Subject: Re: [harryproa] bow design
From: Rob Denney
Date: 5/14/2012, 7:38 PM
To: harryproa@yahoogroups.com.au
Reply-to:
harryproa@yahoogroups.com.au

 

That video is of a boat with a very wide bow, hence the spray. 


A model with removable ends (could have different shapes on each end for testing) is a great idea.   As Rick points out, it may not help a lot going into waves, but would tell you a lot about how much buoyancy is required when running down them, with sail loads pushing the bows down and movable crew weight.    

It is a lot of extra work if you build two boats.  The cost (labour, overheads and materials) of a 30' hull is very little more than a 20'ter, and will give much better feedback as it will have the properties you require.  This is different to scaling up "normal" boats as the 30 footer will be near enough the same weight as the 20, so will behave in a less comparable fashion.  The beams, ww hull and rig will be near enough the same for both boats

With upswept bows, the whole bow hits a wave at the same time, providing more upwards impetus.  A reverse bow hits it more gradually.  Flared bows are great when near the limit surfing, but are pushing water outwards the rest of the time which must be slower, and if you do bury them, there is much more deck, which is usually flat,  to prevent them coming back up.  
rob



On Mon, May 14, 2012 at 1:33 PM, Dennis <spidennis@gmail.com> wrote:
 

There's a new video posted about a proa's bow action in the waves
http://youtu.be/mlXsBgY5TRI
Rick seems concerned about the "funnel" created, I'd be too.
With all the hype on the new types of bow designs, it's even more confusing.
Rob and I have been discussing a possible EC boat entry , about 30' long.
So I've been giving this some thought and looking around at designs ......
The bow(s) of the main hull have me a bit concerned.
I don't care what's "in style" or the "trend" but rather on performance.
I'd like a cleaner cut thru the water.
The proa "Madness" has up swept bows but I hadn't yet seen any video
that shows this boat moving at any real speed but,
I do think this might slice thru the waves a bit better?
Anyway I'd just be guessing until I saw it really working.

The windward hull isn't really a concern .....
as I got a very different ideas on that.
One hull type would be for all out speed,
there's the inflatable idea,
then there's the UFC/expedition type,
and finally there's the removable kayak
which could be a possible UFC version to really play with the rule book!
The kayak idea would be a "boat switch rule" offshoot for stage 4 (out of 5).
Think of the StarTrek Enterprise with the saucer separation from the rest of the ship.
For stage 4 the main hull would get transported via trailer
and I'd paddle/pedal on in the kayak for stage 4 and we'd rejoin back at the beginning of stage 5.

But back to the bows (sorry for the distraction) ...... ideas? thoughts?


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