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AC tech

Posted By: pgp

AC tech - 02/14/10 06:51 PM

During race 2, I heard Smyth say an asymmetric spin would slow the boats down too much. He was also very strongly in favor of bannana boards.
Posted By: scooby_simon

Re: AC tech - 02/14/10 10:09 PM

They are travelling so fast in just 8 kts that the angle of attack of the "jib" is such that you could not fly an Asym.
Posted By: pgp

Re: AC tech - 02/14/10 10:25 PM

Is that primarily a function of the waterline length?
Posted By: ncik

Re: AC tech - 02/15/10 04:42 AM

more a function of power to weight at this size/speed, they are most certainly going faster than "hullspeed" at which point waterline length is the predominant factor.

the length of these beasts is really just to keep it under control in pitch. too much length will just add skin friction drag. if they were racing in perfect conditions with no waves or gusts, the hull lengths could be reduced substantially and the speeds would probably increase.

it'll be interesting to see if a beach cat can make the "Y" form of alinghi's support system work. smaller beams and less twist...
Posted By: scooby_simon

Re: AC tech - 02/15/10 10:56 AM

Originally Posted by ncik
more a function of power to weight at this size/speed, they are most certainly going faster than "hullspeed" at which point waterline length is the predominant factor.

the length of these beasts is really just to keep it under control in pitch. too much length will just add skin friction drag. if they were racing in perfect conditions with no waves or gusts, the hull lengths could be reduced substantially and the speeds would probably increase.

it'll be interesting to see if a beach cat can make the "Y" form of alinghi's support system work. smaller beams and less twist...
]

I'd suggest for proper beach cats no; as we need to come in of the wire and scamper accross; thus we need am uncluttered tramp.

Bigger boats that you "walk over" instaed of sliding; then maybe....
Posted By: waynemarlow

Re: AC tech - 02/15/10 11:50 AM

Originally Posted by ncik

it'll be interesting to see if a beach cat can make the "Y" form of alinghi's support system work. smaller beams and less twist...


I did spend a lot of time trying to integrate this into Bitsa when I built it, slung under the tramp it has a lot of benefits such all the loading of the downward pressure of the mast can be absorbed by the beam, integrating the spinnaker snuffer into the beam cuts down on wind drag, a direct fixing for the front stay means much better jib control, the list goes on and on of benefits.

What I couldn't find was someone who would calculate the loadings and transfer that into carbon fibre layup for not a lot of money, any of the companies recommended by the composite suppliers thought it was for an AC style boat and were wanting to charge accordingly. I had quotes just for calculating the layup ranging from 1000's to 10s of 1000's. At that point I wimped out and built the boat as I did with a sort of central beam type arrrangement. frown

So any body out there wanting to do a quick calculation for me then please PM, I would still like to build it and have the moulds sitting waiting to go.
Posted By: pepin

Re: AC tech - 02/15/10 12:11 PM

Originally Posted by ncik
it'll be interesting to see if a beach cat can make the "Y" form of alinghi's support system work. smaller beams and less twist...
Maybe a good idea but I could do without the dolphin striker hitting the waves when not flying a hull....
Posted By: pgp

Re: AC tech - 02/15/10 12:53 PM

So how much of this relates to us directly? Will we have a 30 knot F16 in the future?
Posted By: Timbo

Re: AC tech - 02/15/10 02:24 PM

Only if we increase the waterline lenght to about...90 feet!

OR...drive it off a cliff!
Posted By: DanTnz

Re: AC tech - 02/15/10 02:45 PM

....and change the box rule to allow hard wings and curved foils.
Posted By: DanTnz

Re: AC tech - 02/15/10 02:48 PM

Originally Posted by pepin
Originally Posted by ncik
it'll be interesting to see if a beach cat can make the "Y" form of alinghi's support system work. smaller beams and less twist...
Maybe a good idea but I could do without the dolphin striker hitting the waves when not flying a hull....


Could solve that problem by increasing the size of the centre pole and giving it a smooth hydrodynamic profile.....sort of like a third hull!
Posted By: Stewart

Re: AC tech - 02/15/10 04:21 PM

look at the sys F16!
has the system in place..
Posted By: DanTnz

Re: AC tech - 02/15/10 04:59 PM

That design has something that is more akin to a bridle foil - the forestay and spin loads are still transfered to the hulls.

