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Old Feb 14, 2012, 12:58 PM
Flying without a licence
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Hi Nathan
Do you mean dreadnought bows, raked back like on most modern catamarans. If so then it's not just their cool looks but they reduce windage and aid wave piercing (allegedly) I'm not sure if you can scale these pro's to a 1m boat. In fact even on Cats there is some dispute if a 5m hull can achieve true wave piercing qualities. I guess it's all in the eye of the beholder!
From my personal point of view I'm not a big fan of flared bows to the extent that my designs have the wetted area of the bow wider than the non wetted area. I do this to increase buoyancy at and below the waterline rather than having the reserve buoyancy in the flare.
Mark
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Old Feb 14, 2012, 06:07 PM
NORTHLAND NEW ZEALAND
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Thanks for that Mark,
just needed to know whether there's a definite no or not.
Im looking at narrowing it up above lwl to prevent it from dinging in like a spade (but still piercing waves) and not coming up, and also not digging a mine down wind. I believe is a matter of trial and error,tuning, and personal preference.

Nathan
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Old Feb 15, 2012, 03:13 AM
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Have a look at the Italian site 'MAINBOOM' for all new things in IOM. If you look at the entry from 7 OCT 2011 you will find a most interesting German IOM
Graham Elliott
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Old Feb 15, 2012, 07:10 AM
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Toulouse
Joined Jan 2007
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Nathan and Mark,

it seems to me that Bantock's Topiko was an attept at a wave piercing bow with a water shedding deck, but he brought back more flare and bouyancy with the Pikanto. Mainboom shows his latest idea with a high bow to cut water and lifting cheeks to delay the nose diving tendancies - a feature revived from long ago, but then so are the fashionable chines.
I like to think that the tumblehome you favour might be good for wetted area and efficient airflow, but at the expense of righting moment. Always a compromise, and can we ever know if the winners are so talented they can get the best out of a 2X4 plank with sails.

Watching your work with interest

Jerry
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Old Feb 15, 2012, 09:27 AM
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Sure seems like a wave piercing bow should work but a reverse bow makes me nervous with that pointed bottom being the leading point and acting like a spear, even with a bow bumper.
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Old Feb 15, 2012, 02:03 PM
NORTHLAND NEW ZEALAND
D design's Avatar
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Quote:
Originally Posted by TedFlack View Post
Sure seems like a wave piercing bow should work but a reverse bow makes me nervous with that pointed bottom being the leading point and acting like a spear, even with a bow bumper.
why do people get so nervous? its not like your sailing on it and risking your life!

spent hours yesterday trying to figure out how to design a deck on Prolines, cant seem to be able to make chines..what do you guys use to design your decks?

cheers,
Nathan
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Old Feb 15, 2012, 02:43 PM
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Quote:
Originally Posted by D design View Post
why do people get so nervous? its not like your sailing on it and risking your life!

cheers,
Nathan
I am only nervous if the bow of a boat with a reverse bow goes through my boat! Wave piercing can easily become hull piercing. And like it or not people sometimes run into each other, as an accident of course but it still happens.
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Old Feb 15, 2012, 06:17 PM
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im more scared of the guy next to me about to throw me off the dock
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Old Feb 16, 2012, 06:57 PM
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John Ball - please check your personal messages.

Thanks, Dick L.
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Old Feb 17, 2012, 05:52 AM
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VMG progress photo's
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Old Feb 18, 2012, 10:51 AM
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Planking....... I'm not going to rush, I'm not going to rush, I'm not goi'g
For something I've been picturing in my mind for a little while now it's great to see it taking a 3D shape
I'll be updating a more detailed build log on my RC Groups Blog
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Old Feb 18, 2012, 12:30 PM
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R6 mid-winter updates

who has access to the action in SD?
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Old Feb 18, 2012, 07:35 PM
FROM THE MIND OF A MADMAN
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Quote:
Originally Posted by sullyelvis View Post
who has access to the action in SD?
So far all I have heard is the winds were light.
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Old Feb 19, 2012, 10:44 PM
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Final from San Diego

1-George Pedrick-Pikanto
2-Craig Mackey-Topiko
3-Zach Alyea-Topiko
4-Denis Rogers-Britpop
5-Stephan Cohen-Pikanto
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Old Feb 22, 2012, 03:28 AM
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Cape Town South Africa
Joined Jan 2010
88 Posts
Hi FWAL,

VMG is looking great!

A couple of observations from my own experience ... which dont necessarily apply to the VMG.

I had a wide (280mm) IOM of my own skiff design. Inspired by the Lintel (before Britpop days), I cut the sides off, creating vertical chines and narrowing the deck to 205mm and the transom to 140mm. The chines were just above the waterline. The end result was the Raptor (black boat) in the pictures.

It went really well, but...
It has too much bouyancy (and wetted area) in the transom. Not very noticeable, but enough to almost (2mm) put the bow in the water as it heeled. This might be considered perfect from a waterline length perspective and it is very fast in flat water, but things change a bit if there is any wave action...

Upwind as you go over a wave, if the wave action is short, then the passing wave lifts the transom and pushes the nose down into the next wave. I have appended an example. I know many boats do this, but it does slow the boat down.

Similar effect downwind, with a wave under the transom, the nose gets pushed down and the boat finds it difficult to climb the wave in front.

The boat was fast and won the national champs, but could be improved on ... like anything I guess

In 2010 I used the same design, but narrowed the transom down to 120mm, with a bit more rocker at the back. It was slightly quicker downwind, but still had too much bouyancy in the aft third I felt.
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