ecgossett Posted March 10, 2012 Report Share Posted March 10, 2012 During the race I noticed sometimes on big waves (chest height in boat) if they rolled under us sideways or occasionally when twisting from behind the rudder would would pull hard or I would hear stress creaks. Any ideas on how to upgrade/beef up cheek blocks & rudder post for a stronger unit? It bothers me that the most common failure on the different races are rudders. Quote Link to comment Share on other sites More sharing options...
PAR Posted March 10, 2012 Report Share Posted March 10, 2012 The pictures of your centerline transom support, show pretty strong grain lines around an imperfection (possible the edge of a knot). I'm not sure where the split was, but did you through bolt the gudgeons or screw them? I'm a big through bolt fan, on items as loaded as these. When in doubt, through bolt. Plywood isn't the best material for rudder blades and cheeks, but the CS-17 isn't highly loaded, so it'll work fine in most situations. Following seas and wakes can cause the rudder to get pushed around, which will test the connections, fastener holding power, etc. Moans and creeks from stressed wood, even plywood are pretty normal and something I personally enjoy hearing. If truly concerned a strip planked rudder, with hard wood cheeks would be an obvious upgrade. A better upgrade would be inert materials for the blade, such as foam cored 'glass composite or HDPE blade with aluminum plate cheeks. This is my usual route on high performance designs. If you think the crack was there to begin with, then you're probably fine with your fix. Moaning wood is normal, much like your other half's insistence with the honeydo list, though possably not as enjoyable to hear. Quote Link to comment Share on other sites More sharing options...
ecgossett Posted March 10, 2012 Author Report Share Posted March 10, 2012 Is there a good place to get a HDPE blade versus building one for a coresound? Quote Link to comment Share on other sites More sharing options...
hokeyhydro Posted March 10, 2012 Report Share Posted March 10, 2012 I do strip build rudders, shaped and sheathed in 6 oz fiberglass with a double up on glass for the leading edge and foot. My cheek blocks are laminated ply, but even with that I truly believe if I grabbed the rudder at the foot and yanked it about while boat was secured to the trailer the first part to let go would be the pintle/goudgens. Might want to upgrade that hardware and as PAR said = BOLTS! Quote Link to comment Share on other sites More sharing options...
Hirilonde Posted March 10, 2012 Report Share Posted March 10, 2012 Might want to upgrade that hardware and as PAR said = BOLTS! I bolted the gudgeons and pintles on my Spindrift. I just see no reason to not do something so simple that is so strong. Quote Link to comment Share on other sites More sharing options...
ecgossett Posted March 10, 2012 Author Report Share Posted March 10, 2012 Mine are bolted. Almost everything removable on the boat is bolts versus screws. I was just worried about strength especially on the cheeks. Another place would be in shallow water with the rudder up and more friction/force because blade is in different position. Quote Link to comment Share on other sites More sharing options...
PinoyPiper Posted March 11, 2012 Report Share Posted March 11, 2012 after several outings on my CS-17, i've had to take the rudder home for repairs twice. The first time was when a stress crack developed at the base of the rudder cheeks below the lower pintle. fixed that by splitting the cheeks a bit where the crack was and injecting epoxy into the crack and putting a bolt as low as I can on rudder cheeks to prevent it from happening again. the second time was when the downhaul line split the rudder a good three inches when it grounded and the auto release cleat failed to work. epoxy saved the day again with that one. drilled a bigger hole for the rudder downhaul line and filled it with epoxy and re-drilled through the epoxy essentially making an epoxy bush. Quote Link to comment Share on other sites More sharing options...
ecgossett Posted March 11, 2012 Author Report Share Posted March 11, 2012 On mine where the downhaul hole goes sideways I drill one into it from the narrow section, then epoxied the inside well. Putting a figure eight into the original with the rest f the rope going up through the other hole in the narrow area made this work better. Quote Link to comment Share on other sites More sharing options...
Peter HK Posted March 11, 2012 Report Share Posted March 11, 2012 the second time was when the downhaul line split the rudder a good three inches when it grounded and the auto release cleat failed to work. epoxy saved the day again with that one. drilled a bigger hole for the rudder downhaul line and filled it with epoxy and re-drilled through the epoxy essentially making an epoxy bush I've had this happen also. The low stretch 4mm downhaul line cut straight though a centre veneer of the rudder blade when the adjustable auto release cleat didn't fire (and I was only going slowly with a 2 hp outboard on idle in a dead calm). I rinsed and let the blade dry, then wedged the crack apart and squeezed epoxy into it and clamped it. Since the problem was the line cutting into the ply veneers at the bottom of the groove that had been cut into the rudder to accommodate the down haul line, I decided to reinforce this point. I drilled a hole through the rudder blade where the downhaul exits and turns to lie in the groove and glued a piece of pultruded fibreglass rod in. The downhaul now bears on this and won't be able to wedge the veneers apart. You can see the rod here and the hole into which it was glued. I don't think that point will fail again. Cheers Peter HK Quote Link to comment Share on other sites More sharing options...
PAR Posted March 12, 2012 Report Share Posted March 12, 2012 Is there a good place to get a HDPE blade versus building one for a coresound? There are several outfits that carve up HDPE (and other materials) as blades for sailboats. Generally, these are CNC jobs and not cheap. If you're a class racer and want t a bullet proof blade with perfect sectional shapes, this is the way to go. I don't know of any that are carving CS-17 appendages. As I've mentioned, I'm big on inert materials for appendages. Cored composite, stiff plastics, even some metals. I'm sure Graham employed the plywood and strip centerboard techniques for the home builder. I think the first step up the ladder would be a strip planked rudder, with a saturated rope leading edge (like the centerboard). Next up the ladder would be a foam core, with biax sheathing. Foam is really easy to cut and shape, but your "goo factor" goes way up. Lastly, other then employing fancy fabrics in a cored build, would be cutting up a hunk of high density plastic. These materials are also easy to cut, but precision is necessary if you want special foil sections (not completely necessary BTW). Getting a block of HDPE or foam blank CNC'd, isn't too bad price wise, if you know someone with a machine that's willing to do a cut file for you. If you'd like, I can provide a quote for HDPE or a foam, cut to what ever profile and section you'd like. Contact me by email. Quote Link to comment Share on other sites More sharing options...
Mike Vacanti Posted March 12, 2012 Report Share Posted March 12, 2012 <snip> These materials are also easy to cut, but precision is necessary if you want special foil sections (not completely necessary BTW). <snip> I'm interested in your statement that special foil sections are not completely necessary. What do you mean by this? Is a simpler shape nearly as good? Thanks. -Mike Quote Link to comment Share on other sites More sharing options...
hokeyhydro Posted March 12, 2012 Report Share Posted March 12, 2012 <snip> These materials are also easy to cut, but precision is necessary if you want special foil sections (not completely necessary BTW). <snip> I'm interested in your statement that special foil sections are not completely necessary. What do you mean by this? Is a simpler shape nearly as good? Thanks. -Mike I believe what PAR means is while highly competitive racers desire a perfectly foiled (say NACA 0010) rudder and centerboard/daggerboard perfection is not needed for a basic homebuilt fun boat. Plenty of boats have rudders etc with rounded leading edge and a quick taper aft with slab sides that work just fine for the intended purpose = fun! That said, I always foil mine. Not perfectly as in CNC perfect, but smoothly foiled to the eye. Good exercise, and I like the aesthetics. Quote Link to comment Share on other sites More sharing options...
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