Design / Build notes for a Wa'apa tacking outrigger canoe

 

 

Dave Pont   6 April  2009

 

Long rambling notes follow, skip to the pictures below when you start nodding off. Any comments, advice, criticism very welcome. Enter comments directly in the text here, use the comment feature or you can post to yahoo the proafile group: http://groups.yahoo.com/group/proa_file/

 

Initial design brief was for a lightweight cartop 16 footer to be handled by 1, and able to take 2 crew at times. Want self-bailing, fast setup, and ability to use a kayak trolley for traversing carparks, beaches etc.

 

Most use will be day trips on lakes. Occasional harbour (ocean) use and possible off the beach in light surf as a 16 footer. The odd overnight sounds interesting.

 

Gary Dierkings Wa'apa design allows a 16 footer to grow to 24 foot with capacity of up to 4 crew. I like this option as it means I could take the whole family out on occaison. So I'm thinking a Wa'apa is the boat for me, the two boats in one idea is a really big selling point.

 

 

Roughed out hull and floor in Carlson Hull Designer for basic displacement calculations to set floor height. Imported hull to Delftship. Linesplan image saved and edited extensively in Gimp to produce images below. Colours are a bit wacky - just wanted to keep distinct colours for different components.

 

Things I'm sort of sure about: 

1. I want a floor to make the hull self-bailing. Used Carlson Hull Designer and came up with floor at 10", leaving a shallow cockpit of ~10". With 4 crew day sailing (820lb all up) on the 24'er this would see the floor at about 3" above waterline. Is that a bit slim? could make plugs for scuppers!
2. Hull bottom 6mm ply, everything else 4mm.
3. Thinking about cartop (at 16'), fast setup and the ability to use a kayak trolley led me to the idea of an aka / pola 'ring frame' with a 'quick connect' ama on 'stub' akas. See Fig. 3. below. With the ama (and stub akas) detached the hull is narrow enough to cartop (I think?) and will balance on a kayak trolley. The ama + stub aka will sit on top of hull for transport, storage. The ring frame would make it very easy for 2 to carry the hull and lift it onto a car roof or trailer.
4. I'd 'like' the 16 footer hull + ring frame + foils + steering to stay under 35 kg (better - 30kg) for hoisting onto car roof singlehanded. I will try an build light and see how it comes out, probably more like 40 or 50! especially with a floor added? 
5. Want to share everything including sail rig, ring frame, foils and ama between the 16 and 24 footers. Loose footed rig where sail would be partly reefed by rolling around the mast for use on 16 footer.
6. Rudder is a Michael Storer slide down style with open-back stock which has bungy wrapped around to allow kick-up and down. Rudder stock normally left on hull, might even use permanant figure 8 lashing instead of pintles.
7. Rudder and leeboard fabricated hollow from ply, 4mm?.
8. 16 footer setup is simply: attach ama + stub aka assembly (just 2 rope lashings), drop in rig, unroll sail off mast, insert rudder - go sailing !  (remembering to push down rudder and lower leeboard on your way out). Rudder stock, leeboard, 'ring frame', steering all stay attached to hull and fully set up so avoiding a lot of fiddly setup time.
9. Subtle change to ply layout for Wa'apa box ama gives two 6' pointy end sections and one straight 4' centre section all from one sheet of ply. 2 6' end sections bolted together for a 12' ama for the 16 footer, and add the 4' centre section to make a 16' ama for the 24 footer. Six foot end sections carry 2 sets of wood struts each for attaching the ama to aka ends at 12' or 16' ama lengths. See Figure below.
10. Have drawn boats with a strange 'Texas Longhorn' tiller for steering (Fig. 2 and 5). Idea from old canoe sailing book. Thinking is: can be steered from hiked out either side, don't have tiller in your back if sitting in the hull and it takes up no hull space, unlike a conventional tiller, which would also need a tiller extension. Lines run from tiller through fairleads inside guwales to rudder stock.
11. Optional foot pedals connected to tiller for foot steering when paddling. (Fig. 2) Pedals adjustable fore/aft.
12. 16 footer has two boards which lie across gunwales or hull to pola for seating and hiking (See Fig. 2 below).
13. 24 footer drawn with speculative 'fold-up deck' (Fig. 5 shows rear section folded out, foward section folded up). Made of foam core planks: 1/4" 4mm ply faces? + 1/2" camp mat foam core?. Planks would be about 1" thick, 12" wide and long enough to span from pola to pola (6' to 7'?). Four planks lashed together with figure eight lashing along long edges allows deck to be folded up. Thinking of two seperate four-plank (four foot) sections. An unfolded section is a 4' long by 1" thick deck, can fold to 2' by 2" thick or 1' by 4" thick. Ties along edges to lash to polas / akas. Full two-section deck 8' long 6-7' wide is large enough for hikers dome tent with double airbed inside for overnighting - yeah!. Two folding deck sections gives many seating options. Can be stowed easily in hull or lashed to akas, ama.  
14. Polas to sit under akas, which sit on gunwales. This means top edges of polas at same level as gunwales so deck will rest across polas and gunwales.
15. Mast and boom to be made from pine and will be hollow using birdsmouth or box construction, using diameters specified by Gary for hollow beams / spars.
16. Akas and polas box construction as specified in plans for double outrigger.
17. Akas lashed to to Tamanu style outboard 'cleats' (or to hardwood wae set below gunwales)? No full bulkheads planned as floor contributes to stiffness, would it be strong enough with ring-frame bulkheads below floor and nothing above? Paul Wilson did this with his nesting Wa-apa, but used beefier gunwales. Thinking of 30x10mm pine floor framing at 12-18" centres.
18. Outwales with spacer blocks to get more stiffness for less weight, plently of places to tie things and keep max internal hull width.
19. Aka - ama connection is the Wa'apa quick-release style. Can it work underslung? as drawn in Fig 6?
20. Inboard end of stub akas locate in wooden 'sockets' with short taper (45 degrees?) and then lashed to pola with rope. Cleats to tie off lashing?
21. Want to be able to separate 24 footer hull sections without unlashing akas. Akas and lash points just under 8' apart so they stay on central hull section (as suggested by Gary for Wa'apa).

