No locating blocks. Part of the attraction for me is being able to leave the straps connected but limp and then just slide the iakos in and tighten them.
Now that you have said it, though, maybe blocks would be a good idea. If they were not too high, I could still slide the iakos in and the blocks would make it less necessary for the straps to be really tight.
My backup right now is a bagfull of 1" rubber strips cut from a truck inner tube. But if one of those herc straps were to fail under load, I can imagine Bad Things happening...
In my long quest to choose which boat I am going to build, I've lost count of the times that I've read Gary Dierking's book, and I keep coming back to the T2.
For those with the book (and Gary could you please help me out here) I refer to a drawing in chapter 2, page 19 RE the competing forces pushing the boat either into or away from the wind. I'm still having trouble getting my head around it and so can someone please explain.
On the diagram it states that the oceanic lateen sail tries to push the bow into the wind (weather helm), while the asymmetric hull turns the bow away from the wind (lee helm).
My problem is that asymmetric proa hulls are orientated the same way as the leaward hull on an asymmetric catamaran (think Prindle cat, ignore the catamaran's windward hull even exists while it flys above the water). Whereas on a Prindle Cat the more flat/vertical side of the leaward hull is on the leaward side, and the more rounded side is on the windward side of the leaward hull. In theory the asymmetric hull will drive the cat to track straight or even creep to windward and thus avoiding the need for a daggerboard. However in the above mentioned diagram the proa hull is orientated the same way with the flatter side to leaward, but the diagram suggests the asymmetry will push the bow away from the wind.
Having never sailed with a lanteen rig, I assume it is almost always going to create weather helm, pushing the bow into the wind.
It would make sense to orientate the hull so that the drive from the asymmetry will counteract the weather helm caused by the sail.
Having said that, it would make sense to orientate the hull the opposite way to what you would find the leaward hull of the Prindle. But that's not what you'll find on asymmetric proas.
Is there something I'm missing?
That said, if you're considering building a T2, build it per Gary's instructions and you won't go wrong. I built one and the boat is great. It's endlessly entertaining trying match all the different dynamic forces with the conditions of the day.
Last edited by Dusty Yevsky; 04-07-2013 at 11:55 AM.
Any lift that an asymmetric hull provides is small compared to the turning moment caused by the waterline plane shape. Any lift would be in a sideways (to windward) direction but not necessarily trying to turn the hull, but just to reduce leeway. An interesting side benefit is that when the platform heels and the ama flies, it's drag goes to zero and the waterplane shape of the hull becomes more symmetrical. Gary
From TdeM's post on Proa_File: http://vimeo.com/31752506
Peter, your boat is quite nice, labor of love...I noted the Malibu O plans...and your interesting mast step arrangement.
Re the above posts concerning (asymmetric) wa or main hull: What if the main hull were symmetric and the ama were asymmetric?
The reason I ask is that I am building a n outrigger using a symmetric main hull and asymmetric ama (basically cast away Tornado Hobie Cat hulls)...working with what I find to sort of recycle them and the fun of refurbishing etc.
Have yet to determine sail (crab claw style ala Malibu or very tall/narrow wing. The former may be oldish but it offers very easy sail set and strike and so on...I have drawings on other computer and will post tomorrow, I remember.
Last edited by BobBill; 05-01-2013 at 06:45 PM.
My mind can rest...much appreciated.
I have a Wa'apa that has to be assembled for each sailing trip. The lashing is the slowest part of rigging the boat. I have been think about Tamanu style lashing blocks. My thought is to install the 4 blocks, which will land on the boat'e bolt-together joints, and when the glue is dry, saw the blocks in half vertically so the boat can still be disassembled. I think it would be easier to align 4 blocks verse 8 and the lashing will still help hold the boat sections together. Has anyone done this?
- Ratchet blocks as in http://tinyurl.com/6ozpqof . I never completely remove them - just loosen enough so the iakos can slide in and out.
- Innertube strips for lashing the ama to iakos.
- A precise sequence of events with everything in it's place.
- Beach wheels as in http://tinyurl.com/c2jbjt3 When I put the vaka on the trailer, the wheels stay on. I just flip it over so it's resting upside-down.
Call it 22-23 minutes most of the time. That's still less time than a lot of windsurfers take to get rigged.
Back in the Hobie 16 days, I could get my 16 off the trailer and rigged ready to sail in something like 9 minutes. Again, beach wheels were an integral component.
Last edited by PeteCress; 05-03-2013 at 10:48 AM.
Going under bridges/causeways was my original thinking, but it turns out I have yet to go under a bridge or causeway... -)
OTOH, once I get the leeboard working the way I want, the causeways are coming....
Current Real-World considerations, though, seem to justify it in my case:
- Winning The Hearts and Minds Of Nearby Beachgoers: Boat sitting on the beach, sail wants to flog. I just strike it. Takes all of 3 seconds... ditto setting it again. Much faster/easier than lowering a regular sail.
- Righting from Capsize: Easier with the sail struck.
- Controllability When Not Under Way: Sitting off of a lee hazard like rocks, dock, whatever striking the sail reduces windage to almost zero as opposed to a luffed regular sail which can, with not much wind at all, generate forces that I can't paddle against.
- Setup Speed: it's a *lot* faster/easier to just stick the stubby in place, attach the safety line, and reel in the halyard than it is to step a regular mast and deal with the sail. I can insert/remove the stubby with one hand while standing on one foot.
Last edited by PeteCress; 05-03-2013 at 11:27 AM.
I know that this forum is not for selling things, but I offered to help Dick Newick find a home for a very interesting boat that he designed.
It's an opportunity to take an experimental boat from the world's most influential multihull designer and experimenting with it further.
