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#144046 - 05/28/08 05:05 AM Re: Prod, prod, prod [Re: Jalani]  

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Has anyone experimented with solid fwd strutts as seen on the M20? Thoughts?

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#144047 - 05/28/08 05:14 AM Re: Prod, prod, prod [Re: ]  
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Rolf_Nilsen Offline
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The M20 dont have a forestay with bridle but a stay going down to each hull. MarstrÝm needed something to hold the spi pole up, and solid stays was the solution. But as there is very little stretch in carbon.. Hmmm..

#144048 - 05/28/08 05:21 AM Re: Prod, prod, prod [Re: ]  
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phill Offline
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Not in F16 that I know of.
They look a bit fragile.


[Linked Image]


BTW:
Technically this is not an M20 because of how it is rigged.

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#144049 - 05/28/08 07:16 AM Re: Prod, prod, prod [Re: Rolf_Nilsen]  
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Marcus F16 Offline
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Rolf,

It wouldn't take much for the distance between the pole tip & the halyard block on the mast to vary by upto 50mm.

From memory the "toe in" of my marstrom T decreased by 12mm when the rig was tensioned & you would only need 5mm to 10mm additional "toe in" to loose the desired setting on the luff of the kite.

Added to this is the potential of the mast to move forward with the gusts also affecting the distance between the head & tack.

The movement would be noticed (performance wise) after about 20-30mm of movement


Marcus Towell

Formula Catamarans Aust Pty Ltd
#144050 - 05/28/08 07:25 AM Re: Prod, prod, prod [Re: Marcus F16]  
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macca Offline
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I reckon the funniest thing about this thread is the fact that there is so much discussion about the boring part (simple strut system to control pole tip flex) and nothing about the interesting detail in the initial photo...

But you seem to be enjoying the banter so carry on <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />






















Why would you paint a boat that colour if it was going to China in very hot conditions.....?


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#144051 - 05/28/08 07:48 AM Re: Prod, prod, prod [Re: macca]  
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taipanfc Offline
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Quote
I reckon the funniest thing about this thread is the fact that there is so much discussion about the boring part (simple strut system to control pole tip flex) and nothing about the interesting detail in the initial photo...

But you seem to be enjoying the banter so carry on <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" />






















Why would you paint a boat that colour if it was going to China in very hot conditions.....?


Hey, we enjoy the banter, and good to see you back here.

And China at the time is just brutal temp wise.

But the paint job same as what was used by Pete Melvin (guessing/conjecture so Wouter won't like one bit) at the recent A-Cat worlds. Some new hi-tech thingymejig to help lower water friction or something. Was mentioned in Seahorse magazine recently explaining the qualities etc etc. Boat certainly felt different compared to normal paint jobs. Wasn't across the whole boat, just the bits in the water. Couldn't take any stickers in those sections, just fell off.

So what do I win if I guessed right? Something from your desk?

#144052 - 05/28/08 07:52 AM Re: Prod, prod, prod [Re: taipanfc]  
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taipanfc Offline
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Linky linky here:
http://www.morrellimelvin.com/webyep-sys...seP1Jan2008.pdf

Explains what I prob confused in previous post, that is if I am right.

#144053 - 05/28/08 08:04 AM Re: Prod, prod, prod [Re: Marcus F16]  
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Wouter Offline
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Wouter  Offline
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Quote

I was reframing from posting this info, but since Wouter & Steve are having a slinging match, thought I might try and help change the tone of the thread



Good move, I'm done with respect to Stephen; no point in continueing there I'm afraid as nothing good can come of it.

Wouter


Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
#144054 - 05/28/08 08:11 AM Re: Prod, prod, prod [Re: Wouter]  
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Rolf_Nilsen Offline
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So Phill produced some good numbers and a way to repeat the test in a good way. Who is up for measuring different F16s, F18s and Tornado? I am hoping Stephen will do his own boat and perhaps a MarstrÝm Tornado.. Then it would be an exercise in geometry to find out how much the tip can move vertically.

#144055 - 05/28/08 08:17 AM Re: Prod, prod, prod [Re: taipanfc]  
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Wouter Offline
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Quote

All conjecture. No real data there. Wouter won't accept this kind of thing. Need evidence, and numbers, lots of them!!!

