Mast Deflection

[Steve Ullrich]

Hello Folks,

I've noticed that I have a slight amount of deflection in my mast on a close reach. I'm wondering if that is typical?  I'm wondering if I have a bit too much tension on my shrouds... or perhaps not enough?  I suspect too much as I am accustomed to tensioning shrouds on a much larger mast and probably over did it.  Anyone out there know how much tension to look for on a Loos Gauge?

Thanks,

Steve

[Rick Klages]

Most of us sail our 16 a bit on the loose side with a bit of forward rake.  The lee shroud should be slack but not floppy.

[Steve Ullrich]

What about mast deflection?

Most of us sail our 16 a bit on the loose side with a bit of forward rake.  The lee shroud should be slack but not floppy.

[Rick Klages]

I haven't noticed any.

[Salty19]

I haven't noticed any mast deflection either.  Both shrouds sailing leeward is as Rick mentioned "slack but not floppy".  The mast leans to leeward maybe 2 degrees off the parallel cabin top surface at most--not really deflection but just a property of aluminum being "bendy".   

My foreshroud is about the same tightness as the leeward shroud (difficult to tell due to rolling furler). It has maybe 1" of deflection in the middle of the lee and fore shrouds.  Sorry, no loos measurements to share or other accurate data.   

[Craig Weis]

Lay on the vee birth and 'site-tube' up the mast through the open deck hatch. You can actually see the standing rigging pulling a bend on the mast. Make her straight.

I will say that on my C-P 19 that when sailing and stress is placed on the mast sails and rig that the two stays/shrouds/standing rigging attached to the chainplates [or what ever you wish to call it] on the lee side, [slack side], are just that. Just a hint of looseness.

While on the windward side the standing rigging is taught. Be mindful that each port or starboard standing rigging coming off the chain plates need their own pin. Do Not use one pin for both standing rigging shrouds. One shroud anchors at the junction of the mast and spreader while the other shroud anchors at the mast head. Two different angles. Additionally assure that the spreaders are horizontal, perpendicular to the mast.

Now fore and aft. With my furler tight and my mast straight up and down, I close up the turnbuckle on the stern till it's kind of tight. Not real tight 'cause there is no reason to try to pull the mast down onto the compression post that the two lag screws holding the post into PLYWOOD need to be bent downward.

What must be avoided at all costs is to place way too much strain on the rig. Don't over tighten anything. Just like setting the sails, sail her loose. Sheet out till she luffs then sheet in till the luff just goes away. skip.

[Potcake boy]

Steve,

With the 3 stay rig of the 16 there is no way of adjusting to bring the mast into column. However as a fractional forestay rig, tension of the mainsheet when sailing on the wind could put bend in the mast if sheeted in hard, though I wouldn't think it to be a significant amount.

Could it be that the mast is slightly bent or twisted as from driving under an obstruction with the mast up?  I did that once.

Ron

[Steve Ullrich]

Ron -I had a very minor bow to windward on either tack. I was just curious whether other's had noted the same thing.  I just replaced my head stay and retensioned the shrouds.  The mast currently appears to be in column on the hard, going to give it a whirl on the water tomorrow and see if I observe the same minor bow I saw before. I have eased the tension on the shrouds from the tension recommended in the Loos Gauge documentation for this shroud diameter. That may have an effect as well.  I was in close hauled in 15-20mph winds with gusts to 25+ when I observed that bowing, the winds may have played a role too...

Steve

Steve,

With the 3 stay rig of the 16 there is no way of adjusting to bring the mast into column. However as a fractional forestay rig, tension of the mainsheet when sailing on the wind could put bend in the mast if sheeted in hard, though I wouldn't think it to be a significant amount.

Could it be that the mast is slightly bent or twisted as from driving under an obstruction with the mast up?  I did that once.

Ron

[adschmid]

The loose measurements on my 1985 cp16 are 35, side, 30, forward. I works well for me. I did the same thing. Tightened the hell out of the stays based on loose recommendation. You just dont need it for these boats. I have just a bit of forward rake to help with the weather helm. I dont get much, if any noticeable, slack in the lee shroud even when its pretty windy (10-15mph).

[Steve Ullrich]

I backed mine off considerably too.  The shrouds on the C-16 are the same diameter as the shrouds were on my Hunter 23.  Much stouter than they probably need to be.  That's nice.  They don't need to be anywhere near as tight as I had them on the Hunter.  I was out in brisk winds today.  I might have them just a tad too loose right now but it was too windy to let go of the tiller and see what they felt like on the lee side.  I'm going to have to rig a tiller tamer.

Thanks for your input...

The loose measurements on my 1985 cp16 are 35, side, 30, forward. I works well for me. I did the same thing. Tightened the hell out of the stays based on loose recommendation. You just dont need it for these boats. I have just a bit of forward rake to help with the weather helm. I dont get much, if any noticeable, slack in the lee shroud even when its pretty windy (10-15mph).

[Potcake boy]

Steve,
Is it possible that a slight hook to windward could simply be the result of the CE being lower than the shroud tangs?  These masts aren't very stout (don't need to be) extrusions.  It doesn't seem like it would be something to have any appreciable effect on a boats sailing qualities, and it doesn't sound like your mast is in imminent danger of falling down.

