What is this? Help needed identifying rig object

[Hermia II]

It could also be the holder of the boat hook

[meirriba]

Didn't the OP write that the top is capped?
If it is for any kind of pole, IMHO the top should be open, the bottom should be capped with a drain hole.

[Clivevon]

Originally Posted by Sailmonkey

Aft shroud meaning backstay?

I’ll wager it’s to contain the flag end of a MOB pole

+1...........

[skipmac]

Originally Posted by meirriba

Didn't the OP write that the top is capped?
If it is for any kind of pole, IMHO the top should be open, the bottom should be capped with a drain hole.

For a MOB flag the bottom must be open for the pole to fall freely out and overboard when released. Cap on the top to keep rain and sun out so the flag on top of the pole doesn't deteriorate.

[Nani Kai]

Originally Posted by boatman61

True.. and mounted higher which is why on my boats I fit two, one above each of the spreaders. The hanging ones are fine for day sailing but on multi day trips in all weather's rehanging due to chafe gets old quick.
But I promise a more forensic examination of the evidence next time..

"...rehanging due to chafe gets old quick." Amen to that. I have been looking for a way to provide a better radar return signal from our boat as well as eliminating chafe inherent in hanging the typical ball. I like your idea of two radar "tubes" above the spreaders. Design questions: (1) How best to pack aluminum foil into the tubes: tightly tamped down or loosely crumpled? Loosely crumpled would seem to offer more surface area? What about wrapping the exterior of the tube in metallic tape, possibly light-reflective as well. Would this increase the radar signature? Would the incoming radar signal penetrate the exterior tape and then be reflected by the denser foil or would it reflect the signal making the foil unnecessary? I guess my question is how does material thickness affect radar reflection?

[Clivevon]

Originally Posted by Nani Kai

"...rehanging due to chafe gets old quick." Amen to that. I have been looking for a way to provide a better radar return signal from our boat as well as eliminating chafe inherent in hanging the typical ball. I like your idea of two radar "tubes" above the spreaders. Design questions: (1) How best to pack aluminum foil into the tubes: tightly tamped down or loosely crumpled? Loosely crumpled would seem to offer more surface area? What about wrapping the exterior of the tube in metallic tape, possibly light-reflective as well. Would this increase the radar signature? Would the incoming radar signal penetrate the exterior tape and then be reflected by the denser foil or would it reflect the signal making the foil unnecessary? I guess my question is how does material thickness affect radar reflection?

I really would not waste your time doing anything like that. Apart from anything else, you are trying to DIY copy (by far) the worst performing of all radar reflectors -- the Mobri tube type. They do look neat. Shame they are next to useless.

The whole subject of radar reflectors is far more complex than that. It really isnt a subject for DIY.
I believe the Echomax, Tri-Lens or Firdell Blipper radar reflectors perform OK-ish as far as radar reflectors go. If you are really serious about reliably showing up on a big ship radar screen on a dirty night you need an active radar target enhancer like a Sea Me or Echomax or your local equivalent. Something like this:
https://www.force4.co.uk/item/Echoma...hoCGBoQAvD_BwE

You can read all about radar reflector performance in the real world in this accident investigation report here: https://www.ussailing.org/wp-content...ector-Test.pdf

The report concludes : "It is recommended that poorly performing radar reflectors are not fitted as it
is possible that the user could be lulled into a false sense of security believing
that their chances of detection has been enhanced."

By the way, simply adding extra reflectors wont work & may even make things worse as the returns they give can interfere with each other.

[RiverRat37]

Long, long ago I recall reading a book (probably by round-the-world sailors or on boatbuilding) that suggested the best radar reflector was a hollow mast (probably wooden) loaded up with crushed foil (aluminum? Tin?) Is it really super-effective?