Although it has the advantage of acting more like a forward beam and therefore adding stiffness to the platform.

Originally Posted by Stewart
look at the sys F16!
has the system in place..
Posted By: ncik

Re: AC tech - 02/16/10 01:53 AM

sys F16? link?

Posted By: _flatlander_

Re: AC tech - 02/16/10 03:37 AM

Originally Posted by ncik
sys F16? link?


wingnuts!
syasperformance
Posted By: Smiths_Cat

Re: AC tech - 02/16/10 03:10 PM

Originally Posted by ncik
more a function of power to weight at this size/speed, they are most certainly going faster than "hullspeed" at which point waterline length is the predominant factor.

the length of these beasts is really just to keep it under control in pitch. too much length will just add skin friction drag. if they were racing in perfect conditions with no waves or gusts, the hull lengths could be reduced substantially and the speeds would probably increase.

it'll be interesting to see if a beach cat can make the "Y" form of alinghi's support system work. smaller beams and less twist...

Critical boat speed is ~1.5 squareroot (lwl in ft) in kts
Surprise, surprise: it is 15kts for 90ft lwl, the speed which the boats had on the upwind leg, so wave drag is about 20% and hence length is of importance. If it is true that BMWO was 130ft long and Alinghi only 100ft, than the wonder wing looks not that good anymore...

Cheers,

Klaus
Posted By: DanTnz

Re: AC tech - 02/16/10 03:40 PM

Originally Posted by Smiths_Cat
Originally Posted by ncik
more a function of power to weight at this size/speed, they are most certainly going faster than "hullspeed" at which point waterline length is the predominant factor.


the length of these beasts is really just to keep it under control in pitch. too much length will just add skin friction drag. if they were racing in perfect conditions with no waves or gusts, the hull lengths could be reduced substantially and the speeds would probably increase.

it'll be interesting to see if a beach cat can make the "Y" form of alinghi's support system work. smaller beams and less twist...

Critical boat speed is ~1.5 squareroot (lwl in ft) in kts
Surprise, surprise: it is 15kts for 90ft lwl, the speed which the boats had on the upwind leg, so wave drag is about 20% and hence length is of importance. If it is true that BMWO was 130ft long and Alinghi only 100ft, than the wonder wing looks not that good anymore...

Cheers,

Klaus


Klaus, isn't that formula pretty much only applicable to traditional displacement monohulls? I think as soon as you get narrow hull forms there are more variables involved, it's beyond me but there's a lot of good links in this post:

Catamaran Hull Speed

I'd be interested to see if you could work out a similar multihull formula smirk
Posted By: scooby_simon

Re: AC tech - 02/16/10 03:42 PM

Originally Posted by DanTnz
Originally Posted by Smiths_Cat
Originally Posted by ncik
more a function of power to weight at this size/speed, they are most certainly going faster than "hullspeed" at which point waterline length is the predominant factor.


the length of these beasts is really just to keep it under control in pitch. too much length will just add skin friction drag. if they were racing in perfect conditions with no waves or gusts, the hull lengths could be reduced substantially and the speeds would probably increase.

it'll be interesting to see if a beach cat can make the "Y" form of alinghi's support system work. smaller beams and less twist...

Critical boat speed is ~1.5 squareroot (lwl in ft) in kts
Surprise, surprise: it is 15kts for 90ft lwl, the speed which the boats had on the upwind leg, so wave drag is about 20% and hence length is of importance. If it is true that BMWO was 130ft long and Alinghi only 100ft, than the wonder wing looks not that good anymore...

Cheers,

Klaus


Klaus, isn't that formula pretty much only applicable to traditional displacement monohulls? I think as soon as you get narrow hull forms there are more variables involved, it's beyond me but there's a lot of good links in this post:

Catamaran Hull Speed

I'd be interested to see if you could work out a similar multihull formula smirk


Correct; Long thin hulls do not obey the same rules. How else would I be able to sail MY F16 at 13kts upwind? (when I get it right!!)
Posted By: Smiths_Cat

Re: AC tech - 02/16/10 05:25 PM

Quote
Long thin hulls do not obey the same rules

But how does water know, that the hulls are thin? confused

Quote
I'd be interested to see if you could work out a similar multihull formula

Michell found the formula to calculate wavedrag, with todays computer we can calculate the drag of a boat hull by ourself.
Here are the plots of absolute hull drag [img]http://www.catsailor.com/gallery/displayimage.php?album=lastupby&cat=0&pos=5[/img]
and in the second picture you see the wave drag contribution to total drag. You can sclae up the speeds with sqrt(LWL), if the boat is four times longer you have to read the value at two times higher speeds. The speed is in m/s with 1 m/s = 2kts.
In short words: Length is important (again), but not as important on heavy and slow monons, because wave drag scales with the finess of the hulls.

