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  #1   IP: 98.242.190.174
Old 12-02-2011, 03:26 AM
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Blower Ducting Set Up

I'm the proud new owner of a '63 Columbia 29 with an uninstalled A4. I am trying to plan my ducting for the engine compartment blower but I have a bit of a problem.
I'm not sure if the typical set up with an intake under the engine in the engine compartment leading to a blower fan and then a rear facing cowl is the wisest set up for my boat. The problem is that the bilge is open to the engine compartment. Therefore any gasoline fumes will collect in the bottom of the bilge instead of the engine compartment. This is potentially dangerous IMO as the typical intake set up will not evacuate the fumes and any spark in the bilge, say from a faulty automatic bilge pump, could ignite them.

So should I
(1) run my intake down into the bilge
(2) have an intake both under the engine and in the bilge with a T connector
(3) do my best to seal up the connection
???

I'm hoping to avoid option 3 because several connection run through this passage, but I realize it may still be the best option.

ps this is my first posting to the forum so let me say thank you to everyone at MMI for keeping so many A4's alive.
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Old 12-02-2011, 03:42 AM
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Blower Ducting Set Up

I'm the proud new owner of '63 Columbia 29 with an unistalled (and neglected- see my introduction post) A4 and I have run into a bit of a problem planning the ducting for my blower.

I'm afraid the typical set up with the intake under the engine leading to a blower fan and aft facing exhaust cowl will not work with my boat because the engine compartment is open to the bilge beneath. IMO this represents a serious safety problem because the gasoline vapors will run into the bilge compartment and will not be vented by the blower. Additionally, a bilge full of fumes may meet an ignition source due to a faulty automatic bilge pump.

So what should I do?
(1) run the intake down into the bilge
(2) install a T and have two intakes, one in the bilge and one in the engine compartment
(3) seal off the engine compartment from the bilge
(4) something else entirely

I'd not prefer option 3 if at all possible because a bilge pump hose runs up towards the transom through this opening.

ps. this is my first post to the forum so let me say thank you to everybody at MMI for keeping so many A4s alive.
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Old 12-02-2011, 09:56 AM
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Welcome to the forum.

Aren't the engine room and the bilge always connected? If not, then what happens to water that gets into the engine room? Anyway, the two are connected on my boat.

The duct to the blower in my engine room runs to the lowest point, just in front of the flywheel cover. There's also a second fresh air inlet duct that terminates on the other side of the motor and somewhat above the first duct.

I think this setup does a good job of evacuating fumes from around the engine and it probably gets most of them out of the bilge (it always passes the sniff test). The engine is the most likely source of ignition, and I don't worry about the bilge pump because it only comes on when it's underwater.
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Old 12-02-2011, 12:51 PM
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Pervention

Two items to consider along this line:
Always turn the fuel supply off at the tank and run a bit of fuel out of the line before shutting the engine off.
Leave the engine area open as possible at all times.
If you are concerned about fumes in the bilge use your personal fume detector. (nose)

If you put the intake tube in the bilge it will float on top of any water in the bilge. If you anchor it down it could end up under water. Either way not the best situation.

Most boats I've seen have an instillation like Loki9 described.

And welcome to the forum.

TRUE GRIT
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  #5   IP: 216.115.121.240
Old 12-02-2011, 01:02 PM
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Welcome,
I think the "tee" option could work, but mine is just same as Loki9's setup.
If you put in a tee, then you might have to balance it a bit. I don't see any real technical hurdles though.

I have a Columbia too. A '68 36. Not really similar boats but family.
I read that the mold for the early 29 was taken off a wooden boat and the lines in the hull were left in the new mold. I found the story somewhere out there in internet land. The boat next to mine in Homer Harbor is a '66 Islander 29. Does yours have lines like a wooden boat?
With all the genetic pooling of boat designers and plants back then I can imagine they might be very similar.

Russ
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Old 12-02-2011, 03:02 PM
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You are correct, if the vapors can seek the lowest point (bilge) that is where the blower needs to draw from. If you simply want to exhaust heat and fumes from the engine, when running, which is a great idea , put a second blower in, drawing from the top side of the engine to do this. Since bilge pumps are generally submerged when they are needed to run I wouldn't be to concerned about it igniting fumes. BUT If you are on the boat, you should turn on the blower before turning anything spark producing on. Good Luck
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Old 12-02-2011, 03:11 PM
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Interesting point - to me, anyhow, because my boats' setup is the same - the engine sits a fiberglass bed, which sits directly above the deepest part of the bilge.

