Anchor Geekdom

Panope

Panope

Super Anarchist
1,425
569
Port Townsend, WA
Alex W said:
Glad to hear that you are feeling better!

This test has forward and reverse bollard pull tests of a lot of props, including a standard 3 blade prop that should be similar to yours:

http://flexofold.com/upload_dir/docs/Test_YachtingMonthly_low.pdf

They only show about a 40% decrease in reverse compared to forward (265kg vs 163kg), where you are seeing a 67% decrease. I wonder what accounts for such variability? Their boat is obviously very different (it is a fin+spade modern cruiser).

They are using a smaller Yanmar engine, but with the same gearbox as yours.
Click to expand...
Alex, hard to say what would be the cause of the difference that you noted. Could be the shape of the hull (Panope is full keel) or proximity/shape of the rudder.

Also, I noticed that my gearbox has the choice of three different forward gear ratios and only the one reverse ratio.

Steve

 
D

DDW

Super Anarchist
6,241
976
Good work. I should have thought about the tach - I have a contact/non-contact digital tach I could have thrown in the box. I am impressed by the peak forward thrust, didn't think it would be quite that high.

 
Panope

Panope

Super Anarchist
1,425
569
Port Townsend, WA
DDW, it was an impressive pull. It makes me think that I could actually set Kim's king sized Fortress FX-85.

Kim, are you headed my way anytime soon?

Steve

 
IStream

IStream

Super Anarchist
10,715
2,922
Hi Steve,

I agree that stretch shouldn't affect it but real lines are pretty far from perfect elastic elements. Probably not a huge effect but given how much of a roostertail you threw I wouldn't be surprised if a fair amount of thrust went from DC to AC and turned into heat in the line. Just a suggestion that if you do a repeat that you try chain or a spectra line from the boat to the load cell.

 
kimbottles

kimbottles

Super Anarchist
8,053
782
PNW
Panope said:
DDW, it was an impressive pull. It makes me think that I could actually set Kim's king sized Fortress FX-85.

Kim, are you headed my way anytime soon?

Steve
Click to expand...
What?? You want to get my brand new pristine anchor DIRTY???

(Yeah, might be up there sometime soon. Will call ahead.)

 
Salazar

Salazar

Super Anarchist
1,162
107
Cape Breton Island, Nova Scotia, Canada
Alex W said:
This test has forward and reverse bollard pull tests of a lot of props, including a standard 3 blade prop that should be similar to yours:

http://flexofold.com/upload_dir/docs/Test_YachtingMonthly_low.pdf

They only show about a 40% decrease in reverse compared to forward (265kg vs 163kg), where you are seeing a 67% decrease. I wonder what accounts for such variability? Their boat is obviously very different (it is a fin+spade modern cruiser).

They are using a smaller Yanmar engine, but with the same gearbox as yours.
Click to expand...
If you allow for the different gear rations in Steve's Panope, 3500 engine rpm in reverse is equal to 2980 (lets call it 3000) engine rpm in forward for the same prop rpm. Looking at it that way, the difference between forward and reverse is about 50%. Panope would have come up with more reverse thrust if the prop could have been brought up to the same rpm as in forward but was limited by engine rpm limits.

 
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Y

Yesac13

New member
45
0
Thought some of you weird anchor nerds might enjoy this article.

It is about the Herreshoff anchor. Otherwise known as fisherman anchor. Many people don't know that the fisherman anchors seen today generally was developed by Captain Nat himself. The anchor form is several hundred years old but around 1870-1910 Captain Nat tested and refined the fisherman anchor.

Extreme nerdery warning: Even includes some algebra!

http://www.woodenboat.com/herreshoff-three-piece-stock-anchor-0

 
Ishmael

Ishmael

≈≈≈≈≈≈≈≈≈≈≈≈
48,398
9,533
Fuctifino
Yesac13 said:
Thought some of you weird anchor nerds might enjoy this article.

It is about the Herreshoff anchor. Otherwise known as fisherman anchor. Many people don't know that the fisherman anchors seen today generally was developed by Captain Nat himself. The anchor form is several hundred years old but around 1870-1910 Captain Nat tested and refined the fisherman anchor.

Extreme nerdery warning: Even includes some algebra!

http://www.woodenboat.com/herreshoff-three-piece-stock-anchor-0
Click to expand...
No tits?

 
Panope

Panope

Super Anarchist
1,425
569
Port Townsend, WA
Good Stuff Yesac,

“The first anchors were set on shore at a time of low tide and the rode was attached to a team of oxen. Pa (NGH) watched the tipping of the anchor, its initial digging in, and its setting under strain. He then redesigned the proportions with particular emphasis on the flukes. Then there were further tests to revise or confirm the design..........."

Sounds like the Herreshoffs could have really used a GoPro camera.

Steve

 
Panope

Panope

Super Anarchist
1,425
569
Port Townsend, WA
Today I tested the Excel at the Sand/Gravel site (Point Hudson). A fair amount of current was running and somehow this has once again resulted in the camera becoming fouled for portions of the videos. Fortunately, the new camera mounts is basically indestructible so no damage to it or the camera.

Steve

Video #33



 
Panope

Panope

Super Anarchist
1,425
569
Port Townsend, WA
45 pound Mantus Anchor.

The anchor has the largest physical dimensions of this group of 45 pound anchors. When stowed, the toe does extend aft of Panope's stem. However, the small hull guard (that was custom made for the Manson Supreme) works perfectly to protect the hull paint.

Mantus%2001_zps3s9tpm5q.jpg


First test is at the "normal" test area of "sandy mud". 3.5 to 1 scope.

Steve

Video #35



 
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Panope

Panope

Super Anarchist
1,425
569
Port Townsend, WA
Fraggler, I have never used a kellet. I suppose they may offer some (small) increase in holding power. If I was seeking extra holding power, rather than adding a kellet, I would just get a bigger anchor.

Steve

 
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