Ok, cutting to the chase...suggestions on HEAVY air mast setting for the Viper

Started by Drew Harper, January 09, 2009, 01:57:50 PM

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Drew Harper

My new boat is soon to be under construction. I want to shorten up my learning curve as much as possible so I'm looking to you guys for some suggestions. Also I'll be running demos in heavy air and really don't want to timber any rigs with prospective buyers aboard, how embarrasing :p

Background:

- We sail no-backstay sporties a lot. U20, U24, A27 so I'm accustomed to the mainsheet and vang being the backstay. Also sailed M24's, 32's, FT 10's, Mumm 30's etc...oh yeah, Windsurfed heavily, Lasers, Finns, 49'ers, Nacras, Hobies and one evil stint on an 18' skiff (never again ;-)

- We sail regularly in 20-25 knots. Some days 30 (unintentionally). Sea state ranges from mild chop (flood tide days) to 4 foot squares (ebb tide).

- I've sailed a wide variety of sportboats on the bay including Thompsons, Melges 24 & 32's,

- I've sailed a Viper once, at Lake Norman, light air.

Sounds like fun, eh?  I'll bring the Velocitek along for some speed logs.

I'd like to get your ideas of settings for shrouds, rake, block and vang loads and if possible, rationale.

Don't worry about coddling me, tell it like it is. I'm thick skinned. I need to prepare buyers to sail in these conditions so the more info, the better.

Thanks, in advance, for your help. Great Class!

Drew - Spinnaker Sailing.


#189 UK Built Mark IV Viper "DILLIGAF"

Dan Tucker

Considerations for a demo are somewhat different than for racing, as I'm sure you're aware.  I should get out my notebook, but off the top of my head (with Hydes):

1. Plenty of uppers, like 35 on the newer style black Loos gauge. Prebend enough to flatten the main. Uppers + gnav are your primary bend tools to remove draft. Overpowered? More uppers.
2. Snug to tight (but not too tight) on the lowers, to help forestay tension. Lowers + main leech tension are your jib draft controls. Too much jib draft? More lowers.
3. LOTS of GNAV upwind. Main leech tension for pointing and headstay tension. IMHO, you should add at least one more purchase to the gnav system below the boom. Ease it before the hoist, better a tad loose leech on the run for a demo.
4. plenty of jib luff tension to keep the draft forward. You know what more does -wider groove, helpful for a demo!
5. SAIL THE BOAT FLAT. Whatever it takes. More hiking, more upper, ease more main. The keel is not as short chorded as some newer designs, but it's not terribly wide, nor terribly deep. It's pretty critical, needs plenty of flow (boatspeed) and to be as close to vertical as possible to generate lift, or the boat goes sideways. Again, not as critical for a demo...
6. Forestay length is pretty much a set it once and forget it. Dial it in for a nice neutral helm. Once it's right, you really don't need to mess with it.

Some say you need lots of main cunningham downwind, I'm not overly sold on that for speed, but as a "keep the rig in the boat" safety factor, probably a fine idea.

Downwind, sail to heel angle, keeping the boat on its feet. Heating it up too much doesn't really help, as you don't gain too much more speed. Once you get up to around 25 knots, you probably do want all 3 crew on the weather rail. Below 20, one will sit all the way forward and to leeward on the cockpit floor.
Race it like you stole it.

Drew Harper

Thanks Much Dan. Very helpful to have the Loos numbers.

Sounds like the lowers run pretty loose. Not too much rig pump in the heavies with it running without much tension?

Also, I sailed "K's" boat at Lake Norman in light air and noticed a strange lee helm tendency when the boat was flat. Is this normal or just not enough rake?

Anyone going to write the tuning guide for the Viper? Sounds like you're a good candidate :-)   (like you don't have enough on your plate already)



#189 UK Built Mark IV Viper "DILLIGAF"

Dan Tucker

Probably not quite enough rake on Kay's boat if it had lee helm in light stuff. Lengthen the forestay a couple of turns. Keep adjusting till it feels right. The Viper should have a sweet neutral helm.

