Ahhh, come on guys !.

Alright I'm the first to admit that there are many factors included BUT to same these numbers are relatively meaningles or that the T can't be compared to the F18's is to go to the extreme on the other side.

With luck we get some extra data as gethered by Jake and either colloborate or conflict with the Marcus data.

But still, we can already say that a 92 marstrom at a greater width and length was measured to be noticeable stiffer than much newer F18's. What do you guys think will happen if a 2004 Marstrom Tornado is measured ?

So we can certainly take away something from the supplied data. Then of course other people are coming in with their own experiences and data I refer to Jake and seating his F18 beams and Macca with his Taipan 5.7. Surely these comments more colloborate the data then conflict with it. Afterall the newly seated beams appear to have made the platform noticeably stiffer.

And does any of us really believe that Marcus would come out under his own name with intentionally rigged data. Yes, there may be difference in the dolphin striker tensions and how tight the bolts are but is it reasonable to believe that all were loose to the extend that they all favoured the Tornado and Blade to this extend.

Would it not be reasonable to assume that these numbers are relatively accurate before new data comes in ?


>>This test was only ment for a rough personal guide for the guys and should be taken as that.

why not take it as a starting point for additional measurements; why not keep these numbers in mind and check your own boat. Under the asumption of reasonability is shows that gains can be made. Even by the sailors themself by seating their beams as Jake has done.

Sure we need to take care to not make to much out of it. But we would be equally foolish not to use this info. Right now it is the only data we've got and for all we know the numbers could be accurate.

And as an ending I would like to add that absolute deflections, uncompensated for hull length or width, is what is important in sailing. A shorter hulled cat may well be relatively less stiff but if it flexes less in absolute terms it takes on waves better than a relatively stiffer platform that flexes more. Not all in real life is relative. Some things only matter in the absolute sense.

Wouter

Hi Wouter,

All I am saying is was not the most accurate test. But can be used as a bit of a guied. I have seen the Blade and I can tell you that they have built a very stiff platform.

They are still working on hull shape to improve its performance through waves and still have some work in rig development to do. I wouldn't say it is the fastest F-18 out there but as proven at the nationals, it is not that far of the pace. With further development...... may be able to give some of the other manufactures a bit of a run.

Best of luck to the guys.

I'll continue the boat price thing on the Hobie 16 section.

Well look. I'm a development engineer so I understand that what we will achieve are not absolute results. I do think it will be interesting to see how round beams, seated beams, non-seated beams, curved beams, and hull construction affect the relative stiffness of the platform. As Rick pointed out, I'm not sure how what we are measuring affects anything; it's not going to be easy to apply any of this information directly to what makes a boat fast. Most of us like to sail a boat that is stiffer and obviously the designers design work towards it as well but I don't intend to answer why that is.

We can show that the only energy available on a sailboat comes from the wind and since we're racers, we're particular focused on using as much of that energy as possible to move the boat foward. Flexing something requires energy so it's natural to assume that a flexible boat absorbs some of the precious energy we need to be fast. However, who's to say that in certain circumstances that flexing the hulls help the hulls align themselves into a more aquadynamic angle and/or help them distribute the buoyancy more efficiently allong the length of the hull? Or maybe it tweaks the rig tension and sailplan angle to make the sailplan more powerfull in spurts as the boat tries to get through a wave?

I don't know if a stiffer boat is faster - but that's not what we're trying to figure out here. I do know that I prefer the feel of a stiffer boat and it feels faster to me - but who am I? I'm really intersted just to know what makes a boat more solid with a twist thrown in for hull construction for the sake of conversation.

>>>I don't know if a stiffer boat is faster - but that's not what we're trying to figure out here. I do know that I prefer the feel of a stiffer boat and it feels faster to me - but who am I? I'm really intersted just to know what makes a boat more solid with a twist thrown in for hull construction for the sake of conversation.


Good point !

Right now all I have to go on personally is what I know from my old P16 and P18's. Both of them were getting old at the end. P16 was from 1975 and the P18 was from 1986. Both of them had tendency to slack on the rearbeam and every now and then I tightened the bolts. The P18 at one time had a soft spot under a rearbeam bolt and one time I places thick and much larger washers under all bolts.

Just like Jake I can testify that the stiffened boats sailed alot more enjoyable. It felt faster. I have no data however that it is faster EXCEPT when sailing in considerable chop. The difference was so noticeable in chop that I know for sure that a tight and stiff platform is faster there.