Most interesting thing about Rev is how small the main hull is and that it seems practically submerged.
I like the crab claw. Does anybody know what he used for spars and whether they are pre-bent or bent by virtue of the sale's shape?
In the second photo at http://www.ptwatercraft.com/ptwaterc...ewick_REV.html with the sail furled and the spars hanging by the halyard it looks almost as if the spars are intrinsically straight - and only bent by their weight where the halyard attaches.
Yowza! Paddling out in thick, overhead sets. What a heavy rush!
Interesting question -- If the spars were bent through halyard/downhaul tension, then the sail would have an "enforced" flat shape, I should think. Then, why the unusual panel placement at the edges, which suggest shape was put in? I think the spars are curved, and they are laying with the curve in a plane toward the camera in the photo of the dropped rig. -- Wade
Okay, the Va'a Motu plans are ready to ship. Have a look at the new page here: http://homepages.paradise.net.nz/garyd/vaa_motu.html
In a gust the leech will twist off - softening the impact.
At the very top, the leech is just plain ugly-floppy. I don't think it creates any lift by itself. Instead it somehow enhances the flow around the rest of the sail. My experience is that sails with that floppy leach at the top give less power than sails without it to the tune of about a half or 3/4 meter of sail size - but are much easier to handle in gusts.
I have no clue as to the details but there are probably articles written on it.
Last edited by Dusty Yevsky; 05-14-2013 at 06:57 PM.
Gary, any plans to do a second edition of your book, to include Tamanu and Va'a Motu? -- Wade
Here's inspiration -- it would just be adding two chapters -- all the rest, good! :-) -- Wade
Those windsurfing rigs are extremely thought-out and technical just to rig.
More on topic, has anyone built or tried building the kir-6 or kir-7 sailing canoes? A link to free plans is at www.tacking-outrigger.com but the plans seem a little sketchy with regard to the bend in the keel and the dimensions of the bulkheads.
I've been fascinated with tortured plywood designs ever since I built a CLC Yare kayak in my late teens. Tortured ply yields sweet lines for a plywood boat. It would be very interesting to see a more modernized and complete tortured ply design (hint, hint.)
Will the latest design Va'a Motu be able to be stretched to 24ft like the Ulua for extra capacity?
Something that one may wish to consider regarding upswept stern sections for vaka hulls... Renowned multihull designer and naval architect, Jim Antrim, has designed a 30' trimaran that goes by the name, Erin. Antrim's design routinely kicks the snot out of equally rigged and LOA tris from Farrier, such as the F31, in tough conditions racing in San Francisco. Erin does not have the pronounced stern upsweep and follows the accepted thinking in fast trimaran design that is practiced by such noted designers as Nigel Irens and the French design firm of VPLP. Irens and VPLP are responsible for the world's fastest trimaran designs over the last 15 years with such maxi-tri work as, Sodeb'O, IDEC, Groupama 5 and Banque Populaire 5.
I think that Farrier has always been looking for ways to, shall we say, enhance, the interior volume of his boats in order to combat some of the sensations that boat buyers experience when they step into the cabin of a trimaran. That would be... that tris, by their very nature, are rather slender vessels and typically, have smaller cabin volumes than their equal length monohull competitors in the marketplace. Smaller cabins make for smaller sales in this day and age. If one makes the cabin volume larger, (increased vaka beam) then that can increase wetted surface area and that takes away one of the trimaran's best assets; it's speed through the water. So, where does one remove some wetted surface area that matters the least?... in the stern.
There's a possible added benefit in this design take in that the stern then will have a tendency to squat some while powered-up and that lifts the bows to oncoming waves, reducing the nasty potential of pitch-poling. It's a clever use of form manipulation, to be sure. The secondary conversation, which has to do with hull angle of attack variations and how they relate to speed through the water, as well as a connection to possible planing claims for the boat is another discussion that is connected to the Farrier design motif.
Chris -- All that is true of the Farrier boats. But as a very satisfied owner of an F27, I've got to point out that Farrier has always said he designs boats for cruising first, and for racing secondly. So to look at these hull shapes for hints of what's the fastest way to go is to look in the wrong place. As you point out, what the Farrier boats do is start with good interior volume, and then see what can be done to make it move easily. The "planing claims" are probably a question of how one defines planing more than anything else. It certainly looks and feels like the main hull is planing when you're moving over 10 knots. But what is also obvious is that the leeward ama has dug in deep -- they run about 110% bouyancy, much less than most other trimarans -- this, plus the tall rigs used to drive these beefy trimarans, means that the main hull is leveraged out of the water as much as it's lifted by the water flow. However you look at what's going on hydrodynamicaly, that big rig will push that skinny ama through the water very quickly.
I find these boats admiral pieces of highly refined design -- Farrier has been working out the details for many decades -- and they do deliver as fast, easily handled cruising boats. But they were never intended to keep up with the out and out speed machines such as Antrims' and Irens' boats.
But back to Va'a Motu: What I wondered even before the Farrier question was raised is this: that apparent upward hook in the stern of the Farrier boats doesn't get bogged down because as the boat speeds up, the displacement shifts to the leeward ama. In Va'a Motu, what happens on port tack?
Everybody has a right to be stupid, but some people abuse the privilege.
I hope that my observations in this thread are not construed as an attack on Gary's latest offering. They are not meant to be, but if they are taken that way, then I truly apologize. Just pointing-out that the form has been explored, but for an entirely different reason, as I and many other designers see it. That's all. It IS worth studying on a real boat that is out in the water and I'm happy that Gary finds the form compelling enough to do so.
Last edited by Chris Ostlind; 05-21-2013 at 12:01 PM.