Paul Young & Hyde Sail's rig tuning philosophy is a dynamic rig. Not so much "pump" in waves as an auto depower in puffs from the flexibility of the carbon rig. They like much looser lowers. I'm not sure too many people REALLY have a great grip on the trade offs and subtleties.

I'm not nowhere smart 'nuff to write a tuning guide. I'm still wrapping my head around how the carbon rig responds, as I started sailing the boat with the aluminum rig, which was a bit different. We tanked in the '08 NA's because I had the rig all wrong for light air, so no boatspeed on Day 1. According to Brian, there is a condition where chocking forward of the mast is fast, I haven't got that down. In light air, chocking is BAD! Learned that lesson the hard way.

Fundamentally though, there are three upwind modes:
1. Underpowered => Fully powered, Full Hike 
2. Full Hike and depowering with rig tune.
3. Rig tune maxed, vang sheeting.

Crossover points are very dependent on crew weight. With me 30# overweight (goal to loose that for Charleston!), our crew weight is ~570. We're in mode #1 to ~ 12-14 knots, mode #2 to ~20-22 knots, mode #3 ~ 22+ knots. Once you're pushing 30+ knots, I'm happiest in Bar mode! Unless the water temp is mid 70's  ;)
Race it like you stole it.

Drew Harper

I've got flyweights for crew. We're going to tip in at 140, 135 and 215 for a total of 490. I think we'll be fine though as I'm 6'3" and can hike hard and long (too much laser/finn sailing). I've got my crew on a steady regime of crunches and situps :-)....they hate me.

The mast on the Viper is pretty whippy...I think 72mm tubes which is small for a 21' foot boat. I'm just going to have to get used to it bending out of column I guess. My U24 has 82mm tubes PLUS a rig tensioner so I can firm it up hard.

My biggest concern is wave stuff decceleration issues. We'll often get planing then stuff into the back of a big one and damn near stop. Loose lowers trouble me in that scenario.

Ok, do me a favor.

Toss me your best guess on tuning up Hull 72 for the Leukemia Cup this coming weekend in AZ. I've got Dennis' boat chartered and I hate to COMPLETELY suck.

I'll work hard on the headstay length. Suggestions?

Thanks again for all your help.

Really a GREAT class here!
#189 UK Built Mark IV Viper "DILLIGAF"

Greg Jackson

Quote from: BoomSlang on January 12, 2009, 09:29:30 PM
I've got flyweights for crew. We're going to tip in at 140, 135 and 215 for a total of 490. I think we'll be fine though as I'm 6'3" and can hike hard and long (too much laser/finn sailing). I've got my crew on a steady regime of crunches and situps :-)....they hate me.

The mast on the Viper is pretty whippy...I think 72mm tubes which is small for a 21' foot boat. I'm just going to have to get used to it bending out of column I guess. My U24 has 82mm tubes PLUS a rig tensioner so I can firm it up hard.

My biggest concern is wave stuff decceleration issues. We'll often get planing then stuff into the back of a big one and damn near stop. Loose lowers trouble me in that scenario.

Ok, do me a favor.

Toss me your best guess on tuning up Hull 72 for the Leukemia Cup this coming weekend in AZ. I've got Dennis' boat chartered and I hate to COMPLETELY suck.

I'll work hard on the headstay length. Suggestions?

Thanks again for all your help.

Really a GREAT class here!

I'll tell ya after the regatta!

Seriously, when Paul (Rondar) was out here to retrofit the masts on the old boats, he said 4" of prebend and chock the front of the mast... no matter what. I'm still very close to doing that, but what do I know... On the new boats, check the length of the forestay and the upper and lower hal's to make sure they are the correct length.

It looks like it is going to be light (0-2' chop, if that.  And 7-11 wind) so you will want to loosen the rig a bit and dump some of your (personal) weight. We have 102, 160 and 175 for 437...

