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rjwilson's picture
Last seen: 1 day 16 hours ago
Joined: 4/28/14
Posts: 42
AC ductwork

I’m looking to get better airflow from the HVAC to the forward stateroom and thinking of increasing the size of the duct to 4”.  Has anyone tried this and did it help improve the airflow to the stateroom?

Bob Wilson
S/V Morning Breeze
2003 Catalina 36, Hull 2122
Williamsburg, VA

Bob Wilson
S/V Morning Breeze
2003 Catalina 36, Hull 2122
Williamsburg, VA
Parsons's picture
Last seen: 1 day 7 hours ago
Joined: 6/2/16
Posts: 77

Previous owner installed his own AC unit under the main cabin settee right in front of the galley sink, and ran four-inch ducts up the port side to three places in the boat, including the forward cabin.  The duct runs behind the port settee, behind the head cabinetry, and exits right next to the reading light on the V-berth bulkhead.  It's neat work, and you cannot see the ducts unless you open up cabinetry.  I attached a couple of photos to help.

As far as flow, a 3" circle has a 7 sq-in cross section, and a 4" circle has a 12.5 sq-in cross section, so the flows are going to be proportionally larger (approx. 80% more).  You may have to boost your AC fan size, however, to take advantage of that additional flow.

John Parsons
"Water Music" 1999 Catalina 36 Mk II - Hull 1771
Tall Rig, Fin Keel
Bay City, MI, USA
LeslieTroyer's picture
Last seen: 1 day 5 hours ago
Joined: 3/13/16
Posts: 427

when I ran heat I used 4" duct - behind the head (I had to remove 1/2" from tip out drawer), then under the sink and under the shower seat - and into the forward cabin just forward of the door when open.  Doesn't take cabinet space that way

Les & Trish Troyer
Everett, WA
1983 C-36 Hull #0094
C-36 MK 1 Technical Editor. 
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