Once we closed on Red Rover almost two years ago, we were then able to be admitted to the wonderful world of the NOG (Nordhavn Owners Group). The NOG is an owners only online forum that discusses all things Nordhavn. One of the topics that first really caught my attention was about keeping engine room temp down as much as possible. As we had just brought Red Rover up from San Diego and performed engine room checks every hour, I knew that ours came up around 110 degrees after being underway for a while. Industry goals target a 30 degree delta above outside temps and the engine room should never get above 130 degrees (for the health of the systems inside and anyone that needs to be in the ER for any amount of time!). As the outside temp on the Washington Coast was probably no more than 60 degrees, Red Rover was pushing an excess of 50 degrees delta – not good! Especially once we head south in to the tropics when temps can get towards 100. Much more air must be moved/exchanged thru the engine room to make a positive difference. So we knew this project would be one that would be addressed at some point.
Fortunately for me, I stumbled across the blog of Peter Hayden. He and Laurie own Tanglewood, a Nordhavn N60. The N60 is essentially a N55 with 5′ of extra cockpit but the rest of the boat is pretty much identical to Red Rover. Flipping thru their blog, I found Peter’s recipe to solve the same issue we had with ER cooling. You can read all of his homework and steps he took to achieve a cooler engine room HERE. We owe Peter and Laurie a nice dinner for breaking trail on this one. What it seems took Peter weeks/months to work thru took me just a few days (over the course of a couple of weeks) to complete. Thanks Peter!
Here is what I started with. The is the aft side of the pilothouse, right where the stack comes up from the engine room.
First thing too do is remove the fiberglass splash guard.
Behind the splash guard is more fiberglass! The top half comes off with 4 screws. Behind it shows the one 5″ hose that vents the air out from the engine room. Not much volume can go thru that hose!
Next thing to do was remove the fiberglass panel that divides the storage space from the stack area.
A better look at that fiberglass panel. Behind it is a large squirrel cage fan that is supposed to draw air up from the engine room and push it out the 5″ hose. The smaller 3″ metal hose is connected to a fan above the engine. That fan pushes air in to the stack insulation and then out this hose. It does get hot!
Here is the large fan that was behind that panel. As Peter notes, it does pull some air up from the engine room but it also is pulling air from anywhere which includes down the stack, which does not help cool the engine room.
Fan gone and you can see the 5″ hole where the hose was attached. You can also see how hot that 3″ hose gets – the fiberglass is brown from heat. The conduit is the power for the fan – it ran down the wall next to that really hot metal hose… keep this in mind for later in this story.
This is looking up the stack cavity. You can see daylight shining down. Part of the project is capping that area off, essentially creating an air dam. We want that done so the new fans only draw air up from the engine room.
I made my “fan panel” from aluminum. It was cut on the CNC router at the office.
3 axial fans are mounted to the aluminum panel. These fans are specifically made for engine room venting.
I prewired up the fans. Easier done here than in the cramped space! The panel is made in two pieces… The large part goes in first and the small cap will close off the bottom area.
Remember that hot metal vent hose from earlier? It cooked the power wires for the fan. Not good! I moved that hose in to the middle of the aluminum panel where it can’t hurt anyone!
Fans and panel in place! This is looking up from the bottom of the closet.
How it looks from the outside!
In place ready for the bottom panel…
Next I added conduit up and over each fan to keep water from running down in to the junction box.
Conduit runs down to the junction box. The bottom conduit is the supply power.
Here is this part finished… still more to do!
Here is a two part aluminum air dam to go around the exhaust stack. This area was accessed from either side of the stack housing on the flybridge level.
The next part was probably the most difficult. Not technically difficult but the type of difficult you run in to when you cut holes in the fiberglass of your really expensive boat! As Peter found in his experience, once you have all the air coming in to this area, it needs help getting out! So holes and stainless grills were added to allow that flow to leave as unrestricted as possible.
This is how Red Rover now looks. We have not had the opportunity to run the boat with this new upgrade but we look to have similar results of cooling in the engine room as Peter found. Peter’s engine room was down to 20 degrees delta of outside temps. This will make engine room checks much more enjoyable!
Kevin,
What model of axial fans did you use?
Thanks
Chris
Chris – we used Delta T brand axial fans purchased thru Fisheries Supply. Part # 500-211115. AC Axial Fans, 11″ – 1100 CFM, 115v. Quiet for how much air is moving!
Did you make any adjustments to allow more air flow into the engine room? Or where does the make up air come from?
Looks great.
Michael – Thanks for your question and comment. On the 55s and 60s, there are two ER intake vents on the aft corner of the house, either side of the cockpit door. These openings are plenty big to bring the air in to the ER and actually well placed for where the fans are located. As the fans pull air up the stack enclosure (located above the engine and in the forward portion of the ER), it is pulling the air in from the aft ends of the ER, across the engine.
Very impressive, Kevin! I salute you for a job well done!
When we began struggling with high engine room temperatures just a few weeks after taking delivery of N4732 in 2005, I learned that the standard-issue squirrel cage fans are very inefficient at pushing air against high head pressure–as in up or down a long hose. Axial fans are what’s needed for a job like that. We fitted a single axial fan to suck air into our ER through the starboard cockpit plenum. That worked fine. HOWEVER, the incoming air was deposited in the after starboard corner of the ER and with more air being pushed in it had to find an easy way out. The natural path for that was out the port side plenum. What that meant was the cool incoming air circulated nicely in the after part of the engine room, but it did little to cool the area surrounding the ER’s big heat-generator: the main engine. Solution: we added 16-inch ducting from the axial fan to the main engine, not pretty but highly effective. That dumped the incoming cool air right at the main engine, forcing the hot air there aft and out the port side plenum. It’s been working like that for 13 years and our ER’s delta-T (temperature differential from outside air) is about 30 deg. F.
Milt, N4732 Bluewater
Milt – thank you! A fun project that will be enjoyed for years to come. As has been discussed on the NOG, each model is different and needs to have their own solution. I was fortunate enough to have Peter be the trailblazer for the 55/60s.
Kevin: Can you do my boat next? I think you’ve discovered a new profession!
Let’s do it! Better be quick, cruising season is right around the corner!
Nice project. Did you tie it into the Fire Control System?
Hi Bob – in essence, yes. I used the same circuit that powered the stack blower to power these fans. That was already tied in to the fire shutdown box, so all good!