The biggest thing is to guess the wind. It's a bitch, unless it is a steady 15 or higher. The all you have to to is play the gusts.

When will you be out? I'm gonna try to be there around two on Friday... I'll seriously talk to you then!

USA 46
heroin

Greg Jackson

I forgot to add to make sure you bring foulies... this year it's going to be cold. 45 over-night and 70 something during the day on Saturday, then around 45 when we get on the course on Sunday (back to 70 when we are done).

Last year was even worse. 70 during the day with 25 average wind... too bad one of my keel bolts didn't take the accidental break from the keel halyard that been installed with the new mast...

Six out of eight boats within 600 miles committed. Two to more to go... do it!

Drew Harper

102?  Sheesh, you packin' Elves as crew? Hmmmm....I better read the class rules about foreign species.

Man is my crew going to be pissed. My bowgirl is shedding weight for the Australian M24 Nationals and I told her she'd have to bulk up for the Viper in the Bay. Me thinks she'd rather be bulking than starving.

Probably best if I don't sail this weekend as I'm the biggy of the team. Are radio controlled helms legal in the Viper class :-))

Thanks for the tips. Do you have the correct measurements for headstay, 1's and 2's?

I haven't sailed LP since I was a kid...um....er....a COUPLE of years ago (pre new dam) It'll be interesting to see how the shifts have changed.

We're rolling in Friday at about 2 am...a couple of hours of zzzzz's then off the gather up #72, rig and sail our brains out to develop some numbers and feel before Sat.

Thanks for the heads up on the foulies. I was going to wear my shorts...damn, guess I shouldn't complain. It IS middle January.





#189 UK Built Mark IV Viper "DILLIGAF"

Brian Bennett

Here are the designers perspectives/ thoughts (at present) on the subject of tune/ set up:

1. The tuning ranges vary based on crew weight. The boat is designed for 560 # crew weight. The competitive weight range is 520 - 580 #. A light crew will excel in light air. Weight (over 600 #) is a disadvantage downwind and only an advantage upwind "breeze on" conditions.
2. Headstay should be set with 1" tread showing on the Ronstan turnbuckle. This will give you the appropriate helm feel.
3. The optimum heel angle for the Viper is 5 degrees. This is true on all points of sail. This is min wetted surface and optimal lines projection along with max waterline length. This is very important to remember. Simply put the Viper will always sail best upwind and downwind at his angle (from a hydrostatics perspective anyway)

4. 4 tuning ranges. This based on 560# crew. The tuning bands move up or down in wind speed based on crew weight and hiking effort / driver skill.

Range 1: O - 5 knots. Uppers at 200lbs. Lowers should be completely slack. You should be able to 8" circles with the slack! The mast should be chocked or purchased forward at the deck. This softens the headstay and prebends the rig to keep the mainsail flat without using undue sheet tension. The amount of chocking will depend on the amount of luff curve in the mainsail. A flatter luff curve will require less early prebend. The critical thing is that the headstay stays soft and provides more power to the jib for this condition.
Jib leads tend forward with optional weather sheeting depending on conditions/ wind sheer present.

Range 2: 6 - 11 knots (or fully hiked). Uppers at 320 #. Slack lowers. Remove all chocks. In this mode you will get to full power where max mainsheet tension can be used as you go up range.
In this range, a lighter crew will get to full power sooner than a heavy crew, and will have to go to Range 3 sooner. A heavier crew will hold on to this range longer, and will probably be fast in 12 knots over a light crew due to the fact that you can hold main leech tension longer.
Jib leads moderate (even telltale break). Sheet tension should be adjusted in the 1-2" range according to mode. At max mainsheet you are tensioning the headstay through mainsheet.

