Shimming Strut
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Boat Maintenance
Forum Discription: Discuss maintenance of your Correct Craft
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=21281
Printed Date: November-20-2024 at 4:32am
Topic: Shimming Strut
Posted By: Greg_SA
Subject: Shimming Strut
Date Posted: April-13-2011 at 5:28pm
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Hi,
I am replacing a strut, shaft and prop on my 1989 Ski Nautique. I fitted the new strut today, and the shaft touches the top of the log - so I assume I need to shim the strut? I fitted a single washer (1.3mm or 0.05" thick) to the two front strut mounting bolts (between the hull and the base of the strut). The alignment now seems correct - the shaft is dead center in the log, if I lift is slightly, so that turning the shaft has the least resistance. Can I just use the washers and fill the gap with 5200 sealant - will this not put too much stress only near the washers> Or should I rather use something like epoxy? With epoxy, I would have to put some could put cling film or release agent on the hull, so that the epoxy only bonds to the strut. Anyone done this? What would you recommend? The other option is to take the strut to a machine shop and machine the base - not sure it would be easy - I think it would be my last resort. Thanks, Greg ------------- 1989 Ski Nautique (SN2001) |
Replies:
Posted By: 8122pbrainard
Date Posted: April-13-2011 at 8:51pm
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Greg,
With only needing one washer, you're fine with just the 5200. BTW, it is discussed in the alignment video Keith just posted this morning. Check at the top of any forum section for the video. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: Greg_SA
Date Posted: April-14-2011 at 6:26am
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Thanks very much - I'll have a look at the video.
So, I assume that the 5200 is a lot stiffer than silicone? So it will spread the load sufficiently. ------------- 1989 Ski Nautique (SN2001) |
Posted By: Greg_SA
Date Posted: April-14-2011 at 9:56am
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The 5200 packaging says "flexible" - will it be solid enough to spread the load across the strut base? I am worried about the hull taking strain near the washers, and other edge of the strut base. ------------- 1989 Ski Nautique (SN2001) |
Posted By: 8122pbrainard
Date Posted: April-14-2011 at 10:24am
Greg, If you are concerned, then do a epoxy base. You've got the correct procedure in mind except put the release on the strut so the epoxy sticks to the hull. Wax paper or plastic wrap works well. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Greg_SA wrote:Posted By: wingwrench
Date Posted: April-14-2011 at 10:41am
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The washer will eventually embed itself into the glass and you will be back where you started if you use 5200. I would fill the gap with something more rigid.
This is how CC solved the problem on my boat, bankruptcy forced them to use what they had on the shelf and sometimes that meant using a strut with the wrong angle. 
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Posted By: 8122pbrainard
Date Posted: April-14-2011 at 12:28pm
Jack, Sorry but I disagree. The 5200 has a shore A hardness of 68 which is towards the high end of the A scale. At .050" max thickness at one end (flat washer thickness) down to zero thickness on the other, that's not much flex!! Don't forget about the amount of surface area the typical strut has on it's base ether. BTW, if you have ever seen a flat washer embedded in fiberglass, I'd say there's some rotted wood reinforcement bedded in the glass issues!   ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: TRBenj
Date Posted: April-14-2011 at 12:40pm
Were you able to confirm that was the work of the factory? It really looks like a shady fix by a previous owner to me. Scary nonetheless! While inserting one washer to dial in the strut angle seems to be perfectly acceptable, we couldnt quite get there on the BFN... we needed at least 2 to get ours within reason. Instead of shimming, we chose to grind down the base of the strut instead. A careful eye on the grinder wheel followed by some hand filing and sanding (confirmed by a straight edge) got ours pretty darn close to perfect- no shimming necessary.  ------------- |
Posted By: wingwrench
Date Posted: April-14-2011 at 1:23pm
Pete, This is off the 3m website on 5200, "Stays flexible and allows for structural movement". Considering the bolt tension and the harmonics transmitted through the strut by the prop shaft I feel the washer will embed over time. We can agree to disagree. |
Posted By: wingwrench
Date Posted: April-14-2011 at 1:33pm
Art at CC confirmed my boat was built in Sept. 62 and was likely 6th American Skier built, Sn. 106. He said when they were getting back on their feet they would use what ever they had and very likely they put the wedge on it. I replaced it with the correct one. If you think that was scarey, you should see the glass work. I took the stringer tabs off the hull with a putty knife. The basic hull layup is good but everything attached to it was really poor. |
Posted By: 8122pbrainard
Date Posted: April-14-2011 at 1:39pm
Jack, Yes, we do agree to disagree. I'm fully aware of the statement about the 5200's flexability. You didn't look up the hardness did you?? Just how many struts have you run across that fit perfectly to the bottom of the boat? The bases sometimes aren't even machined and sometimes the hull isn't real flat ether!! I've seem a washer used to make up the difference from the factory and then RTV and RTV sealants have a even softer durometer. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: Greg_SA
Date Posted: April-14-2011 at 1:58pm
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Thanks for all the feedback guys...
I have used epoxy to create a new bed for the strut (with the washers). I'm sure the 5200 would be good enough, but like most things, I tend to over do it :) ------------- 1989 Ski Nautique (SN2001) |
Posted By: gun-driver
Date Posted: April-16-2011 at 2:23pm
| I did like Tim, grind off what you need and check with a straight edge. No matter what you fill it with it won't be as strong as the whole surface in contact with the hull. |
Posted By: 8122pbrainard
Date Posted: April-16-2011 at 6:39pm
Paul, Sorry but I'm not following you on the strength issue. What's not as strong? A filled epoxy wedge as planned compared to the polyester/glass hull? ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: gun-driver
Date Posted: April-17-2011 at 12:42am
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Maybe I'm not completely following the epoxy idea. Are you talking about making taking a block of epoxy and grinding it into a wedge?
I still think grinding the strut base itself would give you a stronger surface to surface bond with more evenly distributed stress areas. |
Posted By: Greg_SA
Date Posted: April-17-2011 at 7:17am
Thanks for the suggestion, but I have used the epoxy fill, and it worked very well. I filled the "gap" between the strut base and the hull (created by adding the washer to one side) with epoxy - I applied it as an adhesive (with a release on the strut base) and let it dry, then removed the strut again so that I could seal it with 5200. This has effectively added a layer to the hull, that fits the exact gap. I believe that it the epoxy will be as strong as the hull material itself, and the fact that it is a perfect fit between the base of the strut and hull, I believe it is the best solution. I don't have the tools necessary to adjust the surface of the strut base, and make it perfectly flat. Even if the surface was perfectly flat, the hull surface might not be perfectly flat... so I still believe that the epoxy fill is the best solution to spreading the load the most evenly. ------------- 1989 Ski Nautique (SN2001) |
Posted By: 8122pbrainard
Date Posted: April-17-2011 at 8:52am
Greg,
 Now you have a perfect fit of the base. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |