Pumping mast!

[Bash]

By IOR standards, the Choate 40 had an overbuilt rig, so it's probably not too much a concern. Does yours have the hydraulic backstay? If so, you may want to take it down to a couple hundred pounds while you're on the hard. Also, if you're running the halyards to the toe rail you may want to find a way to stow them amidships while on the hard. Maybe run them to the pulpit?

[delmarrey]

Originally Posted by Bash

By IOR standards, the Choate 40 had an overbuilt rig, so it's probably not too much a concern. Does yours have the hydraulic backstay? If so, you may want to take it down to a couple hundred pounds while you're on the hard. Also, if you're running the halyards to the toe rail you may want to find a way to stow them amidships while on the hard. Maybe run them to the pulpit?

I'm sure loosening up the hyd. backstay would have help as well. It's normally set at around 1000 psi which gives the mast a li'l arc, and the halyards goto padeyes on deck.

The point if the thread was to recognize the fact that wear and stress does happen with the boat not in use.

I attempt to reduce this by making adjustments to the running rig on windy days. Goto the local marina on windy days and just listen to the music of hallow masts produced by loose/flaying rigging.

[Target9000]

Originally Posted by delmarrey

The point if the thread was to recognize the fact that wear and stress does happen with the boat not in use.

Not according to the thread title...

When I clicked on it I was expecting a discussion on pumping masts.

[delmarrey]

Originally Posted by Target9000

Not according to the thread title...

When I clicked on it I was expecting a discussion on pumping masts.

See, there ya go! Ya got trapped by an un-descriptive advertisement.

And there should be enough info on pumping masts, as a result.

[Bash]

Originally Posted by delmarrey

The point if the thread was to recognize the fact that wear and stress does happen with the boat not in use.

I attempt to reduce this by making adjustments to the running rig on windy days. Goto the local marina on windy days and just listen to the music of hallow masts produced by loose/flaying rigging.

Ah, good point. I hope the folks that allow their halyards to slat at the dock are listening. Unfortunately, they seem to be the most oblivious among us.

[Cotemar]

Analyzing the airflow over a cylinder will answer the mast pumping problem.

You may see these helical fins on certain industrial exhaust stacks
It turns out that these are known as Helical Strakes for aerodynamic stabilization, to prevent wind vortex shedding from vibrating and tearing the thin metal stack apart.

So if you make a helical rap of a halyard around the mast you should limit the vibration.

[Cheechako]

Originally Posted by Nemo55

A little help for the uninitiated,,,,what is a pumping mast?? Thanks :-)

The mast just bends a little... usually forward and aft from the effect of the breeze and from the tension tuned into the rig. It occillates back and forth.... which many call "pumping". It can be an annoying sound down below for sure.... kind of a harmonic "thrumming".

[delmarrey]

Being a man and stimulated by visual things I think the demo that Target9000 provided, does it for me.

[Cheechako]

He asked what it was...... I didnt think the picture really explained what it was! (ie: annoying sound created by the mast moving) But a nice video anyway....

[Target9000]

Originally Posted by Cheechako

He asked what it was...... I didnt think the picture really explained what it was! (ie: annoying sound created by the mast moving) But a nice video anyway....

Originally Posted by Target9000

it is usually a harmonic oscillation caused by fluctuating vortexes of air passing the mast.

"A harmonic oscillation". The mast is moving. The mast is making noise. Its annoying. I thought it was an explanation. Sorry if it tweren't clear.

[s/v Jedi]

Just a heads up: If you have roller furling jib(s) with the jibs removed, you can get wild oscillations of the furler profile. In that case, turn it so that the track for the luff of the sails is facing AWAY from the wind.

I have seen these vibrate 2 foot or more which certainly can bring a mast down. Jedi can also do this and the whole boat will start shaking as there's a significant weight of the furler involved.

ciao!
Nick.

[Cheechako]

Originally Posted by Target9000

"A harmonic oscillation". The mast is moving. The mast is making noise. Its annoying. I thought it was an explanation. Sorry if it tweren't clear.

Yeah.... your post was great... I was just trying to embellish a little!

[roverhi]

Are you going to be running a staysail?? If so, running backs are really a peace of mind item. Mast will pump with a loaded staysail stay. Depending on the design, it probably won't be a fatal problem but definitely prey on the nerves if you watch it. Your boat beaing being an ex racer, the mast is undoubtedly pretty much designed to the limit. Running backs wouldn't hurt. Nice thing about Vectran, et al is they are st weight less and don't cause the chafe problems of wire. Might consider going that route if you feel the need.

I switched my topping lift to a small diameter vectran et al line and now have a very expensive guitar string holding up my boom. Really creates a racket when the winds up. So much for the strength advantage of these new high tech lines.

[zeehag]

my wooden masts didn5t pump until the wedge was place into wrong place. is matter of tun of rig.