BIPOLAR

Build logs from members building catamarans, trimarans and other multi-hull variants.
michaelo
Posts: 51
Joined: Mon Jan 28, 2008 12:44 am
Location: Melbourne

Re: BIPOLAR

Post by michaelo » Sun Jun 02, 2013 9:05 pm

We didn't have time to do much more than sort out the lines, sail around the dinghy afew
times for the vidoe and head back to the mooring before dark. I did find that the mechanism turning the mast in relation to the boom doesn't have enough travel so back to the epoxy, though it still sailed ok with insufficient mast rotation. Gerald it sounds like you have an aerorig type setup. What sail controls do you have, do the masts rotate ?

he b gb
Posts: 34
Joined: Wed Mar 20, 2013 11:05 am

Re: BIPOLAR

Post by he b gb » Tue Jun 04, 2013 8:47 am

You're right, my masts are aero rig style and rotate freely 180 degrees, they dont rotate in relation to the boom as the booms are permanently attached to the mast.(the masts are round tubes and dont need to be rotated in relation to the boom as your wing masts do). How many degrees of mast boom rotation are you getting? It seems a shame to have to get the grinder and epoxy out so soon for a small performance increase.My sail controls are just a mainsheet,self tacking jibsheet and outhaul.The latter two being set and forget except in light airs to put a little camber in the sails.When are you having your next sail?

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

Re: BIPOLAR

Post by michaelo » Wed Jun 05, 2013 6:26 pm

I couldn't tell you how many degrees rotation, I had a bit of a guess and made the mechanism before the mast were up. The mast needs to rotate a bit more to get a smooth transition from the wing to the sail. It's no big deal, I made the rotation mechanism removable suspecting there might be modifications needed along the way.
The next sail is over the weekend, we plan to spend a couple of days away so we should get plenty of sail time in and with a few crew this time we should be able to give it a good go

Michael

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

Re: BIPOLAR

Post by groper » Fri Aug 02, 2013 4:12 pm

Hey michael,

Hows the boat going? Got that thing flying a hull yet :mrgreen:

Can you give us a run down on the sheeting arrangements and also the mast rotation mechanism and how it works etc?

And have you got anymore videos of you sailing? Love to see a bit more about it mate.

Cheers

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

Re: BIPOLAR

Post by michaelo » Sat Aug 03, 2013 2:04 pm

Our second sailing outing ended up being a series of mishaps. First the dinghy blew away before we even left the mooring, had an encounter with a pier after picking up some passengers, lost the dinghy off the davits on the way out and finally side swiped a channel marker. I think the universe was trying to tell us something.
Finally got the sails up in a good breeze but before long discovered the sail track coming away from the mast. We did have a bit of sailing with one sail up and it was good to learn that the boat sails quite ok and tacks easily under one sail only. Also discovered that there are big forces wanting to over rotate the masts which I hadn't anticipated so will have to beef up the rotating mechanism.
The mast tracks were glued on with screw fastenings at the top and bottom. Theoretically gluing should be much stronger than screw fastenings so I must have done something wrong for the track to separate so easily. I've taken the masts off to put screws in the tracks from top to bottom so there will be no doubt now. That's all done now but there has been a delay in getting the masts put back on so won't be able to sail again for a few weeks or so.

Image

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

Re: BIPOLAR

Post by groper » Sat Aug 03, 2013 4:15 pm

Wow, sounds like youve had better days...

Can you tell me how the sheeting is arranged? Like the attachment points on the boat for beating/reaching and also downwind running?

Im guessing you have a mast spanner type of thing to control the mast rotation? Is this via a rope and small winch, then cleated off to set the rotation? What is the mechanism your using that didnt work?

Im also assuming you have an outhaul on your booms, if you hank on the outhaul, does it reduce or increase the rotation moment, or have little effect?

For the bonding of the track, theres a few tricks to improve the bonding, aswell as special epoxies that bond to metals better, such as ATL`s HPR adhesives - theyre listed on their website but im also assuming you havent fully detached the track and want to get it stuck back on without removing it completely and starting again?

