Progress! Just to follow up in case anyone's interested or for future reference, I managed to get one U-Bolt out. I wrote a blog post on the methods and results: https://svviolethour.com/2017/01/29/rerig-part-4-stuck-navtec-u-bolt-chainplates/
tldr: Lots of heat plus a 24" pry bar / breaker bar. I found an Ericson owner who used a similar method - shroud tension plus heat. He thinks shroud tension was around 1000 lbs, but he had 3/8" Navtec u-bolts. Using a lever arm calculator, I calculated the upward force it took on my 1/2" bolts was around 2000 lbs. Interesting aspects once I got it out: lots of aluminum corrosion dust from the backing block, but the SS was spotless. Bedded in butyl, not silicone. And the deck core here was not wood! Some kind of hard composite I don't recognize - light orange / peachy in color. Very good news because the core is pristine. I doubt it's an epoxy coring from a prior owner (since A) it's doesn't look like epoxy, and B) the bolts looked like they'd never been pulled). Around each U-Bolt the deck has square area about 8"x8" where it's clear something different was inserted between the fiberglass. I thought it was marine ply, but I guess they could've used some kind of board of composite or plastic. The one question I haven't figured out yet is, if the U-bolts were not leaking (I've never observed water from them, even in heavy rains), how did the aluminum corrosion happen? I suspect small moisture over time (interior cabin moisture? Or small amounts getting in from deck while under sail when the u-bolts are under flexion / tension?) contributed to it. Just need a small amount of moisture to get a galvanic medium on the less noble aluminum next to the SS. The material loss is insignificant however. -Patrick 1984 C&C LF38 On Sun, Jan 22, 2017 at 6:44 PM, Patrick Davin <jda...@gmail.com> wrote: > I haven't had any luck unfortunately. I'm probably going to give up for > now and put it back together. It sounds like only about 2 LF38 owners on > this list have pulled their rod U-bolts, so I guess it's a less common > thing than I expected. > > I put about 6-8 hours into one U-bolt over 2 weeks, spraying the aluminum > backing block with vinegar 5-10 times, PB Blaster 3-4 times, BoatLife > Release 2-3 times. I hammered in a paint scraper on the 2 accessible sides, > and then hammered in a cold chisel on one side. That opened a bit of a gap, > but it was starting to tear into the fiberglass. I hammered upwards on the > thrubolts too but the access isn't very good. Also heated with a heat gun > until PB Blaster started smoking. > > There's no way to inject stuff from above deck because the U-bolt plate is > completely flush with the deck - I can't even get a razor blade in. Unless > I sanded off the deck paint perhaps. > > I put some pictures here: https://drive.google. > com/drive/folders/0BxfHpwssU_6NTlRNbXUtSHAtaWc?usp=sharing > > I'm half way tempted to just leave the nuts loosened by 1/8 of an inch and > go sailing in 10 knots or so on a few tacks once the rig is back. I bet > that might loosen it up. Or maybe just tensioning to 1000-2000 lbs would do > it. > > -Patrick > 1984 C&C LF38 > > On Sun, Jan 8, 2017 at 10:39 AM, Patrick Davin <jda...@gmail.com> wrote: > >> Thanks. I'll try the vinegar technique. I also have some BoatLife >> Release, but was hesitant to try that because the seam will be difficult to >> inject into, and the Release chemical is fairly toxic I believe. >> >> I have no leaking from above deck, so I probably won't be able to inject >> anything from above. I'm only opening / inspecting to confirm it's not >> leaking, and because I have the mast out now. >> >> I too had some white dust float down when I loosened the threaded rod. >> >> I'll try tapping up on the bolts too. >> >> On Sun, Jan 8, 2017 at 9:19 AM, Bruno Lachance < >> bruno_lacha...@hotmail.com> wrote: >> >>> Patrick, >>> >>> I have faced the same kind of problem on my boat. It is not exactly the >>> same style of chainplate, but the 33 mkII does have the same aluminum >>> backing block, and it was not moving. I initially tried the wedge, the >>> hammer... With no success. There was some white powder visible, sign of >>> aluminum corrosion. I finally had success with white vinegar, injected with >>> a syringe where I can, from the top of the deck and from below, and a >>> soaked rag taped around the block. I repeated this procedure twice and >>> wait... The day after, I was able to separate everything with a small tap >>> on the bolt, clean and reassemble with good quality butyl. I was happy to >>> find that the core was not exposed around the chainplate. >>> >>> Good luck. >>> >>> Bruno Lachance >>> Becassine, 1987 33mkII >>> New- Richmond, Qc. >>> >>> >>> Envoyé de mon iPad >>> >>> Le 8 janv. 2017 à 11:45, Patrick Davin via CnC-List < >>> cnc-list@cnc-list.com> a écrit : >>> >>> Anyone have experience pulling this style of chainplate? Photo uploaded >>> here: https://svviolethour.com/chainplate/ >>> >>> Wally's site also has a good picture of one once it's open: >>> http://www.wbryant.com/StellaBoat/Projects/newrig/cplates/cplates.htm >>> >>> Wally says his were bedded in silicone, which probably made it really >>> easy to pull, but mine don't appear to be silicone - some white >>> sealant/adhesive which I'm afraid might be 4200 or in the worst case 5200. >>> The backing block is adhered to the fiberglass deck undersurface, and to >>> the bolts of the U-bolt. >>> >>> But mostly it's hard to pull because the block has nothing good to grip >>> on, and it's in a tight location with bulkheads / cabinetry blocking access >>> to two sides. >>> >>> Anyone have tips for how they did it? Did the backing block come off >>> easily, or were there some tricks / gotchas? >>> >>> I've tried: vice grips, flathead screwdrivers used as wedges and >>> hammered on the end, heat gun, pulling up on the U-bolt above deck, and >>> trying to pull down the backing block using the threaded rod itself >>> (over-tensioning it - I stopped this before it got too scary - don't want >>> to break it). >>> >>> The next things I can try are: torch (stronger than a heat gun for >>> melting glue, but I don't want to burn the fiberglass or set something on >>> fire). More hammering on wedges. >>> >>> -Patrick >>> 1984 C&C LF38 >>> >>> _______________________________________________ >>> >>> This list is supported by the generous donations of our members. If you >>> wish to make a contribution to offset our costs, please go to: >>> https://www.paypal.me/stumurray >>> >>> All Contributions are greatly appreciated! >>> >>> >> >
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