...

Apologies Rolf, was just trying to pre-empt Wouter.



Actually you make a good point here when trying to "pre-empt something".

Without quantification you haven't got much at all. Afterall, no-body is saying that a springy pole is beneficial to performance. And absolutely no flexing is impossible in real life. So we are comparing different amounts of flexing and trying to assign different levels of performance loss to those. At some point the differences in loses is too small to matter. We can only find this point after quantifying "the info". And we need to gether these numbers (quantification) in an orderly, scientifically and most certainly reproducable manner (= evidence).

Otherwise we'll end up with the situation analogue to those 2 guys claiming they had achieved nuclear fusion in a glass of water at room temperature. Remember that story ?

There is a reason that mankind has developped so much new technologies over the last 4 centuries out of 30 millenia of existance and that reason is called the Scientific Method (= part of the entlightenment).

Wouter

Last edited by Wouter; 05/28/08 08:58 AM.

Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
#144056 - 05/28/08 08:39 AM Re: Prod, prod, prod [Re: Wouter]  
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taipanfc Offline
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I make good points? Wow, I am impressed.

But all I have been conveying is past experience on my own boat (in the early days of F16), and also what I see in the local F16 fleet here in Singapore (which is still the world's largest).

Next time I am at the club (not this weekend, surfing in Bali instead) I will give you "beach measurements" of the Taipans and Vipers, and the Blade if that is out and about.

#144057 - 05/28/08 08:49 AM Re: Prod, prod, prod [Re: taipanfc]  
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Rolf_Nilsen Offline
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West coast of Norway
A personal thing first, adressed to us all. I dont think there is much value in digging into each other on any forum. I am here on the forum for a purpose, and I think most others also are. Purpose would of course be different from person to person but if a post dont have any value, the forum would be better without that post.


Sounds great that you can do some measurements! Can you do it with the tension meter on the forestay?

#144058 - 05/28/08 08:55 AM Re: Prod, prod, prod [Re: Marcus F16]  
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Wouter Offline
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Quote

It wouldn't take much for the distance between the pole tip & the halyard block on the mast to vary by upto 50mm.

From memory the "toe in" of my marstrom T decreased by 12mm when the rig was tensioned & you would only need 5mm to 10mm additional "toe in" to loose the desired setting on the luff of the kite.

Added to this is the potential of the mast to move forward with the gusts also affecting the distance between the head & tack.

The movement would be noticed (performance wise) after about 20-30mm of movement




Yes, but these problems are not solved by the pelican striker setup as shown in the initial picture. This is actually the second tangent of my argument.

The hulls flex right ? Then they also do so at the bridle fittings allowing the bridle strop and strut to move upwards and taking the pole with it. The strut is about 40% of the full pole length so any movement upwards at the bridle strop will get amplified by 250% at the tip of the pole.

Additionally, the total relaxation of the spi luff is the result of multiple factors like tip flexing, toe-in hulls, mast flexing forward and stretch in the halyard and cloth itself. To name a few, every element in the rig is in movement and varying, yet we implicetly assume that luff relaxation is mostly determined by the tip of the pole flexing as a result of the "small" angle of the tip support wires. And then we also assume that the full pole flexing is also seen due to relatively small variations in luff tension while the spinnaker is sheeted. Why not have the tip of the pole flex upward by say 30 mm after hoisting and sheeting and then only see it flex continiously between say 25 mm and 35 mm while sailing ? Causing what ? 10 % differences in spinnaker draft ? Is that alot compared to other disturbances like waves hitting the hulls and shaking the platform ?

In scientific discourse this is called "jumping to conclusions". There is too much going on to be able to derive a foundation for such a conclusion upon inspection of the setup itself. Ergo we need specific test and numbers (=measurements) which many people feel is a dirty word these days.

Personally I don't really understand the long luffed spinnakers either. I see no real benefit to dropping the pole and luff down to between the hulls or just above it. Lots of turbulance down here due to waves and the lifted hull and also the wind speeds are really low so low above the water surface. I feel the longer luff HERE is not worth the additional hassle of securing the pole that low. But I have nu numbers to support that either I'm afraid.