Cheers,

Klaus
Posted By: Smiths_Cat

Re: AC tech - 02/16/10 05:26 PM

ok, I am good in fluid dynamics, but bad in adding pictures here...
Posted By: Smiths_Cat

Re: AC tech - 02/16/10 05:27 PM

2nd attempt

Attached picture abs_catamaran_drag.jpg
Attached picture normal_catamaran_drag.jpg
Posted By: ncik

Re: AC tech - 02/18/10 01:30 AM

they were doing about 18-22 knots upwind and waterline length was between 110-130 feet. 1.34 * sqrt(110) = 14.1 knots. so like I said, beyond "hullspeed", ie. most definitely going faster than a wave of the same length as their hull. at some point, adding length for a given power will just add drag through skin friction.

Michell's slender body method works well for slender hulls, but these beasts may be out of the traditional bounds of applicability for the maths. even moths fall outside the range. ie. they are too narrow for what has been verified with this method. not to say it isn't accurate, just that it hasn't been tested and proven to be accurate. although that could've changed since I last read up on it.

sys F16 doesn't appear to have a bridle network with diagonal beams under the tramp, infact they say it is striker-less.
Posted By: Stewart

Re: AC tech - 02/18/10 07:06 AM

yes sys doesnt have a system under the beams al la Alinghi.. But the kite tube and pole is the system it appears..

Posted By: pgp

Re: AC tech - 02/18/10 02:30 PM

I came into the class after the bannana board debate. Anyone care to offer a synopsis? I don't want to reopen the debate, just trying to understand the rationale.
Posted By: Stewart

Re: AC tech - 02/18/10 05:04 PM

*bites my tongue* cry
Posted By: Kris Hathaway

Re: AC tech - 02/18/10 05:16 PM

Originally Posted by pgp
.... just trying to understand the rationale.

That they are not allowed or theory behind their function?
Posted By: pgp

Re: AC tech - 02/18/10 05:27 PM

Both if we can do it without burning our house down. But, judging from Stewart's reaction, I'm almost afraid to ask.
Posted By: Anonymous

Re: AC tech - 02/18/10 08:12 PM

Insure your house then ask again at the closed forums.
Posted By: Jalani

Re: AC tech - 02/18/10 09:03 PM

Why be scared of discussing legitimate issues????

My PERSONAL 2 cents worth:

Bananaboards would be a very interesting development on an F16. This would be especially true if coupled with T or L foil rudders. Apart from not being allowed under the rules, the time is probably not right for such a development since the class would, in all likelihood, implode if a bannanaboard boat proved ultra fast or ultra competitive. I firmly believe there is a bright future for innovation, development and experimentation within the rules as they currently stand - without introducing a potentially expensive and damaging (in class growth terms) complication such as bananaboards.

I'd love to see the rules opened up in the future to permit experimentation with curved boards (and other freedoms) but I'm talking at least 5 years or even 10 years on.

Of course, outside of class racing or the F16 banner there's nothing to stop people experimenting - but to protect the growth of the class by providing some stability, bananaboards must of necessity be banned.

Don't forget, the current ban was the result of a class wide ballot back in 2007 before the current rules were finalised.

Once again, this is my personal view, it's perfectly possible that the F16 Governing Council may decide in the future to ballot for such developments to be permitted during one of the constitutionally permitted 5 year reviews of the rules.
Posted By: Kris Hathaway

Re: AC tech - 02/18/10 09:06 PM

Hold on. It's straight forward! At least in a layman's view and should not require any flame suits.

F16 is not an "arms race" class but yet is not a "stagnant" class either. Curved boards are still the extreme and cutting edge for beachcats. You will have an extreme gap of the "Have" and "Have Nots". Incremental changes within the box rule are OK; ie. moving back the forward beam and moving foward & lower volume. Or main sail cut.

