Hi All,
Just removed the foremast from Fyne Spirit. It took over an hour to get the seal to let go, even with the crane applying a lot of force. Ended up drilling the seal all the way roubd to reduce the grip of the taper and got her out that way. Still the bow was lifted a foot or more to do it, so I dont know how you guys casually take out the masts to travel canals and so forth. And Marno, you must have very strong blokes to carry the big mast. It took 4 of us to carry the little one. Lack of Vegemite I suppose. Any way, this leaves me with the problem of getting a new seal. Can anyone suggest where and if not, does anyone know what the compound is that it is made of. Or are there any alternatives. One thing is for sure, there was no chance of that mast coming out in a capsize!
Regards,
Mike,
You can make new wedges and/or seals from two part polyurethane compound. A well known branded product is Spartite. I use PMC-790, an unbranded industrial compound of a greater hardness (durometer Shore 90A) than Spartite, which is durometer Shore 55A. Spartite is formulated for shrouded masts, they claim themselves. You can use vaseline to prevent the seal from clinging to either mast or deck. Even with the harder PMC-790 I sometimes see the mast move a bit. PMC-790 must be protected against UV radiation with tape or a boot. I omitted this in 2006 when setting my masts and now my deck seal leaks. Whatever you use to set your mast, don’t create hard points in the deck partners, e.g. by using wooden wedges. The CF mast may dent and buckle.
I sealed mine with a good grade of black silicone (the caulking tube/gun size). To keep it from “dripping”, build a dam of saran wrap anywhere it would run through at the bottom.
Do this on a dry day, mask the deck collar and surrounding surfaces as well as the mast itself at & above the desired height of the seal. Use MORE than one layer of blue masking tape. You want the “mast side” of the seal to be slightly higher than the “deck collar” side of the seal. Trim the tape at the seal edge of the deck collar so that you aren’t “trapping” any of it beneath the silicone. Put a layer of masking paper down on the deck (taped flat and sealed to the outer edge of the deck collar before you tape the collar itself. After taping the collar, put another layer of masking paper down taped “not quite” to the seal edge of the tape around the collar.
Proceed as follows:
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Cut the tip off the caulk tube so that you’re getting the full diameter of the “nozzle” rather than a little dribble that runs out (it’s easier to control the flow by pulling back on the plunger that way, and the job goes faster). Poke several holes in the membrane (not just one)
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Gun in enough silicone to provide more than enough. Work your initial squirts down into the bottom of the area that you’re sealing
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Allow it to set long enough to “self level” into any crevices, but not long enough to “skin” over
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Tool it smooth with an ICE CUBE, working any excess off onto the masking around the deck collar. The surface will be glass smooth. Leave only the barest feather edge at the edge of the tape on the mast and on the collar.
Make sure you put enough down in the initial application, as the melting ice will wet the surface of the wet silicone and prevent a seal between layers if you have to put more down. Pull up the top layer of masking paper (trapping most of the mess inside), then pull the tape off the mast and collar while the silicone is still wet.
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Thanks for your advice. The area to be sealed/filled is quite large and would take 2-3 600 mm tubes of sealant. What came out appears to be a cast or extruded product that works a bit like an o ring except the ends were not joined. The approximate dimensions are those of a tapered wedge, 30mm at the top, 22mm at the bottom and 52mm deep. It is completely uniform all the way around. It appears it is a pre manufactured product which is inserted and then clamped/driven into place by the cast aluminium mast collar. I take the point about shore hardness as it appears this arrangment takes the lateral loads while the mast collar applies vertical downward pressure to hold the seal in place. I wonder about making a mold and casting this material. Any comments?
Thanks,
There should have been some “nylonish” looking wedges in all of that…these are held down by the mast collar & take the lateral loads. You don’t need to bury them completely in the sealant (hence the “dam” made of saran wrap.) If they’re not there, I don’t rightly know what to suggest to you as a replacement.
Katorpus,
the material removed was not sealant but rather a harder cast or extruded compound vey similar to that I have seen in some engine mounts. The seal had a definite join so I think it was manufactured and then installed as oppose to cast in place. I think Michel might be onto it with those compounds he mentioned. I also recall a product called chockfast which was used in very large engine installations. So I start searching for the compounds or chockfast. At least we should be able to measure shore hardness from the sample.
Thanks and regards,
Mike, what you describe is the original all round wedge of extruded PU. I had these on my UK built F33/35 of 1986. This wedge is clamped down with the deck collar. The water seal is then made on top of the wedge, inside the deck collar. You could use any decent sealant for that. As Katorpus describes, nylon wedges have also been used. I would keep the original PU wedge if it’s still good. Saves a lot of hassle. I missed these on the F44 and had to cast my own wedges in situ, which is a dirty job, even though stains and drips of the two part PU is easily removed once it’s cured. I used a bit too much vaseline so I have hose clamps around the mast under the deck to prevent the wedges to shove down along the mast.
Michel, that sounds about right. The old seal had to be drill around its circumfrence to get it to release so a new one must be made. The idea of casting one in-situ does not appeal due to difficulty keeping the mast still and in the right position while the stuff sets. Also, in order for the mast collar to push the seal down into place and apply some locking force, the rubber would need to be proud of the deck by 2or 3 mms. So i thought i would make a mold and cast one. Also a precast uniform product will put the mast in exactly the right place.
I had a look at PMC 790 which is not availabe in NZ shore 90a, and spartite shore 90d, which I think would mean the spartite would be harder. I will get the old seal tested for hardness and take it from there. It seems to me that the seal is the main retaining device for the mast and takes all the lateral compression loads, the mast collar being mainly the means of driving the seal into place. I can get spartite and chockfast in NZ, though I am not entirely sure of the suitability of chockfast.