 

Things I'm much less sure about: 

1. How to join hull sections together when there is a floor. Would require hatches at ends of hull sections, but could be awkward to get to bolts at bottom corners of hull. Can hull sections 'slot' together somehow at bottom of hull and just bolt at upper edges? Similar story for ama.Try this one.  Dan.    Excellent, thanks for that Dan. I was thinking of similar but made of ply, I guess this would be aluminum (or stainless?) which can be smaller, lighter, stronger. Yep this idea is a keeper. Dave.
2. Folding foam core deck would be relatively expensive: Probably need 4 full sheets of 4mm ply plus suitable foam core. What about 3mm doorskin ply? Could cost more than the hull itself! Is it going to be quite a bit of extra weight? I like the idea and the seating, lounging options it might provide but it is an utterly untested idea. May be too weak and/or just an expensive 'thing' that doesn't really work in practice. Just rip planks from suitable solid ply? say 12mm? as long is it wont sag under adult weight over the 20" span across gunwales or ~24" gunwale to pola.
3. 24 footer to be transported on a standard domestic 8'x4' trailer? in 3 seperate sections? or one 16' and one 8'?

 

 

Things I have NO clue about - the sail rig

1. Rigging the loose footed sail is still a blank for me. Check out the raptor 16 idea or the Holopuni idea...  Let me know if adding this bugs you or is OK.  Dan.    Any method is fine by me but adding comments directly in text actually works real well as it keeps everything together. Dave.      

2. Here is Kevins suggestions re mast from Yahoo proa_file forum:

   " I'd use a windsufer mast, extend it if you need to, buy a few feet of carbon sock to wrap around the base to take the load at the partners and you're in business. I don't think you need real bearings, just make the mast step (tube) out of pvc wrapped on the outside with glass cloth, and make the mast fit with 1/8" clearance or so and as smooth and you can manage it, it will spin fine. Put a hunk of 1/4" UHMW plastic on the bottom of the mast and in the base of the tube and it will spin even better." 

