Boom-Mast Orientation

[TBOT422]

This may sound like a silly question, but is there an optimal angular relationship between the boom and the mast. Simple logic seems to be that it should be 90 degrees between the mast and the boom, but the question becomes at what time is that angle appropriate? Obviously this angle is adjustable between the boom vang and the topping lift. As I believe the gas spring in our boom vang has failed and needs to be replaced, we can adjust this angle to whatever is appropriate by changing the position where the boom vang connects to the boom. I just don't know what is appropriate. Our boom vang has a mark on it from the previous owner that we have always assumed was the appropriate length for the boom bang. Now that the sail is 6 years older (10 years total) and likely stretched out more than it was whenever the mark was created with brand new sails, I wonder how appropriate that mark is. Any ideas on how to adjust the boom vang connection so that the sail furls and unfurls properly and also has the proper tension on the leech when deployed? Is 90 degrees a starting point or not relevant at all?

Note, we do have a furling main.

Thanks

[JohnNorton]

The boom vang adjustment is there to improve sail shape, there is not a static "best" position. If you read about using a boom vang on the internet you'll better understand (and read more than one source).
As to the mark the previous owner placed it may be there for furling/unfurling. For this there is a "best" position. Too high of boom will place wrinkles in the wrap possibly resulting in a jammed sail. Too low of boom angle may make it difficult to furl as the tension is uneven along the mast. If your sail is bagged out you may want to be careful with this, may be why the previous owner made the mark on the vang.

[Mark Sutherland]

The rigid boom vang on my boat is adjustable via twisting the outer tube. Most of what I've read about furling says that the boom should be slightly higher than horizontal, or about 85 degrees to the mast. The rigid boom vang has a length limiter on it, so you don't want to pull against this limiter with the topping lift. Instead, loosen your main sheet (and vang lines, if any), twist the rigid vang tube, and extend the boom vang until that you achieve the 85 degree boom to mast orientation. Once the sail is set, you can pull the boom down with the main sheet or vang line (if any) to achieve desired sail trim.