Herbie the Volkscruiser Proa
Robert Wise blogs about “alternative” cruising over at Volkscruiser, i.e., simpler, cheaper, DIY, and one of his oft repeated sayings is that multihulls have no business in the volkscruiser cheap seats, since they are complicated and expensive when compared to monohulls. This bothers me, even though he’s right, and I sat down a few weeks ago to conceptualize a small multihull cruiser, that might just possibly squeak into the volkscruiser category.
To my way of thinking, there isn’t much reason to go to all the trouble a multihull entails unless you get back something you can’t already get in a small keelboat, and that “something” is speed under sail. You can make arguments that a faster boat is safer than a slow boat (and vice versa) but the simply truth is that I enjoy sailing light and responsive boats, and a 4KSB won’t quite do it (admirable as their other qualities may be).
Which is why this multihull volkscruiser is named after the most famous VW race car in the world! Herbie is a 34’-5” LOA plywood/epoxy cruising proa, that was designed with the guiding words “simple, safe and fast” repeated mantra-like, over and over, eventually becoming “SS&F”. The cheap aspect was handled by my own innate Unca Scrooge-like personality.
A proa, by it’s nature, is the simplest, lightest, cheapest multihull, being just one hull and one ama. However, the devil is in the details and it’s surprisingly easy to design a complex and expensive proa - I’ve done it many times.
I was inspired by Dave Culp’s The Simplest Proa thread , as well as Tink’s TP03, a lug rigged schooner proa, to start with the rig. The balanced lug has many advantages (see here) mostly in favor of simple and cheap, but the balanced nature of the rig is particularly suited to a proa, because the C.E. is close to the mast, sheet loads are small, and thus shunting the rig is less tiresome, and the boom is self-vanging. I would use two of them in schooner formation, masts separated as far as possible, to employ the “air rudder” effect. The C.E. can be widely adjusted fore and aft simply by playing the sheets, thus steering the boat.
In concert with the rig, there is an adjustable leeboard on the ama to shift the CLR fore and aft (again for steering), and the automatic kick-up feature makes navigating the coral reef entrance to your favorite tropical atoll a bit less worrisome.
This proa should barely require rudders, but let’s face it, when you need a rudder, you really need one! And thus we return to the proa Achilles’ heel. Because Herbie is so well balanced, I’m proposing simple rudders on each stem that do not extend below the keel. That avoids raising/lowering rudders during a shunt, as well the complexity. I’m picturing steering with the aft rudder, and pinning the fwd rudder. Tiller details remain to be seen. 😉
The hull shape is a flat-bottomed sharpie (simple and cheap) with considerable flare to achieve some interior volume. Headroom is only 5’-6”, (6’ under the hatch), so sitting room only. There is a 14” step in the hull well above the waterline, to enable self-righting from a knock-down, but also providing better living room. The self-righting aspect gets an extra big check mark in the “safety” category.
Perhaps Herbie’s most distinctive feature is the wide “aircraft-carrier” bows. This is mainly to create a safe working deck for sail handling, reefing and furling. However, the possibilities for model aviation should not be ignored.
If the interior is rather minimal, the cockpit between the beams is borderline luxury. This area was inspired by Alexander’s superlative Nixie . There is plenty of good seating, room for a table, and I’ve roughed in a small canvas shelter to provide weather protection both at sea and at anchor. The outboard motor can fit under a cockpit seat on a “sled” that raises and lowers to the water.
So there you have it, the multihull volkscruiser. What do you think?
Cool! (I think that was a saying in the 60s.) I very much like the approaches taken with the rudders, and with increasing the internal hull volume.
I really like this design, but I don’t think the rudders will work. They just aren’t big enough to do anything. When you most need them, the boat will be down by the bow and the active rudder won’t even be in the water. I would remove the leeboard on the ama and just have a pair of sidehung, linked dagger rudders, possibly with a worm drive somewhere in the steering system so you don’t have to worry about the rudders overbalancing. Otherwise, a great concept.
Can you explain, why you choose these junk style bows? What is the benefit? To enlarge the hull volume for more accomodations don’t need such a design. IMHO it brings a lot of unnecessary weight to the ends, and may be dangerous in steep waves.
I like the hull shape. The overhangs remind me of Bolger’s Chebacco, but accentuated. Good in chop.
I’m concerned about the effectiveness of the rudders. They need more area. Maybe articulated ends, like KiaKia, but under the fixed battleship decks?
Keep the designs coming…
I agree with Mal that the rudders may be marginal at best in two cases. One close maneuvering, two downwind. A sweep will do for the first, second one will take some thought.
Overall concept is marvelous, will digest it slowly for a while, lot to like.
