Actually the toe-in stiffness says alot more about the build of the hulls with respect to material. However the fact that the home-build timber hulls with a proper beam landing design can outperform the glass boats with their beam landings does suggest that Timber is not so old fashioned and nearly everybody thinks.

The simple fact that an skillful but amateur boat designer (Phill) and two amateur "gone semi professional" builders can produce a superior boat by a factor of 4 in (beam landing) stiffness when compared to the big boys says a whole lot more then nothing ! The use of low tech ply makes it all the more interesting. No high tech fibres or special new high pressure infusion proces with high end product quality. Just sheets of ply glassed over.

Lets face the music guys the, Marstrom 1992 Tornado showed no less than 2.5 times the flexing this home build boat did ! Sure old boats flex more but they don't deteriorated that much. Besides everybody claims how good Tornado's keep their stiffness over many years of sailing.

Now either Marstrom 1992 boats are [censored] (but still significant stiffer than much newer Tigers and Nacra F18's by a factor of almost 2) or the Blade boys did something very right.

Looking at the numbers I say they did something very right.

We just have to ask Marcus for the toe-in stiffness to see how much is the result of timber as the material or just the superior beamlanding design.

But no matter what the cause the platform is way stiffer than the measured competition and THAT is what you'll notice on the water. Who cares if it is cause by little gobbling insides the hulls or whatever.

Wouter

>>>Like Eric, I cannot believe that someone has not put together a production two man boat in the 18-20 foot range that weighs less than 300 lbs other than the F-18HT.


Any particular reason why you explicitely exclude 240 lbs 16 foot doublehanders ?

Besides would you classify the Marstrom M20 as a production boat or not ? At 265 lbs, 20 foot length and being a double hander it sure fits your definition.

Come to think of it even 70's Dart 18's doublehanders come in at 309 lbs and therefor end up nearly level with you guys.

And than of course we have the Taipan 5.7 at 300 lbs and is a sloop rigged doublehander with spi at 19 foot length. Talking about taking much higher loads then a uni-rig. Halve of the US 18HT doesn't even beat the 300 lbs limit themselfs.

I'm sure that if I put my mind to it that I can find 1 or 2 other production designs that would equal or beat your specified condition. Ohh I got one already : Stingray 18 footers in Australia. And so on.

Take it from me; You may think you are something special but you guys really didn't set a new benchmark in light weight production.

This is nothing against any class or sailors; I'm just amazed that you simply overlooked these doublehanders while all except the Stingray 18 are well known boats in the US.

Wouter

With regards to the stiffness test - that's not a very scientifc way to go about it. Were the beams on the Nacra seated? I removed my hulls and bedded my beams in epoxy (mostly to get rid of the squeeking noises! ). However, most of the flex measured by lifting the hull is generated within the beams themselves, very little the hull to beam joint, and practically none of it by the hull itself. You should see practically no hull flexure on any cat by lifting the bow. This kind of flex characteristic indicated by your test has to do with the length and type of cross beams. Impressive, yes...but still not the whole picture.

Remember Wouter the hulls are hundreds of times stiffer than the beams, even if you were to double the stiffness of the hulls you would probably only see a few % increase in the "(beam landing) stiffness" on those tests.

So dont waste your time looking at the hulls for the increase in platform stiffness.

Hi Rhodysail

One factor that must be taken into account is team size.

I am 6' 3" and weigh 205 buck naked.. so.. to race a H16.... I need an 80 lb crew...

To race an 18 foot spin boat... I need a 130 lb crew (I personally don't know ANY guy who weighs in at 130 lbs)

To race a 20 foot spin boat... I can get away with a 160 lb crew. (I still don't know many guys who fit the bill much less can sail)

So... no matter what the local sailing scene is...racing a Hobie 16 or a F18 are not viable options for me.

My point is that simply looking at the numbers of racers in a class in a region won't give you much guidance unless you happen to fit the profile of the class. Likewise... simply pointing to the number of boats on the line is not the complete story (unless you are at that ideal weight that gives you options for any boat out there)

IMO, a tremendous advantage of the F18 class was the ability to race the boat at Hobie 16 type team weights with smaller sails in the F18 class.

Final point, Of the I20 owners in the area... I can think of only 1 owner who weighs less then 190 lbs... Almost every I20 team is routinely sailing at least 10 percent over the optimal weight in a region where 15 knots is an atypical great day!

Take Care
Mark

PS (The particular 18HT that you reference was a unique circumstance and most of the boats fit between the F18 and Tornado in price (EG: Chris B's boat that won the LAC competition was not significantly upgraded from the stock Bim F18HT)

Yes, team size will definitely be a factor in determining what class is right for you. What I’m pointing out with those numbers is the simple fact that making your class of boat afordable is more important than covering it in carbon fiber when it comes to class growth.

