40 sedan bridge forum

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https://www.usgs.gov/science-suppor...declination-varies-considerably-across-united
 
ZZ13 said:
Excellent. I have found that's a good maintenance routine on these units. The evaporator fins can get gunked up pretty easy and a good spray foam cleaning does wonders.
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Pierpressure1 said:
I used the foaming spray.
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What Spray foam did you use? Need to get this accomplished on both units as well as a thorough vacuuming mid season.
 
ZZ13 said:
What did it calculate the deviation to be? I had to move my heading sensor just a bit when I removed the stateroom bunk. These posts finally got me to recalibrate it a few days ago. It reported a deviation of 20, which implies there is probably too much metal around it. It's now closer to the vacuflush pump than it used to be. Manual recommends to relocate it if the deviation is more than 15. But it's now just about spot on with the compass at all headings except for a small area where it's off by about 4 degrees. So I'm inclined to leave it as is and call it done.
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mine was 3 degrees so not too bad. It doesn’t agree with the compass at all headings however and that drives me nuts. But really, I only use the AP for holding course, not following headings.
 
I’ll come back to the compass discussion shortly. In the mean time who has the airsep filter part numbers handy for the Cummins 6CTA’s? I think the main is 7-1/2 x 8” and is the Walker CD176? Is that right? And what about the turbo airsep?
 
scooper321 said:
I’ll come back to the compass discussion shortly. In the mean time who has the airsep filter part numbers handy for the Cummins 6CTA’s? I think the main is 7-1/2 x 8” and is the Walker CD176? Is that right? And what about the turbo airsep?
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Yes the 8" CD176. Although Walker now recommends to use the 9" CD177 for our engines. But I just rotate through a couple pairs of the 8" annually. I only know one person who actually switched to the 9". He says it sticks out pretty far. The little filter is CD180
 
scooper321 said:
mine was 3 degrees so not too bad. It doesn’t agree with the compass at all headings however and that drives me nuts. But really, I only use the AP for holding course, not following headings.
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You’ll never get a magnetic compass to agree 100% with an electronic compass.

I did compass swings on aircraft wet compasses. I would put the airplane (or helicopter) on a compass rose and perform the procedure, then record the cardinal headings and deviation on the compass card.

The wet compass is for reference only.
 
CaptRonn said:
You’ll never get a magnetic compass to agree 100% with an electronic compass.

I did compass swings on aircraft wet compasses. I would put the airplane (or helicopter) on a compass rose and perform the procedure, then record the cardinal headings and deviation on the compass card.

The wet compass is for reference only.
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So if my wet compass and my plotter GPS are 14 degrees different, that’s ok? Looks like I live and boat about 11-12 degrees of negative declination. Is the GPS based of true north? Should I match the AP with the GPS?
 
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ZZ13 said:
Yes the 8" CD176. Although Walker now recommends to use the 9" CD177 for our engines. But I just rotate through a couple pairs of the 8" annually. I only know one person who actually switched to the 9". He says it sticks out pretty far. The little filter is CD180
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Thanks. After I posted the question I found that 400 maintenance schedule you posted a while back, with part numbers. CD176 and 180! I should’ve looked first!

I’n going to buy a second set of each. But no way I’ll go to the 9”. The 8” were hard enough to reinstall. I just got done cleaning and re-oiling mine. Don’t know when thy were last done but it’s been at least 2 years. They were due. The big boys look like they’ve been around the block a bit, each with a few dents here and there. But nothing major. They were really hard to reinstall. Note to self and others: it’s going to be much, MUCH easier to do if you open the hatches from above. Lesson learned. Perhaps I’ll swap new ones in when I change the oil when I winterize...
 
scooper321 said:
So if my wet compass and my plotter GPS are 14 degrees different, that’s ok? Looks like I live and boat about 11-12 degrees of negative declination. Is the GPS based of true north? Should I match the AP with the GPS?
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The plotter lets you select whether the bearing mode is displayed in magnetic or true. Sounds like it may be possible yours is set to true.
 
For those that havent tried flushing their ac condenser coils, here are some pictures of how simple it is. 5/8" od hose fits in discharge thruhull nice and snug. No need to disconnect any hoses on that end. Im using phosphoric acid prep and etch diluted with water 50-50.
 

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CaptRonn said:
Good deal. Just don't try to align the plotter with the wet compass perfectly.
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Right. Thanks for clarifying that point for me. At this point, I just want my boat's icon on the Axiom to point in the same direction as the heading line, so it doesn't look like I'm driving a junker that needs a frame alignment! :)
 
scooper321 said:
Right. Thanks for clarifying that point for me. At this point, I just want my boat's icon on the Axiom to point in the same direction as the heading line, so it doesn't look like I'm driving a junker that needs a frame alignment! :)
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Depending on wind and current, it may not exactly line up. I've flown jets in the flight levels with 160 knot crosswinds that gave a large crab angle. We actually get that in boats depending once again on wind and current, just not to the large degree. So a slight crab angle wouldn't be out of the question.
 
CaptRonn said:
Depending on wind and current, it may not exactly line up. I've flown jets in the flight levels with 160 knot crosswinds that gave a large crab angle. We actually get that in boats depending once again on wind and current, just not to the large degree. So a slight crab angle wouldn't be out of the question.
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What CaptRonn says... Don't worry about where the boat is pointed... look at the track it should parallel your intended course.
 
Steve S said:
What CaptRonn says... Don't worry about where the boat is pointed... look at the track it should parallel your intended course.
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It does track the course properly. It just messes with my head when I glance at the plotter and it looks like I'm headed off course.
 
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