The stiffened platform would punch through the chop and keep speed up. When they were more flexible they tended to hit the chop, shake considerably, halt and then accellerate again. We can get some serious chop overhere where I sail. Well it is more like short stubby waves with a wavelength of about 10 to 15 meters.

Eventually I would tighten the bolts when I saw that the chop was present on the race course.

I need to say however that the the holes in the beam were worn out a little, so that a only slightly looser bolt quickly allowed the beam to move over the hulls. So the magnitude of gain due to tight bolts may have been greater on my boats than on newer ones.

There is another thing I believe in (and I say believe intentionally) and that is that a stiffer platform has better dive recovery. I noticed from stiffening up my old P16 and P18. But it also makes sense. When the leward hull bites so to say a stiffer platform drags the luff hull in quicker as well. Often this results in a more direct application of reserve bouyancy. The speed of the biting is important here. A more flexible platform take longer to bring the other hull in and the deflection between the two hulls can be quite large at such shock loads. Again it is a believe, I have no scientific data. However I was far more comfortable pushing the boat and I certainly pitchpoled less.

Maybe it is like flexibility in your steering colom of your auto. A good driver can still go fast with it by learning additional mental skills (I know control computers can) but a sharp and crisp steering colom allows less skilled drivers to go just as fast. Pretty much people don't like controlling systems with delays and overshoots. The human mind is best adapted to systems that approximate pure integrating system. (can you tell this part of my field of study)
Systems that are "less stiff" have noticeable higher order components that appear to the human mind as unpredictable or to complex to control easily. The result is sloppy control where a human being feels insecure and uncomfortable.

It all is an interesting topic though.

Wouter

Surely stiffer must be faster as any energy moving (twisting) the boat cannot be translated into forward drive.

Anyone remember a Formula 40 trimaran named Adrenaline?

I vaguely rember reading something about it. Wasn't the leeward ama designed to be submerged or something like that?

The amas where designed to pitch independently from the main hull. The boat cleaned up in the Formula 40 class until it finally broke.

Interesting...kinda like Kathy Kulkowski's Wave. Go figure.

really? Not when I last costed the materials.
Here a foam/glass/carbon skiff hull is less than 10% below the cost of a nomex/carbon. But then we tend to forget that a big cost in any hull manufacture is labor.

May I suggest you read Bethwaites book, especially on the difference attitudes to hull construction between the "richer" northern hemisphere builders and the "poor" southerners..

merry Christmas

I have a batch of the F 40 videos from the Prosail Television series and none have adrenaline winning anything. some times it does ok, but it was never the fastest.

For my money, I prefer a stiff platform.

Merry X-class
Eric

Absolutely stiff is better, thank gawd for the little blue pill. Oh wait... what were talking about again?

Ok...I'm still in the stiff is better camp and I have done the epoxy bedding thing with my beam to hull connections. However I'm not dismissing the flexable idea altogether. It makes sense to me that in some condidtions a platform that flexes will allow each individual hull to respond more freely to the waves it experiences. A stiff platform forces a compromise response to the wave state each hull encounters. I can see this working on a Wave which is more likley to ride over the waves than punch through them. Just a thought, I could be all wrong. (BTW this is not an attempt to explain Kathy's victory. I know why she won, she is a damn good sailor).

Adrenaline was winning F-40 events in Europe before there was a Pro Sail series in the US. I suspect that it was an old boat by the time Pro Sail started. It was also a tri so the rig was connected to a solid platform. I think that is what allowed the concept to work.

I had my personal bet regarding who was going to be the first - I had been holding back but knew it wouldn't be long.

heh...heh...he said "stiff".

Sure - flexing a boat absorbs energy. But what is less efficient? Flexing a boat and allowing one hull to change it's angle of attack to an incoming wave so that it's stern is still in contact with the water....OR.....driving in the front 1/3 of the boat (including the deck) sumberged into the wave while elevating the stern? Secondly, as the leward bow comes up, it allows the rig to rake back slightly and tilt to windward making it more efficient...don't the ORMA60's have canting rigs so they can lean them to windward?

The question is intended to be rhetorical but I think there may be something to it in some limited situations.

In a small cat with the forestay attached to both bows the situation you described will allow the mast to increase longitudinal rake temporarily.

However, the leeward shroud is always slack and increasing slack will do nothing to the transversal mast angle. As a consequence, it will not cant to windward.

Luiz

Did any of this stuff ever get done?

Gareth

No - unfortunately it did not. I ran out of time due to a unplanned last minute rear end and brake overhaul on my motorhome prior to leaving (good lord that's a huge brake drum!). I didn't have time left to get anything together to perform the measurements.