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When I was at the factory taking a tour of the MAC70 they told me that sweating was a new problem that occured when they started putting fiberglass liners in boat. The full hull liner in the X boat was considered an added feature at the time. You can see here that the liner for the X boat is a FULL liner that covers the entire hull for added insulation:

This made good insulation in the X boat, but also resulted in moisture, so when they made the M boat they added another layer of fiberglass to the hull and just skipped the hull liner altogether:

So when they did the M boat there is no liner on the hull - they are just bare walls covered in carpet:

This did stop the sweating along the hull where the beds are. It did not completely stop ALL sweating - if you load up the M boat with 5 people all sleeping at night on a cold day you will get some moisture on the upper liner.


The marine plywood with the teak and holly should be able to take moisture if you finish both sides with Epiphanes - I did both sides lightly.

In an attempt to reduce humidity from sleeping crew at night and creating additional ventilation in general,I installed two opening ports. These are opposite each other (port & starboard), and far back in the cabin. Right at the beginning of the aft berth.

Yes I copied Rays Mod two 14" opening Beckson portlights in same location but also added two 10" opening Beckson portlights forward one in the head S/B & one opposite port side all four have rain shields installed so as can b left open during rain fall ,have also a 10" glass opening hatch installed into the big opening man escape hatch above the V- berth , another 10" opening glass hatch installed into the sliding hatch . two 3" low profile cowl vents installed in dorado boxes I fabricated installed on either side of the mast just in front of the D/B slot they can both b closed off from inside the cabin roof , also a 12" or 14" can,t remember oval opening hatch installed into the top section of my two piece plexy glass entrance hatch & thats all topped off with a bilge blower fan installed in the stern vented thru both sides just under the helm seat, intake vent is piped & runs all the way from stern to the bow outtake vent vents out under helm seat thus bilge fan vents totally all bilges bow to stern

So my boat has lots of ventilation on these really hot summer days we had when I lived in Ontario Can.

J

Hi BOAT, NiceAft & Highlander!


Thanks for the back story on the Mac26X vs Mac26M and the wall sweating BOAT.
We like the Mac26X full fiberglass liner for the easy wipe down cleaning, not so much for the sweating aspect we encountered in cooler/cold weather conditions.

We like the idea of installing the opining portals NiceAft and Highlander mentioned. We assume they have screens? Are the rain shields something extra or did you have to fabricate them yourself?

The glass deck hatches are a great item to add! Light and Ventilation! Especially in the bow!
As long as they are strong enough to stand on and can’t shatter those would be good additions. We are going to have to look into these and screening/shade options.

The bilge/inter-panel ventilation forced air suction blowers are also a good idea!

These all will help in the warm/hot seasons.
Depending on the volume flow rate of the blowers those should help even in the cooler weather conditions as well!

Thank you for the suggestions!
They are appreciated!

Best Regards,
Over Easy