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LUTRA
30ft x 5.75/4ft x 1ft
...a Sampanic Shorpie? |
LUTRA -- Genus name of otters, order carnivora, family mustelidae.
Sampanic -- Having a bow resembling a sampan.
Shorpei -- Sharpie / Dory / Shorey (as distinct from any one of those?).
Meso-Cruiser -- Bigger than a micro-cruiser, smaller than a full-sized cruiser?
LUTRA: One More @%! Boat
Well, here we go again.
A quick recap of our so-called 'retirement plan'... WAYWARD, our home of the last decade is capable and comfortable, but requires a deal of physical input to sail and maintain. As we age, we expect that it would become our less mobile live-aboard. To stay mobile for longer, we added MUSTELID to the mix as an easily handled camper-cruising forager.
MUSTELID's sea trials showed us that she is more than a fair weather sailor, and quite comfortable for longer term life aboard. We feel that we could, in a pinch, make her our sole live-aboard, though in spartan fashion. By nature, however, we lean more to hedonism than asceticism.
Got us thinkin'; always a dangerous activity.
Easy handling is optimal in the smaller vessel, but maintenance on the two vessels is more than WAYWARD's alone (duh). M's lack of insulation and light build puts her at the wrong end of the comfort spectrum... for about six months of the Alaskan, rainforested year, it's cool to cold living. Stowage is minimal (only enough for about four months if depending on food stores). Tools are limited to band-aid level repairs (not reconstruction). No copper plate.
Hmm.
We decided that an enlarged version of MUSTELID would meet our needs in one package. Easy handling, less maintenance, comfortable (and better organized) living aboard with enough displacement to carry longer term gear and outfit. When we're out cruising, with all eggs in one basket we won't worry about the boat left behind.
LUTRA vs MUSTELID
LUTRA is designed on the same general plan, but 6ft longer than M and twice as deep (1ft vs 6in for nearly 2x displacement). We've raised the cockpit sheer by a foot to allow self-bailing decks, wider footing and more storage in the T-locker. The resulting, higher (and widened bow) yields more lift over seas... this might be necessary to counter the increased momentum of a heavier boat.
- 9ft rowing cockpit (vs 8ft) relaxes our spacing.
- 3ft aft locker (vs 2ft) adds 'deep' stowage area and extends the aft deck.
- 12ft cabin (vs 8ft)
- Adds room for a small 'chest of drawers' each (more efficient storage).
- Allows bedding to be moved forward, clearing a space for cook and fire while one of us slugs abed (we call the doubled bedding 'Cloud-Nine' 😴 ).
- Double displacement floats thicker walls and double windows (improved insulation), copper plate, extra stores and gear, and a thermal-mass rocket stove (design in the works).
A longer, deeper hull, heavy bottom and copper plate will increase form stability and add considerable ballast stability for an even stiffer boat. This allows a more powerful rig, though we'll keep it snug against the sudden williwaws to which our area is prone. Dimensions shown are about the max we might be comfortable with. Reefing is (supposed to be) a snap and sheets are very easy to release, so we'll see.
In particular, we're trying another possibly hare-brained idea:
The mid-sail is drawn quadrilateral, spread by a sprit and boom inspired by
Holopuni Quick Rig. First reef is to brail the sprit vertical (leaving a Leg O' Mutton, triangular sail standing) and rotate the mast one turn to wrap sprit and bunt. From that point, reefing is all roll-furling around the mast as .we've been doing. With luck, this will retain the easy handling of the simpler, LOM (Leg O' Mutton) sails from M.
This increases sail area and drive while moving the CE aft a ways. This will decrease lee helm from the forward sails and hopefully enhance windward performance. With luck, we'll get away with hanging the off-centerboards (which double as filler planks for a cockpit platform) from the forward end of the cabin in the blindspot at the chest-of-drawers.
We've widened the sampan bow which will allow us to use a foremast case. We'll be able to drop it without lifting it clear of the partners (a spooky operation when wind and water 'get up'!). It will be self-bailing and drain clear of the water.
Another departure is eliminating the cabin tumblehome in favor of one-piece sides. This simplifies construction, adds knockdown buoyancy in the
BIRDWATCHER style cabin and helps reduce rain on the windows for better visibility.
Other than that, we'll be keeping most of M's features, only adapting as necessary.
The as yet open question is whether we'll be able to row LUTRA at speeds approaching 3kts. On the one hand, her longer waterline length affords about 7kts of Hullspeed (vs M's 6 1/3kts). On the other, we are doubling the underwater cross-sectional area and increasing wetted surface, both of which increase resistance. We'll be thrilled if we gain speed under oars; content to match speed; mildly disappointed to lose a little; chagrined to lose a lot.
