and 50mm, Normal
-Between 30mm and 40mm, Very good
-Less than 30mm, Exceptional



2. Keel thickness:

Measure the keel thickness (with a normal keel width of 80mm>90mm).

Reference values:
-More than 7mm, Not so good
-Between 6mm and 7 mm, Good.
-Between 5mm and 6 mm, Perfect.
-Less than 5mm Not so good.




3. Boat vertical mass distribution:

Use a chair as shown on the picture:
Image
Control that the distance between the hull and the lower bulb side is 420mm and the total boat weight has to be ready to sail. Find the equilibrium vertical point. If the boat bow, or
stern, is heavy, the boat could rotate: that could be normal, let that the boat find its lateral equilibrium point. When the boat will be perfectly stationary, measure, as shown on
the image, the distance between the lower part of the bulb and the equilibrium point:
Image
The shorter is the distance and the better the boat is.

Reference values (with a standard keel+bulb 420mm distance):
-More than 250mm, Not so good
-Between 250mm and 240mm, Normal
-Between 240mm and 230mm, Good
-Between 230mm and 220mm, Very Good
-Less than 220mm, Exceptional



4. Boat rigidity:

Put your boat on a rack as shown on the picture:
Image
Control that the distance between the hull and the lower bulb side is 420mm, the total boat weight has to be ready to sail and that the two rack arms are perfectly flat.
The bulb has to be outside one arm of the rack.
The distance between the second rack arm and the hull has to be nearby 110mm,
as shown on this picture:
Image
If the boat rotates laterally block the hull putting a little weight on the rudder.
Masure the distance between the floor and the mainmast head as shown on this picture:
Image
Then measure the rack height and calculate the boat flexion:
(Rack height)-(mainmast head height).
The lower is the value and the rigid is the boat.

Reference values:
-More than 400mm, Not so good
-Between 400mm and 300mm, Normal
-Between 300mm and 200mm, Good
-Between 200mm and 100mm, Very Good
-Less than 100mm, Exceptional
Last edited by matthias72 on 01/11/2010, 19:03, edited 9 times in total.
--------------------------------------
THE LIFE IS SHORT: SAIL HARD!
--------------------------------------

User avatar
MartinL
Posts: 21
Joined: 06/01/2010, 21:25
Location: Masa e Sharif, Afghanistan
Contact:

Re: 4 EASY TESTS TO CHECK YOUR BOAT EFFICIENCY

Postby MartinL » 01/11/2010, 13:16

Hey Matth,

Nice tests. I will put my AC to the test. Hopefully she will do fine.... ;)

User avatar
matthias72
Posts: 1752
Joined: 04/07/2008, 16:33
Location: ROMA

Re: 4 EASY TESTS TO CHECK YOUR BOAT EFFICIENCY

Postby matthias72 » 01/11/2010, 23:00

Martin have you some data?
--------------------------------------
THE LIFE IS SHORT: SAIL HARD!
--------------------------------------

Gravitar
Posts: 5
Joined: 12/11/2009, 18:20

Re: 4 EASY TESTS TO CHECK YOUR BOAT EFFICIENCY

Postby Gravitar » 02/11/2010, 17:43

Mat


Are those numbers just to make me feel good about my boat? if so, it was not neccessary!

Lets see, from memory: Keel deflection, 27 mm with 3kg weight. Measured 3 weeks after epoxy set (160 gram keel).
Balance point, my memory is fuzzy here..... but I think I was at the 250 point, but my Mast is heavy! (home made groovy)

Rigididty? Who knows!

But the important measure shall not be forgotten - the size of the smile on my face when she glides away from the dock!

Mike

User avatar
MartinL
Posts: 21
Joined: 06/01/2010, 21:25
Location: Masa e Sharif, Afghanistan
Contact:

Re: 4 EASY TESTS TO CHECK YOUR BOAT EFFICIENCY

Postby MartinL » 02/11/2010, 22:15

Matth,

Sorry, not yet. I had to work late, just finished it.... :cry:
If I have some figures, I will surely post them. :roll:

By the way, what happened to your boat? She's desperately needing a polish :lol:
Martin

User avatar
matthias72
Posts: 1752
Joined: 04/07/2008, 16:33
Location: ROMA

Re: 4 EASY TESTS TO CHECK YOUR BOAT EFFICIENCY

Postby matthias72 » 02/11/2010, 22:23

Mike you done a great work to a 27mm flexion keel (of course it depends on the keel thikness too..how mutch?), compliments!!!

Martin yes, I have to polish the boat :D
--------------------------------------
THE LIFE IS SHORT: SAIL HARD!
--------------------------------------

Gravitar
Posts: 5
Joined: 12/11/2009, 18:20

Re: 4 EASY TESTS TO CHECK YOUR BOAT EFFICIENCY

Postby Gravitar » 02/11/2010, 22:43

Matt
Opps, keel thickness is 8.5 mm top, 7.5 bottom. Tappered keel as per the dual build thread. I can't remember, 100 mm top, maybe 80 bottom????
Perhaps that helps the stiffness! Bulb + keel = 2.992 kg (just measured). I originally measured the keel deflection using a scale hooked on the bulb attachment point, and pulled down to 3 kilos.

Mike

User avatar
matthias72
Posts: 1752
Joined: 04/07/2008, 16:33
Location: ROMA

Re: 4 EASY TESTS TO CHECK YOUR BOAT EFFICIENCY

Postby matthias72 » 02/11/2010, 22:55

Of course, it helps a lot, but on a boat all is a compromise: a thin keel helps to decrease resistence, but you sacrifice rigidity...
--------------------------------------
THE LIFE IS SHORT: SAIL HARD!
--------------------------------------

Astute Composites
Posts: 19
Joined: 26/01/2010, 22:32
Location: Valencia, Spain

Re: 4 EASY TESTS TO CHECK YOUR BOAT EFFICIENCY

Postby Astute Composites » 03/02/2011, 12:15

Hi,

SWE 96 is as follows:


Fin - 7mm x 83mm @ top 6mm x 70mm @ bottom

Balance test - 213mm

Boat flex test - 50mm

I'm happy with that!!
Cheers, Jim

User avatar
matthias72
Posts: 1752
Joined: 04/07/2008, 16:33
Location: ROMA

Re: 4 EASY TESTS TO CHECK YOUR BOAT EFFICIENCY

Postby matthias72 » 03/02/2011, 12:22

:shock:
Great job Jim! You have a top boat! And the result for the test 1?
--------------------------------------
THE LIFE IS SHORT: SAIL HARD!
--------------------------------------


Return to “Tecnical Topics”

Who is online

Users browsing this forum: No registered users and 1 guest