Subject: Re: [harryproa] Re: Beam width
From: "Rob Denney" <proa@iinet.net.au>
Date: 6/19/2006, 2:04 AM
To:
Reply-to:
harryproa@yahoogroups.com.au

G'day,
 
Playstation was a relatively narrow boat, not helped by a huge rig and stays which prevented the main being eased.  These are not problems with harrys so pitchpoling is less of a possibility.   When I did it, there was plenty of warning, and it only happened because I was pushing too hard.
 
regards,
 
rob
----- Original Message -----
From: Mike Crawford
To: harryproa@yahoogroups.com.au
Sent: Friday, June 16, 2006 7:56 PM
Subject: [harryproa] Re: Beam width

<<I thought you didn't like a nice wide safe multihull for a minute.>>

  Steve Fossett's Playstation maxi cat was originally built at 105' LOA, with a beam of 60'.  I believe the choice was made to maximize righting moment with a wide beam, while keeping weight down with the shortest hulls they thought they could get away with.  However, it had a tendency to pitchpole at this beam-to-length ratio, and was lengthened to 125' to make it more stable.  It added a lot of weight, but they are much happier with the boat now.  I've also heard rumors about upwind performance, but can't substantiate them.

  In any case, while additional beam does provide more beam-wise righting moment, it doesn't increase length-wise righting moment.  It's possible to generate so much righting moment with a wider beam that the boat becomes too short to sail safely with the extra power.  Playstation went from a length-to-beam ratio of 1.75 to 2.08 to deal with this effect.  A 3.8m beam on an Elementary gives a ratio of 1.97, while extending it to 4.5m brings the ratio down to 1.66, below that of the original Playstation.

  If you're going to be cruising with appropriately-reefed sails, then this is a non issue, and the wider beam will be safer.  It also won't matter if you're racing and don't mind the risk.  It's something to consider, though.  After a point, wider only means safer if you're not pushing the boat.

  Personally, I'd rather capsize than pitchpole, especially at speed, but it all really depends upon what you want to do with the boat.  As Rob says, it would be interesting to see what the additional beam does.  Everything else is conjecture at this point.

       - Mike



Doug Haines wrote:
Rob,
 
Thats good - I thought you didn't like a nice wide safe multihull for a minute.
 The sail designer (Rolly Tasker) advises to use a bolt rope luff , for reefing with some long cruise I've planned. So suppose strip planking should now be an aero foil shaoe rather than the round mast that takes the luff sleeve. Not quite as big as your wing mast, but strip planked in the 6mm kiri and just straight all the way up. What would a good width/length be?
 
Doug

Rob Denney <proa@iinet.net.au> wrote:
G'day,
 
I meant than 4m.  For traillering reasons.  Be interesting to see how it sails at 4.5
 
regards,
 
rob
----- Original Message -----
From: Doug Haines
To: harryproa@yahoogroups.com.au
Sent: Friday, June 16, 2006 9:51 AM
Subject: Re: [harryproa] Re: PLOYSTYRENE AS A CORE MATERIAL?

Rob,
 
What do you mean you wouldn't go wider 7.5 x 3.8 seems a bit narrow?
 
It'll stay in the water.
 
6oz US dacron. Rolly Taskers Phuket
 
Doug

Rob Denney <proa@iinet.net.au> wrote:
beam is what fits on the trailer in the telescoped position.  Can go wider, but I wouldn't.  Good deal on the sails.  What are they made of?  I will try to get to Maylands next week.
 
regards,
 
rob
----- Original Message -----
Sent: Thursday, June 15, 2006 3:51 PM
Subject: Re: [harryproa] Re: PLOYSTYRENE AS A CORE MATERIAL?

Thanks, thats a good idea about the 3mm ply, I'll try that as i have bought the polystyrene anyway.
 
Laying out the beams now it strikes me as being quite narrow. The whole boat that is. I've got about 3.8m overall beam. Can I widen this to 4.5m? Is that length 3.8m to do with still fitting on the trailer?
 
I've decided to kind of fix the beams in the building, and leave the option to maybe some other owner who could convert this back to a demountable pinned type of beam. This is just easier for be right now.
Also I'm heading off from Mandurah next Tuesday to complete in about 4 weeks at Maylands boat yard, so call in to Maylands later in the week to see me.
Ordered two sails, luff sleeves, 6m luf for bridges from Phuket US $960.
 
I hope to make your rudder set up in a couple of weeks.

Rob Denney <proa@iinet.net.au> wrote:
G'day,
 
Sorry, I missed this.  Doug, please send any questions to me as well as to the group as I am having continual problems with Yahoo.  Ta.
 
Polystyrene will not work on areas where you are walking on it, as it dents, then leaves a void under the glass.  Eventually it all falls off.  You can put 1-3mm ply each side but it is better to use a decent core.  Foam, polypropylene (Boatcote or Polycore Aus) or paper honeycomb (ATL) are recommended.   
 
regards,
 
Rob
----- Original Message -----
From: Robert
Sent: Tuesday, June 13, 2006 10:31 AM
Subject: [harryproa] Re: PLOYSTYRENE AS A CORE MATERIAL?

For long term use I'd stick with a quality foam or honeycomb. The
resin , glass and exposure to nasty materials is still the same price
for a core that can out gass and generally not perform as well. For a
discourse on this there is something on the proafile yahoo group I was
wondering for the marginal extra cost of going to 20mm for the core in
polycore polypropylene honeycomb,
Robert --- In harryproa@yahoogroups.com.au, "doha720" <doha720@y...>
wrote:
>
> Could it be used to make the flat platform on the camper?
>
> 15mm expensive foam sandwiched with 400db is stated on the plan.
>
> Was buying the polystyrene for the end caps today and thought...
>
> Doug
>




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