Time will tell!
Getting Going
We were all set to build in a beautiful, remote location near Tenakee, but not too near (allowing us to concentrate on the build). Unfortunately, some friends suffered a series of misfortunes and we stepped in. We were glad to help out, but summer and a chunk of fall evaporated with no sure end in sight. We were offered a site in town, so moved back in and got started in late September of 2024.
It's cold and slow going. We're not as resilient as we used to be. Town life is lovely as always, but full of attractions and distractions. But we're chipping away at it.
At present, the hull is complete and we are about to copper the bottom with plate stripped from WW. It's well below freezing, at present, so we're prepping the plate and hoping for a few days of higher 30ºFs/low 40ºFs to render a waxy tape (sealant for the copper) more pliable.
Here's from a few days ago:
That is a significant jump in size upp from mustelid. Much more living utility I imagine. It will be interesting to see if the how the rowing performance is affected because it is such an attractive part of the mustelid design, with a length to beam ration between 7 to 7,5 an a one foot draft the little ship should be easily driven, you are approaching multihull numbers. The hull looks mighty pretty. Looking forwards to seeing your design spiral progress on this build. :)
ReplyDeleteHi,
DeleteYes, it's right about double the displacement.
I'm guessing she'll row easy. Here's hoping!
Dave Z
Looks interesting.
ReplyDeleteEver use a Ro to propel your craft?
http://douglasbrooksboatbuilding.com/ro.html
I saw a gentleman using one in Bermuda to propel his 32 foot yawl into the harbor.
Was amusing to see the harbor patrol getting after him as you "Had to be under power" to enter harbor.
I bought the gentleman, and the harbor patrol a beer so we could discuss it. He was ignored by the Patrol after that.
Hi Michael,
DeleteBlessed are the peace-makers... I appreciate your creative intervention!
We've never tried a Ro but did use yulohs for years and have now switched to a Doug Martin style, vertical blade sculling oar, rigged as a Yuloh.
For those reading along, a Ro is the Japenese version of a Yuloh... both are horizontal blade sculling oars. The Ro is reported to be more efficient.
Doug Martin and Atsushi Doi took very different approaches to the vertical blade approach. These are theoretically more efficient than horizontal blades since they have one vs two leading edges. Our experience confirms this.
Dave Z
Hi Dave, what a nice development of your Mustelid design. Eliminating the tumblehome is a good move as is increasing freeboard, imho.
ReplyDeleteHave you thought of making plans available at some stage?
"Double displacement floats thicker walls and double windows (improved insulation),"
Does this mean that thicker ply for the hull will give increased insulation value? If so, what thickness have you gone for?
Cheers, Jim
Hi Jim,
DeleteThe tumblehome was prettier, to my mind, but it's main advantage in M was to keep the build ultra efficient. LUTRA's higher sides make those savings moot, and geometrically difficult.
I'm thinking of making up the plans, but will need a window of time to do it.
And yes... the 3/4in walls provide half again the insulation over 1/2in, which sweats pretty badly in the PNW. Our first boat was 5/8in larch, and it seemed to have turned the corner (little sweating).
Also, the bedding cushions are turned up along the sides during the day, and fill much of the space below the windows. If necessary, will extend them with some similar padding in the cabin.
The galley alcove seems to stay very dry, thanks to the stove's placement.
All in all, we're hoping for decent insulation without ply-foam-ply construction.
Wish us luck!
Dave Z
Good luck!!!
DeleteThank you for your reply, Dave. 3/4 inch ply would be a lot simpler. And bombproof!!
You will have one plans sale from me if you do manage it.
Another question if you will indulge me.
Given the slender hull ratio, would you consider outriggers like you contemplated once with Mustelid?
I realise it's a complication but ...
Cheers, Jim
Yes, we'll have the possibility for outriggers (which we get pretty much for free with the spacered outwales system). We haven't tried it on MUSTELID, but hope to have more dink-around opportunities on LUTRA.
DeleteLife has been one durn thing after another, lately, but we're hoping to head back out into the wild blue yonder!
Dave Z
Lovely evolution of the original design.
ReplyDeleteBolger had a ultra slim steel sharpie called Weston Martyr (45 X 6-8) that had a huge central quadrilateral sail and a small sprit on each end for fine tuning. It was heavily ballasted with a bombproof 1/2" steel plate bottom. Never built but you're proving out the general shape. I also would be interested in eventual plans. Curious why you didn't opt for a lower CE array of 3 lugsails given how tender it is (if it is!!). Way cool..... you GO Dave & Anke!!!! Pushin the volkscruzer proletariat window and a lovely view from the boatbuilding cheap seats.
