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Martec Folding Prop Installation On Tapered |TOP|
Abovedeck, the T-shaped cockpit is spacious, with wide side decks and well-placed coamings for the Lewmar 58 self-tailing winches. All lines are led aft, so all sails can be handled from the cockpit. The tapered Hall Spars triple-spreader section is supported by Navtec rod rigging.Belowdeck, the J/130 is bright and airy, with lots of off-white Formica and teak trim. The galley to starboard features an Origo alcohol stove/oven, Formica counters, and a 6-cubic-foot icebox. Forward, there is a pair of settees with pilot berths outboard and a folding table. An enclosed head and shower can open into the spacious double berth and settee forward or aft into the main saloon.Our test boat had an optional aft full-headroom stateroom, with a double berth, on the port side; the nav station is moved forward. There are two options for the forward nav station. In one, the navigator sits on a main settee; the other is an outboard-facing station, with a swing-out seat. Standard auxiliary power comes from a three-cylinder Yanmar 47-horsepower diesel with a Martec folding prop.The J/130 debuted last October, and, no surprise here, there are lots of orders in hand. If you're a sailor who hates to give up performance to get nice cruising accommodations, put the well-equipped J/130, on your short list of boats to consider.
martec folding prop installation on tapered
I do, being pushed by a Palmer P60, which is only an 18shp motor, not much by today's perceived engine size needs, but in range by the two horsepowerper ton rule. So in my case a good prop match is more important than ifyou're running 40shp, and can bury prop losses by turning up the whistle.I've used a fixed two blade prop: good efficiency, but way too muchdrag in light air. Then an old style Martech two blade folder; veryinefficient, expensive to change pitch, no backing oomph. But it will getyou out to the start line and back if you're a hardcore racer.So I got a two blade MaxProp, presently on the boat. It's expensive, buthas a nice feature: easy repitching (out of the water). I've fiddled withthe pitch and now it's just right. They look sort of fragile, the edges arethin and ding easily, but they're used on high speed powerboats so theymust be fairly tough. I've heard if you shift from ahead to astern at fullrpm the steel puzzle pieces inside the hub that allow adjusting pitch canstrip the bronze teeth. Not much of a problem when running 18hp. Theyrequire maintenance, refilling with grease every few hundred engine hours,out of the water old style, zerk fitting new style. Mine's been in service13 years with no problems, but I haven't hit any logs either. It's alwayssnapped open, feathering below 3kn is iffy. Once feathered, boatspeedcan drop to 0kn with no opening.Not sure if they're still made in Italy, but the whole thing used to be(is?) hand lapped so all the gear gimcrackery doesn't bind, and the greasedoesn't get spun out of the housing. There's no gaskets, all metal to metal.Very tight tolerances compared to a floppy MarTech. Perfect balance right out of the box. If you break an interior part, the whole prop has to go tothe shop, you can't just buy a replacement gear thingy.The force which feathers the prop is not great at low boatspeeds because ofthe geometry, so the gearing must rotate freely. A spinning out of gear MarTechwants to keep spinning; a MaxProp wants to feather. The well written manualsays you have to be going 5 knots at shutdown to ensure complete feathering.The shaft should not turn when feathered, but leaving the engine in gear isenough if the transmission is not hydraulic, unlike the big brake neededwith fixed blade props. The force to keep them closed is negligible (low drag), unlike aMarTech which, if one blade is straight down it will open at low boatspeeds.So there's no need to align the shaft after shutdown, although some say a twoblader MaxProp should have blades at 6:00 and 12:00 because of shaft angle,the opposite of a MarTech. I think that's being picky.They are not as efficient as fixed props, because the blades have no twist,i. e., they're flat as pancakes when viewed edge on. Therefore theycavitate a lot at certain rpms, sounds like a hyperactive christmas treebubble-light. I saw an underwater view of twin MaxProps on a powerboatfiring up and they shot a cylindrical shaft of cavitation bubbles thelength of the boat comin' out of the hole. Of course they were runninglotsa hp and rpm. My setup doesn't perform well in headwinds and seas,dropping to 3kn because of prop slip; don't know if it's a horsepowerproblem or the inefficient nature of a prop with no twist, a 3 blader mighthave less slip.MaxProps are symmetrical so they back *better* than a fixed blade. I canstop in two boatlengths from hull speed, with wash gurgling up the cockpitscuppers. No change in prop walk. It catches kelp more than my otherprops, because when deployed, the blade edge which fairs into the hubprojects out like a cleaver. Backing down on moderate infestations cutsweed right off (not poly rope); I haven't tried powering into a kelp bedwith it yet, though.As far as MaxProps and I36s go, there are some installation issues. Bladetip to hull clearance with my shaft length is only 1 1/2 inches with atwelve inch prop, and MaxProp didn't