Moth sailing

nige

Super Anarchist
"Baron von Richthoven: Ah, and the Lord Flasheart. This is indeed an honour. Finally, the two greatest gentleman fliers in the world meet. Two men of honour, who have jousted together in the cloud-strewn glory of the skies, face to face at last. How often I have rehearsed this moment of destiny in my dreams. The panoply to encapsulate the unspoken nobility of a comradeship.

[Flasheart shoots von Richthoven]

Lord Flasheart: What a poof! "

 

ferrero

Member
92
0
I have a friend who recently joined the RAF and has taken to using 'woof woof' in conversation. I think that gives reason for some concern, either that or he just didnt get blackadder.

 
Alright so I've been tossing this about in my mind a bit. Doug, in the design brief you said you wanted to make the bow finer, but then you go on to disregard lowrider hull shape considerations, saying low ride speed will soon be irrelevant. This seems a little contradictory to me. It seems to me if you are going to design a hull shape based solely on foiling wouldn't you want to go the other way and add volume to the bow? Once you're foiling the only time the hull matters is when you crash or come down off the foils in a maneuver, and then you just want to bounce back up on foils as quick as you can. So the last thing you want to do is have a supper fine bow that is going to stuff the bow deep before gaining enough reserve buoyancy to pop you back up, or worse you crash hard enough to trip over the bow and go doggy style. In my mind the way to avoid this is to design as much pitch resistance in as you can, which means pushing volume into the ends, not taking it away. In the limit I would think you would want a big surf board up there to smack the water and bounce. Sure it might be jarring, but who cares. From a pure physics stand point you loose the least energy by not piercing the surface at all.

Granted there world be a windage penalty but looking at the way aclass cat design is going, pushing volume down low into the bow seems to be the way to go. Steve's Josie IC design has about as much volume low in the bow as he could get while keeping the entry angle as low as possible, and there is a significant amount of dynamic being created by the front foot and a half of the bow. I've got to believe moths are going fast enough they could easily get enough flat volume in the bow to generate enough dynamic lift for the bow to always skip.

I haven't spent nearly enough time in a moth myself to know why I am wrong, but if someone else could tell me that would be great.

Oliver

 

nige

Super Anarchist
I think you have just improved the stock price of the old skippy's from the mid 90's.

Skippy 2 pic - designed 1998. You could lose some foredeck height for sure, but where would you put the beer??

(the boat to the right is also a skippy2 and the one behind a skippy1 - more rounded, more foredeck but still the volume low in the bow - they were great in light wind and flat water, not sure anyone ever put foils on one)

sk2beer.JPG

 
Last edited by a moderator:

gui

Anarchist
I think you have just improved the stock price of the old skippy's from the mid 90's.
Skippy 2 pic - designed 1998. You could lose some foredeck height for sure, but where would you put the beer??

(the boat to the right is also a skippy2 and the one behind a skippy1 - more rounded, more foredeck but still the volume low in the bow - they were great in light wind and flat water, not sure anyone ever put foils on one)
http://ph.groups.yahoo.com/group/int-moth-.../view/babd?b=10

I could have asked for 2 six pack instead of one???

 

gui

Anarchist
Alright so I've been tossing this about in my mind a bit. Doug, in the design brief you said you wanted to make the bow finer, but then you go on to disregard lowrider hull shape considerations, saying low ride speed will soon be irrelevant. This seems a little contradictory to me. It seems to me if you are going to design a hull shape based solely on foiling wouldn't you want to go the other way and add volume to the bow? Once you're foiling the only time the hull matters is when you crash or come down off the foils in a maneuver, and then you just want to bounce back up on foils as quick as you can. So the last thing you want to do is have a supper fine bow that is going to stuff the bow deep before gaining enough reserve buoyancy to pop you back up, or worse you crash hard enough to trip over the bow and go doggy style. In my mind the way to avoid this is to design as much pitch resistance in as you can, which means pushing volume into the ends, not taking it away. In the limit I would think you would want a big surf board up there to smack the water and bounce. Sure it might be jarring, but who cares. From a pure physics stand point you loose the least energy by not piercing the surface at all.
Granted there world be a windage penalty but looking at the way aclass cat design is going, pushing volume down low into the bow seems to be the way to go. Steve's Josie IC design has about as much volume low in the bow as he could get while keeping the entry angle as low as possible, and there is a significant amount of dynamic being created by the front foot and a half of the bow. I've got to believe moths are going fast enough they could easily get enough flat volume in the bow to generate enough dynamic lift for the bow to always skip.

I haven't spent nearly enough time in a moth myself to know why I am wrong, but if someone else could tell me that would be great.

Oliver
Flat boards aren't fast in light air. I'm all for a quick light air hull, and I think you have the tooling for one!

If your boat is digging that much, it means that a)you're doing a flip downhill. or b)your control system is crap.

