Ganzi 3 Posted July 3, 2020 Share Posted July 3, 2020 I am rebuilding the 2 flanges/cheeks that attach the tiller to my cassette rudder. They are made of carbon fiber. The helm is attached to those flanges with bolts, and the corresponding holes in the flanges became oval (this cassette has an history of abuse, dont ask). I would like to reposition precisely those holes and make sure that they stay true The flanges are not very thick - 5 mms maybe - so I am thinking of inserting a stainless steel washer in the middle of the laminate (therefore they will be sealed with carbon on both sides when I am finished). Any reason not to do that ? Better solutions ? I thought of G10 1/4 inch but it seems much more work to integrate in cleanly in the schedule. thks Quote Link to post Share on other sites
PaulinVictoria 99 Posted July 3, 2020 Share Posted July 3, 2020 I don't think stainless likes to be deprived of oxygen, although in this application it probably doesn't matter much. How about a titanium washer? Not sure what the wear characteristics are compared to stainless, but it'd be cooler. Quote Link to post Share on other sites
SloopJonB 8,594 Posted July 3, 2020 Share Posted July 3, 2020 No. Every example I have seen of metal embedded in plastic has ended badly. 2 Quote Link to post Share on other sites
CaptainAhab 166 Posted July 3, 2020 Share Posted July 3, 2020 No. Stainless washers are sloppy out of the box. Likewise I wouldn’t bury a piece of metal inside composite unless it was a chunk of aluminium like they do on high-end bikes. The more typical way would be to have a couple of bushings made up. The holes are enlarged as the bushings have larger external flanges. If it’s a 1/4” bolt the bushing would be 1/2” the flange would be 3/4”. It distributes the load. Limits the damage to the composite. Gets rid of washers. Quote Link to post Share on other sites
CaptainAhab 166 Posted July 3, 2020 Share Posted July 3, 2020 You might be able to have them turned by a machinist with a lathe. Delrin(acetyl) plastic might be better with carbon vs metal. Quote Link to post Share on other sites
SASSAFRASS 587 Posted July 3, 2020 Share Posted July 3, 2020 Does the tiller need to be separated from the rudder? If not what about gluing G10 rod where the bolts went and going over the whole thing with carbon. Seems like it's sticks close to the original setup without alot of rework or added weight and should be stronger. Quote Link to post Share on other sites
bgytr 348 Posted July 3, 2020 Share Posted July 3, 2020 5 hours ago, PaulinVictoria said: I don't think stainless likes to be deprived of oxygen, although in this application it probably doesn't matter much. How about a titanium washer? Not sure what the wear characteristics are compared to stainless, but it'd be cooler. Titanium is very bad in cyclic bearing. Quote Link to post Share on other sites
Diamond Jim 52 Posted July 3, 2020 Share Posted July 3, 2020 How about a slice of G10 tube or cast an annulus of filled epoxy? Quote Link to post Share on other sites
bgytr 348 Posted July 3, 2020 Share Posted July 3, 2020 Can you close the tiller flanges at the aft end to make a continuous structure? Then slide it over the cassette and try to make it as tight a fit as possible, if needed put shims at the corners to make a snug fit. Then the loads get directly transferred into the composite much more spread out instead of a very concentrated bearing stress at the bolt. Quote Link to post Share on other sites
Diamond Jim 52 Posted July 3, 2020 Share Posted July 3, 2020 The West System folks have tested strength of G/Flex bonds to various materials including 316 stainless. https://www.westsystem.com/specialty-epoxies/gflex-epoxy-adhesion-data/ 1 Quote Link to post Share on other sites
Kenny Dumas 294 Posted July 3, 2020 Share Posted July 3, 2020 They specifically DO recommend it, see:“bonded hardware” Quote Link to post Share on other sites
Bruno 119 Posted July 3, 2020 Share Posted July 3, 2020 No, needs shield. Quote Link to post Share on other sites
Diamond Jim 52 Posted July 4, 2020 Share Posted July 4, 2020 Needs shield? Quote Link to post Share on other sites
ctutmark 237 Posted July 4, 2020 Share Posted July 4, 2020 instead of flanges on both sides can you add a top and bottom so it is a box the the tiller slides into? Would make things less prone to flex. Could still use bolts. Add G10 tubes in the tiller for the bolts too. Quote Link to post Share on other sites
Ganzi 3 Posted July 4, 2020 Author Share Posted July 4, 2020 thks all, tiller needs to flip up when I remove the cassette (which I do as soon as the boat strays docked for some time). so, no permanent bonding of the axis. titanium, I dont have. closing the flanges + shims, yes but no, as it would be in the way of the pin. bushings ... Got some nylon bushings today from hardware store, and then looked at this interestign chart - thks Diamond Jim - and now it seems that SS will actually have good bonding (wat’s nylon on this chart ? PPE ?) Still, I think I ll go this way - if it fails I wont have to destroy the flanges to replace them ... Quote Link to post Share on other sites
Zonker 2,858 Posted July 4, 2020 Share Posted July 4, 2020 Don't do it. Carbon + s.s. = electrolysis The s.s. gets eaten, the carbon is more noble. You isolate the s.s.with a thin layer of regular fiberglass. If you look at composite chain plates, you'll see the thin glass layer between carbon and the s. s. Bushing. 3 Quote Link to post Share on other sites