According to the commentary on ESPN360, the concept of curved boards have been around for a while. Their function is to lift hulls. For example; A-Cats are carrying less volume/ft than the F16s (especially the newer F16s) and are more true to the wave piercing concept. They are more likely to benefit from curved boards. Whereas, the Viper and Falcons are proving to hydroplane very quickly "as is" and anymore lift may make them less stable at speed, especially with a shorter LWL.

The F16 box rule does have a compromise? It allows for a nominal amount of fixed cant in the dagger well?
Posted By: macca

Re: AC tech - 02/18/10 09:51 PM

I would think that the difference in cost to build a boat with curved rather than straight boards would be less than the increase in cost to build it with carbon beams, mast and hulls as the current class rules allow...

Posted By: Karl_Brogger

Re: AC tech - 02/18/10 10:59 PM

I was just thinking that storing curved daggerboards would be a pain in the rear.

But man are they cool looking. Performance enhancing or not, I don't care. To me they're like boobs. They could be totally useless, (minus the nursing), but I love them.
Posted By: scooby_simon

Re: AC tech - 02/19/10 10:37 AM

Originally Posted by macca
I would think that the difference in cost to build a boat with curved rather than straight boards would be less than the increase in cost to build it with carbon beams, mast and hulls as the current class rules allow...



Carbon is cheaper than Alu extrusions in some parts of the world.
Posted By: Jalani

Re: AC tech - 02/19/10 01:18 PM

The point is though Andrew that switching to carbon extrusions won't give any major change in performance whereas a change of foil format could (possibly a vast change). As Kris has pointed out this would create the 'haves' and the 'have nots' and that is NOT GOOD.

Having some all or part carbon boats might make a slight difference but is unlikely to create an arms race as the greatest variable and effect on performance will still be the sailor on the tiller.
Posted By: macca

Re: AC tech - 02/19/10 01:35 PM

Originally Posted by scooby_simon
Originally Posted by macca
I would think that the difference in cost to build a boat with curved rather than straight boards would be less than the increase in cost to build it with carbon beams, mast and hulls as the current class rules allow...



Carbon is cheaper than Alu extrusions in some parts of the world.


Can you give me the contact details? I would love to get a couple of hundred carbon beams made up...

Posted By: scooby_simon

Re: AC tech - 02/19/10 02:28 PM

Originally Posted by macca
Originally Posted by scooby_simon
Originally Posted by macca
I would think that the difference in cost to build a boat with curved rather than straight boards would be less than the increase in cost to build it with carbon beams, mast and hulls as the current class rules allow...



Carbon is cheaper than Alu extrusions in some parts of the world.


Can you give me the contact details? I would love to get a couple of hundred carbon beams made up...



Talk to Rolf; he is making Carbon beams becasue they are cheaper than buying in alu extrusions and fitting them out in Norway.
Posted By: Wouter

Re: AC tech - 02/19/10 02:29 PM



Quote

Can you give me the contact details? I would love to get a couple of hundred carbon beams made up...



This situation only arises in places where the metal-guy charges astronomical prices to import a very small number of simple alu extrusions and the buyer himself is able to produce his own carbon beams (negating labour costs).

I have never seen a situation where the production of commerically available carbon beams is cheaper or even just as expensive as extrusion of high grade alu beams. In fact I don't believe we will ever see that happen at all, especially not when ordering more then 50 sets in one go (500 kg combined).

For those production batches, extruded alu beams of the 6005 T5 variant are incredibally cheap. The same applies to alu masts.

I'm not allowed to say how cheap exactly but trust me on this, carbon will never win over alu in that area. And I'm not talking about alu being cheaper by factor of 2, 3, 4, 5, ..., ..., ... either.

It is just one of those freak occurences when you live in some far of place without a sizeable industrial base of along an international shipping route.

Wouter

Posted By: Anonymous

Re: AC tech - 02/19/10 11:28 PM

[quote=Wouter]
I'm not allowed to say how cheap exactly but trust me on this, ....quote]

I can... 500kg of extrusions should cost about AUS$3500-4000 or $70-80 per boat (assuming Wouter's 50). You'll pay a premium beyond that depending on the tolerances you demand. The premium is based upon wastage and also how often the die will need to be replaced.
Posted By: Wouter

Re: AC tech - 02/20/10 08:02 AM

Quote

$70-80 per boat (assuming Wouter's 50).


