BIPOLAR

Build logs from members building catamarans, trimarans and other multi-hull variants.
groper
Posts: 239
Joined: Sun Nov 18, 2012 11:23 am
Location: cairns

Re: BIPOLAR

Post by groper » Sun Aug 04, 2013 6:26 pm

Ive spoken to Rob Denney about unstayed carbon masts in some detail, ive seen the engineering spec for his 12m balestron rig...

The cost is simply the fact that we have 2 masts made of carbon fibre allbeit smaller than Micahaels, 2 sets of bearings, 2 fully battened mainsails plus the other associated gear... all this adds up pretty quick. A conventional rig is cheaper, no doubt about it. But a conventional rig didnt give me the very aft CE which i need to suit my hull with its relatively aft CLR location, unless i ran a very long mainsail boom with short jib. This would mean i have to sheet the main from the rear beam which completely stuffs up my layout for sports fishing etc and the large boom would shade my solar array more... i want to keep the back deck / cockpit clear of clutter and im relying on a significant solar array capacity to avoid heavy/noisy genset...

Another consideration is simply the aesthetic appeal, i dont want to do all this work and have it worthless because it looks like a gins camp... everything still needs to look nice or its not worth doing IMHO, resale value is a pretty important consideration. So a single ballestron rig is kinda out on that score... at least i think so anyways...

michaelo
Posts: 51
Joined: Mon Jan 28, 2008 12:44 am
Location: Melbourne

Re: BIPOLAR

Post by michaelo » Sun Aug 04, 2013 6:33 pm

I didn't set out wanting to pioneer anything. At the start of the build I expected that I'd be following after the other bi-rig builders, but it hasn't turned out that way. Despite the odd set back and headache concerning the bi-rig setup it has been the most interesting and satisfying part of the build.

groper
Posts: 239
Joined: Sun Nov 18, 2012 11:23 am
Location: cairns

Re: BIPOLAR

Post by groper » Mon Aug 05, 2013 9:31 am

Michael, do you have any pics or other info regarding the reinforcement you made to the deck and base of your stub masts? I did a quick calculation on some 10m masts and the bending moment at the deck was around 3.6t.m @ boat tip over moment. Your 15m poles would be significantly more than that on a bigger boat... Interested to see the bearings or any of that pe of stuff...

groper
Posts: 239
Joined: Sun Nov 18, 2012 11:23 am
Location: cairns

Re: BIPOLAR

Post by groper » Mon Aug 05, 2013 9:31 am

Michael, do you have any pics or other info regarding the reinforcement you made to the deck and base of your stub masts? I did a quick calculation on some 10m masts and the bending moment at the deck was around 3.6t.m @ boat tip over moment. Your 15m poles would be significantly more than that on a bigger boat... Interested to see the bearings or any of that type of stuff...

michaelo
Posts: 51
Joined: Mon Jan 28, 2008 12:44 am
Location: Melbourne

Re: BIPOLAR

Post by michaelo » Mon Aug 05, 2013 9:02 pm

Bottom bearing. Inside ring machined s/steel self aligning. Outside machined ring of acetal all held together by a ring of glass. The bearing is glued to the post and bolts to the bottom of the mast.
Image

Image
Top bearing is a metal self aligning bearing on a s/s stub at the top of the carbon post and slips inside a rib inside the mast.
Image

The deck reinforcement was straightforward consisting of replacing the core with plywood where the post went through the deck and applying multiple layers of 450 d/b glass on the outside of the deck centred on the post hole. I can't remember, would have to find the drawings but I think it was something like 6 layers extending out to about a metre around the hole and tapering down to one layer. The reinforcing at the bottom of the post was similar with multiple layers on the cabin sole and extending up the chamfer panel

Michael

groper
Posts: 239
Joined: Sun Nov 18, 2012 11:23 am
Location: cairns

Re: BIPOLAR

Post by groper » Mon Aug 05, 2013 10:56 pm

Wow, the size them really hits home... Some serious hardware there... Thanks for the pics.

Going off some dead reckoning of your sail area, I think you have quite a powerful rig on your boat. It should sail quite fast when you get it all sorted. I can't wait to see the video when you get it out in some heavier air :mrgreen:

Jim
Posts: 691
Joined: Fri May 19, 2006 8:25 am
Location: Cairns

Re: BIPOLAR

Post by Jim » Sun Aug 11, 2013 9:44 am

I totally agree with Sean, there is some great info to be had on this forum, and it doesn't matter what you are building.
I launched my boat, Leslie James 5 years ago and still read it all the time. As I write this I am just off Cape Cleveland/Townsville smashing into a 15 knot wind, on the nose, of course, on the way down to the Whitsundays. Didn't know it was race week, so may be a bit busy there.
Anyway, keep up the excellent contributions people.
Cheers,
Jim.

groper
Posts: 239
Joined: Sun Nov 18, 2012 11:23 am
Location: cairns

Re: BIPOLAR

Post by groper » Sun Feb 09, 2014 6:48 pm

Heard some news from Rob Denny, he mentioned that you cut 3.75m off the top of each mast because it was a bit of a handful at anchor or on a mooring?

He also published a little performance details of 18knots boat speed in 20-25kt winds? And most impressive was the upwind performance shown below; I hope you can give us some more details about your boat and the performance, seems like the biplane rig is working really well for you..

michaelo
Posts: 51
Joined: Mon Jan 28, 2008 12:44 am
Location: Melbourne

Re: BIPOLAR

Post by michaelo » Tue Feb 11, 2014 10:03 pm

I think we've finally got the rig sorted out and can spend time sailing instead of fixing or changing things. It became apparent early on that we were way over powered and I was worried about being caught out in strong winds and not being able to control the boat. So I bit the bullet and took the masts off and shortened them by about 25%

Image

The change has improved manouverabilty and control under power in a wind with little decrease in light wind sailing performance. In anything over a light wind there is more than enough power and over 20kts or so of wind we only need a deeply reefed sail on each mast.
The boat tacks easily with just a turn of the wheel and sails equally well with one sail up. We're still learning and every time we go out we learn something new about how to handle the boat or the rig

groper
Posts: 239
Joined: Sun Nov 18, 2012 11:23 am
Location: cairns

Re: BIPOLAR

Post by groper » Wed Feb 12, 2014 8:27 am

excellent!

If i build another boat, it will be unstayed wingmast biplane rigged cat like this. I knew the performance would be excellent, and its so easy to deal with... i think you made a good choice with your boat michael.

I would love to modify my existing boat to take this type of rig, but i just cant figure out a way of doing it without the masts getting in the way of the interior below. I have a plan where i can slip my boat and convert it to a sailing cruiser. It only involves a transom extension including rudders, daggerboard cases, and the rig.

If you dont mind more of my questions, where are your masts in relation to the interior layout? Do they get in the way of things below? If you could do it again, would you put them in the same location or do you think theres a better place for them further aft in the hull?

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