Hi Roberto,
ReplyDeleteThanks for the kind words! I'll likely work up the plans, but I should have added @Jim that I'll wait until after sea-trials for a better informed set.
RE Sails and stability... since the idea was mostly off-wind sailing, the forward Ljungstrom sail is a great tractor combined with easy handling, while still suitable for windward sailing in good conditions.
The mid-sail has to be a hands-off rig as it's difficult to reach the sail from the cabin (at least, it's undesirable in the pouring rain!). Roller-furling around the mast is a workable solution, but rules out standard sprit rigs. The one I've drawn is modified within constraints that let us reef the sprit from the cockpit. Hopefully, it'll keep the advantages.
MUSTELID turned out to be way more stable than even hoped. In both, we carried the aft bottom full width (4ft, or 1 sheet wide) all the way to the stern. This maximizes form stability worked just fine on the barges. Lutra's copper and wider bow should double down.
The rig's initial CE is pretty low - at full sail, it's not a lot for this size of boat - and is easily reefed. All in all, we're expecting it will be a solid ride.
That being said, there's always the BIRDWATCHER knock-down insurance! 8)
Dave Z
Sounds like fun.... you will soon be famous like the Ferrells ;) who also built many boats in the PNW. Re: rocket mass heater. I have often wondered if, for a boat, replacing the mass with a tin pocket would allow smaller "mass size". The idea being that the tin would melt inside it's pocket during the heating phase and then provide more heat storage for it's size/weight/mass than cast iron/soap stone/etc. due to needing a phase change to cool below it's melting temperature. I would suggest in this case a thin insulating layer on the outside to regulate the heat output such as welding blanket. I had also thought such a tin pocket might be detachable from the stove and used without its jacket to heat an oven or even a pot of water and with a double jacket be used for area heating in some cooler corner of the cabin like a hot water bottle. I think for a really small space such as you are thinking, even with just mass, some insulating cover might be a good idea both to keep from being burned and to extend the heat output. Keeping the heater "skin" at the lowest usable temperature will give the most efficient use of fuel and probably be the most comfortable as well.
ReplyDeleteHi Len,
DeleteFarrel's are a big pair of shoes! 8)
Your Tin Pocket idea is fascinating! It would pair well with a Retained Heat Cooker, too. I'll have to look up phase change advantages (above my pay grade!).
One of the nice things about living where we do is that efficiency - at least in the fine tunings - isn't too important. If we manage broad efficiency, the give-or-take of small change isn't too important. But you never know, and every little bit helps.
Dave Z
I did some calculations. It turns out temperature range is very important. If the mass is only heated to just over 450F (I used 500F) and useful heat is down to 200F (300F spread) 1 cubic inch of iron will hold 9.36 BTU and in Tin it would be 12.038 BTU. However, if instead the mass is raised to 800F (for 600F spread) then that same iron would hold 18.72 BTU and the Tin would only hold 17.186 BTU. Iron holds about twice what Tin does per degree so the wider the temperature range the better iron outperforms tin. Tin's melting point is in this range and so for less than one degree change, tin gives over 500 times what iron does in one degree. So the closer the working temperature is to Tin's melting point the better for tin. As I don't know what temperature your mass heater will run at, it is hard to know if Tin pockets are worth while. Maybe just some for use in a retained heat cooker or for making tea.
DeleteAnother point to consider is that the lower the skin temperature of your heater the more efficient it will be. If we compare heat to electric, the higher the voltage is for a resistance, the greater the current flow. With heat it is the same. Your outside wall is the resistance and the temperature of your heater skin is like the voltage so a lower temperature that lasts a longer time will get more useful heat out of the same fuel. This is why I would suggest using an insulating cover on the outside of your heater to keep your mass warm for longer while keeping the outside skin at a better more useful temperature. A removable insulator would allow for those "I'm freezing and want hot" while taming those "I'm too hot lets open the window."
Hi Len,
DeleteThanks for that very interesting analysis! Sadly, I've got quite a learning curve ahead of me if I'm going to follow your thoughts with understanding.
Rocket stove combustion chambers (insulated) burn in the 1600-1800F range if all is going well. At the top of the upright (where the pot sits) it can approach 1000F. Our hood likely drops that down considerably, but it seems to cook about the same as our ~700F range.
For the thermal mass vs skin temps, I'm less sure. Our current EcoZoom hasn't gotten too hot to touch at its skin, though 10 seconds is about all I can take. That or just a little cooler seems a pretty good target.
