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Old 12-05-2011, 07:10 PM   #21
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RE: Outboard Aux Engine for Marine Trader 44

Thanks for that picture craig. So if I decide to go ahead I know now I won't be the first to fail..**anyway what I am planning to do if I go ahead with the*diesel outboard is I will install a seperate steering system and throttle control on my flybridge. I will have 2 steering wheels! HAHA! My main concern is will the 36hp be enough to get it sailing to 4 knot at least? I've made comparison with the nordhavn get home system. The horse power seem comparable except for the prop size. Are the feathering props much bigger than outboard motor props?
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Old 12-05-2011, 09:57 PM   #22
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RE: Outboard Aux Engine for Marine Trader 44

Capn Craig -

Boats don't turn around their propellers, they turn around their center of lateral resistence (CLR).

The turning force is a product of the moment created by the distance between the CLR and the rudder (D), and the velocity of the water moving past the rudder (V).

Moment = D times V.

In reverse, the prop walk is opposite, although weaker than what you are used to. The rudder is also much less efficient since the force is only boat speed thru the water, and not the accelerated flow seen in forward.

In addition you are pushing the blunt end of the boat thru the water rather than the sharp end.

I'm not sure I understand your description of how your boat responds to the rudder in reverse.

Miller Light? Wow, they still make that stuff?

Mike
Palm Coast FL
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Old 12-05-2011, 10:45 PM   #23
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Outboard Aux Engine for Marine Trader 44

Quote:
Mike wrote:
Miller Light? Wow, they still make that stuff?

Mike
Palm Coast FL
Indeed they do Mike.* The drink of choice of my sailboating friends.* (Not entirely true, one of them drinks Rainier, better yet.)*

Funny thing though, I buy both a half rack of Miller Light and Rainier when I know they are coming over and do they drink it?* No. . . They drink my Corona!!* When I go over to their boats, guess what they offer me?* Funny how that works.


-- Edited by Edelweiss on Monday 5th of December 2011 11:46:28 PM
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Old 12-06-2011, 04:19 AM   #24
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RE: Outboard Aux Engine for Marine Trader 44

The question is THRUST , or weather the aux propulsion can get HP into the water.

A minimum of 1 hp per ton should move the boat , if you can pump that into the water.

Loads easier to do with a hyd unit chained or belted to the shaft and powered by the noisemaker.
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Old 12-06-2011, 05:42 AM   #25
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RE: Outboard Aux Engine for Marine Trader 44

Quote:
Mike wrote:The turning force is a product of the moment created by the distance between the CLR and the rudder (D), and the velocity of the water moving past the rudder (V).


Moment = D times V.
What?????

Moment is force times distance, velocity is small part of the formula to determine that force.

Rudder force calculations involve several components.

Rudder Force= Cr= 132 x A v(squared) x K1 x K2 x K3 x Kt x N

Where:

v = Speed of the vessel.

A = Area of the rudder.

K1 = Coefficient depending on aspect ratio


K2 = Coefficient depending on the type of the rudder.

K3 = Coefficient depending on the location of the rudder.

As far as the pivot point is concerned, it is usually about a 1/4 to 1/3 of the hull length aft of the bow, it moves forward as speed increases. If the boat is stopped, it is near the longitudinal center of gravity. Going astern, the pivot point is at or near the rudder.

CLR is more of a sailboat term since it is greatly altered by keel design. Power boats use PP or pivot point.
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Old 12-06-2011, 07:31 AM   #26
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RE: Outboard Aux Engine for Marine Trader 44

Ahhh, the pivot point discussion. Rick is absolutely right that the pivot point is nearer the bow for a vessel moving*slowly through the water and*big rudders. But this is one of those discussions that depends on if you are talking about a canoe or an IPS drive twin Grand Banks. Further to complicate it are twin outdrives vs twin straight shafts, bow and stern thrusters*and all manners of hull and rudder shapes. Or a vessel on plane at 40 mph vs a 7 knot Krogen. For sure, the single vs twin debate comes into this during maneuvering while*moving slowly through the water.*If you are a kayaker, surfer or a slalom water skier you will/must understand pivot point even better.

With a little outboard on the swim platform of a 40' plus trawler, pray for good weather and no currents as you move it around. As Fred, Keith and others have said, some type of inboard auxiliary is more common - for a reason. Me, if no*good backup*I'd rely upon mechanical savvy and spare parts to get me out of a jam.

Once again I note the misconception that the*majority of diesel engine failures are fuel related. Don't run out of fuel (a big part of the Boat US statistics), buy fresh, have a good filter system and this issue becomes insignificant.
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Old 12-06-2011, 08:15 AM   #27
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RE: Outboard Aux Engine for Marine Trader 44

Quote:
sunchaser wrote:
With a little outboard on the swim platform of a 40' plus trawler, pray for good weather and no currents as you move it around. Me, if no*good backup*I'd rely upon mechanical savvy and spare parts to get me out of a jam.

Once again I note the misconception that the*majority of diesel engine failures are fuel related. Don't run out of fuel (a big part of the Boat US statistics), buy fresh, have a good filter system and this issue becomes insignificant.
*I agree with this. My personal back up plan to the above would be to call for a tow. The secondary backup plan would be to rig the dink with my 15 hp outboard and try to move the boat if I had to(but that would have to be in calm conditions only).

*
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Old 12-06-2011, 08:59 AM   #28
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RE: Outboard Aux Engine for Marine Trader 44

Jay says "The secondary backup plan would be to rig the dink with my 15 hp outboard and try to move the boat if I had to(but that would have to be in calm conditions only)."