solosailor 379 Posted July 4, 2020 Share Posted July 4, 2020 Stainless is used against carbon all the time. I'll have to go tell my gooseneck 316 stainless pin to begin rusting as it's lazy ass is still like knew 12 years later. As well as my t-bar fittings, as well as my backstay pin, sheave pins, sheave boxes..... all stainless.... all rust free a decade plus later. Yes of course you can encapsulated stainless in fiberglass first for any application you can't inspect or replace like in a rudder tube insert, etc. Quote Link to post Share on other sites
Russell Brown 803 Posted July 5, 2020 Share Posted July 5, 2020 It's true that stainless doesn't get along with Carbon. Sometimes you have to use stainless fasteners with carbon because titanium fasteners are so cost prohibitive, but replacing them at intervals is kind of important. Titanium plate and rod are not cost prohibitive and it's not the worst stuff to work with. Makes bright white sparks when grinding. Watch out for breaking taps when tapping titanium. It's kind of sticky and rubbery. Allied titanium is a good place to buy from and they have metric and imperial stock. Quote Link to post Share on other sites
CaptainAhab 166 Posted July 5, 2020 Share Posted July 5, 2020 On 7/4/2020 at 11:19 AM, Ganzi said: (wat’s nylon on this chart ? PPE ?) Still, I think I ll go this way - if it fails I wont have to destroy the flanges to replace them ... Nylon is very slippery. It’s got one of the lowest coefficients of friction. Comparable to polyethylene. Same problem as a bearing material. Soft. Delrin(Acetal) is the go. Strong easy to machine. Nylon is a great material when reinforced with glass fibre. Harken & Ronstan use it for the cheeks on their blocks. http://www.dotmar.com.au/propertiestables.php Quote Link to post Share on other sites
Kenny Dumas 294 Posted July 9, 2020 Share Posted July 9, 2020 I’d be surprised if you got ohmic contact between ss and carbon unless you drill or machine the composite after cure. Casting in place with epoxy should be insulated. Any evidence to the contrary? Quote Link to post Share on other sites
Zonker 2,858 Posted July 9, 2020 Share Posted July 9, 2020 If consolidated well, fibers will touch the s.s. I have always thought of it as "best known practice" for 18 years or so. Quote Link to post Share on other sites
Kenny Dumas 294 Posted July 15, 2020 Share Posted July 15, 2020 Have you ever measured it with a meter? Ohmic contact to carbon nanotubes is not simple. But I readily believe a fastener or machined surface would conduct. Quote Link to post Share on other sites
gspot 189 Posted July 21, 2020 Share Posted July 21, 2020 Some of my older carbon sails have very visible corrosion on the stainless grommets and cringles. Sailmakers have since learned that the stainless needs to be better isolated from the carbon to prevent corrosion. Quote Link to post Share on other sites
Kenny Dumas 294 Posted July 23, 2020 Share Posted July 23, 2020 I would guess crimped cringles are similar to mechanical fasteners with pressure between fibers and metal as opposed to bonded Quote Link to post Share on other sites
Zonker 2,858 Posted July 23, 2020 Share Posted July 23, 2020 It's simple to avoid - a single layer of fiberglass between them is normal/best practice. Quote Link to post Share on other sites
slug zitski 297 Posted July 27, 2020 Share Posted July 27, 2020 On 7/2/2020 at 9:08 PM, Ganzi said: I am rebuilding the 2 flanges/cheeks that attach the tiller to my cassette rudder. They are made of carbon fiber. The helm is attached to those flanges with bolts, and the corresponding holes in the flanges became oval (this cassette has an history of abuse, dont ask). I would like to reposition precisely those holes and make sure that they stay true The flanges are not very thick - 5 mms maybe - so I am thinking of inserting a stainless steel washer in the middle of the laminate (therefore they will be sealed with carbon on both sides when I am finished). Any reason not to do that ? Better solutions ? I thought of G10 1/4 inch but it seems much more work to integrate in cleanly in the schedule. thks No problem with stainless the photo is a carbon mast , built Switzerland 1993 the gooseneck saddles are stainless the halyard exits are stainless the Swiss have a habit of using a layer of eglass between metal hardware and carbon This is a very old carbon spar, you might contact the west guys for current best practice I believe the gooseneck saddle bonding surface is sand blasted resin system was Gurit Quote Link to post Share on other sites
Bruno 119 Posted July 29, 2020 Share Posted July 29, 2020 "the Swiss have a habit of using a layer of eglass between metal hardware and carbon " Quote Link to post Share on other sites
BOI Guy 141 Posted July 31, 2020 Share Posted July 31, 2020 I have two through bolts holding my tiller to the rudder stock, the holes were slogged in the stock. I heated some long bolt shafts and coated in wax, wiped off and cooled. Set these in place and poured epoxy to fill the gap. Bolts easy pull out when set. Tiller solid now. Quote Link to post Share on other sites
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