We're planning to flank the stove with 2.5in of wood storage (about what we had in Mustelid)... pieces to 2in can be laid along each side for relatively quick and effective drying, which helps on wet collection days. Once dry, they offer some thermal mass and stove insulation. Quite warm to the touch.
One possibility I've been mulling is a small hot water tank built into the stove... it could be tapped for drinking or left in for thermal mass. Could drain it in summer for lower radiant and kept topped off in winter for more.
I like your insulating cover idea... could even be 'stepped' for varying degrees. Could even use the thermal mass itself, wearing two hats? By increasing the layer count of, say, ceramic tiles, we'd get increasing thermal mass but also the thermal gradient between inner vs outer tiles?
Hmm....
Dave Z
i was sort of staying away from clay (tile or brick) which has a similar specific heat but a lower density. My reasoning is that on a boat space is everything so a storage mass with greater density and good specific heat. So pound for pound, iron will store just a small amount more than fired clay but volume for volume iron will store much more. However, this is your home we are talking about and you have experience with brick and tile. Doing experimental work using iron or tin in the same living space as you may not be wise. While I have built a rocket stove using metal and brick parts, I have not experimented with metal heat storage mass. So anything I have are just ideas. I do think that metal heat storage would require some insulation more effective than clay tile/brick to make it worth while using metal mass instead of clay. BTW Walker Stoves has interesting designs of "riser-less rocket mass heaters" but I think even the small core and mass would take more real estate than you would want to give up.
DeleteGood points. In this case, we're likely to be budgeting both weight and volume. That and juggling available materials, but those can be added if planned for ahead of time.
DeleteWhat we did on MUSTELID was put our lidded, cast iron Dutch oven on a riser on the stove top. It worked well for that size space any time the fire was going (down to about 18deg F) and has the big advantage of wearing more hats. On this next stove, we should have more cooking surface so can supplement with water pots. Given our better insulation, this may well keep up.
That said, there's space for dedicated thermal mass, and your thoughts are spot on!
Checked out the Walker Stove site, and like what I see... I'll forward that to some of the folks here in Tenakee who are Rocket curious.
Dave Z
Dave, what is the rough build time for this new boat compared to mustelid? Im looking at possibly builiding something because i want to get off my deep draft cruiser and reduce the need for fossil fuels. Without having land and probably having to rent a space, the speed of build is a factor.
ReplyDeleteIm also a solo cruiser and thinking the smaller mustelid would be betrr sized for one person. if material costs and labor arent radically more expensive
Published early. If cost and build time arent much more having room for a future partner would be nice
DeleteHi,
DeleteIt's so hard to say... some of our skilled friends speak in terms of weeks(!!!).
MUSTELID took us about two months (2 people, long days). But we're not particularly skilled. LUTRA is taking us much longer, but more because we're building outdoors in winter... I would say between 2 and 4 months, depending on your skill?
In general, I'd say that LUTRA is the better live-aboard for two. On the other hand, we feel that we could get by on MUSTELID in fair comfort. Stephen and Ginny Ladd went far and for long in a SEAPEARL 21, which is yet smaller than M!
It's very true that the lighter the boat, the cheaper up front, the easier to handle and generally more fun. We trade a bit of that away for comfort aboard, and never know if it was a GOOD trade until hindsight has its say.
Good luck!
Dave Z
PS. You might consider designing your own for one as a starter boat at, say, 20ft... mainly that would chop the rowing cockpit down for a single rower. If you keep the max bottom beam at 4ft, you've got a snug double berth in all variants.
Thank you for the quick response. Its nice to get the insider information from the pros. I have thought about a 20ft single person version as well. My first sailboat was a west wight potter 19 and its felt plenty roomy for one and easily muscled around when needed. Then I got the classic 1 ft-itis and slowly grew to 36ft before down sizing back to 30. 30 is still more space than I need and I am really starting to feel like something I can row and explore the shallows might be my next adventure. I need more simplicity.
DeleteAh yes... the Great Circle of Ambition! We know it well. 8)
Delete"Go small as you dare." is a pretty good rule-of-thumb!
Fair winds!
Dave Z
Dave did you lose your TEOTWAWKI link?
ReplyDeleteOr hidden under the Mustelid video?
Looks like it's still there... I moved it down the right-hand bar, and in this post, the extra large photo of LUTRA is sitting atop it. But if you look close, it's still there and appears to be working.
DeleteBTW, I appreciate your(?) comments over there!
Dave Z
Found it, pretty camouflaged as the print is the same color as the raw wood.
DeleteDid you see the Regenerative Ag link I dropped there?
Yeah... blogspot has some limitations.
DeleteYes, I saw your comment and just got to a response...
See ya there!
Dave Z