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Old 21-03-2010, 01:52   #31
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I found a very interesting web site from France. I think I found it here on this forum.

Go to [alain.fraysse.free.fr] and have some fun. He offers a number of excel spread sheets that calculate all kinds of scenarios re: anchor rodes.

The first part has a wind force calculator. Based on ABYC data. He concludes that data has about a 3x safety factor based on actual measurements on boats and analysis of different 40' boat profiles, head on and at 30 degrees off the wind. So I used a boat length of 30' (instead of 26')and reduced that by 50% for my calculations. I noted this based one of the tables he has for a boat head on to the wind vs. 30 degrees off the wind (yaw), the force doubles. So for my max force I doubled what the wind force calculator gave me. (Which was reduced by 50%)

This guy really gets into the math. A very good read! His conclusions recommend chain and line combo. Don't worry, he summarizes. And the spread sheets are easy to use.

So I took his spread sheets and ran 2 scenarios for a 26' Falmouth. one all 5/16 chain, and one 100' of 1/4HT and 1/2” line.

I came away from this endeavor with these conclusions that were new to me or reinforced some of my previous conclusions.

All chain puts much higher dynamic force on the whole system. If you were to use all chain 5/16, it may as well be HT because of the increased dynamic loads it incurs and the next size up for an anchor. Now we are really getting into some weight.

It’s good to have at least 25-30’ or more of nylon line payed out with the chain. This really takes some dynamic load out of the system.

When the wind gets up to 30kts, it’s time for a second anchor. With all chain you will be easily surpassing the WLL of 5/16 BBB when yawing.

The first section of the chain as it comes off the bow adds very little to the centenary effect of the chain weight. So it may as well be line.


So enough for now. I have posted all this and more over on Shanti’s blog at [garyfelton.com]

Have fun!
Gary
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Old 22-03-2010, 10:31   #32
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great link - very technical & impressive stuff. also great resources on your blog - thanks for both excellent links! you've obviously been down this road of difficult decision making before and have the first hand experiences (great story!) to support your current setup...so on 27' boat you would probably recommend 100′ of 1/4″ HT and ˝” multi-plait line?

No windlass either for me so that makes it a bit less heavy up front, maybe due to that I could go 5/16" ?
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Old 22-03-2010, 11:01   #33
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100' of 1/4" HT = 75#'s
100 of 5/16" HT = 110#'s

so the difference is 35#'s ... however I wouldn't have the shackle & over-sized end-link hassle with the 5/16" and I do appreciate the comments on this thread about the added security of 5/16" if unfortunately wrapped around a coral-head, and the comments that it would be easier to weigh by hand than the 1/4" ...

It's definitely going on a Manson Supreme 25# (Not the 35# which is not practical on my bow roller) so as someone mentioned, going with the 25# Manson makes going with the 5/16" HT the better choice. Despite not being practical on my bow, the 35# Anchor would only add 10#'s as opposed to the 35# I gain with the bigger sized chain.
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Old 24-03-2010, 12:31   #34
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Matrix,i think the fluke area is more of a factor than the weight with the newer anchors.I will be very interested in seeing what you eventually select as your boat is about the size of mine. What is your boat anyway.
Steve.
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Old 25-03-2010, 16:11   #35
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hey thanks for all the great feedback and advice on this thread. have not pulled the trigger yet but it's about to happen, i've just had some family obligations this week that have slowed me down. I'm leaning towards 100' of 5/16" at this point, but i'm all over the place

My boat is a Matrix 27, built by a local builder in Ventura, CA, who had previously worked on the Flicka and Allega 24 with Fred Bingham so it has a little bit of the spirit of those boats in terms of construction-quality and strength, but is a little more of a modern performance cruiser...I am certainly not claiming it's the best/ideal boat but I feel comfortable/safe in it and am happy with its performance and hope to take it voyaging by late fall of next year, probably Mexico to start!
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Old 25-03-2010, 17:14   #36
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G'Day Matrix,

Wow, that boat is a long way from a Flicka... and in the right direction, too!

Nice looking boat, and 100' of 5/16" will help keep it that way!

Cheers,

Jim and Ann s/v Insatiable II lying Church Point, NSW, Oz
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Old 26-03-2010, 06:36   #37
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Hi Matrix,Thats a very nice boat,ill have to look up the specs.
Steve.
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Old 26-03-2010, 10:40   #38
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matrix specs

They only made two of them, mine is #1 of 2, , and it's funny because around town in Ventura, everyone knows the boat... We just had a rigger come over to evaluate the condition of the standing rigging and incidentally he owned the yard where the boat was built, and said that he remembers the laminate impact/strength testing they had performed having impressive results and that everything was built "stronger than it needs to be." For now we have a lot of sailing and local cruising to do, but the channel islands are a great training grounds.