Slip
Thanks for the comments, much appreciated. The rough consensus is that the rudders won’t work.
but I don’t think the rudders will work. They just aren’t big enough to do anything. When you most need them, the boat will be down by the bow and the active rudder won’t even be in the water. I would remove the leeboard on the ama and just have a pair of sidehung, linked dagger rudders, possibly with a worm drive somewhere in the steering system so you don’t have to worry about the rudders overbalancing.
I like this suggestion, and will work something up as time allows.
Can you explain, why you choose these junk style bows? What is the benefit? To enlarge the hull volume for more accomodations don’t need such a design. IMHO it brings a lot of unnecessary weight to the ends, and may be dangerous in steep waves.
More interior volume, and better deck area for working the sails. I’ve always liked the general shape of the sampan, and wanted to try a riff on that for some time. The underside could provide dynamic lift in a seaway, much like the bifurcated bow of a traditional baidarka. I admit that the pram bow might be over-proportioned, but in for a penny, in for a pound when it comes to concepts!
Michael
Michael,
I basically like the concept and fully agree with Mal’s comments…...
My only other comment for the time being is why do the hulls have to be symmetrical above the waterline???
Proa hulls are the perfect vehicle for hiding lots of (reserve) buoyancy on the leeward side, where there is much less wind and wave resistance. It especially applies to the ama. The ama hull relative to its own waterplane will never heel, just lift, so that means that you could do a one sided “aircraft carrier” which gives you loads of reserve buoyancy and storage (in the best place for righting moment) and should the bows dig in, you not only have extra buoyancy but also half a surfboards worth of dynamic lift. Greater security also in being caught aback.
Rob
Hi Michael,
I like this boat. I think that you are the all-time free-thinker of proas these days. It looks really simple and it looks like it would have lots of volume for cruising. Steering probably would be an issue, but that is only a detail. Having used the Newick style rudders for so long, it’s hard to imagine using anything else, but I’d love to be proven wrong.
Good on ya’ Michael,
Russell
I really like this design, but I don’t think the rudders will work. They just aren’t big enough to do anything. When you most need them, the boat will be down by the bow and the active rudder won’t even be in the water. I would remove the leeboard on the ama and just have a pair of sidehung, linked dagger rudders, possibly with a worm drive somewhere in the steering system so you don’t have to worry about the rudders overbalancing. Otherwise, a great concept.
The nice thing about paper designs, is that they can easily be tweaked!
Regarding the rudders - as others have noted - perhaps it’s just a matter of scale. Lengthen them, and they *may* work fine.
If the rear rudder lifting clear of the water is an issue, then here’s an alternate approach: STEER FROM THE FRONT, using the front rudder. And use a worm drive, instead of a tiller mechanism, to turn the rudder. That should resolve issues around a front steering rudder wanting to inherently increase its deflection away from the centreline.
Cheers,
Paul
Will Herbie Mk II have racing stripes?
If the rear rudder lifting clear of the water is an issue, then here’s an alternate approach: STEER FROM THE FRONT, using the front rudder. And use a worm drive, instead of a tiller mechanism, to turn the rudder. That should resolve issues around a front steering rudder wanting to inherently increase its deflection away from the centreline.
Steering using the front rudder will only work if you can get the CLR far enough aft, which means you would need to lower a fixed board somewhere way aft on each shunt, so it adds more parts complication. If you don’t shift the CLR, which would naturally be only about 25% aft of the bow, then there is not enough leverage for the bow rudder to work. Also, the worm gear idea will help as you suggested, but with the rudder now working fully in reverse the loads will be very high and the amount of friction in the steering system may be unacceptable.
Mal.
I like this a lot. One advantage I see of the deck to leeward is sheeting angles. As I play with the schooner model, I’m basically needing a strut to leeward for the aft sail to insure a narrow enough sheeting angle to force the current bow to windward when steering with the sails. I’m complicating this by stepping the masts as far to windward as I can in the hull, but I would assume you’d do the same on this boat both for interior accommodation and getting the COE as far to windward as possible for balance. The reserve buoyancy and interior volume are great bonuses as well. Maybe some beam hung rudders just windward of the carrier deck?
My only other comment for the time being is why do the hulls have to be symmetrical above the waterline???
Proa hulls are the perfect vehicle for hiding lots of (reserve) buoyancy on the leeward side, where there is much less wind and wave resistance.
Rob, this is an excellent point and I will need to muse over it.
Russell, thanks for commenting. The only reason I did not use Newick rudders is simply to try for something new, and it may well be that Herbie winds up with them.
And yes, Paul, the next Herbie renderings will have racing stripes!