Regards,
Michel,
Just to shift the topic slightly, you may recall that the main reason for removing the mast was to deal with some movement at the base. I Have removed the top hat and the vertical surfaces show no wear so all wear must be inside the mast. There is some wear on the horizontal surface where the mast sits and has been oscillating. The top hat is retained by six bolts on a pitch circle, and it is made of grp. My thought to prevent movement in the future would be to cutout a 6mm stainless steel flange to bolt ontop of the top hat flange and weld a tube 80mm high bored to outside diameter of the mast to provide a socket for the mast to land in. I would cut two vertical slots in the tube and weld two plates with bolts each side so that the tube can be tightened onto the mast. Any thoughts?
Thanks,
Mike,
Your solution sounds very substantial, but perhaps also overkill. The 6mm plate may well cause more chafe, and be quite destructive, if it is not an exact fit. I would have thought that a more simple solution, with less possibility of future wear, would be to apply relaese agent to either mast _or_top hat, and some epoxy filler to the other, when you re-step the mast, let it set, then put a bolt or two throught the mast and top hat to prevent rotation.
If you have access to machinery that will bore to the diameter of the mast, then build up the base of the mast with CF and epoxy, then bore it to the diameter of the top hat. Drill, tap and bolt to prevent rotation as before. Less likelihood of chafe damage, and it’s a repeatable repair.
Or have I misunderstood the basic problem?
Regards,
I wouldn’t do anything at all to put any kind of compression on the mast base, since you don’t know what kind of stress you’re inducing to the mast. One single bolt does not compress the diameter of the mast base (only the mast wall where it’s tightened down). Anything else brings a whole 'nother set of forces into play here.
The “build up the top hat” approach sounds most reasonable to me. Building up and boring out the inside of the mast is un-neccessarily complicated, and getting a proper bond on the inside of the mast at the base is problematical. Remember, the thickness of your buildup will be miniscule, and you can grind down the top hat quite a bit in order to obtain an adequate thickness of buildup…but you wouldn’t want to do that to the mast.
As far as “repeatability” of repair goes, it would be a whole lot easier to make a new tophat down the line if things get too “worn out” to work…and…for that matter, you could cut 80mm off of the bottom of the mast and start “fresh” if it ever came to that…as long as you did it BEFORE you got a mast failure.
The bolt hole is there for two reasons…to keep the mast from rotating and to keep it from “bouncing” off of the top hat. One bolt, and the deck level compression ring (combined with the taper of the mast) is going to prevent the mast from falling out in a knockdown. Anchoring the mast base TOO firmly will induce stresses between the mast base and the deck ring that weren’t there before.
If the bolt hole is too “wallowed” out, you can either overbore the mast base & the female threads and re-thread for a larger bolt or change the orientation of the base so that the anchor bolt is “somewhere else” around the diameter of the mast base…then bore a new hole in the mast base. As long as it’s more than 3 or 4 diameters away from the existing hole, I doubt that you’d ever have a problem with weakness. Don’t, however, just “rotate the mast” and bore a new hole, as there are too many things on the mast that rely on the rotational alignment (halyard exit plates, masthead truck, and anything else attached to the mast including gooseneck (if you have one) would all be “out of whack”)
Mike,
I had the same problem with my foremast as you are having now by the sound of it, with the wear on the inside of the mast. It has been fixed twice.
The first time, some release agent was applied to the inside of the mast and then some epoxy was applied to the top hat as the mast was lowered onto it. It lasted a couple of thousand miles and the mast started moving again in the early stages of our first trip across the Atlantic (I almost turned back). The way I figured it, the epoxy needed something to hold it together.
Fix number two, lift the mast out, light sand, fill then paint the top hat to make it nice and smooth, then apply release agent to the top hat. Cut to size, two rings that sat on top of the top hat and hung down the sides, one of biaxial cloth and one of light cloth, glass on using West System slow and lowered the mast on while still wet (didn’t get it lined up right the first time and had to be raised and relowered doh!!!). Make sure when you put the release agent on, you put it around the base of the top hat as you’ll find the epoxy get squished out the base and comes out the bottom.
15663 miles and two oceans later, it is as solid as a rock ( I get paranoid and check from time to time). Hope this helps. Make sure to eat your vegemite!!
Regards
Marno
Mike, I made thick plywood circles that just fit around the masts and bolted these under the deck temporarily to keep the masts in the middle of the hole and to provide a floor for the PU resin wedge. To have a look: http://www.flickr.com/photos/alabama_queen/287929517/ and http://www.flickr.com/photos/alabama_queen/287930077/
I must add that my deck opening on the F44 is not conical like it was on the F33/35 and probably on your F39PH, so for me there was no possibility to compress an around-the-mast wedge into the hole.
I must say, Marno’s solution sounds very good and it’s proven too. I have no top hats but collars just like on deck. There are bolts through the mast and collar and I have put in a few soft wood wedges between mast and base collar. There is not enough room between mast and collar to pour in resin.
Michel, I remembered you mentioning the collar and wedges in a previous thread which is why I had thought of engineering a stainless collar with clamping arrangement which could of course be adjusted or wedged without the need to remove the mast. But like you, I also like Marno’s approach ( vegemite must be good for the brain as well as muscles). As I have the top hat out of the boat, it would be relatively simple to fill the gap with cloth and resin and get it to the right size. I know this mast was out before by th PO and it did not move for the first year we owned it. It looks like it make have had a thin layer of resin similar to Marno’s initial repair. I have some heavy double bias cloth that might do the job nicely. On the subject of the urethane ring I have found a company in Auckland who can cast a new one of the same hardness. The hadness was shore 75A by the way. I think I will get a spare cast at the same time.
Thanks for your help guys,
regards,