Anyone want to source a PAIR of carbon beams for that price ? grin

Wouter
Posted By: macca

Re: AC tech - 02/20/10 09:27 AM

I wonder why Rolf didn't just order a set of beams from a current manufacturer....

Posted By: DanTnz

Re: AC tech - 02/20/10 10:34 AM

Hobie seem to be the only manufacturer that prices it's parts list online Europe (in english!) the cost for a Tiger front crossbeam is over £1000, that's probably the complete assembly but then even the tiller crossbar is £200.

edit: Hobie UK Parts

I have seen N6.0 beams being advertised second hand at about £200 each from when I was looking for some for mine. But then we are comparing new for new here.
Posted By: DanTnz

Re: AC tech - 02/20/10 10:39 AM

Another one by way of comparison only (i.e. not up to spec for an F16) Dart 16 main beam is £225.

Dart 16 Parts
Posted By: scooby_simon

Re: AC tech - 02/20/10 11:13 AM

Originally Posted by macca
I wonder why Rolf didn't just order a set of beams from a current manufacturer....



Because they were more expensive than he could make them out of Carbon! Simples.
Posted By: Smiths_Cat

Re: AC tech - 02/20/10 11:37 AM

I once asked for a custom shaped alu extrusion (rudder foil). The simple answer from a well known rigging supplier was: "You wan't pay it. Make it form glass or carbon fibres."
It works fine for standard shapes like tubes. We got 4m spin pole from 40mm alu for 150€ or so.

By the way, if you are close to a company working with CFRP, you may ask for cutting scrap (or however it is called in english) or expired prepregs. Sometimes you get it for free.

Cheers,

Klaus
Posted By: macca

Re: AC tech - 02/20/10 11:56 AM

Originally Posted by scooby_simon
Originally Posted by macca
I wonder why Rolf didn't just order a set of beams from a current manufacturer....



Because they were more expensive than he could make them out of Carbon! Simples.


A beam extrusion, even from one of the big manufacturers (at full retail) will still be a lot less than someone could build one in carbon.

I understand the challenge in building your own beams in carbon, but to try and justify that its cheaper than an alloy beam is just not reasonable.

Posted By: waynemarlow

Re: AC tech - 02/20/10 01:46 PM

For reference on beams try

http://www.aluminiumwarehouse.co.uk/index.html gobsmackingly cheap tube and it is delivered the next day.

and for carbon tubes try http://carbonfibretubes.co.uk/ some of the big boat spinnaker poles are just the right size for us and its surprising the low cost on smaller tubes for tiller sticks etc, talk to them they always seem to have a bit laying around from a production run somewhere.

Why didn't I use carbon beams on Bitsa? Carbon is a great product for tensile strength, it is terribly weak and much inferior to aluminim if hit with something sharp or given the usual sailing abuse. To protect it you must use a reinforcing glass or kevlar outer layer which brings the weight right up to that of similar Aluminium tube. Aluminium is a great product, it just doesn't have the kudos of carbon fibre.
Posted By: Smiths_Cat

Re: AC tech - 02/20/10 02:13 PM

it is as with girls. We looks always for the bling bling, never for character.

But back to the original question: Are canted riggs class legal?
Posted By: Jalani

Re: AC tech - 02/20/10 04:47 PM

If you want to start a race with the rig canted permanently on one tack then - yes! laugh

Class rules state:

1.7.1 It is not permitted to adjust the following items while racing: the rake of the mast, the tension of the standing rigging, the angle or length of the spreaders or the position and height of the gennaker boom.

1.7.2 It is permitted to adjust the diamond wire tension while racing or to adjust the items named under 1.7.1 between the races.
Posted By: macca

Re: AC tech - 02/20/10 05:24 PM

With that rule, its easy to change the rig canting. You just have to think about it a little...
Posted By: Stewart

Re: AC tech - 02/20/10 07:36 PM

you forget about the spirit of the rules..
Posted By: macca

Re: AC tech - 02/21/10 07:10 AM

Ahh, yes the "spirit" clause.... the get out of jail free card..