Yes the particular 18HT I was racing on was more expensive than the rest but isn’t this the way the class will go if it gets more popular and more competitive? The new A cat is $19,200. and evidently that is a special promotional offer. Now if you have the money that’s great but a price tag like that will limit class growth. Some people love carbon fiber and to them it’s worth having smaller fleets. Will the A cat go the extra step and allow hydrofoils? What will happen if all those expensive new boats become obsolete? I don’t think the class will go that far because they know that there needs to be a balance between affordability and technology. Will the Formula 18 add a carbon mast? Where you draw the line depend on what niche your class is going to fill.

Lance Armstrong wrote a book titled “It’s Not About the Bike”, never read the book but I guess my point is it’s not about the boat for me it’s about the sailors.

Hi Rhodysail,
I agree with your basic point... Its' not about the bike.

I would argue that the social (people aspects) are probably the most important factor in a class or clubs's long term success.

Nevertheless, Lance is not tooling around on my 1975 Schwinn either. My point is that there is a fundamental difference between the simple 16 footers... and the technology embodied in any of the other formula boats listed below. People are attracted to one or the other. I don't think you can compare the mindsets of the two very different groups of sailors here. (and you can't really judge their choices either) For the Formula sailors.... it's not about the bike..... SO LONG as it has the bells and whistles that make sailing the boat fun, exciting, and easy... (See Eric Anderson's comments) I think the sailors recognize that it will cost a bit more to play in this game. However, they get large dose of enjoyment by sailing a finally tuned machine compared to a boat that is clunky (See Bob Hodges comment about his P19). After you factor this wow factor in... then you have the class issues (popularity, dedication to going racing, convenience, social structure, etc etc) that one design fleets and ANY sailing club deal with.

Personally, I think that we as the catsailing community should be very clear how the fleets below fit together and make sure a prospective racer understands their choices and the costs involved.

You mentioned the costs to go play as an important factor. I ballparked the prices.
H 16 7K
F16 12.5K
F18 15K
F20 17 K
A Cat 19K

My point would be... Those are the costs!.... What you value in a sailboat will determine what you are willing to pay for. I would not tell anyone to compromise solely on the basis of money... They won't be happy and we could loose them in the end.

PS... I believe you highlighted a fleet building notion that came up in the one design forum. The idea was that one of the fleet rock stars would debrief the racing of that day for an hour over beers at the end of the day.

I instantly remembered Wally Myers and Jim Glanden (I think) running just such a talk after a Gunpowder regatta. They talked about the days racing and preperation for a 16 nationals. The following year John Holmerg did the same kind of thing. The tent was packed both times and even the experienced racers took home some insights.

We forget the great ideas that work so easily. Thanks for the reminder.

Mark

Mark;FYI division 11 has adopted a new H16 class for the 05 season. The new class is the brainchild of Chris Begrow. It is call payload 700 and basically means that the total weight of boat and crew is greater than 700lbs. Im sure the guys would love to see you come out and sail in the 700 class. Consider it cross training for your T.

On the technology question I agree with Bob, Faster doesnt mean more fun. Before I came to the US I sailed in the 505 and Tornado classes. When I got here I was disappointed to discover no active Tornado class in the area. After a few years racing Prindles I ended up in the Hobie class. Its not about the boat for me. I will sail in whatever class is best organized and offers the best access to good OD (and I consider formula OD) racing. In this area that means a Hobbie. Sure I would like a lighter boat but until one comes along that offers better racing opportunities than I can get with my H17 it no going to happen.

And as a follow-up, Mark... I weigh 130 pounds, but I wouldn't want to see you sailing buck naked... or even regular naked.

Another boat in the mix - the Mystere 4.3 is reportedly the largest one-design fleet competing in Ohio, there are 50 boats in the US with a possible 2005 nationals, it is a spinnaker boat that is fun and easy to sail, and they cost just over $4,000 new. Guys bought them initially as a second boat, because it was too good a deal to pass up, or to teach their kids to sail. I had hoped the Dragoon would be the US equivalent, but they cost more than a new 16.

I'll put my horn down now.

My favorite tech advance? Firstly sail controls - line and blocks (thank you Gotfried Maffioli and Olaf Harken!). Close second - Gore Tex... I'm having an affair with my dry suit. Much better than the wet suit I used to wear.

A few things :

You can get a new Hobie 16 for $7000 in the USA ?

Overhere we pay around 12.000 Euro's for a new one. Makes the difference to other Formula boats alot less.

I do agree fully on the need to have a significant and attractive class structure.

That but also to the WOW factor as mark described. I sailed a clunky 16 footer (Prindle 16 from 1975) for years and loved it to bits. Loved the simplicity. Now I sail the other thing, a highly tuned technology boat and again I'm thrilled. The new boat just moves and handles so beautifully. Even graciously.

