Engine air

[DavidDW]

Hi Guys,

I am just doing some thinking around the engine air supply on my boat.

Instead of using a dorade in the side of the boat, I am considering mounting a pair of 8" ID GRP pipes that are mounted under the combings (one each side) just rear of the saloon bulkhead.

The engines in this case are 240hp perkins (2x) - diesel.

8" pipes should give me ~201sq" per side (402sq" total).

I am wondering, looking at the 0.5sq" per hp theory as a rough guess at what is required, would my plan to use the pipes give the enignes enough air for both engine air intake and out take?

I am thinking I could force feed more air in by using a 9" delta t fan mounted to the bottom of one of the pipes if needed.

What do you think guys?

[CaptPatrick]

David,

The area of a circle is

8"d = 4"r so 4x4x3.14 = 50.24 sq in per 8" pipe...

[DavidDW]

Whoops - Thanks Patrick.

Doing things late at night can be dangerous. Back to the drawing board! :wink:

[In Memory of Vicroy]

Wait a second....pie are round, cornbread are square?

UV

[CaptPatrick]

I started to add that, Vic, but I knew I'd be steelin' your thunder...

Yo' Fren

Patrick

[DavidDW]

Has anybody had any experience with forced engine room induction using something like this?

http://www.deltatsystems.com/dtsp-9_inc ... l_Fan.aspx

I guess I am trying to determine how much extra air over and above the traditional unassisted air vent. It might be the case that it's possible that by using the fan like this it would be possible to have a smaller hull side cut-out.

If the fan is 9" in diameter, how much air does it force into the engine room through a 9" cut out when compared to a 9" cut-out with no assistance.

Keen to hear your thoughts.

[Harry Babb]

David
Before you start adding Fans and more stuff to break and maintain I suggest that you talk at length with Bob Lico.....

I am pretty sure he will chime in here when he sees this post.

He has a pretty slick air inlet for his engines.....I believe that he has 330 HP engines.

Mr Lico built air intakes that pull air from the cockpit....and pretty cool setup......no moving parts and plenty of "open Area"

hb

[DavidDW]

Thanks Harry -

I remember reading a post that went through what Bob had done but found it difficult to work out exactly how it worked.

In essence, I think I am trying to do something fairly similar and am hoping to draw air in from the cockpit.

I'll take another look at the thread as a starting point.

[Harry Babb]

David
The short story about what Bob did is......he is taking the air, naturally, thru vented openings on the outboard side of each engine and below the gunwale.....he did this by modifying the....what I call the engine box wing panel.

He extended it back into the cockpit about 18" (but still inside and underneath the gunwale) and put a couple of baffels to dampen the noise.....very simple and very effective

I am pretty sure there are pics here in the sandbox if you can find them.

hb

[DavidDW]

Thanks Harry.

I found this thread : http://bertram31.com/newbb/viewtopic.php?t=7598 and saw some of the pics of Bob's cockpit.

I have a similar type setup in my boat but don't have any engine boxes.

I am going to encase the area under the gunwale in an equivalent area to where I think Bob has done his good work.

In this area, I was going to install 8" GRP pipes each side. I basically turned the pipes into rearward facing cowl vents (with a 90 degreee bend) that would mount under the gunwales.

I could put a portion of the "wing panel" back in to stop water getting down into the engine room. There is a risk that if I don't do this, the engine room might flood given all the backing up when fighting marlin I know that will take place.

It's all a balance, but I would much rather get air under the gunwales than putting vents in the sides.

I might take some photos of the inside of the boat and put them up to get some ideas from sandbox members. 8)