Posted By: Stewart

Re: AC tech - 02/21/10 09:33 AM

suck it up mate..
Posted By: pepin

Re: AC tech - 02/21/10 04:52 PM

Originally Posted by Jalani
If you want to start a race with the rig canted permanently on one tack then - yes! laugh

Class rules state:

1.7.1 It is not permitted to adjust the following items while racing: the rake of the mast, the tension of the standing rigging, the angle or length of the spreaders or the position and height of the gennaker boom.

1.7.2 It is permitted to adjust the diamond wire tension while racing or to adjust the items named under 1.7.1 between the races.
For once I agree with Macca (I feel dirty smile. I don't see anything there preventing canting. You can't change the amount of tension, but nothing prevents you moving the mast side to side without changing the tension.

And sometimes those rules are weird: Pulling the jib halyard pulls the mast forward. Does this mean I can't adjust the jib tension on the water as it changes the mast rake? What about when I'm solo without a jib up? The halyard on my boat is still there, can I tension it?
Posted By: geert

Re: AC tech - 02/21/10 07:50 PM

What am I missing? don't see a problem in this rule.

If you move the mast top by manipulating the stays or whatever, you ARE raking the mast in a direction. And that is not allowed.
And putting the mast foot on a rail won't help either.

Am still with John Here.

Geert
Posted By: macca

Re: AC tech - 02/21/10 08:35 PM

Nope, thats why we call fore and aft changes "rake" and sideways changes are "canting"

and by having a closed loop system you can change the mast cant without altering mast rake or rig tension.
Posted By: Darryn

Re: AC tech - 02/21/10 10:39 PM

Originally Posted by DanTnz
Another one by way of comparison only (i.e. not up to spec for an F16) Dart 16 main beam is £225.

Dart 16 Parts

Mosquito main beam or rear beam $45AUD or 27GBP.

cheers,
Darryn
Mozzy
1782
Posted By: Aido

Re: AC tech - 02/21/10 10:45 PM

Arrow cat aluminium mast section is $70au. I like to see you buy the carbon cloth for double that price.

Does seem that canting rigs would be ok under the rules. You could even use a canting system to help right the boat. Light crews would not need a righting pole or bag.
Posted By: Darryn

Re: AC tech - 02/22/10 12:01 AM

Originally Posted by macca
Nope, thats why we call fore and aft changes "rake" and sideways changes are "canting"

and by having a closed loop system you can change the mast cant without altering mast rake or rig tension.

If the forestay remains the same length and one side stay is lengthened with the other shortened wont that reduce the mast rake slightly?

Darryn
Posted By: ncik

Re: AC tech - 02/22/10 12:28 AM

I believe delivery costs for a full aluminium extrusion vs a roll of carbon cloth distorts the price for some ppl in certain out-of-the-way locations to the point that homebuilding in carbon becomes the cheapest option. That is the argument being put forward. Ignoring this aspect will certainly put aluminium extrusions ahead of carbon in price, but it isn't always that simple.

My personal experience was trying to buy a replacement mosquito mast a few years ago. If I lived near the major fleet it was a cheap exercise to just drop by the class stores and drive away with it for something like $300. I could not get one of these shipped to Brisbane, issues with length and fragility. So instead I had to search for alternatives locally and found a windrush mast supplier (which turns out to be very similar, it not the same), but the cost was near $700. At this price, it was nearly worthwhile building my own carbon mast, with easy availability of materials and my own labour. Maybe I didn't look hard enough for a viable transportation option.

But back to the topic. Where can I get some of that shark skin film?
Posted By: ncik

Re: AC tech - 02/22/10 12:34 AM

Originally Posted by Darryn

If the forestay remains the same length and one side stay is lengthened with the other shortened wont that reduce the mast rake slightly?

Darryn


yep, if the forestay to bridle connection is above the mast base relative to the platform.

if they are at same height then rake will not change. the canting rotation occurs around a line from mast base to bridle (imagine a triangle being rotated about one of it's sides)

this is if you measure rake from mast top to rear beam on centreline.
Posted By: Aido

Re: AC tech - 02/22/10 02:24 AM

3M do the shark film I think. Not as simple as slapping it on as it has to be made to suit the speed and length of you boat. An expensive exercise. Not sure that it's legal in any dinghy or cat classes either. I know polymer is definitely banned.

