How much bend in the furling mast

[meb135]

I have a new to me, 2004 H33 with the selden furling mast. My question is one that i cannot find the answer too in the selden documents, online or in print. How much bend is recommended for a selden furling mast so as not to hinder the operation of the furler. The mast is up, the main has not yet been installed and using the main halyard as a guide, i see approx. 4 inches of bend. Is this too much for this type of mast?
Thanks all.

Marc

 

[Jake N Eggs]

I put 2" of bend in the mast when it is on the stands. When the mast is on the boat, straight and the outer shrouds under tension, I adjust the diagonals to pull the bend out of the mast. The mast is dead straight as the final installation. The B&R data is somewhat confusing as it states that the maximum bend is 2" for the furling mast in the first paragraph of the installation instructions. See below.

I would say that 4" is too much.

1. Start with all the rigging slack. Then
induce the mast bend by tightening the
reverse diagonals (diamonds). Measure
the bend by tensioning a line or the main
halyard between the masthead and the
gooseneck. The maximum amount of
bend should be no more than 8” [203mm]
for the standard rig and no more than 2”
[50mm] for the furling mast. Measured
perpendicular from the aft face of the
mast to the halyard at the deepest part
of the bend. It can be less than that
based on the sail shape and your own
preference. The bend should also be
evenly distributed along the mast to give
a smooth shape. Keep in mind that
bending a furling mast may make it more
difficult to furl and will not do much to
flatten the sail as in a standard rig. It is
very important that the mast also be
straight from side to side at this time.
Tighten or loosen the reverse diagonals
to achieve this.

 

[PKFK]

I agree with Jake and will second that 2" max prebend.

My Selden manual for my mast (H36) also has the same tip - for a fuirling mast, max is 2" when the mast is being pre-tuned while of the boat.

Paul

 

[Nodak7]

I put 2" of bend in the mast when it is on the stands. When the mast is on the boat, straight and the outer shrouds under tension, I adjust the diagonals to pull the bend out of the mast. The mast is dead straight as the final installation. The B&R data is somewhat confusing as it states that the maximum bend is 2" for the furling mast in the first paragraph of the installation instructions. See below.

I would say that 4" is too much.

1. Start with all the rigging slack. Then
induce the mast bend by tightening the
reverse diagonals (diamonds). Measure
the bend by tensioning a line or the main
halyard between the masthead and the
gooseneck. The maximum amount of
bend should be no more than 8” [203mm]
for the standard rig and no more than 2”
[50mm] for the furling mast. Measured
perpendicular from the aft face of the
mast to the halyard at the deepest part
of the bend. It can be less than that
based on the sail shape and your own
preference. The bend should also be
evenly distributed along the mast to give
a smooth shape. Keep in mind that
bending a furling mast may make it more
difficult to furl and will not do much to
flatten the sail as in a standard rig. It is
very important that the mast also be
straight from side to side at this time.
Tighten or loosen the reverse diagonals
to achieve this.

Jake, the Selden manual states:

"A general rule is that the pre-bend should be
1% of the distance from the masthead to the gooseneck,
measured at the centre of this distance."

However mine is a little more than that but it works fine on my rig!

 

[meb135]

Thanks for the info guys. That's what i was looking for.

Marc

 

[Jake N Eggs]

Jake, the Selden manual states:

"A general rule is that the pre-bend should be
1% of the distance from the masthead to the gooseneck,
measured at the centre of this distance."

However mine is a little more than that but it works fine on my rig!

If we say it is 45' from the mast head to the goose neck on the 33, 1% would be 5.4". That sounds correct for a standard rig. I am pretty sure that the furling rig would be different.

Is your rig standard or furling?

 

[Nodak7]

If we say it is 45' from the mast head to the goose neck on the 33, 1% would be 5.4". That sounds correct for a standard rig. I am pretty sure that the furling rig would be different.

Is your rig standard or furling?

Jake, the Selden Manual does not distinguish between furling and non-furling pre-bend. They specify "B&R Rig without backstay". Therefore I assume it refers to both types.

"The amount of a pre-bend depends on the cut of the
mainsail. A general rule is that the pre-bend should be
1% of the distance from the masthead to the gooseneck,
measured at the centre of this distance. The mast must
have no lateral bend. All pre-bend must be in the foreand-
aft direction."

My current mast has a P measurement of 50' 08". My prebend should be 1% of that or approximately 6.08". I had a 33 with the mast specifications of 41' 0" and the prebend was 4.92". Both were furling masts. When I rigged these two boats I used this method and furling was not an issue with either. Please note that Selden states it depends on the cut of the sail. So that does complicate it a bit.