Mast Bend Aft

[JaxMacX]

Hi all, so we got the mast up over the weekend for the first time. The shrouds seem to have good tension with a low hum when plucked. We attached the furling system with help from the mast raising system and a bit of pulling. Then we connected the back stay. Everything looked great till I looked at the mast. I swear it looks like the top of the mast is bending toward the bow of the boat. Is that normal or did I rig something wrong?

[Piddle and Futz]

Hi there,

On the the mast should take aft.

Will let the experts who have one tell us how much.

[rsvpasap]

As per the manual, the mast rake should be 4 degrees toward the stern.

https://macgregorsailors.com/resources.html

[pitchpolehobie]

As per the manual, the mast rake should be 4 degrees toward the stern.

https://macgregorsailors.com/resources.html

It looks like a lot more than other boats in my marina but I checked and its the correct 4 degrees so it looks exaggerated.

[JaxMacX]

Ok … I guess what I mean to say is that the middle portion of the mast curves toward the rear of the boat. I will take a photo in the morning and try to post it so you can see. Thanks for your help!

[JaxMacX]

Here is what the manual says on bend
MAST APPEARANCE AFTER PROPER TUNING. All support wires should be tight. Do not tighten the backstay so tight that the mast is bent severely to the rear of the boat. Ideally, the mast should have about a 2" bow. In other words, the center of the mast should be about 2" forward of a straight line drawn from the top of the mast to the base of the mast. The downwind wires will be somewhat slack when sailing
hard. The backstay may be slack when sailing into the wind, since the mainsail takes over the task of supporting the mast from the rear.


I thin mind is bending the other way

[Jimmyt]

Lower shrouds and forestay may be too tight and upper shrouds too loose. You need to use a plumb line to verify you are actually seeing a bend in the mast. If so, try loosening the lowers and see if it straightens up.

It shouldn't look like you describe. With a tight backstay, it should be bent the other way.

[JaxMacX]

Thanks! I’ll adjust accordingly

[Tomfoolery]

The upper side stays are held apart by the spreaders, and they are also swept backwards. So tensioning the upper shrouds will push the center of the mast forward which is how the bend gets there. The lower shrouds will counter that forward force component. If they lowers are too tight, they will pull the center of the mast backward, which sounds like what’s happening.

I’d suggest tensioning the upper shrouds for proper preload, then adjusting the lowers for mast bend. That’s after adjusting the forestay for mast rake, of course. And note that the 4 deg angle is from the deck, not from the center of the earth. And it is more than most other boats. Many/most owners don’t use as much rake, as it causes the boat to round up more easily.

There are tension numbers out there that can be used with a Loos gauge, but I can’t find my notes anywhere. They’re out there (here) somewhere, though.

[JaxMacX]

Wowser!! Thanks for the tips!