Athena 38: Sailing with Genny only

[rom]

Originally Posted by FSmith

I believe fp does not recommend sailing with only the Genoa, no mainsail, on my Athena. What is the problem if you have a tight topping lift and a tight mainsheet. Wouldn't this support the mast?

Here we go again ... Why don't you RTFM ?!

(And for Lagoon owners having the same "belief", please stop perpetuating rumors, the ONLY restriction is 2 reefs in main with full genoa. No problem with jib, genny or spi alone, been doing it for years, 45+kts DW)

[Michael Pope]

The point here is that the mast is a hollow tube and not even of circular cross section so it is hard to reliably calculate the bending moment experienced by the spar when it has a large compression load. This load being mostly from the
for stay and head sail halyard . But one must not neglect the intermittent load of the weight of the rig being moved around by the Hulls interaction with the sea surface. Any mainsail sheeted tight will act as a damper for fore and aft
Rig Inertial loads and rig deflection ,so it is a help. If the rig has diamonds or other deflection limiting rigging on the fore side then a main is going to balance the situation by tending to keep the spar "In Column" so it can resist
the major load which is the compression load ( a much larger force than any of the others) Now if that doe not confuse you then you should be a RIGGER I hope you enjoy your new Profession. Have no worry though as soon as you get more confident you can dispense with the "Training Hulls" and you will gain a friend as a ballasted hull will lie down on its side and relieve
the rapidly built load cases due to a cat's rapid reaction to the sea surface. Just remember to buy A Felco cutter the one with the 30" handles or a Guillotine Cutter with a 10 lb sledge hammer. Happy Sailing Mike Pope

[thinwater]

Originally Posted by rom

Here we go again ... Why don't you RTFM ?!

(And for Lagoon owners having the same "belief", please stop perpetuating rumors, the ONLY restriction is 2 reefs in main with full genoa. No problem with jib, genny or spi alone, been doing it for years, 45+kts DW)

You could post the relevant section rather than resort to swearing. It would be more helpful.

[a64pilot]

Originally Posted by jmh2002

PS: a64pilot, you might be quite concerned to see just how much the rig moves on many racing boats, especially the top portion of a fractional rig.

Yes, but these aren’t race boats, their masts are less stiff I believe to allow for this movement?
I am certainly no racer, not even close, but I do understand the “system” well enough to know that the mast unless unstayed of course, isn’t much strength, it’s the rigging that carries the load, the mast should hopefully stay in compression shouldn’t it, but even then it shouldn’t be able to be pulled off its base, aren’t they attached in some way? Mine is keel stepped but still is attached to the deck, to pull it you must first remove the rod that runs though the mast and the plate that is attached to the deck.

[jmh2002]

Yes of course as I mentioned earlier the boats we are talking about here should have a much greater safety margin.

My post re racing boats was only for information and example purposes because some members seemed to have trouble understanding the situation, conceptually.

[jbinbi]

I think the original supposition is incorrect. I have heard lots of stories about going west to HI with 2 jibs, or jib and gen naked.

Basically sailing the way with no main.

[Ram]

I bought the last Athena that sailed out of the factory in April 06
Now have 40k nm on it, just rerigged it
And have sailed with jib only for 1000s of miles, in all kinds of wind and weather,I never heard of this limitation but I'm glad I didn't cuz maybe I would have paid some attention to it when I bought the boat new...
It doesn't seem to be any trouble at all...

[Michael Pope]

Hi I once knew an old sailor who liked two masted vessels that he usually built himself . He used to go to Hawaii every few years usually departing southern cal.
He would re rig his current boat with a square Sail for he trip with a small jib. Claimed as he was single handing it was the most reliable rig minimum chafe failures . When he was in Hawaii he would take down his spars and re rig for the balance of his trip.
He has a point Think about it. Michael Pope

[RaymondR]

Because it's not hanked onto a stay the genaker should only put compressive loads on the mast unlike the main which is fastened at the tack and would generate bending loads. From this it would appear that having only the column buckling loads of a genaker would be less likely to buckle the mast than having concurrent loadings with the addition of the bending loads imposed by the main.