I would lead the exhaust duct down into the bilge, if this causes you concern.

Another thing to consider, which I have partly setup, is to purchase at least one, and preferably two, Nicro solar "day/night" vent fans. Set one to pull air into the boat, and the other to draw air out. Install the "inbound" one forward in the boat - e.g., over the main cabin; install the "outbound" one in the lazarette or similar area. This will cause a constant, gentle current of air to flow through the boat and help not only keep everything dry inside the boat, but also help prevent an accumulation of vapors.

I also have read of people attaching a duct to the aft fan and leading the duct down into the bilge. This setup is even better - you get a flow of fresh outside air coming into the cabin, and then being directed down into the bilge and ducted up and out the aft end of the boat.

Just as a little data point, my boat is a 1968 and has an Atomic 4 in it since new, and the exhaust duct ends just behind the engine - i.e., not all the way down in the bilge. Evidently, it hasn't been a problem yet. Not to make light of the possibility, but is it possible that your concern of having sufficient gasoline vapors in the bilge to cause an explosion may be greater than necessary? Assuming, that is, that the fuel line and associated fittings are in good condition and working order and well-maintained...
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Old 12-02-2011, 03:14 PM
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We've got two identical threads going on this question.
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  #9   IP: 98.242.190.174
Old 12-02-2011, 05:24 PM
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Yep, the dual threads are my fault. I wasn't aware of the posting lag for the moderator. I'm going to continue the discussion on this thread if at all possible.
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  #10   IP: 75.192.160.17
Old 12-02-2011, 05:51 PM
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Threads merged.

Bill
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  #11   IP: 65.15.109.176
Old 12-04-2011, 04:45 PM
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i have 3 ducts in my bristol one forward facing intake that terminates above the engine one aft faceing that ends a little below the engine ,and one with a blower attached the ends down in the bilge 3ft below the engine
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Old 12-04-2011, 11:22 PM
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Quote:
Originally Posted by snook91901 View Post
...I'm afraid the typical set up with the intake under the engine leading to a blower fan and aft facing exhaust cowl will not work with my boat because the engine compartment is open to the bilge beneath....
My 70's era Pearson was the same way. One of the recommendations that the surveyor made was to extend the blower pickup hose to the lowest part of the bilge.
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Old 12-05-2011, 03:19 PM
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Quote:
Originally Posted by edwardc View Post
My 70's era Pearson was the same way. One of the recommendations that the surveyor made was to extend the blower pickup hose to the lowest part of the bilge.
Last spring, I picked up some blower hose and did exactly this same thing myself. My engine is in the middle of the boat and the hose stopped aft of the companionway steps..I extended it to just in front of the flywheel, which is in the middle of the bilge on my boat, so it is getting the fumes out tout suite!

Welcome to the new guy, too!
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  #14   IP: 76.28.45.109
Old 12-01-2014, 06:15 AM
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Blower Location?

I am considering moving my squirrel cage blower to make room for a relocated battery. The blower is currently in the space under the quarter birth directly in line with the engine.( the deepest and widest spot) The intake is directly behind and below the engine. That isn't my concern.

How much would it affect the cfm being moved from the intake to the discharge if the location of the blower along that route is changed?

Now a 2' intake run and a 10' run to discharge. I would increase the intake run by 4' and shorten the discharge by the same amount if I relocated the blower to the aft end of the space under the quarter birth. It would seem that with the total run being the same the volume of air getting moved wouldn't change?

In the current location the blower clutters up some valuable real estate.

George
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Old 12-01-2014, 10:03 AM
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Originally Posted by gfatula View Post
How much would it affect the cfm being moved from the intake to the discharge if the location of the blower along that route is changed?
Without going into Boyle's or Bernoulli's territory too far, the effect on total cfm moved would be negligible given the distances invovled. You are most likely affected more by voltage drop to the blower than anything else, including friction within the duct hose itself.

Move that puppy to less valuable real estate!
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Old 12-01-2014, 11:11 AM
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Thanks Tom,

The other option is to replace the squirrel cage with an In line blower. The squirrel cage seems to be the better choice. I could add a second, in line, blower? I could increase the diameter of the inlet hose but it would shrink back down at the blower?

