Anchor Size?

[O.T.Water]

Hi All and Merry Xmas, So I buy this boat 16' Sport Craft CC with an 85 Force.
It came with an anchor big enough for the Queen Mary. Small boats have small storage compartments and I want to buy the right size anchor for the boat. Is there a formula? Thanks, O.T.

 

[boat1010]

Re: Anchor Size?

There are all different types and sizes of anchors. It all depends on what type of bottom you have on the lake. Then the size of the boat come into the picture. So I'm am sure there is some sort of formula but what you are using it for will come into the picture. Is there a lot of wind? Sandy bottom? So many variables with the anchor. Don't know if this helped any but hoping it would. Merry Christmas..

 

[tashasdaddy]

Re: Anchor Size?

a flute style anchor, and 3 feet of chain will hold your boat fine in 99 % of conditions.

 

[Chris1956]

Re: Anchor Size?

I am sure there is a formual, however is it pretty loose. I would think that a boat of that type would need a fluke type anchor, one step up from the smallest. If the anchor is made of steel, a 4 or 6 pounder will work. This presumes you are anchoring in sand, mud or some other non-rock or hard bottom.

 

[O.T.Water]

Re: Anchor Size?

OK, I have a Fluke style but it's enormous almost comical. I'll go get the same style but alot smaller. Appreciate the comments. O.T.

 

[macsfriended]

Re: Anchor Size?

And Now - Back to the Bible.

Chapman's - 66'th edition - Chapter 9 - Table 9-1 - Suggested Sizes for Working Anchors.

It's called the Bible for good reason and it has been on sale at West Marine for $30.00 and about $6 more at Amazon with free shipping.

Everybody responsible for boating safety should have access to the Bible.

 

[Texasmark]

Re: Anchor Size?

The idea is to hold onto the bottom material, whatever that is and is it a temporary mooring in calm or rough water, or permanent.

Assuming you are the average boater out for a Sunday afternoon's cruise, I totally agree with tas. It's amazing what that 3' of chain can do for you with adequate slope on the line; hence plenty of anchor rope. I forget the number (someone on here will know) for amount of line required as a function of depth...like 3 to 1 kind of thing....length of line 3 x the depth where anchored. Not only that, the fluke and appropriately sized chain is not very heavy considering the holding power you get. Also, # for # Flukes are probably the most efficient style of anchor. Last, the chain acts as a shock absorber absorbing the shock (in having to lift it off the bottom) of the boat jerking on the line and keeping it away from the anchor. Rig one up in clear water and you will see what I mean.

Mark

 

[O.T.Water]

Re: Anchor Size?

Points well taken. I do have a 3-4 ft length of chain on the existing anchor so I'll use that with the new smaller anchor I buy. Thanks, O.T.

 

[rbh]

Re: Anchor Size?

I believe we made our anchor choice based on the length/weight of our boat, we bought a danforth anchor, and they're web site had a guide.

 

[Snobike Mike]

Re: Anchor Size?

I forget the number (someone on here will know) for amount of line required as a function of depth...like 3 to 1 kind of thing....length of line 3 x the depth where anchored.

The scope should be somewhere around 7:1 depending on the conditions. Less scope may work but if you get rougher/tougher conditions you're much less likely to stay on the hook.

 

[Capt'n Chris]

Re: Anchor Size?

Hi All and Merry Xmas, So I buy this boat 16' Sport Craft CC with an 85 Force.
It came with an anchor big enough for the Queen Mary. Small boats have small storage compartments and I want to buy the right size anchor for the boat. Is there a formula? Thanks, O.T.

I have used Danforth anchors all of my life on all types of boats, bottoms and conditions and so did my dad. Just as you would not skimp on the quality of a life jacket, an anchor can also help save a life.

http://www.danforthanchors.com/hitensile.html

 

[Boatist]

Re: Anchor Size?

I been boating since the 1960 and have used many anchors but by far the best is a 4 pound FX-7 Fortress. It rated for 16 to 27 foot boat. I always carry 2 anchors and still do but my current backup anchor a 8 pound Danforth has not been out of the floor storage for over 10 years.

The Fortress 4 pound aluminum anchor is half the weight but the thin sharp flutes dig in as soon as it hits bottom. The old 8 pound Danforth on lakes with hard bottoms would sometimes drag a long way before digging in. When it drags of course it can drag under a log or rock pile making it very hard to get back up.

Wife can pull the 4 pound Fortress with no problem. It is not a cheap anchor but for us well worth the extra cost.

One lake we always had trouble getting the anchor to hold at had a very hard bottom and our best anchor would drag and many times we would have to go back out from shore and again try to set a bow anchor to hold us off the shore before we backed into the beach. The Fortress has always dug in as soon as it hits bottom without dragging.

Since it is very light and we only have 3 foot of chain it does have one thing that is a little different. When you come to your spot and are ready to set the anchor it is not a good idea to just put engine in reverse and lower the anchor. Since the anchor is light it may troll out in front of the boat like a fishing lure instead of sinking to the bottom. Instead you come to your spot into the current or wind and put the engine in reverse as normal but as soon as you get a little stern way take the engine out of gear and lower the anchor until it hits bottom then put back in gear and pay out what ever scope you want. When you stop the line and tie it off it will set instantly.