This will work only if you have enough hp in the dinghy.
I lost power in my sailboat (5 tons) and was able to manouvre it easily with 15 hp in the dinghy. The dinghy hp exceeded the boat hp. When I moved up to a 10 ton sailboat, same dinghy, I was able to move the sailboat with the dinghy strapped on the stern quarter, but only in the direction the current and wind would permit, and the operation required two people, as steering was difficult. Here the boat hp was 55, versus 15 in the dinghy.
I tried once on the 22 ton trawler and gave it up. 15 hp was not enough to do more than exasperate the operator.
I now carry 40 hp on the dinghy, but haven't been motivated to try it as an aux. After all, I have twin 200s.

Now if I was running 250 hp in the dinghy, I wouldn't doubt its ability.
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Old 12-06-2011, 09:26 AM   #29
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RE: Outboard Aux Engine for Marine Trader 44

Quote:
dvd wrote:
It is perfectly logical that a couple of beers will make one smarter.
*You had to know this was coming. But sure beer makes you smart.

It made Bud wiser.

Ta da.

SD
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Old 12-06-2011, 11:41 AM   #30
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RE: Outboard Aux Engine for Marine Trader 44

SD you stole my line...but I am still laughing
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Old 12-07-2011, 04:13 AM   #31
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RE: Outboard Aux Engine for Marine Trader 44

"The secondary backup plan would be to rig the dink with my 15 hp outboard and try to move the boat if I had to(but that would have to be in calm conditions only)."

Outboards come with different specifications.

If I were contemplating using the dink as an emergency engine ,

I would purchase the "Hi Thrust" variant that is sold to move sailboats , not a small prop dink motor.

Many mfg. sell these with gear deeper reduction and larger diameter props.
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Old 12-07-2011, 05:04 AM   #32
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RE: Outboard Aux Engine for Marine Trader 44

Anybody who wants to tow their trawler with a dinghy should get out and try it some time in nice weather. Have fun.
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Old 12-07-2011, 05:08 AM   #33
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RE: Outboard Aux Engine for Marine Trader 44

Quote:
Keith wrote:
Anybody who wants to tow their trawler with a dinghy should get out and try it some time in nice weather. Have fun.
*I guess my point was missed. Not that I would want to, however I have in the past moved the boat in CALM weather in an anchorage, and would only attempt in an emergency in calm conditions.
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Old 12-07-2011, 05:12 AM   #34
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RE: Outboard Aux Engine for Marine Trader 44

I was serious... you have to try it to see how everything will react. Don't try it for the first time in an emergency in bad weather.
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Old 12-07-2011, 08:36 AM   #35
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RE: Outboard Aux Engine for Marine Trader 44

Kieth, Good advice. You never know.

SD

*
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Old 12-08-2011, 09:15 AM   #36
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RE: Outboard Aux Engine for Marine Trader 44

Quote:
Keith wrote:
I was serious... you have to try it to see how everything will react. Don't try it for the first time in an emergency in bad weather.
*Actually that would be a good warm summer day project. Better than cleaning the teak if the admiral grants permission.
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Old 12-08-2011, 04:10 PM   #37
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RE: Outboard Aux Engine for Marine Trader 44

At Herrington Harbor North (Deale, MD) the launch drill is for*the yard to put*your boat in with the travel lift then they*tie their outboard powered work*boat snug*to your aft quarter.* The two person yard crew then delivers your boat to the appropriate slip and ties it up.**With experienced hands, this is done very quickly and with great control as they are*maneuvering vessels though fairly crowded fairways and into docks with not much clearance.* Our Pilgrim is 40' and about 26,000 lbs displacement.

A few years ago we had to remove the engine from our previous 30', 12,000 lb displacement trawler.* To get the boat from the shore crane back to our slip (sans engine), we rowed it using a singular 15' sweep (long oar).* The distance was about 800 feet and fortunately there was room on deck to swing the sweep.* Slow but sure assuming you have the patience.
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Old 12-10-2011, 05:40 AM   #38
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RE: Outboard Aux Engine for Marine Trader 44

We had the tranny in our 18,000 lb GB 32 quit just after passing thru Hell Gate right in front of the Riker Island floating prison and quickly put the 10ft dinghy with 9.9hp 2 stroke on the hip - worked fine, but no waves, just a breeze and a knot or so of head current. We could have gone all the way to City Island if we'd had enough gas...
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Old 12-10-2011, 07:22 AM   #39
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RE: Outboard Aux Engine for Marine Trader 44

Yeah, it could have been really dicey, but even with a knot or so of foul current we made headway. The bigger issue was that Boat US tow wanted us to anchor before they would come out (probably that 'rescue vs tow' definition), and the Riker's Police boat wouldn't let us go into the cove on the N side, so we ended up anchoring out of the channel but still in the current. Interesting that once the tow boat had us in sight he asked us to weigh anchor and meet him in the channel, where he picked us up... probably just convenience for him All ended well.

- Roland
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Old 12-10-2011, 07:23 AM   #40
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RE: Outboard Aux Engine for Marine Trader 44

I have tried to move the Rose with my 28' center console with two 250's on it, that 500 hp. The most I could do is have a passing conversation with the stern to please go a little port or a little starboard. As some have said this is probably a bad idea. I am a firm believer of not creating a crutch. I go offshore all the time and see people all broke down, stuck and hungary because they thought their cell phone would work instead of having a proper vhf. It seams you are going the route of the dingy with outboard, that is a good plan but I would also make sure your ground tackle is sufficient for your area (mud/rock anchor) Back up plans are good to have but are no replacement for properly maintained and operating equipment. I think old stone sums it up talking about stainin' your undies.
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