Range 3: 12 - 18 knots (full power) Uppers at 380. Lowers now come on to "check" the mast bend (according to main luff curve) this will vary depending on sailmaker. The lower tension should never exceed the upper tension, as the rig is designed for 4" of prebend. This is desireable and provides safe downwind rig geometry.
Chocks and/ or preventer in front of mast, which in situ with lowers will counteract the headstay and begin to provide critical headstay tension. As the breeze builds this is the governing factor in a fast and controlled rig geometry. (similar theory to all single swept spreader rigs).
Jib leads back 1 hole. Ease jib 1" in puffs.
Jib halyard on to remove any softness between tabs.
Main cunningham on up range.
Vang/ GNAV. on up range. This dependant on need to depower. The Vang is a depowering tool intended to be used in conjuction with mainsail ease.
Ease vang a little downwind to allow for safe Jybes.

Range 4: 18 + (over to severe over power). Uppers at 450. + 1 1/2 turns on the lowers. Max chock in front of mast (but still maintaining positive prebend).
You will be vang/ GNAV sheeting predominantly at this point. My rule of thumb is that you should start to ease the main once the vang has taken over as primary control tool. The more the breeze is on the more that vang is the go fast tool upwind. Remember though that an over  eased main will NOT help you to go upwind.
Jib leads back 1-2 holes. Ease jib in the puffs.
Driver should keep the boat feathered and flat (5-10 deg). Excessive heal is slow.
Again ease vang downwind. Too much mainsail leech tension through the vang can "bind" you in a Jybe. You want to make sure your jybes are free,  "carved", and concise, especially in big breeze.

Will add more shortly.

Brian


Drew Harper

#189 UK Built Mark IV Viper "DILLIGAF"

Dan Tucker

Brian,

Hugely helpful!

My question is on chocking in #3 & #4 -what are you looking at to determine the amount of chocking? i.e. how much is the right amount? And how do you tell?
Race it like you stole it.

Brian Bennett

My observations from sailing boats like Etchells indicate that chocking at the mast gate or mast partners is critical to headstay tension. On the Viper there is only limited mechanical advantage due to the fact that the distance from gate to step is short. While chocking is an effective tool (on the V), it is not as effective as some other boats with a deeper bury. (the distance from deck to mast heel).
Remember too that once you transition to Vang/GNAV sheeting, mainsheet tension is reduced as an option to keep the headstay tight. (In all boats with backstays this is not a problem) This is also the reason that a heavier crew will be faster in the upper range 2 to lower range 3 upwind condition. Carrying mainsheet tension is the primary instrument to point/ height mode sailing. Vang sheeting does diminish this slightly, but when sailing uprange, rig balance and control is more important.

The key is to to have the appropriate mast bend for the luff curve in your mainsail. In range 4, your main will backwind and invert if A) the sail is too deep or B) the jib sheeting is too tight or not allowing enough openness or twist (Jib leads aft, and sheet eased).

At present there is are some differences in philosophy regards sail shapes. I suspect that these will come together over the next few seasons, and the 8" luff curve that Hydes use will moderate to around 5-6". Norths are there now.

Paul Y.  and I marginally disagree on some areas of rig philosophy. He favors the auto rig (minimal control) method, which I think works well in Range 2. I favor a controlled rig philosophy, which is more sophisticated, and will be required to really get the best performance through the practical sailing range.

Fundamentally you should chock the mast aft in stages from Range 2-3+ and forward in lower Range 2 - 1. The rig needs to me moded for the conditions, and all available instruments used. The V is not unusual in this respect.

A full designers tuning guide will be forthcoming along with the new Mk 3 boats.

Brian


Jay Harrell

Quote from: chris_76 on January 14, 2009, 01:13:19 PM
Mk 3 boats ?????

As they build new boats, Paul and Brian continue to note mostly minor process improvements to help them get the job done faster and better.  They have also built some new molds - to same class specs of course, but there are some minor changes in the deck mold for example, once again designed to improve the build process.  Mk 3 refers to the third generation of this process improvement cycle.

Felipe Payet

Wow, what a fantastic thread.  Thanks, Brian (and all)!

And BoomSlang, you may be brand new to the class, but you're already bringing huge value by having been the catalyst for this discussion.

Have fun in AZ, and good luck building the west coast Viper presence!

Cheers,
F.