3. The Raptor seems to have a rigid connection between boom and mast. I don't think I can engineer this setup with my 'sticks and string' techniques.
4. The Holopuni has a mast much as described by Kevin above, so far so good. It appears to have open boom jaws - so what holds up the boom when outhaul is released??? my head!? Does reefing / furling work as follows: release outhaul and lower boom into hull, roll up sail,  take in outhaul which raises boom, fasten outhaul ?  Instead of a fixed boom you could just have a loop of rope through the clew and around the boom (like every single laser dinghy). This would stop the boom from falling on your head when the outhaul is loosened, also the boom would come up as the sail is reefed, ultimately ending up parallel next to the mast when completely furled. Seems simple but maybe I'm missing something? Is this what you meant by a parrel ring?  Thomas (posted at proa_file)          Thanks Thomas - thats exactly what I was looking for. Sorted - a loop of rope! just my kind of technology. Dave
5. PS: The Holopuni site also shows a 'HSS' rig - seems to be a realisation of a interesting 'crab claw' prototype (made of pvc tubing and blue polytarp) I've seen somewhere out there in cyberspace. I can't even figure how to rig a simple loose footed sail, so why am I intrigued by a rig that requires simultaneous twiddling of 3 lines to control it, and actual 'sailing knowledge' to set it to the wind...
6. Can mainsheet go to block on tiller head so sheet and tiller held in one hand (seen this on some dingy set ups) - hey I might want to scratch an itch,  or hold a beverage... stronger tiller assembly needed?.

 

 

 

 

Two-Section 16 Footer

Figure 1. 16 footer side view. Loose footed sail partially furled by rolling on to mast.  (oops - I drew the ama on the wrong side - doh!). Two section 12' ama (6' + 6') with stub akas connected to outer mounts on ama.

 

 

Figure 2. 16 footer plan view. Note stub akas overlapped more for narrower beam as 16 footer. As 24 footer these akas only reach side of hull for increased beam (see Fig. 5). Or could make two sets of stub akas, shorter set for 16' and longer set for 24'.

 

 

Figure 3. 16 footer plan view, ama + stub aka assembly removed for transport. With ama + stub akas and furled rig balanced on top this would travel nicely on a kayak trolley.  I have a C-Tug trolley, good sturdy Kiwi technology, it'll handle the load no sweat! Your average outrigger is not amenable to trolleys, darn ama dragging like a broken wing! and removing it is usually means unlashing akas, ama, pola(s), easily 6 seperate lashings. My stub-aka + ama assembly would be just 2 lashings!

 

 

Three-Section 24 Footer

 

Figure 4. 24 footer side view. Loose footed rig fully unfurled. Front deck section fully unfolded, rear deck section folded up to 1' by 4" thick as a seat. Three section 16' ama (6' + 4' + 6') with stub akas connected to inner mounts on ama.

 

 

Figure 5. 24 footer plan view. Rear deck section fully unfolded, front deck section folded up to 1' by 4" thick as a seat. Possible tramp between pola and ama as somewhere to lash 'stuff'.

 

 

Figure 6. 24 footer (and 16 footer) end view.  Do you want the bow to be effectively a pram?  Attaching a rudder would be easier on a square stern too.  I'm dealing with the same issue on my Tamanu.  Dan.   

The bow is drawn coming to a point but I'm planning to build with the narrow stem pieces specified for the Wa'apa which taper from 3" at gunwale to 3/4" at bilge. So this effectively a very narrow pram? This would be fine for attaching rudder, especially for figure 8 lashed hinge I am contemplating. Could make stern one a bit wider to give more rudder mounting options, but I'm liking pointy ends. Pram ends would want to be above waterline to avoid drag? Dave

 

 

 

 

Figure 9. Slight change to ply layaout for Wa'apa ama allows construction of 2 6' pointy ended sections and one 4' section from one 8x4' sheet of ply. The two 6' end sections bolted together give a 12' ama. Bolting in the additional 4' centre section gives a 16' ama. Bulkheads to close off the ends of the sections would have to come from scrap ply left over from the main hull.