I really like this design, myself. In no particular order, the whole idea of the “simplest” proa was/is balancing the helm via over/under sheeting the well-separated sails. The rudders are only for fine balancing and maneuvering, so can be small. I’m nervous about “pinning” a bigger forward rudder when it is essentially being backed onto the entire time it’s at the bow. Even using a beefy tiller and tying *that* down, I can easily imagine forces strong enough to tear the rudder head off and slam what’s left hard over. OTOH, it is perfectly possible to balance a skeg-hung rudder. You just take the lower gudgeon point and move it well “aft” of the skeg—the hinge line is not parallel to the skeg, rather cants forward (at the top of the rudder). There’s been a lot of talk over on mhml about doing just this—including Bill Gibbs’ very powerful 51’ cat Afterburner. I wouldn’t want the rudder completely balanced or it’ll lose all feel, but enough so that the forward rudder isn’t seeing such large forces. Now you can make it larger if you need to—though I really don’t think you’ll need to. I would absolutely try these rudders—but I might hedge my bet by pre-framing for replacement Newick rudders as well! I certainly wouldn’t complicate the boat with worm-drive tiller systems or the like. Anything left out of a design cannot break.
I don’t understand Mal’s comment about the CLR being at 25% of the waterline behind the bow—don’t most “foil-like” structures have their CLR at 30-35% aft of leading edge, not 25%? More to the point, this boat specifies an “adjustable leeboard” in the ama already which will bring the CLR back much nearer amidships, don’t you think? Between that and the schooner rig, the design brief calls for a balanced helm. Is Mal suggesting this is not possible? Similarly I don’t understand two comments regarding the boat running bow down to the point of lifting the aft rudder out. Anybody who trims their boat bow down, and most especially in a shallow draft boat, is going to experience steering and tracking problems. Why do that?
As to hull shape; without a couple of sections I can’t comment precisely, but I’ve no problem with the aircraft carrier bows as I understand them. Assuming the midship section is the usual “T” shape, with the lower sides coming to very narrow, battleship-slim vertical angles forward, then sure I can see potential for slamming the overhangs, as well as generally lively pitch. OTOH, if the lower hull is well flared—right to the bows if wanted—the designer has complete control of how much buoyancy there is and where it’s sited. As to problems in “following seas” I have a hard time imagining this boat seriously being taken offshore. Possible, but I don’t think the Ed had that high on his list of priorities. For running bars, the boat will have the engine running full tilt as well as sails, and should have sufficient maneuvering capability, I’d think. I would almost be happier carrying the outboard in a well closer to one bow and taking the hit that the same bow is always forward when motoring, then in making these rudders much larger.
I also vote for asymmetry in the plan view, but I kinda like the looks of the symmetric one as drawn. Apropos of nothing, I’d make the ama longer; at least 30% Narrower is OK too, but longer for sure. Taking it further, though I know they’re anathema on this forum, this design strikes me as a serious candidate for “repurposing” into a harryproa/Atlantic proa via hugely lengthening the ama and carrying it to leeward.
Nice boat!
I don’t understand Mal’s comment about the CLR being at 25% of the waterline behind the bow—don’t most “foil-like” structures have their CLR at 30-35% aft of leading edge, not 25%? More to the point, this boat specifies an “adjustable leeboard” in the ama already which will bring the CLR back much nearer amidships, don’t you think? Between that and the schooner rig, the design brief calls for a balanced helm. Is Mal suggesting this is not possible? Similarly I don’t understand two comments regarding the boat running bow down to the point of lifting the aft rudder out. Anybody who trims their boat bow down, and most especially in a shallow draft boat, is going to experience steering and tracking problems. Why do that?
For asymmetric (cambered) sections, 30-35% may be right, but for symmetrical sections, 25-30% is more the norm and in engineering you should consider the worst case. Similarly, the worst case scenario for the rudder is when hard pressed downwind (down by the bow) and decelerating into the back of a wave.
A schooner rig will give you the ability to balance the boat, but if that is your only means of steering then the rig will be operating inefficiently because the aft sail will always be under-sheeted. Even taking into account the leeboard in the ama, the CLR will still be forward of midships, plus you have drag of the ama causing a turning moment to windward as well. To get the best out of the schooner rig, you still need some method of shifting the CLR aft.
The Newick style rudders are probably the most efficient. However, I like side hung linked rudders because you don’t have to raise and lower them on each shunt (good for tight situations) and because there are no penetrations through the hull taking up space. OTOH the linked rudders are a bit like the schooner rig in that one of the rudders (the forward rudder) will usually be operating at low lift, so you are paying a penalty in unnecessary wetted surface.
Mal.