I think I will move the blower. Ugh! Another mod. Move the blower. Move the batteries around. Build a secure location for them. Wish I had seen this coming when I built the current secure platforms. I will be able to move the "heavy" tool box from its location under the port cabin seat to the batteries "old" location. It will be easily moved out of the way when necessary. O-well! I DO NEED THE ROOM MOVING ONE OF THE BATTERIES WILL PROVIDE. I can't get my shoulders into the aft engine space with all the batteries secured in their current operating locations. Disconnecting and lifting a 75# battery out of the way to adjust the packing nut "comfortably" is not a good option. A boat with an engine room next time!

G
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Last edited by gfatula; 12-01-2014 at 12:38 PM.
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Old 12-01-2014, 01:57 PM
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Columbia 29

Good Day,

Welcome to the forum. You'll get excellent advice and a lot of help here.
I thought I would send you some information about the Columbia 29 you may find interesting. I'll send it to you via personal email so as not to confuse the thread.
I owned a '61 Columbia 29 hull #3 for many years which came to me with some excellent history about the origins of this boat. It's a wonderful boat, and I wish you luck.
If anyone else happens to be interested in this history just drop me a note.
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Old 12-01-2014, 02:03 PM
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Quote:
Originally Posted by lat 64 View Post
I have a Columbia too. A '68 36. Not really similar boats but family.
I read that the mold for the early 29 was taken off a wooden boat and the lines in the hull were left in the new mold. I found the story somewhere out there in internet land. The boat next to mine in Homer Harbor is a '66 Islander 29. Does yours have lines like a wooden boat?
Russ
Not at all true. I owned Columbia 29 #3 built in 1961 for many years and am privy to quite a bit of the history as a result of researching this boat. PM me with your email if you want me to send some of the letters I have.
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Old 02-11-2015, 08:35 AM
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Originally Posted by TomG View Post
Without going into Boyle's or Bernoulli's territory too far, the effect on total cfm moved would be negligible given the distances invovled. You are most likely affected more by voltage drop to the blower than anything else, including friction within the duct hose itself.

Move that puppy to less valuable real estate!
Tom

On your t30, do you intake air at the calling duct by the mast.and discharge at the vent I the cockpit, above and between the slippers I the cockpit?
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Old 02-11-2015, 05:21 PM
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Originally Posted by BadaBing View Post
Tom

On your t30, do you intake air at the calling duct by the mast.and discharge at the vent I the cockpit, above and between the slippers I the cockpit?
Bill, my blower picks up right below the carb and the hose runs under the port settee and quarterberth and then exits in the cockpit just to port of the rudderpost. I do have a day/night solar fan mounted over the chase where the standpipe lives that runs 24/7 exchanging air in the cabin. My T30 has louvered doors in the head, so fresh air is drawn in through the head (and every other gap) when the blower is running.
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Old 02-11-2015, 07:29 PM
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Thanks. Your ducting for the blower sound like how mine is set up. I had a second blower under the stand pipe blowing down into the bilge to suck air down the on deck intake over the stand pipe enclosure. I removed the secondary blower for my current project and am considering mounting it above the stand pipe, blowing down on or over the stand pipe and pushing great air into the engine compartmen.
The cowling over the stand pipe area, that provides fresh air to the engine compartment has no dorad, which seems to be the norm on T30s that I have seen.
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Old 02-12-2015, 10:18 AM
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Quote:
Originally Posted by BadaBing View Post
Thanks. Your ducting for the blower sound like how mine is set up. I had a second blower under the stand pipe blowing down into the bilge to suck air down the on deck intake over the stand pipe enclosure. I removed the secondary blower for my current project and am considering mounting it above the stand pipe, blowing down on or over the stand pipe and pushing great air into the engine compartmen.
The cowling over the stand pipe area, that provides fresh air to the engine compartment has no dorad, which seems to be the norm on T30s that I have seen.
Bill, when I got my T30, the blower was actually mounted just forward of the A4 down by the base of the mast with the ducting running inside the chase in the head where the original standpipe was located. When I changed from a waterlift back to a standpipe, there wasn't enough room in the chase for both so I went back to original ducting under the settee and out the back. The '77 model has two dorades, one in the head and one in the saloon. I have a day/night solar fan pulling air out of the chase over the standpipe that does a pretty good job of keeping moisture down. Since my blower exhausts into the cockpit, I know right away if fuel fumes are present.
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Old 02-12-2015, 05:35 PM
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Thanks Tom, I found just about the exact same thing except the PO of my boat had squeezed the flex duct into the cavity along side the standpipe.

Im thinking of making and adding a dorad box for this cowling. I also have two dorads for the cabin vents. Would like to try to precent rain from such easy access to my engine compartment.
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