What is your Bigness Factor?

[Delfin]

Originally Posted by minaret

Maybe something more catapult-y? Mast becomes a trebuchet?



Garbage disposal, LOL!

Way ahead of you. That's why I put my mast on a tabernacle.

[Delfin]

Originally Posted by minaret

Reloads might be a problem, should probably be a repeater-just in case. Could be done on a big power boat like yours...

Sniff. That's what crew is for....

[Nicholson58]

Originally Posted by Kettlewell

Anchor size poll above. Take your main anchor weight in pounds (1 kg=2.2 lbs) and divide by your LOA in feet (1 meter=3.28 feet). The result is your Bigness Factor.

For example, my Finnsailor 38 carries a 45 lb. main anchor, so 45/38=1.18, or on the high side of what I have labeled "Normal."

Let the quibbling begin about the factor ranges!

The LOA is almost irrelevant. What counts is mass or displ. We are an older "classic" with 55,000 disp and 36 tons on the hook. When that mass is tossed by waves, it doesn't matter if we are 40 or 80 feet long. The new Rocna 55 kg replacing the 74# CQR still looks like tin foil pasted to the bow.

[bobconnie]

Hay ! Still have my Beer Can Cannon !! It will shoot a beer can filled with concrete over 200 yrds!! Bilt from Naval Bronze! a bit heavy but it sure is fun !! and a hell of a flag cannon

[minaret]

Originally Posted by Delfin

Sniff. That's what crew is for....

Come on, do it for the technical challenge!

[minaret]

Originally Posted by bobconnie

Hay ! Still have my Beer Can Cannon !! It will shoot a beer can filled with concrete over 200 yrds!! Bilt from Naval Bronze! a bit heavy but it sure is fun !! and a hell of a flag cannon

Yea, but can it shoot an anchor?

[minaret]

Originally Posted by Delfin

Way ahead of you. That's why I put my mast on a tabernacle.

Tabernacled mast trebuchet could work great....

Punkin Chunkin- Catapults - YouTube

Punkin Chunkin World Championship 2009 - YouTube

[Kettlewell]

The LOA is almost irrelevant. What counts is mass or displ. We are an older "classic" with 55,000 disp and 36 tons on the hook. When that mass is tossed by waves, it doesn't matter if we are 40 or 80 feet long.

Only when you get some pretty big wave action--windage is the thing that creates most of the force on the boat and on the anchor until there is a big surge. Most people seek shelter in a big blow, so there usually isn't significant wave action. Sure, it would be different in six-foot seas during a hurricane, but that is not a normal situation.

Bottom line is that in most anchoring situations it is windage that matters the most. Note that almost all anchor selection tables from the manufacturers use LOA as the determining factor. Sometimes they add some vague language about going up a size if the boat is unusually heavy. Take a look at this anchor selection guide.

[JonJo]

Originally Posted by Kettlewell;

Sometimes they add some vague language about going up a size if the boat is unusually heavy. [URL="http://www.pyacht.com/lewmar-anchors.htm"

Take a look at this anchor selection guide.[/URL]

Obviously not frequent observers of CF.

Jonathan

[Delfin]

Originally Posted by minaret

Tabernacled mast trebuchet could work great....

This is why God loves us so much. You have to love a critter that goes to all that trouble just to toss a pumpkin.

[minaret]

Originally Posted by Delfin

This is why God loves us so much. You have to love a critter that goes to all that trouble just to toss a pumpkin.

Hilarious ain't it? Come on, lets start a trend! "Anchor Chunkin" 2013 could be in Puget Sound!

[Delfin]

Originally Posted by Kettlewell

Only when you get some pretty big wave action--windage is the thing that creates most of the force on the boat and on the anchor until there is a big surge. Most people seek shelter in a big blow, so there usually isn't significant wave action. Sure, it would be different in six-foot seas during a hurricane, but that is not a normal situation.

Bottom line is that in most anchoring situations it is windage that matters the most. Note that almost all anchor selection tables from the manufacturers use LOA as the determining factor. Sometimes they add some vague language about going up a size if the boat is unusually heavy. Take a look at this anchor selection guide.

I may be wrong, but it seems to me that displacement is completely irrelevant. The force applied to a 65 ton boat with zero wind is the same as a 10 tonner with equivalent windage. Same with 5 knots or 50 knots because the force acts against the surface presented to the wind, not the weight of the water displaced. Heavy displacement might actually be beneficial in the sense that when another force - waves - act against the hull, the vessel with greater displacement will be more resistant to movement resulting from that force than a lighter vessel.

[Kettlewell]

This discussion of how to compensate for displacement of the vessel brings up another factor, which is how much stretch there is in your anchor rode. The more stretch the less the force on the anchor and the boat. Nobody would jump off a bridge with anchor chain tied to their legs, but they do it happily tied to big bungie cords that absorb lots of the force. In really extreme conditions you need lots of bounce in your rode to mitigate the forces--either really long snubbers or long lengths of nylon on the end of your chain. I have never done so, but I've wondered about shackling a nylon rode directly to the anchor in addition to the chain for hurricane conditions so that the chain acts more as a backup (and extra drag on the bottom), which you would of course have to attach to the boat with long snubbers anyway.

[Delfin]

Originally Posted by Kettlewell

This discussion of how to compensate for displacement of the vessel brings up another factor, which is how much stretch there is in your anchor rode. The more stretch the less the force on the anchor and the boat. Nobody would jump off a bridge with anchor chain tied to their legs, but they do it happily tied to big bungie cords that absorb lots of the force. In really extreme conditions you need lots of bounce in your rode to mitigate the forces--either really long snubbers or long lengths of nylon on the end of your chain. I have never done so, but I've wondered about shackling a nylon rode directly to the anchor in addition to the chain for hurricane conditions so that the chain acts more as a backup, which you would of course have to attach to the boat with long snubbers anyway.

That's why we use a fairly long snubber for everyday anchoring, but would attach a 100' snub line 150' out if we were threatened by really high winds. We use 5/8" 3 strand, and it is tight as a harp string in anything over 20 knots.

[Kettlewell]

I may be wrong, but it seems to me that displacement is completely irrelevant. The force applied to a 65 ton boat with zero wind is the same as a 10 tonner with equivalent windage.

I basically agree, but I don't think it is "completely irrelevant," though it is interesting how little it is discussed in most anchoring treatises. Where displacement comes into play is when the wave action gets big enough to start surging the boat back against the anchor rode. This is one reason really long scope is needed in storms--allows the bow of the boat to rise freely because of the lack of downward pull from the anchor rode.