I once trailed my 16 with the mast up under an overhead wire and caught it just above the forestay.  Being alerted to this error in judgement by the resounding bang behind me, I assume the the boat was lifted partially off the trailer and surely the mast flexed to allow the wire to pass over.  The mast appeared to be unscathed, but close inspection revealed a slight torque twist to the mast.  Never the less, she sailed fine there after - a testament to how sturdy these rigs are.  Ain't never heard of a Compac gettin' dismasted.

Ron

[Steve Ullrich]

Potcake - I completely agree, but thought I'd ask the forum.  I was surprised that nobody else noted a slight bow so remained a bit concerned for a little while. Maybe I'm just a little more observant? Maybe the shrouds are still a tad too tight?  Easing the shroud tension from my original tune seemed to reduce the effect considerably but it is still observable on a close reach on either tack in winds of 16 knots and up.  After yesterday's excursion in gusts to 20 knots and above I'm pretty confident it isn't significant.  I may ease the shrouds a couple of more turns before the next outing.  I don't want loose shrouds to leeward though, too much potential damage to the tabernacle and coach roof on a tack or jib as the mast slams across center.  Recipe for a dismast if there ever was one...

Lucky you didn't pull down a hot wire with your mast.  That would have sucked a lot.  I try to watch trees and crap over the launches  and rigging areas carefully but, even so, I've nicked a couple of small and flexible branches overhead.  A lot of public launches weren't designed with sailboats in mind.  I complained to the DNR about the public access lot and ramp at Prior Lake as it is closest to home. Maybe it will do some good, maybe it won't. 

Steve,
Is it possible that a slight hook to windward could simply be the result of the CE being lower than the shroud tangs?  These masts aren't very stout (don't need to be) extrusions.  It doesn't seem like it would be something to have any appreciable effect on a boats sailing qualities, and it doesn't sound like your mast is in imminent danger of falling down.

I once trailed my 16 with the mast up under an overhead wire and caught it just above the forestay.  Being alerted to this error in judgement by the resounding bang behind me, I assume the the boat was lifted partially off the trailer and surely the mast flexed to allow the wire to pass over.  The mast appeared to be unscathed, but close inspection revealed a slight torque twist to the mast.  Never the less, she sailed fine there after - a testament to how sturdy these rigs are.  Ain't never heard of a Compac gettin' dismasted.

Ron

[multimedia_smith]

Are you talking about mast curve or bend forward and aft?  Or are you talking about deflection side to side?
I noticed when I was sailing reefed in a strong wind that there was considerable side to side deflection as the pressure was more on the mid mast area as opposed to being spread over the entire length.
I made a set of "lowers" (side shrouds from the spreader down) and they virtually eliminated that... It also gives me the peace of mind that if a side shroud broke loose, I wouldn't be dismasted immediately before I had a chance to release the main sheet.
If the forestay ever broke, at least you have the sail and halyard to keep the mast up, but with only one side shroud...
Anyway, here is a pic of my rig... hope it helps...
Happy sails to you
Dale

http://groups.yahoo.com/group/com-pac/photos/album/712582202/pic/705800588/view?picmode=&mode=tn&order=ordinal&start=1&count=20&dir=asc

  Sorry, I haven't figured out how to insert an image here... the link is to the "other" ComPac site's gallery.

[Steve Ullrich]

Dale,

I've noticed a slight curve in the mast when sailing in heavy air, mid mast. When I eased the shroud tension a bit the curve wasn't as pronounced but it is still there. Easing the shrounds allowed side to side deflection instead.  Again, slight but I'm aware of it. My last two sailboats had lower shrouds, I might have a couple made for me just for peace of mind.  I couldn't get to the picture you recommended, access denied, but thanks.  I know what it should look like.

Steve

Are you talking about mast curve or bend forward and aft?  Or are you talking about deflection side to side?
I noticed when I was sailing reefed in a strong wind that there was considerable side to side deflection as the pressure was more on the mid mast area as opposed to being spread over the entire length.
I made a set of "lowers" (side shrouds from the spreader down) and they virtually eliminated that... It also gives me the peace of mind that if a side shroud broke loose, I wouldn't be dismasted immediately before I had a chance to release the main sheet.
If the forestay ever broke, at least you have the sail and halyard to keep the mast up, but with only one side shroud...
Anyway, here is a pic of my rig... hope it helps...
Happy sails to you
Dale

http://groups.yahoo.com/group/com-pac/photos/album/712582202/pic/705800588/view?picmode=&mode=tn&order=ordinal&start=1&count=20&dir=asc

  Sorry, I haven't figured out how to insert an image here... the link is to the "other" ComPac site's gallery.

[NateD]

Steve,

    I'm still messing with my shroud tension too. The mast deflection is definitely due to tension on the side stays. Whether it is bad, good, or indifferent, I don't know? A few weeks ago when I was on Pepin, I had my shrouds fairly tight, and even reefed in 25-30 mph I was getting some deflection (and quite a bit before I reefed). Before my lee shroud would be visibly slack and there was no noticeable deflection in the mast. I'm going to keep messing with it, there has to be a happy medium between slack and deflection. Probably going to depend on whether it is a I or a II also.

Nate