Would I race in OD H16 races if I was asked to crew ? Yes, for sure.

Would I want to miss my technology boat. No, it is the next step for me and that is the reason why both stay around. The simple boats introduce people to catsailing without much hassle and after a while the technology boats allow sailors to grow further.

I do fail to see how these two approach conflict with eachother and how one class or line of thinking is desroying cat sailing as we know it. I think this is all misplaced fear. No beginner is going to lay down 15.000 Euro;s for a new formula boat, hell they WON:T even lay down 12.000 Euro's for a new Hobie 16 (or stealth F16). I really don't think the two classes are in much conflict. That is at a reduced cat scene because we had to many OD classes. However I truly believe one or two OD classes will survive next to 3 Formula classes and the Tornado. Will make everybody happy.

Wouter

Grob,

I was talking about toe-in stiffness as a measure of material stiffness not about "beam landing stiffness" as you call it.

I actually did the number crunching on the beams already.

I can tell you that the vertical stiffness is mainly the result of the beams and beamlanding fixtures both in bending and torsion.

Toe-in stiffness is a different matter here the hulls themselfs are the dominant factor. It may be relative easy to flex the beams in bending and torsion but not the direct axial compression. 600 kg axial compression on both beams (toe-in stiffness measurement) result in about 1 to 2 mm length difference between the beams resulting in less than 5 mm flex at the bows. The toe-in measurements showed 25 mm - 40 mm toe-in flexing at the bow tips in various designs. So it isn't the beams that is the cause of the toe-in flexing.

In vertical flexing like I have expressed earlier that the beams are the dominant factor with some noticeable contribution of the beamlandings themself. This includes the area around the beamlanding that has to transmit the loads. I know very well how a less then tight bolt on my P18 would kill the stiffness. I tightened them once every 2 months. On my P16 I had a small soft spot under a beam bolt ring and that sure didn't help stiffness.

But then again the point of the post was to show that ply (timber) isn't really as old-fashioned as many think. With building care a superior boat can be build using this methode and the Blade F18 numbers show how much superiour you can be. In the Taipan area the bare timber boats (no glassing of hulls) came out equal to the glass boats. I won't say where they ended up in relation to big beamed boats like the big builder F18's.

Also I have already wasted time on the beams, I actually have an excel sheet that runs all the math for me on beamflexing and the resulting bow tip movements.

Wouter

>>With regards to the stiffness test - that's not a very scientifc way to go about it.

Huh, all boats were tested in the same way and in the case of the F18's all dimensions of leverage and weight were identical. How do you go more scientific ? By putting on a white coat ?


>>Were the beams on the Nacra seated?

What do you mean by seated ? If you mean glued in than that is fair as the Blade F18's weren't glued as well.


>>I removed my hulls and bedded my beams in epoxy (mostly to get rid of the squeeking noises! ). However, most of the flex measured by lifting the hull is generated within the beams themselves, very little the hull to beam joint, and practically none of it by the hull itself.


I partially agree with you here, as I indicated in my other post. The design of the beamlanding itself is important. I know the Cirrus F18 has laminated in large stainless steel plates under the bolts and this boat is the stiffest F18 by far. Its beams aren't much different from say a Tiger of Nacra. But again I agree that when lifting the hull the hull stiffness itself is indeed not the dominant factor. It is completely difference when looking at toe-in stiffness.

Jake did you glue your beams in ?


>>You should see practically no hull flexure on any cat by lifting the bow.

This is absolutely not true. Marcus didn't invent the measurements. They actually did the test and got the numbers they got.

Personally I use a different methode on the beach. I put a boat on it cattracks with the track right behind the mainbeam and then move the bow up on and this I find the resonance frequency. At that stage you can really see the hulls make significant movement in opposite direction of each other. The ratio between frequency and hull weight is a good rule of thumb for the vertical stiffness. It is not exact but gives a rough indication of stiffness. Note how resonance is not dependent on any leverage arms only on weight of the hull and stiffness of the platform. I found a similar situation using this methode.

The Cirrus boat could almost not be brought to oscillation as the frequency required for it is was almost beyond human capability. The Nacra and Tigers were easy to bring in resonance and my own homebuild F16 was a little harder to put in resonance.(higher frequency required)

You should do this one time on your boat you'll be amazed how independently your hulls can move from one another.

The way Marcus and others did the measurement will show noticeable flexing on any catamaran platform. Remember the boat is only supported under its sterns !

>>This kind of flex characteristic indicated by your test has to do with the length and type of cross beams. Impressive, yes...but still not the whole picture.