You would have to have some serious skills to attempt carbon beams and masts. And when time is factored into the equation the price becomes outrageous.
Posted By: ACE11

Re: AC tech - 02/22/10 03:08 AM

Slight correction here Aido - the Arrow mast comes delivered to Brisvegas for $70 + a carton of Coronas for freight.
Posted By: waynemarlow

Re: AC tech - 02/22/10 11:21 AM

Originally Posted by ncik
Originally Posted by Darryn

If the forestay remains the same length and one side stay is lengthened with the other shortened wont that reduce the mast rake slightly?

Darryn


yep, if the forestay to bridle connection is above the mast base relative to the platform.

if they are at same height then rake will not change. the canting rotation occurs around a line from mast base to bridle (imagine a triangle being rotated about one of it's sides)

this is if you measure rake from mast top to rear beam on centreline.


Its irrevelent at what height the front stay joins the front bridle, as long as the front stay base remains on the centre line, as soon as there is any rotation of the top point an arc will form however small ( basically the radius of the distance between top point and bottom point looking straight down ), causing the mast rake to change.

I personally would favour a change in the rule to allow mast rake, it would on long distance racing help reduce an over powered rig. After all we are a semi develpment class, whats the problem.

However from other class's which have gone down this route, around short form racing, the time lost to set up the canted rig far out ways just sailing the boat and keeping in front in clean air.

Any way Macca is bored and just raising pedantic points of no real worth to the class to basically wind people up. When Macca designs, builds and races a boat within the class then I think we should start to take more notice of his internet scribblings. Up until that point he is just another interested internet scribe in my view and his views are just that, internet musings.
Posted By: ncik

Re: AC tech - 02/22/10 11:58 AM

Bridle height does influence change in rake with cant...see image.

Other than that, I agree with your sentiments about macca.


Attached picture cant to rake with bridle height.jpg
Posted By: pgp

Re: AC tech - 02/22/10 12:30 PM

F.5.1 RULES
(a) The bowsprit shall be on the longitudinal centreline of the boat

"THESE RULES ARE CLOSED CLASS RULES
WHEREBY IF IT DOES NOT SPECIFICALLY SAY THAT YOU MAY – THEN YOU SHALL NOT."

http://www.formula16.net/forum/showthread.php?t=163

There is an amended version in the works.

Posted By: macca

Re: AC tech - 02/22/10 01:30 PM

Event though I have paid my membership fee, I am still unable to log into the F16 forum thingy, so I can't download the latest and greatest rules.

For all I know, the Minimum weight has been changed to 125kg and carbon beams and masts are banned... smile

Posted By: pgp

Re: AC tech - 02/22/10 01:45 PM

You need to contact the web guy to get you in.
Posted By: waynemarlow

Re: AC tech - 02/22/10 03:35 PM

Originally Posted by macca
Event though I have paid my membership fee, I am still unable to log into the F16 forum thingy, so I can't download the latest and greatest rules.

For all I know, the Minimum weight has been changed to 125kg and carbon beams and masts are banned... smile


Dreams are free, my advice is to dream of a very pretty girl and ask her for her telephone number, when she replies and you wake up, try ringing that number. The odds of that same very pretty girl being on the end of the line would be about the same as "the Minimum weight has been changed to 125kg and carbon beams and masts are banned" smile
Posted By: waynemarlow

Re: AC tech - 02/22/10 03:39 PM

Originally Posted by ncik
Bridle height does influence change in rake with cant...see image.

Other than that, I agree with your sentiments about macca.


Doing a Macca here, altering the front stay bottom position alone will not cant the rig, the side stays length have to be altered or the mast base position ( easiest and most beneficial in our boats ).
Posted By: Wouter

Re: AC tech - 02/22/10 04:06 PM

Quote

"THESE RULES ARE CLOSED CLASS RULES
WHEREBY IF IT DOES NOT SPECIFICALLY SAY THAT YOU MAY – THEN YOU SHALL NOT."



If this is a serious proposal then I'm furiously against it.

This goes against everything the F16 was funded upon.

