Shimming Strut

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

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.

Greg_SA wrote: 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.

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.

wingwrench wrote: 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.

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!

8122pbrainard wrote: wingwrench wrote: 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. 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!

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.

wingwrench wrote: 8122pbrainard wrote: wingwrench wrote: 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. 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! 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.

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.

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.

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.

Greg,
Now you have a perfect fit of the base.