Stopping a stress crack in its tracks

I have one really small stress crack near my tower mount that's gotten a little bit bigger in the last month. It's so small it looks like a hair that's about 1/2 an inch long.

It's not a big deal, and I don't really need to fix it right away, but I want to stop it from spreading if I can.

Any suggestions for stopping it? I was thinking super glue near the termination point, but I don't want to make it look worse. I'll also go re-visit the tower mount to make sure there's plenty of back plating there.

As I understand these are similar to a crack in glass that can keep going becuase it is brittle. Has anyone every tried drilling a small (1/8") hole at the end of the crack to stop it? If you just went through the gelcoat then sealed it may be a quick fix until you can get the gelcoat done.

You can very likely get the gelcoat from Spectrum at 800 754-5516. All you need to tell them is the color and year of your boat.

I have heard about the 1/8th inch hole to stop it. It's just so so small, I didn't want to make it look worse. If I could freeze it where it stands today, I would probably leave it alone since it's so minor.

I'm afraid if I were to drill a hole, I'd be forced to fix it while risking making it look worse at the same time. There's a good chance I would screw up the repair too and then I have to dish out the big bucks to bring it to the shop.

John,

If you can lift the tower mount and champher the hole it will probably remove the stress from the gelcoat causing the crack. If the edge of a bolt is pressing against the gelcoat it will probably keep moving. Do it with a countersink bit running in reverse.

I don't think I would be drilling any 1/8" holes in that nice boat of yours to stop a small gelcoat crack.

I retract my previous statment, mouth engaged before brain.

Since it's a half inch dont worry about it unless it grows. If it does, go to http://www.spectrumcolor.com and order the patch kit for your Malibu (primary gelcoat supplier to the boat builders).

If it ever grows get the patch kit and just find a good fiberglass person. At that time you'll want to take off the base, make sure the holes were chamfered well and make the repair to the hole for the base. If you take the base off and all they have to do is the repair, it's maybe an hour or two job so it should'nt cost much.

Sorry about my moment of senelity above. Dont do that drill thing, bad idea.

I'll take the base mount off later tonight and check it out, but I'm positive I chamfered the holes when I put the tower on. Maybe I didn't do it enough.

I guess I could also put a bit of super glue under the base mount where it will not show and it might strengthen the gelcoat that's already cracked.

Thanks for the advise.

Stop the crack from spreading by addressing why your gel is cracking in the first place. Even if you repair the gel, the crack(s) will return if you don't address the problem with the tower/mounts. You must be getting a lot of sway/flex in the tower and/or you don't have enough reinforcement at the tower mounts.

Is the crack radiating from one of the holes? If so, then you probably didn't do a good enough job of chamfering the holes. If not, however, you probably have another issue putting too much stress on a small area. Some things to consider:

1. Is the fiberglass thick enough where you mounted the tower and are the mounting points far enough from any holes (cup holders) or edges to avoid bending? If not, you may need to reinforce or relocate.

2. Do the mounts follow the same curve as the hull? If the mounts are flat, is the hull flat? If you have even a slight curve in the hull, the use of straight backing plates can cause damage. There are two ways to solve this: a). Create a flat surface by glassing in a metal plate or some plywood w/ structural epoxy filler filling the void between the plate/wood and the hull. b). Just use the structural epoxy filler directly with the backing plates (note: if the plates are aluminum, you should buy an acid etching prep kit if you'd like the filler to adhere to the backing plates.

3. Make sure you have isolated both the feet AND the backing plates from the hull with sheets of rubber. This should keep them from exerting stress along their hard metal edges.

What ST said.

The tower has been on the boat for about three years with no issues until now. The mounts are on a very slight curved surface, but there are rubber sheets under the mounts on both sides. I've also got a pretty large slab of plywood between the mounts too to spread out the force. There's really no void to speak of that I remember. I'll check the void again tonight though. If there is a void, I'll make sure to fill it. The OEM fiberglass is pretty thick there from what I remember it's about 1/2 inch or so.

The one thing that has changed is that I added tower speakers and they're pretty heavy. Maybe the added weight and hitting double ups is causing more downward stress on the front mount than I've ever had before.

So I removed the base mount and found that the crack is originating from one of the mouting holes. In-fact there are several new cracks starting that are not visible when the base plate is covering the holes.



I guess the best course of action is to:
1. Use my dremel tool to chamfer out the holes more than I did originally to relieve the stress. Obviously I didn't chamfer them enough when I originally put in the tower.

2. Put super glue on the non-visible parts of the existing cracks to provide some additional strength and hopefully stop the progression.

3. Coat the entire edge of each hole with super glue to prevent chipping in the future.

3. Do the same thing on the other side even though there's no cracks on that side that I can see.

Any other suggestions?

Bump.

I really chamfered the heck out of each hole and put super glue on any crack that was not visible.

Any other advise?

John,

Make sure the bolts stay good and tight so the bolts don't get the opportunity to apply any shear forces on the holes. Based on the gelcoat chip at the rear of the top right hole it appears that there may have been some shear forces between the bolt and the hull in the direction toward the crack? Make sure the holes are big enough to accomadate the rubber's deflection without allowing the bolt to bind in the hole.

The bolt on the top right is the rear bolt. All forces would be pulling in the opposite direction of that bolt I'm pretty sure except for downward force from hitting rollers with boards on the rack.

Maybe the bolt was not tight enough. I noticed it was slightly bent when I took it out. I guess it's also possible that it happened when I was erecting the tower. I have to bring the legs to the front and put them on the brackets. I know once I kind of dropped it slightly and hit hit the base bracket pretty hard but that was a couple of years ago.

I have been "snugging" up the bolts, not cranking on them. Maybe I should tighten them more? I don't want to put too much stress on the hull though.

The chip is gone now cause I dremeled it out.

One more thing, try not to pull deepwater starts without the boat being straight inline with the boarder directly behind, the deadweight side pull is a source of great stress.

Mike:

Thanks. That's actually a good tip. I usually try to pull straight unless it's a little kid. They pop out in idle!