But maybe not.

So, when are you icelander joining the fun?

 
I think you have just improved the stock price of the old skippy's from the mid 90's.
Skippy 2 pic - designed 1998. You could lose some foredeck height for sure, but where would you put the beer??

(the boat to the right is also a skippy2 and the one behind a skippy1 - more rounded, more foredeck but still the volume low in the bow - they were great in light wind and flat water, not sure anyone ever put foils on one)
Foils are on both of those boats - I think the daggerboard position on the red boat was too far back for the boat to be successfull as it stood - needs a new box... The white one is going OK.

 

Phil S

Super Anarchist
2,606
233
Sydney
Doug,

I too wondered about your hull. Also the Velociraptor.

My ideas are that the moth is so short that it needs as much volume as possible low down or it sinks too deep and gains too much wetted surface. To this end your concave or flat surfaces are not as good as well rounded or even square shapes.

But I can see how your bow will split the waves nicely. Allister Warren has done something similar with his IC/DC Monkey and it goes pretty quick.

We still need a low drag hull up to 6 or 8 kts boat speed and judging by what used to be good in light winds before foiling, my take is that a well rounded hull with a little extra spring should be the way to go. If not we could not go far wrong with an Claridge or Hungry Tiger shape.

 

dougculnane

Member
348
0
Alright so I've been tossing this about in my mind a bit. Doug, in the design brief you said you wanted to make the bow finer, but then you go on to disregard lowrider hull shape considerations, saying low ride speed will soon be irrelevant. This seems a little contradictory to me. It seems to me if you are going to design a hull shape based solely on foiling wouldn't you want to go the other way and add volume to the bow? Once you're foiling the only time the hull matters is when you crash or come down off the foils in a maneuver, and then you just want to bounce back up on foils as quick as you can. So the last thing you want to do is have a supper fine bow that is going to stuff the bow deep before gaining enough reserve buoyancy to pop you back up, or worse you crash hard enough to trip over the bow and go doggy style. In my mind the way to avoid this is to design as much pitch resistance in as you can, which means pushing volume into the ends, not taking it away. In the limit I would think you would want a big surf board up there to smack the water and bounce. Sure it might be jarring, but who cares. From a pure physics stand point you loose the least energy by not piercing the surface at all.
Granted there world be a windage penalty but looking at the way aclass cat design is going, pushing volume down low into the bow seems to be the way to go. Steve's Josie IC design has about as much volume low in the bow as he could get while keeping the entry angle as low as possible, and there is a significant amount of dynamic being created by the front foot and a half of the bow. I've got to believe moths are going fast enough they could easily get enough flat volume in the bow to generate enough dynamic lift for the bow to always skip.

I haven't spent nearly enough time in a moth myself to know why I am wrong, but if someone else could tell me that would be great.

Oliver
You may be right but this is my (and Adams) theory. I am not saying we are right but I am explaining the thinking.

Big bows are a bitch because you trip over them. Forget 10kg of bouancy we have 100KG doing 20 knots. The dynamics far outweigh the statics when you crash down off the foils. So limiting decelleration will have more change for stoping you cartwheeling than extra static boyancy. So I suspect this boat will go underwater when she crashes but hopefulls she will slow down slowly and pop out at some point and then I can sail on. Rather than crash stop and throw me off and or cartwheel.

Doug,I too wondered about your hull. Also the Velociraptor.

My ideas are that the moth is so short that it needs as much volume as possible low down or it sinks too deep and gains too much wetted surface. To this end your concave or flat surfaces are not as good as well rounded or even square shapes.

But I can see how your bow will split the waves nicely. Allister Warren has done something similar with his IC/DC Monkey and it goes pretty quick.

We still need a low drag hull up to 6 or 8 kts boat speed and judging by what used to be good in light winds before foiling, my take is that a well rounded hull with a little extra spring should be the way to go. If not we could not go far wrong with an Claridge or Hungry Tiger shape.
How do you make a round hull out of flat pannels? If i had made a mold then I would still be building next spring.... Also the front sections shed the water to reduce wetted area. This helps at take off. OK it is shit when lowriding but I would rather be in the bar and the envelope for low riding is so small now that maybe it can be ignored...

Her hull is a compromise. She started with the breif of easy fast build with no molds which means flat pannels. The flat pannels also give us the chance to to a speed boat type hull at the front so if the hull makes contact with the water she sheds it and does not get sucked down into it. Low riding is going to suffer but the rocker means that the wetter surface area is probably not too bad compaired to the hungry tiger type hulls with round hull but very flat rocker.

Does she work? We shall see but so far I think it is working out well.

 

dougculnane

Member
348
0
PS: Also becuase there are no molds involved we could take a chance on the design. If I was going to build molds I would be very conservative so that the molds could be reused for more than one boat. So her design is a jump on the deveolpment curve rather than the next iteration. Wheather it is a jump too for or in the right direction is the question.