Wouter


Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
#144059 - 05/28/08 08:59 AM Re: Prod, prod, prod [Re: Rolf_Nilsen]  
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taipanfc Offline
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Ummm, tension meter, Singapore. If you want it Sailing Anarchy style I can get a local girl to help out, but don't expect the results to accurate or consistent, but will be worth it for the pics!

But realistically, it is hard enought to buy decent blocks and ropes locally, let alone something like that. Can try and work something out and it maybe a different method/style of measurement.

#144060 - 05/28/08 09:02 AM Re: Prod, prod, prod [Re: taipanfc]  
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macca Offline
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Long luff = speed and depth (both good things.)


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#144061 - 05/28/08 09:08 AM Re: Prod, prod, prod [Re: Wouter]  
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Rolf_Nilsen Offline
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The fun is in trying to improve, even if we have to do it with small steps and incrementally. Looking at the tip of the spi pole is one area. We do what we can where we can <img src="http://www.catsailor.com/forums/images/graemlins/smile.gif" alt="" /> Good point though! Looks like Johnny and Charlie though it was worth to check out.

#144062 - 05/28/08 09:18 AM Re: Prod, prod, prod [Re: taipanfc]  
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Wouter Offline
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Wouter  Offline
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Quote

I make good points? Wow, I am impressed.



Well, you shouldn't be.

I'm absolutely stringent in applying the scientific method to these situations and indeed won't accept generic gutt based story-like explanations. More often then not these are wrong by mechanism of oversight. Several people on this forum however take this stringent stance as some personal affront when indeed it isn't.

On the other hand when comments are well founded in science then I will say so immediately without having earlier dealings colouring this judgement. Afterall, a person can be wrong at one moment and absolutely right at another. We all learn and we all have moments of absolute glarity. Therefor each comment should be judged on it own.

By the same token, I will readily and publically admit to being wrong when proven so. And indeed I have done so in the past in the few instances were this has turned out to be the case. To my own relief these instances have been rather few indeed.

I have been around in academic circles for quite a while now. I have worked on real life test setups many times (where models are validated or disproven), have instructed people and students in such environments and indeed this is what I have learned. Sometimes the teacher learns from his pupil even when this pupil had been wrong many times over in the past.

The only "completely unbiased" and "fail-safe" judge or criterium in all of these cases is the scientific method and that is why application of it is soooo important. Hence my total dedication to that.

Now back to the numbers and thinking up tests. Maybe we all together can advance catamaran design understanding this way.

Wouter

Last edited by Wouter; 05/28/08 09:19 AM.

Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
#144063 - 05/28/08 09:25 AM Re: Prod, prod, prod [Re: macca]  
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Wouter Offline
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Wouter  Offline
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Quote

Long luff = speed and depth (both good things.)



Let me clearify.

Indeed "Long luff = speed and depth", but is lengthing the luff at the bottom of the spi so it moves between the hulls just as beneficial as lengthening the luff at the top.

I think you'll find a great difference here. Therefor I postulate that "Long luff = speed and depth" is not accurately enough in describing the situation and therefor possibly misleading or indeed wrong for a given seet of setups.

We need to get away from overly simple (Neatherthaler) statements of the kind "Steel and concrete = good, wood = bad"

Wouter


Wouter Hijink
Formula 16 NED 243 (one-off; homebuild)
The Netherlands
#144064 - 05/28/08 09:28 AM Re: Prod, prod, prod [Re: Wouter]  
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taipanfc Offline
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Lighten up dude. Life is not meant to be that serious. For the majority of us sailing is a hobby and this is a place we like to discuss it. Maybe you need to go over to www.boat-design.net as that is for those who are into the technical aspects you crave. For the rest of us, stumbling around, passing ideas, this place is ideal for us.

#144065 - 05/28/08 10:18 AM Re: Prod, prod, prod [Re: macca]  
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Stewart Offline
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Western Australia
agreed.. the speed of a asymmetrical kite is linked to the luff length much more consistently not the sail area...

Monkey did a lot of work on this area in the early years on Prime.. Doubt if its changed.

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