Do anchors scale?

[Marin]

nomadwilly wrote:
Marin,

I don't think the Supreme or the Rocna penetrate very deep unless they are in very soft stuff. And I think that the roll bar reduces their ability to penetrate much after initial setting.

I guess that depends on which video you watch * In the underwater videos I've seen of Bugel and Rocna anchors setting both of them just disappear into the bottom or dig in until just the very top of the rollbar is barely visoble.* This was in sand and firm mud as I recall.

 

[Nomad Willy]

That's not deep Marin. One, 2 and 3' is deep. If you put a drag chute on the top of the tail of an airplane it would obviously pitch up and try to climb. The roll bars are considerably above the center of drag on the anchors use them and it's obvious they will pitch the anchor up as it moves fwd. Not good. The roll bar and the "up elevator" style trailing edge both probably contribute to the anchors poor short scope performance as mentioned in several to many anchor tests. Fortunately the pull on the shank mostly overcomes the up pitching tendency or the anchors would'nt work at all. Excluding whatever the shank may contribute to the up elevator force the XYZ has a "down Elevator" trailing edge that insures the fluke pitches down and continues to penetrate deeper. If the roll bar anchors could penetrate deeper their short scope performance would be improved.

 

[Marin]

In one of Rocna's videos their anchor disappears completely into the bottom (wet sand) and they have to dig down to find it. But I know you don't believe anything Rocna says about anything which is why I didn't mention this in my post

And I think you may be over-rating this up-elevator, down-elevator business. Aircraft controls have effect because of their speed and the very fast flow of air over them which generates tremendous pressure (which caused the Reno Air Race accident, for example). An anchor oozing through the bottom at a snail's pace isn't going to be affected anywhere near what aircraft controls will be. So it's my guess that the little angle to the base of the fluke of the Rocna and other anchors, while it looks like it might do something and is probably why the designer included it, in reality doesn't do much at all regardless if it's angled up or down. The angle of the fluke to the direction of pull, the shape of the fluke, and so on, have a huge effect on what the anchor does when you pull it along the bottom. That little three of four inch lip of slightly bent steel I bet doesn't generate any influential force at all.


-- Edited by Marin on Monday 24th of October 2011 05:44:11 PM

 

[Peter B]

I agree with that. The fluke/shank angle is everything in this case. That and the sharpness and shape of the actual fluke tip and blade.

 

[Nomad Willy]

Not sure what you're say'in here Peter. Sharpness yes. I wonder if one got out a grinder and made the claw flukes a lot sharper (would only take a few minutes) if the dang thing would work better? Don't see how it could harm it unless you made them too thin and they broke. Yea I know the rust. Some of these claws are so cheap maybe I'll do that. Marin I think the up elevator element is there and working fine but counter acted by other forces. Do'nt worry about the penetration thing Marin as you're Rocna and the other roll bar guys seem to work fine penetrating as far as they do. I think the Delta and Spade penetrate deeper * *...but don't seem to work any better anyway. I think the up elevator on the Rocna is put there to increase holding power just like it is on the Spade. I think the angle of the shank and fluke overpower the trailing edge elevators and provide more resistance and holding power. The "elevators" have a significant effect I'm sure as my XYZ would'nt even set without it's down elevators. Thought about you today Marin * .....was looking at a GB 36 single engined woodie.

 

[Marin]

nomadwilly wrote:
.....was looking at a GB 36 single engined woodie.

*My guess is sharpening the edges of the flukes on a Bruce would help it set faster and perhaps a bit deeper.* Not sure if it would do enough to overcome the basic deficiencies of the design that make themselves so apparent in the smaller sizes, though.

A GB36 woody single can be*a very*nice, economical boat to buy and operate.... IF.... the structure is sound and has been well maintained and protected from the elements.* There are a number of woodie owners on the Grand Banks owners forum and from what I can tell their boats are probably in better condition than the average twenty or thirty year old fiberglass boat.* But if they get away from you...... it can be a long uphill race to catch back up again as I'm sure you know.

 

[skipperdude]

Peter B wrote:
The fluke/shank angle is everything in this case. That and the sharpness and shape of the actual fluke tip and blade.

*It is all about the pressure on the point. either weighted or by design.

A spade, plow, Roll bar or the like is the best.

A larger anchor allows you to sleep better at night.

SD

 

[Nomad Willy]

Dude,

On the test that involved the Rocna, Supreme and Ray (Bruce/claw) the claw had by far the greatest weight on it's fluke when in position to set. Perhaps that's why they set so quick. See post w quote from the anchor test on Anchor design and Performance.