I hope that explains the thinking only hinsight will show it to be right or wrong, but at least there was some thinking.

 

Phil S

Super Anarchist
2,606
233
Sydney
My perception of crashing from long and frequent experience is that the bow hits the water at a steep negative angle, (The bow hits much the same time as the foil gets back to being underwater which means height 1m , length bow to fin 1.5m. Tan 1/1.5 is 34, so the bow is pointing down at something like 34 degrees)> I would say that at this angle that the design shape is pretty irrelevant. The boat virtually stops in the crash and its only the length and total volume of the bow which decides if it pops out upright or continues to roll over bow first.

The big foredeck of my present H Tiger has saved me many times while one of the Chainsaw versions had the mast only a half M from the bow and no foredeck hump and would almost always nose over in a crash. So when I build again the bow will be quite high and the sections very rounded top and bottom.

Good luck with your ideas Doug, the class is based on free thinking new ideas, innovation and consequent successes and failures. More of it please.

 

MT14er

Member
418
1
MT
I was thinking about the touchdown issue too when I was working on the design for my yet-to-be-constructed boat. The solution I came up with has a knuckle bow profile so in theory a large portion of the bow will hit the water at approximately the same time instead of knifing in from a pointy tip. May or may not work, but this boat too is a simple prototype that can be tossed with little remorse if it doesn't work. I'm also hoping that the knuckle bow helps a bit in lowriding.

 

dougculnane

Member
348
0
I was thinking about the touchdown issue too when I was working on the design for my yet-to-be-constructed boat. The solution I came up with has a knuckle bow profile so in theory a large portion of the bow will hit the water at approximately the same time instead of knifing in from a pointy tip. May or may not work, but this boat too is a simple prototype that can be tossed with little remorse if it doesn't work. I'm also hoping that the knuckle bow helps a bit in lowriding.
If you are building a boat you need to do a blog or the boat will not be class legal (Section 12.4a of IMCA rules). So what is the address of the blog?

 

MR.CLEAN

Moderator
46,682
4,726
Not here
I sent this to the Ed last night, but he didn't run it...

Like Moths to a Flame

There isn't a class in the world with a more widespread presence on the web than the International Moth – there are so many blogs, youtube videos, and SA threads on 'em that we dubbed the IMCA the “Internet Moth Class Association” a few months back. They're at it hardcore now, and one of the best blogs for keeping up on the lastest news in foiler world is from top Aussie foiler Scott Babbage. Babbage has come out with his “form guide,” laying his predictions for the 2008 Worlds on the line – and the reasons for his picks. We're happy to see that Babbage has picked our buddy Bora Gulari to win the thing, and we're even happier to see the shitfight in the blog's comment section over his picks. When normally reserved Brits start flinging public poo, someone's really got their panties in a bunch.

05/16/2008

 

dougculnane

Member
348
0
Nice one Mr Clean.

The shit fight is a bit close to the edge at times but it is fun.

A quick background to understand the trash talk.

- Aussies and Brit fleet are old and long term rivals, that never miss a change to whind each other up.

- Rohan is on the edge of deciding to sail or not and the Brits are trying to draw him in to sailing becuase they have a good chance of beating him in lighter winds.

- Bora is an unknown and doing really well but the established fleets do not want to be beaten by a newbie (Moth newbie).

That is my take on it all.

 

MR.CLEAN

Moderator
46,682
4,726
Not here
Nice one Mr Clean.
The shit fight is a bit close to the edge at times but it is fun.

A quick background to understand the trash talk.

- Aussies and Brit fleet are old and long term rivals, that never miss a change to whind each other up.

- Rohan is on the edge of deciding to sail or not and the Brits are trying to draw him in to sailing becuase they have a good chance of beating him in lighter winds.

- Bora is an unknown and doing really well but the established fleets do not want to be beaten by a newbie (Moth newbie).

That is my take on it all.
So long as it is all fun and games, I think the trash talking is a good thing. Fun shitfights have done wonders for participation in the local fleets that use SA to hype their events (e.g. Detroit Melges 24 fleet), but Bora's a sensitive soul :)

I think it would be great if Rohan shows up, but given his confessions on his lack of physical fitness, I don't know if he'll do it - unless he's just saying that to catch people off guard.

 

MT14er

Member
418
1
MT
If you are building a boat you need to do a blog or the boat will not be class legal (Section 12.4a of IMCA rules). So what is the address of the blog?
Hmm, my rules end at Section 11. I guess I don't have the latests version. I better get on that. :blink: Actually I've been working on some content for the blog, but I'm going hold off posting till I can have something to keep readers interested. My current pile of wood, carbon, and epoxy isn't too thrilling. I still need a name too. How about the Montana Moth Movement!

 

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