Designing an engine room air intake system is a complex process, full of tradeoffs. Before you start you need to have a clear goal for the system. For us this is simple: we want a system that minimizes water incursion through a variety of weather conditions with the boat upright, knocked down, and inverted.
How do we accomplish this?
It starts on deck with the positioning of the intake. The closer to the centerline your intake, the more heel the boat will stand before the air intake is submerged. On the FPB 64 the air intake is on center.
Next is the exposure of the intake to wind driven rain, spray, or solid water from breaking seas. Centerline and aft facing, in the lee of the house structure, happens to be an optimal location for mitigating upright risk factors.
The special intake grill in the lead photo is another part of the story. It is designed to block solid water and reduce heavy rain intrusion. What does get by the grill’s many fins drops to the bottom of what is in effect a giant Dorade box and is drained before it drops into the engine room.
Posted by Steve Dashew (January 22, 2010)
January 22nd, 2010 at 6:34 pm
Is there a filter or dehumidifing system and blowers in the intake part ?
Carlos
January 22nd, 2010 at 7:35 pm
Hi Carlos:
The intake grill sheds a high percentage of rain, spray, and solid water. More important is the location in the lee of the house. The bottom inside the engine room is designed as a catchment with a drain into the bilge. Rather than use blowers which are noisy and a reliability risk, we size the intake for passive air flow.
January 22nd, 2010 at 11:15 pm
I’m continually amazed at how many yacht designers think that engines don’t need air to run. Recently delivered a new 55′ sport fisherman to Mexico that developed 190 degree temperatures in the engine room. Twin 1,000 hp MANs plus gen set and AC, supposedly supplied by two little bilge fans and air vents on the hull sides that have minimal ability to prevent water intrusion.
On the sail side, a number of years ago I was the project manager for a 112′ cost-is-no- object motor sailor drawn by the country’s oldest and most revered design firm. The engine room air exhausts had multiple 90 degree bends to conform to the stylist’s desires. I conferred independently with factory trawler acquaintances who suggested that perhaps we should take a second look at the air supply requirements. Was told to stick to boat building and leave the designing to Naval Architects. Bottom line, whenever the 20 million dollar yacht travels in the tropics the engine room doors have to be left open into the crew’s quarters and deck hatches opened to supply air or the two engines and three gen sets won’t run properly.
So, if you don’t buy a FPB, make sure you hire somebody who knows how to calculate air flows to do an independent analysis of your boat before heading off into the sunset.
January 23rd, 2010 at 1:09 am
Hi Steve .
Thanks. Is there any else can be done (simple way) to lessen salt content in aspirated air?
Carlos
January 23rd, 2010 at 10:48 am
Hi Carlos:
I don’t think the salt content is any higher than normal ocean interfaced air. We have been told to expect 20,000 hours minimum (and possibly a lot more) from an engine run in this environment.
January 23rd, 2010 at 10:32 pm
Thanks Steve. Was thinking more about long term effects on many metal engine room components with regular sea air. Hate what we call “salitre” in Venezuela and rust.
Love corrosion x.
Me keep learning/enjoying in 64 progress
Any new DVD in the near future?
Carlos
January 24th, 2010 at 7:29 pm
Carlos:
This has not been a problem for us in the last 30 years.