Designer's Description:
"The Matrix 27 embodies safety, performance, and attention to structural detail. The single skin hull is built of Biaxial TM E-glass reinforcement, osmotic blister resistant Ashland Acrylic Modified Epoxy resin and PVC core deck, hand laid, in excess of American Bureau of Shipping Standards. This laminate has over 2.5 times the flexural strength of the conventional laminates. A fabricated “double bottom” in likely collision points adds still another safety feature. The bottom profile reveals a fine entry, powerful sections aft, a flat run, and an elongated fin keel with a skeg hung, steel-reinforced, rudder. All of these factors combine to make an uncommonly stiff and strong structure capable of extended offshore passage making. "

LOA: 27' 8"
LWL: 23' 2"
Beam: 8' 5"
Displacement: 6600 Lbs (after wing-keel & rudder modification)
Ballast: 2900 Lbs (after wing-keel & rudder modification)
Draft: 4' 5"
Aux. power: Yanmar 1GM10

I will hopefully be purchasing the anchor and chain this weekend...but first I need to install the Lavac Head that has been staring at me all week!
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Old 27-03-2010, 19:48   #39
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Hey!

This Matrix boat looks up to something!

I dig it. I do not think is way away from Flicka. Just a continuation towards using the new knowledge towards a better boat! Way cool.

1) why is the waterlength 'only' 23'?
2) she seems to be sitting low in the water aft in the photo left - why?
3) would a smaller fore / bigger main be the next step you think?

Regards. I like your boat!
barnie
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Old 29-03-2010, 11:33   #40
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Originally Posted by barnakiel View Post
Hey!

This Matrix boat looks up to something!

I dig it. I do not think is way away from Flicka. Just a continuation towards using the new knowledge towards a better boat! Way cool.

1) why is the waterlength 'only' 23'?
2) she seems to be sitting low in the water aft in the photo left - why?
3) would a smaller fore / bigger main be the next step you think?

Regards. I like your boat!
barnie
Thanks! I am not sure why the LWL is only 23'. It seems longer, it could be a typo or oversight on the survey, because it appears to the naked eye to have a more balanced LOA/LWL ratio. I'll have to do some more research. I hope to meet with the designer in the coming weeks and get some more information about her nuances.

She is sitting a little low in the water aft and it is the fault of my own weight/gear distribution within the boat. The aft cockpit locker on that side is extremely large and deep, and I have since learned not to keep all my anchors, outboard gas tank, propane tank, air-floor dinghy (rolled up), and more in there. The real problem on this particular weekend trip was that it was a surf-mission and I had the other side of the boat loaded with lots of surfboards which take up a lot of space physically but are very light, so having the quarter berth full of boards still leaves the boat unbalanced... for longer term cruising I am thinking I will resolve this issue by keeping the boards somewhere else (probably the V-berth), and have the quarter berth completely loaded with the same amount of weight as the cockpit locker on the other side. I am working on expanding storage, and trying to add storage in the most reasonable areas, but it's always a compromise of sorts...

The boat is quite sensitive to weight-placement and initially, it's really pretty tender, but once it gets to a certain point of heel, it seems to stiffen up dramatically, once it gets its "shoulder in the water." I had a Catalina 30 before that, which had a really impressive initial stability, it took a lot to make her heel, but then she continued to heel more and more. Here, it's sort of the opposite sensation/experience. It heels easily but then stiffens up noticeably.

3) I think your suggestion on the next-evolution of the sail plan is a great idea. However, I am lucky in that the current sails I have are in "cruise ready" condition (like 9/10 condition) and we are having them reinforced with triple-stitched seams/panels at the moment so I am going to keep your suggestion in mind but for 2-4 years from now when I will be looking more seriously at new sails. Short boom, tall mast I guess means a high-aspect ratio rig which maybe is not ideal for down-wind but I do appreciate the way the boat sails to windward, feels really good. Down-wind it is nice to sail as well, but the beam of the Cat-30 seemed to make it more "surfy," more of a sitting-on-top-of-the-water as opposed to in-it feeling.

Like all boat projects, this weekends' install of the Lavac Head was more difficult than it seemed in theory, so I have not yet purchased the chain/anchor, but will do so and post my actual decision ASAP. Thanks barnakiel and others for all the great info on here.
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