Subject: Re: [harryproa] Re: bow design
From: Rick Willoughby
Date: 5/14/2012, 5:56 PM
To: harryproa@yahoogroups.com.au
Reply-to:
harryproa@yahoogroups.com.au

 

Dennis

On a ship 100m long, the 10 to 20m that constitutes the bow is worth fiddling with alone regarding wave piercing as this is significant relative to waves up to about 4m high.  With a boat that is 10m long intended to do similar speeds you need to consider the whole hull even if your largest waves are only 1m high.  It is also a function of the intended boat speed.

A small boat that will be operating in wave heights significantly greater than its draft will see rising drag in relation to the amount of reserve buoyancy.  The lower the reserve buoyancy the smaller the increase in drag due to the ambient waves.  A hull with very low reserve buoyancy will ride lower; closer to the level of the troughs than the peaks.  It will experience less pitching.   Accordingly it needs higher deck clearance to avoid having the deck driving through waves.   

Point is that playing with say 1m ends on a 10m hull that is going to be doing 10kts in  1m waves is only a small part of the considerations.

Given hull shapes and other parameters such as displacement, LCG, VCG, moment of inertia and VCE I can analyse quite accurately what it will do in waves of varying height.

Rick
On 14/05/2012, at 10:22 PM, Dennis wrote:

 

So this is what I'm thinking right now
before I go out on my morning beach jog .....

why not have a removable bow(s)?

I got the same mid section with the same rig and everything,
then I can just bolt in the new bow(s) to test.

Use a foam core and glass over it?
I could test many different variations this way,
all in the same day? (once built of course).

i thought about a model size to do this
but don't think it would give me enough real world testing,
besides it might take just as much time to build 1:1 anyway?

Now I'm thinking about what size main hull to use ......
not as big as the 30 footer but big enough to still be useful,
and still have pretty much the same geometries acting in the waves/chop.

--- In harryproa@yahoogroups.com.au, "Dennis" <spidennis@...> 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?
>


Rick Willoughby




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