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Sunday, October 18, 2009

Anchor Roller Test Lab: Preliminary Results

From Building A Westsail 42: Latest Activity
Yesterday I setup the apparatus intended to help design various anchor roller configurations for different style anchors. The goal is to get a design that self launches, easily retrieves various style anchors. The idea is to design the "cheek" plates to allow placement of the rubber-like rollers in different places for different anchors.

The apparatus is simply an existing work table with two pieces of plywood simulating the cheek plate, approximately the size expected and then some (so I could cut them down and really dial it in). Two rollers are mounted between the cheek plates using two pieces of all-thread as an axle, through holes strategically drilled through the plates. Also included is a 15 foot section of 3/8" chain and a standard shackle to test deploy and retrieval of the anchors to help simulate a real world setup.

I started with the bow roller placement from the initial CAD drawings done a couple weeks ago. This initial setup worked pretty well for all anchors I had on hand (Bruce, CQR, Delta). But the Bruce and CQR had trouble self-launching. Moving the aft roller up about an inch fixed this. Finally, I jacked up the front of the table to an incline I expect the pulpit to be at in order to match the sheer of the boat. It is about a 6 degree incline. Again the Bruce and CQR had trouble self launching, so, the aft roller goes up another inch to fix this.

In the end there are a series of holes in the cheek plates with pairs matching the optimal position for each style anchor.

Testing is not done however. I will be exchanging the 44lb Bruce for the 66lb this week to see if there is any significant difference for roller placement.

As for the "rollbar" style anchors like the Rocna, the problem is the rollbar hitting the underside of the pulpit as it is pulled in. The easiest solution is to drop the forward roller a couple inches. However, we cannot build that extra drop length into the cheek plates as it will screw up the optimal setup for the other anchors (like the Delta and CQR). Specifically, the cheek plates will hit the flutes of the anchor and block it from being retrieved into the fully stowed position. So, I am considering a couple removable "tangs" that will attach to the cheek plates and drop the forward roller. If we use a Rocna style anchor, we add these tangs and drop the forward roller. If we go back to another style, we remove the tangs and move the roller back up. That is the idea at least. Clear as mud? I will probably have a CAD drawing here shortly to clarify things.

From Building A Westsail 42: Latest Activity
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