[Rapanui]

Contrary to myths aired here, here is an extract from the official FP Athena manual. Its alittle confusing as the formatting has been lost, but the data is in pairs, the first wind speed and sail config for winds from the ahead sector, the second is for off the wind:
SAILS
1. Operating principle
For your safety and comfort, and to avoid any fatigue of the craft and rigging
in general, the sails should be shortened according to the wind force.
Below we give the recommendations according to tack and apparent wind
force.
Close to the wind and close reach Rear wind and broad reach
0 to 18 knots:
Mainsail and jib 0 to 15 knots: Mainsail and Genoa
18 to 24 knots
Mainsail to 1 reef
Genoa 1/2 unfurled
15 to 20 knots: Mainsail to 1 reef
Genoa 2/3unfurled
24 to 30 knots:
Mainsail to 2 reefs
Genoa 1/3 unfurled
20 to 25 knots: Mainsail to 2 reef
Genoa 1/2 unfurled
30 to 34 knots:
Mainsail to 3 reefs
Genoa 1/5 unfurled
25 to 30 knots: Mainsail to 3 reefs
Genoa 1/3 unfurled
34 to 40 knots:
Mainsail to 3 reefs
Genoa slightly
unfurled
30 to 35 knots: Mainsail down
Genoa unfurled (1m
only)
Note that for 30-35 kts off the wind, it recommends no main and part genoa

[Rapanui]

The forces on the mast from the genoa or any headsail is a tension force in line with the forestay as the point it is attached to the mast. This is resisted by the tension forces transmitted by the shrouds in line with them. For the Athena, the shrouds and forestay meet the mast at the same vertical position, so there should be neglible moment applied to the mast which could cause bending.

The spinnaker halyard exit is slightly above the shround attachement points, the spi force is transmitted as tension in the halyard in the direction it enters the spinnaker sheave, this is resisted as before by the shrouds and a bending moment which tries to pull the top of the mast forward and below the shrouds aft. This is resisted by the swept aft diamond stays on the mast.
The 3 diamond stays on the mast (1 forward and 2 swept aft) are there to prevent the mast buckling from any moment loads applied to the mast due to the compressive loads applied from the shrouds, forestay, and main, genoa and spinnaker halyards as well as any bending loads applied by the main via the full length battens and boom.
It is a pretty normal configuration for a modern cat and fairly bombproof, provide none of the 3 bits of string holding up the mast fail.

[a64pilot]

Originally Posted by Rapanui

The forces on the mast from the genoa or any headsail is a tension force in line with the forestay as the point it is attached to the mast. This is resisted by the tension forces transmitted by the shrouds

And that resisted force by the shrouds is why the mast is always under compression.
Think about it you have a triangle, pull a force on any leg of the triangle and that force is resisted by the other leg which means the top of the triangle is being pulled down.

There is no force that any sail can put on my rig that I can comprehend that won’t result in the mast being in compression, but then I do have back stays.
In fact my boat spent the first 27 yrs if it’s life with the mast just sitting on its base, the pin through the plate on the deck was not installed, other than the rig and gravity, nothing held the mast on its base.
Not sure how being a Cat would change those forces, excepting that Cats won’t heel much, so assumption is that they would have even stronger rigs than a mono.

[FSmith]

Really Mike Pope...after owning 5 mono's, I thought I would try a sailboat with "training hulls". Thanks for your expertise.

[FSmith]

Ok, myths it is. I heard this from another FP owner and thought I saw it in print but wasn't sure and glad I asked.

[mark0978]

Originally Posted by rom

Here we go again ... Why don't you RTFM ?!

(And for Lagoon owners having the same "belief", please stop perpetuating rumors, the ONLY restriction is 2 reefs in main with full genoa. No problem with jib, genny or spi alone, been doing it for years, 45+kts DW)

Well, my manual says the following:

"Warning: Any sail combination differing from these requirements may cause the mast to break.

In particular: 100% genoa with 2 reefs in the mainsail is totally banned."

It then has a table that shows the amount of reefing for different wind speeds.

They of course completely ignore the possibility of a spinaker or code-X or anything other than the Genoa and Mainsail which is ever so helpful of them.

Thank you lagoon.