I'm painting my Pearson Flyer that I just bought and was wondering about the
color of the mast. The mast is now primed flat black and gets very hot
sitting in the sun.

That's a lot of aluminum expanding as the temperature changes. How much does
this expanding affect the rig tuning (if at all)?

I think I'll end up painting the mast white, but I am curious if anyone has
opinions about the rig tuning being affected.

Dennis

Dennis Vogel wrote:

I'm painting my Pearson Flyer that I just bought and was wondering about the
color of the mast. The mast is now primed flat black and gets very hot
sitting in the sun.

That's a lot of aluminum expanding as the temperature changes. How much does
this expanding affect the rig tuning (if at all)?

I think I'll end up painting the mast white, but I am curious if anyone has
opinions about the rig tuning being affected.

Yes. My opinion is that it will not affect the tuning.

DSK

Dumb people. My friend's Santana 30/30 has a black mast. On hot days we need to
use sails from a Rhodes 19 to get a proper fit. We usually have to change the
stays as well because the mast can change more 3' in height.

RB

Oh Boy. Coefficients of Thermal Expansion!

The several degrees of extra heat captured by the black mast might come out to something
like a fiftieth or twentieth of inch expansion on a long mast. A bigger issue might be if
the mast is setup and tuned on a cold Spring day - the temp rise to a hot Summer day could
be 50 degrees, which might result in an expansion of maybe a part in 2000, which would be
around half an inch for a long mast. I think I'll ask my rigger if they take this into
account.

(These number are all SWAGs - Scientific Wild Ass Guesses)


"Bobsprit" wrote in message
...

Dumb people. My friend's Santana 30/30 has a black mast. On hot days we need to
use sails from a Rhodes 19 to get a proper fit. We usually have to change the
stays as well because the mast can change more 3' in height.

RB

be 50 degrees, which might result in an expansion of maybe a part in 2000,
which would be
around half an inch for a long mast.

Half inch would be a LOT.

RB

Thanks Jeff, but the mast gets too hot to touch hanging horizontal waiting
to be painted. So it's a lot more than a few degrees.

Dennis

Oh Boy. Coefficients of Thermal Expansion!

The several degrees of extra heat captured by the black mast might come
out to something
like a fiftieth or twentieth of inch expansion on a long mast. A bigger
issue might be if
the mast is setup and tuned on a cold Spring day - the temp rise to a hot
Summer day could
be 50 degrees, which might result in an expansion of maybe a part in 2000,
which would be
around half an inch for a long mast. I think I'll ask my rigger if they
take this into
account.

(These number are all SWAGs - Scientific Wild Ass Guesses)


"Bobsprit" wrote in message
...

Dumb people. My friend's Santana 30/30 has a black mast. On hot days we
need to
use sails from a Rhodes 19 to get a proper fit. We usually have to
change the
stays as well because the mast can change more 3' in height.

RB

Dennis Vogel wrote:

Thanks Jeff, but the mast gets too hot to touch hanging horizontal waiting
to be painted. So it's a lot more than a few degrees.

If your mast is currently setting on sawhorses, you can test how much it expands
very very easily. Fix one end, and pad the supports, and tape a ruler to another
sawhorse at the free end so you can measure the expansion.

You can look up the coefficients yourself and figure it out, I calculated that a
50' mast undergoing a 50 degree F change in temp will lengthen by .411" if it
made of the alloy with the highest possible expansion rate. More likely it'll be
between half and a quarter of that, say between 3/32" and a 1/4". Is that enough
to affect tuning, when the shrouds & stays are also undergoing thermal
expansion?

I'd suggest not.

If thermal expansion were a problem, then it wouldn't be likely that so many
racing boats have black painted spars (OUCH! especially in the South), or
perhaps that sailmakers would have a temperature incorporated into their tuning
guides.

Next question.

Fresh Breezes- Doug King

If the Flyer mast is 40 feet, a 50 degree change is 1/4 inch (I think!). Its roughly
linear for our purposes, so I'd guess that the black might cause an expansion equal to one
turn on the turnbuckle.

Since you have the mast down, why don't you measure it early in the morning, and then in
the afternoon sun. You can report back and be the envy of the group!

BTW, I never liked black masts - I think white would look nice.


"Dennis Vogel" wrote in message
ink.net...
Thanks Jeff, but the mast gets too hot to touch hanging horizontal waiting
to be painted. So it's a lot more than a few degrees.

Dennis

Oh Boy. Coefficients of Thermal Expansion!

The several degrees of extra heat captured by the black mast might come
out to something
like a fiftieth or twentieth of inch expansion on a long mast. A bigger
issue might be if
the mast is setup and tuned on a cold Spring day - the temp rise to a hot
Summer day could
be 50 degrees, which might result in an expansion of maybe a part in 2000,
which would be
around half an inch for a long mast. I think I'll ask my rigger if they
take this into
account.

(These number are all SWAGs - Scientific Wild Ass Guesses)


"Bobsprit" wrote in message
...

Dumb people. My friend's Santana 30/30 has a black mast. On hot days we
need to
use sails from a Rhodes 19 to get a proper fit. We usually have to
change the
stays as well because the mast can change more 3' in height.

RB

DSK wrote:
More likely it'll be
between half and a quarter of that, say between 3/32" and a 1/4". Is that enough
to affect tuning, when the shrouds & stays are also undergoing thermal
expansion?


Doug, don't forget the the stays are expanding too, albeit not as much but
it does make the delta smaller.

I wouldn't loose any sleep over it.

Cheers
Marty