At the lake with the hard bottom where we go offten and know we need between 90 and 100 feet of line out to make sure we have a good scope and keep the bow from swinging from side to side. We always had trouble kowning when we were 100 feet from the beach so some times we would get the anchore too far out and sometimes too close in.

With the Fortress FX-7 we pull out 100 feet of line and tie it to the bow cleat. We coil the line on the deck and out about 250 feet out we start backing in to the beach. We lower the line in the deeper water and the anchor stays up off the bottom as we back into the beach. When we get within about 5 feet of the beach and I kill the kicker motor and raise it out of the water. When the boat gets to shore I step off with a stern line in hand. The Fortress settles on the bottom and the wife pulls in about 10 feet of line and ties it off. I wrap the stern line around something and pull the boat back to me and step back on. On cold days we do this without getting wet at all. Bottom line is we get the exact amount of line we want out every time and it is fast and easy to get boat set up right where we want it.

At the Fortress Anchor site click on the test from the Navy or any other. You will see a much lighter anchor has more than double the holding power of the Danforth that is much heavier.

Also read some testamonials if you want.

One other thing I like about the Fortress is the finish is slick and mud and other bottom stuff does not stick to the anchor so much eaiser to get back in the boat with out a lot of mud or other stuff stuck on it.

http://www.fortressanchors.com/

http://www.iboats.com/Fluke_Anchors/dm/*******.048005754--**********.161025793--view_id.238311

 

[timmyjoebob]

Re: Anchor Size?

+1 to Snobike Mike. The scope (the length of your anchor line) should be at a ratio of 7:1, meaning you need a length of at least 7 times the depth from your deck to the bottom (taking into account high tide). It's 10:1 in rough seas and the VERY minimum should be 5:1.

When calculating the total depth, it would include your freeboard (the distance from the waterline to your gunwale). The last three feet of your anchor line (your "rode") should be chain, especially if you might be anchoring on a rocky bottom and tear up the line. It's not the weight of the anchor that holds you, but how the anchor digs into the bottom. Normally, fluke-style will dig into any bottom if the rode is long enough and there is sufficient angle for it to dig in.

 

[HappierWet]

Re: Anchor Size?

Although it it often overlooked, The other job of the chain ( and the reason for a longer length ) is to help keep the shank of the anchor parallel to the sea bottom, thusly allowing the flukes, mushroom, or plow to dig as effectively as possible into the sea bottom. Yes, it also acts as a shock absorber for wave action, before someone flames me

 

[themaniam1]

Re: Anchor Size?

Anchor size? It is not the weight the generates holding power as much as the ability to dig in. So for a 16' the second size from the smallest fluke style should work in mud, sand or gravel bottoms.

Anchoring 101
HappierWet has it correct. The purpose of the chain, which is to help keep the anchor shank as close to parallel to the bottom for maximum holding power and keep the anchor rode (anchor line) from get abrasions. Chain does not stretch so there is no shock absorbing. the sag in the chain if it is long enough will provide some shock absorbing as it straightens out. In studies and in Chapman's, it is suggested that chain length should be 1/3 to 1/2 the length of the boat. I have found the 1/3 works great. The rode and scope (the angle of the rode to the boat) is what act as the shock absorber, which is the sag and stretch of the anchor line. That is why three strand nylon is the choice of line. I has great stretching capabilities as well as strength.

Scope: The angle of the line (rode) from the anchor to the boat.
A scope of 3:1 (a lunch pick) is good for up to 15mph breeze. 5:1 is good for up to 30mph winds and 7:1 is for overnight and up to 60mph, and you are nuts to be out on the water in those winds! 10:1 the maximum practical holding power but not practical because of the length of anchor line needed. That is why 7:1 is advocated.

Free board = distance from the water to the top you your gunwale or side of your boat.

How to how much line to let out for a particular scope = (Depth x desired scope) + (free board x scope). If you are anchoring in 10ft of water and want a 5:1 scope and your bow is 3ft above the water. (10 x 5) + (3 x 5) = 65 or 50 + 15 = 65 ft of anchor line, this includes the length of the chain.

Below is a chart for the above example. The 3ft free board is included.

Depth
Scope........10ft 20ft 30ft
3:1............39....78.....117
5:1............65....130....195
7:1............91....182....273
10:1..........130...260....390

I have marked my anchor line every 13 feet, free board + 10 ft. This makes it easy to set anchor. If I want a 3:1 in 10 ft of water I let out three marks with the third mark resting at bow height. If I want a 5:1 I let out 5 marks and 7:1 I let out 7 marks. I double the marks for 20 ft of water and triple in 30ft and so forth. That way anyone can set anchor. I just say let out # of marks and tie it off. Then all I have to do is set the anchor. Easy peasy.

 

[redone4x4]

Re: Anchor Size?

I prefer navy style anchors.....alot of grab in a small package, but weighs about 25 lbs or so. super easy to store just about anywhere on the boat. I also have 6' of chain on the rhode as well.

 

[a70eliminator]

Re: Anchor Size?

I also prefer the navy style anchors smoothness, there aren't any sharp spear like projections than can instantly puncture upholstery not to mention an arm or leg. That is main thing that keeps me away from fluke anchors plus my anchor locker fits my navy anchor just right.
As far as holding ability, I boat mostly on mud and rocky bottom lakes and I've never had a problem staying put or getting hung up.