make 12" inch three bladers back then.MaxProps are best on larger boats with more room, because as prop size goesdown, hub diameter doesn't decrease (the internal gimcrackery is the samesize) which means an 8" MaxProp would be mostly hub and no blades. Theadded drag because of the unusually large hub (12" size) means a goodMarTech folder probably has less drag. Some racing fleets rate featherersslower than folders just from the wetted surface standpoint. Also, because the MaxProp completely encloses the end of the shaft (doesn'tslide on, bolts on like a shaft zinc), the threads for the classiccastellated shaft nut which holds a fixed or MarTech folding prop on cannotproject much beyond the end of the shaft taper. Part of the shaft threads had to be cutoff my shaft so the MaxProp would clear the shaft end, which means I mayhave to get a new shaft to switch back to the fixed or MarTech prop. OTOH,some Santa Cruz 70 sleds switch to fixed props for long deliveries, sohub work on a fixed prop might allow the remaining threads to catch acastellated shaft nut.Sysnopsis: Maybe a 10% fuel consumption hit compared to a fixed prop. I'mhappy, but I'm running a low horspower auxiliary. Don't know howperformance would change when running a 25-35hp diesel.Back when I bought mine there weren't many low drag prop options on themarket, now there's several new designs available which may be worthsome research. $1,000 for a MaxProp two blade 12" prop is a lot of money, and the 3 bladers are more expensive. And, if you don't care aboutultimate sailing performance, a fixed prop is hard to beat concerningcost, simplicity and durability. If money is no object, clearly a variablepitch prop while underway is the ultimate setup.Mark WyattS/V AXOLOTL
J/92 Specifications Hull & Deck Lloyd's approved, end-grained balsa construction using biaxial and unidirectional E-glass for optimum strength. Interplastic vinylester resin for a 10 year hull blister warranty. Innovative, lightweight and strong hull/deck joint bonded with 3M polyurethane elastomer bonding agent and finished with 3M 5200. White gel coat hull with tapered molded bootstripe & J/logo decal on aft hull corners. Large open racing cockpit with raised 2" coaming, low profile mainsheet traveler on sole, high traction non-skid, and optimized hardware layout. Large companionway opening with light weight molded seahood and curved slider. GRP molded main structural bulkhead, bonded to hull and deck providing superior support for shroud chainplates and optimum hull & deck stiffness. Individually bonded light-weight structural bulkheads. Individually bonded FRP fiberglass structural keel support grid. Aluminum mast step "I" Beam with transverse beams fastened to main bulkhead and structural support grid. Lead & antimony fixed 5.9f draft bulb keel for low CG, bolted, epoxy bonded and glass wrapped to deep reinforced structural hull stub. 1.25" toe rails on foredeck. Power & Steering Yanmar 9 h.p. 1 cylinder diesel engine with water, dirt, and fuel filters. Engine instrument panel in cockpit with tachometer and alarms for oil pressure and temperature. Balanced, light weight, high aspect spade rudder with carbon fiber shaft turning on two teflon rudder bearings. Varnished, curved, & laminated mahogony tiller with stainless steel straps and Spinlock adjustable hiking handle. Lightweight, low profile, stainless rudder head fitting. 12 gallon fuel tank with inspection port, gauge, and shut-off valve. Martec 13 x 11 folding bronze prop with 3/4" Aquamet S.S. shaft and molded custom strut. Deck Hardware Two Harken 40.2A 2 speed primary cockpit winches. Two Harken 32.2A 2 speed secondary winches for halyards, reef lines, and spinnaker sheeting. Antal mast base halyard stand-up blocks. Antal Master Series stoppers mounted forward of secondary winches. Two 3* X 1" clear anodized jib tracks. Two 3f x 1" genoa tracks (shipped loose). Two Schaefer jib lead blocks w/stainless cars. Harken Mid-Range adjustable mainsheet traveler system on cockpit sole w/3:l control line purchase. Harken 1541 mid-range blocks mounted on aft "U"-bolt and mid range hexaratchet blocks mounted on stanchions for spinnaker sheet leads. Three clear anodized aluminum mooring cleats. Lewmar 19" x 19" bronze Ocean Series hatch for quick deck storage, interior ventilation and light. Lexan companionway drop board with inside/outside opening, lockable stainless hasp. Two single 10" Antal aluminum lock-in winch handles w/roller bearing handles. Henderson Cockpit Operated Bilge Pump. Two PVC winch handle holders. Two plastic cowl vents for bow & stern. Double white PVC coated lifelines. Custom stainless stemhead fitting. Stainless split stern rail with center gate. Spars & Rigging Hall Spars 152 6061-T6 aluminum aerodynamic mast section, w/tapered upper panel, double tapered spreaders, welded mast head crane, internal halyards, wire halyard exits w/s.s. chafe bars, cast aluminum mast shoe, mast collar w/custom fit boot and wedges. Mast & boom finished with off-white awlgrip. Stainless 1x19 wire headstay, upper, lower and intermediate shrouds with open body adjustable turnbuckles, and backstay . Main halyard of 7x19 stainless wire spliced to 3/8" XLS white code dacron tail with headboard shackle. Jib halyard of 7x19 stainless wire with Nicro snap shackle spliced to 3/8" XLS solid blue code dacron tall. 350c69d7ab