Thanks for your patience everyone while things went quiet over here. Ravenswing has made various short daysails but we’ve had a lot of business and family commitments this fall. In mid September we convinced Charlie to tow his F27 TriChi to theSummer Splash multihull gathering in Southern Cal. After racing to Catalina, the skipper gets to anchor in a whole fleet of fast-movers.
It was a great weekend – thanks again Charlie and Jim. It was bittersweet to NOT have that be Ravenswing’s first coastal trip, but the boat was not at all ready for ocean work. In Marina Del Rey, walking thru the trailer yard Jim said, “hey, there’s a little MacGregor powersailer like yours in the ’90s”. I got a few steps closer, and dang if it wasn’t our own time capsule! Kind of sad that it’s sitting there neglected, but also a trip to see it exactly as we sold it 20 years ago. Weird.
From LA it was ‘more west’ … at the Hong Kong Maritime Museum I was reading about the first Chinese junk that sailed to England in the 1840’s.
And we thought Ravenswing has some heavy helm issues – imagine their nights at sea:
We don’t know how far sailing will take us, but the Hong Kong Yacht Club would not be a terrible stopover.
Finally after 12 days in Asia humbled by the scope of port automation projects like this in Quingdao
attention came back to the boat. Thinking more about the heavy-effort steering, we realized that in building the rudder cassette we didn’t compare the F39 plans’ for gudgeon height above the water to our custom F36 stretched stern. The result is not enough forward rake ahead of the pivot point, so all the water force is transmitted through the tiller. See the red line drawn on the rudder here – that’s how much surface area in the water should be ahead of the pivot.
Here the straightedge shows how much we actually created (the left edge)
So now we will make a permanent shim inside the cassette that tilts the rudder to achieve this
Good news for the folks who’ve helped on this – there’s enough room in the cassette to make the needed insert, and hopefully not cut in to the amazingly strong and complex carbon work.
The other major change is to walk away from the linkage & pivot steering system. We reported 2+ years ago about not believing a simple straight tiller to the rudder would work. But we haven’t been totally happy with the gear, and decided to mock up a simple tiller approach:
Charlie and I strapped this junk in place and pulled off the dock to find out if the tiller can swing far enough side to side between the tower legs. Yea! The boat can still spin in its length and is sufficiently agile at various engine / hulll speeds. The existing gear actually lets the rudder turn too far, causing stalls or being a brake. We’ll set up the new tiller for soft landings on the tower legs to safely limit the rudder travel. That’s the new theory anyway.
A question for the engineers / experienced out there- what shape will make the strongest tiller that is narrow side to side ? We want the maximum distance throw up against the tower, so a skinny tiller is important. Charlie’s suggested some type of carbon I-beam configuration. Square tube? Round tube? What do you think?
Laminate hardwood strips with carbon strips between, epoxy of course. Lay up on a form/jig with a pleasing longitudinal curve/recurve. Keep it skinny with a taller profile than a standard tiller layup to get lateral rigidity. Any hardware, tiller ext ( Ariba hot stick), autopilot, etc, just makes it stronger. 6 coats of schooner varnish, maybe a little “marlinspike” whipping on the grip. I’ll bet you have some cool woods you can rip into strips left from interior work. My F28R runs 18 Kts with two fingers on the helm (knuckles are white though), lot of forward rudder rake/hydro balance. Trial and error with factory swing rudder pivot location and zero play attachments. Go slow on changes because an over balance is dangerous. A little weather helm is faster and lifting, and when you drive the leeward float through a wave at speed it will yaw you down, so you don’t want totally neutral. Really enjoyed following your build, thanks.
Hmmmmm, Bill, I’ll think about breaking the no-wood-outside design scheme. My carbon/foam tiller weighs under a pound and is very strong; figured I’d do that again only longer. But I kind of like the shiny pretty wood concept. Stay tuned.
And yes, I know not to over rake the foil and make it dangerous. Good call out.
Square tube is clean and strong, I beam eliminates one shear web but it’s got more surface area to finish and looks awful
Keith, I agree, and I think I’ll use the same longitudinal plus hoop approach as we did to the mast. Need to get the new tiler stock made and attached to the cassette, then take that back to the boat and finally get the angles figured in rough wood before shaping the tiller foam. I expect this second time around to go much faster :)