Sure it but the wider beamed 1992 Tornado beats one and two year old big builder F18's with their reduced width and the Blade F18 is of the same width as the same reference F18's. That leaves type of crossbeam, beamlanding design and hulls as the only explanations for the difference. We can cross out the hull itself. Now how much bigger beam do you need to come out a factor 4 better ?

Take a look at the picture How much bigger are the Blade beams ?



I can assure you that the wall thickness of the beams isn't 4 times the thickness of the nacra or Tiger beams.


Wouter

I'm nice and argumentative aren't I. Be assured that I don't mean anything (personal) by it.

For some reason I feel like jumping on stuff right now. So forgive me for that please,

Wouter

Wouter
12,000 Euro for a 16?????
Are you sure?
May be time to start an export business.

naahhh - I'm with you. I'm being argumentative too but don't mean anything by it either.

Seriously though, if you're trying to measure the difference in stiffness of the plywood hulls vs. the composite glass hulls, why are you fooling with all the beams inbetween? That's what I meant about being scientific about "hull stiffness". You're measuring "platform stiffness" which has very little to do with the actual hull stiffness that we've been discussing. In other words, most of the platform movement you show in your measurements does not come from the hulls but instead from the beams and beam joint in between.

To 'scientifically' (I admit to using that term loosely - no lab coat required ) measure hull stiffness in the vertical axis, you would do something like support a hull under the bow and under the stern and place weight in the center - then measure the deflection there. A horizontal measurement would be a little more difficult with the boat assembled but I'm sure you see what I'm saying.

However, I am impressed with the platform stiffness of the Blade F18 compared to the other boats. While Phil may have not glued in the beams, I bet his beam socket was a bit more refined than what I had on my Nacra. I'll see if I can get a measurement on mine soon.



I thourghouly waxed the beams prior to joining them with the hulls hoping that that would aid in future removal if ever necessary. But I sanded the socket in the hulls, applied an epoxy slurry with microballons, put a bead of 3M 5200 around the perimeter, and snuggly bolted the beams in place. After allowing the epoxy to get to a 'firm but soft' state, I fully tightened the beams. The beam and hull union was NOT a good one from the factory - the socket in the hulls was not smooth and had bumps in it. While sailing, even after putting in as much 'grunt' as I dared to the bolts, I could see movement between the hull and beam while under sail. I sailed the boat before and after this operation and the difference was very noticable.

Of note - some weird reaction happened between the 5200 and the epoxy and where they both came out of the joint, the 5200 seemed to almost instantly cure. I probably wouldn't use them together like that again.

I've been thinking about measuring the platform stiffness on my Nacra, but I have an issue with how the above test was performed. Several factors may influence the results; the ground may be slightly uneven - were the boats all tested in the same exact spot? The boats themselves may not be perfectly flat and may have some pretwist in it - were the measurements taken from each side and then averaged? Truthfully, even before I seated my beams, 95mm (3.74 inches) of deflection simply by lifting an opposite bow sounds unrealistic on my nacra...it's SO much stiffer than my 6.0 was (I would believe it on my 6.0).

Instead of doing the test as described above, I propose that we perform our own independent test. We should start by loosening the rigging substantially so the rigging doesn't help support the hulls and beams adding a variance to different width boats. Then we support the boats by both sterns and one bow and measure the height of the unsupported bow from the ground. Then apply, say, 10kg to that unsupported bow and measure again. That will give a more accurate indication of vertical axis platform stiffness and would also remove some of the ground level variance and most effect from any preexisting platform twist.

Of course I probably won't have access to the Blade F18, or any Tornados soon, but would very much like to see the results there too. Can someone help with that?

Mary, if you're still putting up with this thread, can we submit a Catsailor article on the test results? Perhaps we can do some testing at Tradewinds. Wouter, want to co-author it?

here's what I propose to try and measure at Tradewinds:

(2) Inter 20's - one older, one newer (noting whether or not beams have been seated)

(2) Nacra F18s - one with unseated beams, one with seated beams

(2) Tigers (noting whether or not beams have been seated).

(1) Nacra 6.0 (2 if possible) - round beams might be interesting.

A Supercat of some sort (Eric, how about your 21?)

(1) Hobie 16 (just for comparison - since we're really talking about modern construction I thought this might be interesting but not really part of the study).

(?) Anybody else willing. Hobie Wave?

I'll put together a step by step test proceedure in the next day or so if you guys want to proceed.

Need help with the following that probably will not be at Tradewinds. I think we can get comparable results on the test whether or not the test boat is rigged since I plan to do all testing is done with loose and floppy rigging.

Blade F18, any other F18s, Tornados, Acats??

light weight boat building is more a mental barrier more than a technological one..

Where can I find 4x8' sheets of balsa wood?

Stewart, I thought it was mostly a cost barrier.