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

Re: BIPOLAR

Post by michaelo » Sat Aug 03, 2013 6:38 pm

The boom sheeting consists of a single line from a winch on the cockpit coaming up through the cockpit roof support to a swivelling block on the roof then to the boom end. The sheet is double ended, continuing from the boom end into the boom to an electric winch inside the boom to give a limited adjustment to the sheet from a switch at the helm. The rig has a solid vang so there is only horizontal loads on the sheet and should be much less load than on a normal sheet arrangement.

The masts can rotate 180deg or more so the usual arrangement or a spanner arrangement connected to the deck wouldn't work. I have a spanner type arm from the trailing edge of the mast just above the boom with a line leading to a electric winch in the boom to control the mast to boom angle. With the wind pressure wanting to rotate the masts this just limits the amount of rotation with respect to the boom. The original arrangement I had was a quadrant like setup just above the boom also with an electric winch in the boom which rotated the mast in relation to the boom. The new setup lets the wind rotate the mast and it just limits the rotation angle.

The out haul doesn't effect the rotation moment. The way I see it the mast and the boom in a sense pivot around the gooseneck pin and the out haul force goes through that point so has no effect.

I did use a high strength specialist epoxy from ATL for the mast track. The track may have been contaminated or maybe I didn't carry out the correct preparation. I have just left the tracks in place, most of the adhesive is intact , and put in ss screws and backing nuts from top to bottom.

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

Re: BIPOLAR

Post by groper » Sat Aug 03, 2013 8:44 pm

I see... so when you want to run downwind, you just keep sheeting the booms out until, potentially, they can face aft if you let them out far enough?

And so for mast angle trimming, youve basically got push button control via the boom winch... neat! Have you got a little wind vane on the leading edge of the masts so you can see the where the stagnation point is to determine ideal mast angle trim?

I would have thought that more outhaul tension reduces camber by tightening the sail with respect to the mast track and thus reduced mast rotation? If left slack, the the sail naturally cambers more and pulls the mast around to a grossly over-rotated attitude? I could be wrong, i havnt thought about it in any detail... I remember the old windsurfer rigs i used to play around with and we had "camber inducers" wrapped around the mast. These were so when the outhaul was yanked on hard for a nice tight sail and very bent mast, it would flatten the sail too much which reduced lift. So they invented the camber inducers which pressed the battens out near the mast pocket so as to induce more camber and improve the power whilst maintaining the high tension in the sail.

Ive come to the conclusion that a biplane rig is the most practical solution to rigging my "powercat"... ive also concluded that its unfortunately the most expensive option :(

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

Re: BIPOLAR

Post by Jim » Sun Aug 04, 2013 9:46 am

Wow, sounds like a day to forget. I admire you for what you are doing, good on you.
Pioneering anything, is not easy or for the faint hearted, nor do results usually come easy or early in the process, but you will nail it, then everybody will want one, and you will be one of the experts they will turn to for advice.
Jim.

mahnamahna
Posts: 579
Joined: Wed Aug 02, 2006 4:48 pm
Location: Gosford NSW

Re: BIPOLAR

Post by mahnamahna » Sun Aug 04, 2013 10:44 am

groper wrote:
Ive come to the conclusion that a biplane rig is the most practical solution to rigging my "powercat"... ive also concluded that its unfortunately the most expensive option :(
Have you thought about an aero rig (balestron). Might be a cheaper option into an unstayed rig for a motor sailer? Halyard winch on mast, so only deck rigging would be sheeting winch and maybe a sail track if you go for traditional centre stepped mast. Post stepping (as per our bi rigs, a post glassed into the boat as a male bearing for a matching female bearing in the mast. The cost of this rig option might not be so prohibitive. Rob Denney of HarryProa would be the one to talk to about it.

My understanding is you are a motorboat with sails rather than a sail boat with motors, so just as we sail boats have small aux motors (ie 20hp) and large powerful sail plans (so we theoretically sail twice as fast as we motor), you have the opposite, powerful motors but your sail plan would be modest therefore so too would be the rig and all that goes with it including cost. No?

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