Wouter
Posted By: pgp

Re: AC tech - 02/22/10 04:49 PM

uh oh [size:11pt] [/size]
Posted By: Jalani

Re: AC tech - 02/22/10 05:34 PM

Wars have started over less...... laugh

Nothing better than using a quote out of context - ehh Pete? wink grin
Posted By: macca

Re: AC tech - 02/22/10 05:40 PM

Originally Posted by waynemarlow
Originally Posted by macca
Event though I have paid my membership fee, I am still unable to log into the F16 forum thingy, so I can't download the latest and greatest rules.

For all I know, the Minimum weight has been changed to 125kg and carbon beams and masts are banned... smile


Dreams are free, my advice is to dream of a very pretty girl and ask her for her telephone number, when she replies and you wake up, try ringing that number. The odds of that same very pretty girl being on the end of the line would be about the same as "the Minimum weight has been changed to 125kg and carbon beams and masts are banned" smile


Wow!!! I just had the most amazing dream!!!

The pretty girl answered when I called the number, just like you said! Fantastic stuff Wayne, what other tricks do you do??

Can't wait to see the new class rules smile
Posted By: pgp

Re: AC tech - 02/22/10 06:31 PM

Originally Posted by Jalani
Wars have started over less...... laugh

Nothing better than using a quote out of context - ehh Pete? wink grin


Did I!? sick Correct it please!
Posted By: scooby_simon

Re: AC tech - 02/22/10 08:14 PM

Originally Posted by macca
Event though I have paid my membership fee, I am still unable to log into the F16 forum thingy, so I can't download the latest and greatest rules.




What user name or emial address did you register with on the forum Macca?
Posted By: macca

Re: AC tech - 02/22/10 09:06 PM

My normal one, but i'm not loosing any sleep over it..

When I need a login I will sort it out.
Posted By: scooby_simon

Re: AC tech - 02/22/10 09:07 PM

There is noone called Macca registered on the F16 class forum.
Posted By: waynemarlow

Re: AC tech - 02/22/10 09:41 PM

Originally Posted by macca
My normal one, but i'm not loosing any sleep over it..


Dreaming about pretty girls answering telephones and 125kg F16's smile ah well the forums will be quiet without you.
Posted By: pgp

Re: AC tech - 02/22/10 10:27 PM

"Wow!!! I just had the most amazing dream!!!

The pretty girl answered when I called the number, just like you said! Fantastic stuff Wayne, what other tricks do you do"??

Dude, you're really scaring me now! shocked Don't ask Wayne things like that! Ask HER what other tricks SHE can do!
Posted By: ncik

Re: AC tech - 02/22/10 11:55 PM

Originally Posted by waynemarlow
Originally Posted by ncik
Bridle height does influence change in rake with cant...see image.

Other than that, I agree with your sentiments about macca.


Doing a Macca here, altering the front stay bottom position alone will not cant the rig, the side stays length have to be altered or the mast base position ( easiest and most beneficial in our boats ).


arrrgghhh. my explanation is not enough...looking at the picture it is arranged for two boats, one with a high bridle (as normal for a beach cat) and one with a low bridle (not normal and used for illustrative purposes only).

the rakes are shown for the upright positions of the rigs.

then beside each of those is the canted rigs (with sidestay adjustment) for high and low bridles. notice that the high bridle decreases rake with cant and the low bridle increases rake with cant.

the only way to cant the rig without also changing the rake is for the forestay attachment to be at the same height as the mast step. this is with a fixed length forestay which our class rules require with the rig tension adjustment requirements.

mmm...pretty girls on pretty boats...it is my happy place

Posted By: ncik

Re: AC tech - 02/25/10 05:29 AM

is it dead?
Posted By: Karl_Brogger

Re: AC tech - 02/26/10 04:22 AM

Being able to slide the mast base is an interesting idea.
Posted By: Steve_Kwiksilver

Re: AC tech - 03/09/10 10:21 AM

Can you cant ?
No, you can`t..
I`m sure I can cant.
Well you can`t cant unless you can keep mastrake and rig tension unchanged.
Can`t I do that ?
Well, you can if you cant.
I`m confused, think I`ll just sail the boat.
Posted By: Timbo

Re: AC tech - 03/09/10 01:35 PM

It's simple really, you can't cant unless you can cant without changing your wire tensions...
Posted By: Jalani

Re: AC tech - 03/09/10 01:50 PM

Originally Posted by Timbo
It's simple really, you can't cant unless you can cant without changing your wire tensions...


......or rake
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