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Hi - we are new to the forum and to boat ownership. There is a crack in our Mac 26s about 4 to 6 inches to the aft of the mast in the interior above the sink near the pop up. It is worse with the mast up.

Have others had this issue? Found the former owner had the aft stay fairly loose.

Is this a repair we need to do? How concerned should we be about sailing before repairing?

Thanks in advance for any information/advice.

Hi welcome to the forum. Maybe a photo would help us see the problem?

Thanks. Let me try to attach photo again that I thought I god up in first post (and can view from my side).

I could see the photos from your earlier post. Just don’t own a 26S so hoped others would respond.

The 26S owners may recognize where your photos are taken. However, the rest of us will need a shot or two from more of a distance so we can get oriented.

Does the 26S have a cosmetic liner, like the M, or is that part of the cabin top structure?

If it is structural, you’ll need to fix it properly. The fact that it changes with the rig up, makes me think it could be structural.

You can do a one-side repair by grinding out the cracked area to a 18:1 slope (minimum), and re-glassing it.

Once you establish where this is in the boat, and we determine how structural it is, the feedback can get more detailed.

And… Welcome to the forum! Glad to have you participating!

Hope you can get it repaired and start posting sailing pics instead!

This isn’t our boat but shows the area where the crack is.
We are going to try to determine the answer to the cosmetic liner question.

Still not quite able to get oriented completely, but looks like it is probably structural. I’d be tempted to grind down to good glass well past the crack on both sides. Then, put several layers on around the entire gusset; reinforcing the corner, and extending well out the straight sections. In addition to doing the crack repair per the methods in the above video.

Hi Tdb Frt!

Welcome to the forum!

Based upon your photos I agree with JimmyT that this is part of your top deck structure and needs to be adequately repaired.

The flex aspect when a load is applied pretty much confirms it. The “loose” back stay is probably as a result of the ability of the top deck to flex. A little bit of angular movement near the base gets multiplied as it goes up the mast. So yeah, yer gonna have to fix it before it gets worse with each flex.

To do that I’d first determine what you can access and drill “stop crack holes” at the ends of any crack. The diameter of the “stop crack holes should be a minimum of 3x the material thickness. I’d recommend doing these holes first before any grinding. That way you can definitely know where the ends are BEFORE things get messy and blurred over.

Given that this area has already fractured its best to clean up an area larger than just the immediate area as there may likely stress damage to the area surrounding the crack, especially in the directions of crack propagation.

If the material is 1/4 inch thick that means an area to each side of the crack needs to be ground back by a minimum of 4-1/2 inches. More is better. This will give you the 18:1 slope that JimmyT mentioned. Less than that and there won’t be enough uniform load transfer back into good material.

For structural repairs You might want to open up the crack so you can get some backside reinforcement into place if that’s an option. Occasionally I’ve done that by drilling several extra holes around the cracks, flushing the back face with solvent to clean it up, mixing resin with 1 inch long glass fibers and working it through the holes and flattening it along the back face with something akin to an Allen wrench from the widened ground open crack. (Note: You need to adjust your surface grind back accordingly.)
The back surface reinforcement thickness should be about as thick as the original material.
Use slow cure non waxing resin.

While the back surface reinforcement (if you decided to go that route) is still wet start applying your exposed surface layers to a thinly wetted surface one layer at a time working out any entrained air. Ideally one would want to apply enough progressively wider layers to at least match the the original fiberglass surface being careful to roll out ANY air pockets and excess resin. The wetted fiberglass is the strength. Air and excess resin are useless, Especially in structural repairs.

When setting up your fabric pieces it’s a god idea to rotate the weave directions if possible to obtain a stronger finished structure. After you are finished apply a protective layer of waxing resin to seal. Let it cure throughly then de-wax. Sand to contour and apply thin layers of gelcoat. Allow to cure, sand and repeat as required.

Hopefully this helps.

Best Regards
Over Easy

I don't know if the 26S is the same as the 26D in this area, but in my 26D there is a void behind that area. There is space between the interior liner and the top deck. About 3/4" if memory recalls correctly. I remember thinking this would make a nice "wire chase" if I needed to run wires over to the port side. You should be able to removes the panels above the sink and the port side of the daggerboard trunk to be able to access the repair area from the backside.