Engine compartment ducting

[Tony Betz]

I am in the process of replacing squashed and tattered 3" ducting (in a CD 33 with Volvo MD llC - engine air intake to port). The two sections of ducting lay port and stbd. on the bottom of the compartment, ending just aft of the stuffing box. I am wondering what the optimum height and placement of the two tubes would be for most efficient fresh air circulation (one high, one low/one front, one back?), and how the respective exterior aft air scoops should be accordingly directed.
This is the type of quandry one gets into after thinking about something too much.
Regards to all from Casco Bay, Maine. Tony Betz, "Wildings"



wildings@ncia.net

[Ken Coit]

Tony,

I have no idea, but thanks for a hearty laugh this morning.

Ken Coit
a former New Englander

I am in the process of replacing squashed and tattered 3" ducting (in a CD 33 with Volvo MD llC - engine air intake to port). The two sections of ducting lay port and stbd. on the bottom of the compartment, ending just aft of the stuffing box. I am wondering what the optimum height and placement of the two tubes would be for most efficient fresh air circulation (one high, one low/one front, one back?), and how the respective exterior aft air scoops should be accordingly directed.

This is the type of quandry one gets into after thinking about something too much.
Regards to all from Casco Bay, Maine. Tony Betz, "Wildings"

parfait@nc.rr.com

[Neil Gordon]

Hi Tony,

>>I am wondering what the optimum height and placement of the two tubes would be for most efficient fresh air circulation (one high, one low/one front, one back?), and how the respective exterior aft air scoops should be accordingly directed.<<

Starting on deck... the vents should face in opposite directions... one forward, one aft. As for which one, I'm sure that the British Navy has a tradition, in this country it would be the other way around, but I don't know either one. <g>

My hoses are low, one on either side of the engine compartment. One is long, the other short, so the air flows through as much of the engine space as possible. I'd suspect that whatever you want to vent out of that space is heavy, so vents lower down are a better idea.


Regards, Neil
s/v LIQUIDITY
Cape Dory 28 #167



neil@nrgordon.com

[Chris Reinke (CD330 Innis]

Tony - Neil looks to have a much better grasp on the "correct" way of doing it. I can only offer an observation of how my CD330 is set up. I presume from the condition of my ducting that it is original. The port scoop faces forward and the ducting ends just below the rudder post. The starboard scoop faces aft with the ducting ending just aft of the transmission. The ducting is held in place with a few cable ties around the shift cable.

From this layout I would agree with Neil that the fresh air enters high and aft, so the circulation flows down across the bilge with the fumes getting sucked out down low. However, I then recall my 5th grade teacher mentioning something about heat rising. I guess you need to decide on what is more important:
1 – Discharge starting low to pull the fumes and harmful vapors out of the bilge
2 – Discharge starting high to pull the heat and heated CO gas out of the engine compartment.

I guess the solution is to add 6 or seven additional air scoops. Better yet – lets peal off the cockpit flooring and all sit around with Japanese paper fans blowing fresh air into the bilge.

Tony – have a great season.

Chris

I am in the process of replacing squashed and tattered 3" ducting (in a CD 33 with Volvo MD llC - engine air intake to port). The two sections of ducting lay port and stbd. on the bottom of the compartment, ending just aft of the stuffing box. I am wondering what the optimum height and placement of the two tubes would be for most efficient fresh air circulation (one high, one low/one front, one back?), and how the respective exterior aft air scoops should be accordingly directed.
This is the type of quandry one gets into after thinking about something too much.
Regards to all from Casco Bay, Maine. Tony Betz, "Wildings"

chris.reinke@transamerica.com

[Mark Yashinsky]

Look for an earlier posting on this subject that I started (and opened a can of worms).