Date   

Re: [Amel Yacht Owners] Re: Flexofold Prop

greatketch@...
 

That's how I taught people to do it for almost ten years.  For most beginning big boat skippers it was the most intimidating of the lessons.  Putting an expensive 40 foot boat into a space less than 50 feet wide, and requiring them spin it on its axis to get out of the dead end. Certainly terrifying to start but very rewarding when they figured it out!

One of the main reasons we spent so much time on the "back and fill" lessons was to give the novice skippers the idea that prop walk doesn't have to be a bug, it can be a feature if you know how to take advantage of it!  

I have helmed full keel boats with keel hung rudders that had poor steering in reverse, and almost no prop walk.  They were truly nightmares in reverse. Almost brownian motion. Give me moderate, predictable prop walk any day!

Bill Kinney
SM160, Harmonie
Fort Lauderdale, FL


---In amelyachtowners@..., <simms@...> wrote :

Hi Bill,

I can't disagree with your input but I offer my thoughts. When a boat is stationary, or changing from forward to reverse initially the prop is turning in the water and the linear flow of water over the blades has not established the propeller just acts like a wheel and walks through the water. That's why prop walk is most pronounced when reverse is engaged from forward, (and on fishing boats with huge diameter props). Then as the flow settles down over the blades the effect diminishes. The auto prop has much less walk than other props because of its free blades adopting optimum angle for the forces applied, torque, rpm, load etc. Not so like a wheel. That's my reasoning anyway.

That aside. If you want to turn a super maramu  on her axis try this. At idling speed forward put your helm hard to port. Apply full throttle fast. As the boat gets forward momentum, cut the throttle, click to neutral, click to reverse. Apply full throttle in reverse.  The bow will swing fast to port. As it slows, cut throttle and click click through to forward, again apply full throttle fast. The helm is held hard to port all the time and you must allow her to move a bit forward and reverse before you change gear.

Repeat the process until you have turned to where you want. This method won't overcome a strong cross wind but works very well.

The spectators are always very impressed.

Regards

Danny

SM 299 Ocean Pearl



topics that will create tons of correspondence

eric freedman
 

Having been on a number of sailing websites over the years I find it interesting that certain topics create endless correspondence. I mean nothing negative by this. I just find it interesting.

 

Sail Cloth

Deck shoes

Anchors,

Propellers

Varnish and paint

 

Fair Winds

Eric

Kimberlite Amel Super Maramu #376

 


Re: [Amel Yacht Owners] Re: Flexofold Prop

Danny and Yvonne SIMMS
 

Hi Bill,

I can't disagree with your input but I offer my thoughts. When a boat is stationary, or changing from forward to reverse initially the prop is turning in the water and the linear flow of water over the blades has not established the propeller just acts like a wheel and walks through the water. That's why prop walk is most pronounced when reverse is engaged from forward, (and on fishing boats with huge diameter props). Then as the flow settles down over the blades the effect diminishes. The auto prop has much less walk than other props because of its free blades adopting optimum angle for the forces applied, torque, rpm, load etc. Not so like a wheel. That's my reasoning anyway.

That aside. If you want to turn a super maramu  on her axis try this. At idling speed forward put your helm hard to port. Apply full throttle fast. As the boat gets forward momentum, cut the throttle, click to neutral, click to reverse. Apply full throttle in reverse.  The bow will swing fast to port. As it slows, cut throttle and click click through to forward, again apply full throttle fast. The helm is held hard to port all the time and you must allow her to move a bit forward and reverse before you change gear.

Repeat the process until you have turned to where you want. This method won't overcome a strong cross wind but works very well.

The spectators are always very impressed.

Regards

Danny

SM 299 Ocean Pearl

On 28 November 2017 at 09:07 "greatketch@... [amelyachtowners]" <amelyachtowners@...> wrote:

 

There have been many explanations for prop walk written over the years.  The best that can be said about most of them is that they are "creative."


The idea that it was caused by the angle of the prop shaft was a popular one that has appeared in a number of popular sailing books and instructional materials. If that was the reason for why we have prop walk then an Amel SM, with its horizontal prop shaft, would have none.  But of course it does.  Not a lot compared to some boats, but enough to prove that explanation is just plain wrong or, at the very least, incomplete.

Here is how I explained it to my students when I was teaching big boat maneuvering:
An ideal propeller in a perfect universe would move through the water like a screw moves into a wood plank. A propeller with a 14" pitch would move a boat forward 14" for every turn.  But there are no perfect propellers, we do not live in a perfect universe, and water is not wood, so propellers "slip".  A propeller with a 14" pitch will move a boat (very roughly) 10" forward for every turn, and some water will be thrown in the opposite direction.  This is the "slipstream."

Because a propeller is spinning, its slipstream is also rotating as it move away from the prop.  Now comes the hard part without drawing on the napkin...  

Imagine you are behind a boat in reverse. the prop is spinning counterclockwise as you look forward. The slipstream is moving forward, and while it moves forward, it also is spinning counterclockwise.

The top of the slipstream is moving from your right to your left while moving forward.  It hits the hull and/or keel. Very close to 100% of its horizontal momentum is transferred to the boat, pushing the stern to your left (the boat's port).

The bottom of the slipstream hits your boat hull and/or keel moving from left to right.  Less than 100% of its momentum gets transferred to the boat because some of it escapes by going under the hull and/of keel.  It does push the boat somewhat to the right (starboard) but it is less efficient, so the stern of the boat experiences a net push to port.
There are probably other things going on here too, but this model seems to explain all the variations I see.  For example, when  you first shift into reverse, the boat is not moving.  Slip is close to 100%, and prop walk can be dramatic. As soon as the boat begins to move, slip decreases, and prop walk decreases even if you don't correct at all with the rudder.  Maybe you could argue that this is the time you are most concerned with and the YM test is a reasonable model.  I would argue I prefer to know if the boat can be steered once it starts moving, because that is more important to me.  So...  maybe I was a bit harsh to say "almost useless" :-)  At least I didn't write "totally useless!"

In a typical sailboat propeller installation the slip is about 30%.  Yes, it will be higher in reverse, but close enough for argument.  The way YM ran their tests the boat was tied down and could not move.  So the slip must be 100%.  The slipstream is roughly 2 to 3 times stronger than it would normally be.  The difference between the amount of propwalk in the real world (where boats actually move)  with different props is caused by the changing ratio of thrust to slip. The test they ran takes that completely out of the equation. In the test as they ran it the prop that moves more water will always show more propwalk.  

There are so many variables, that I would hesitate to ever predict the differences in prop walk magnitude between two different boats. But I'll say this, if there is a difference between a Maramu and a Super Maramu, it is not because of the angle of the prop shaft.

Bill Kinney
SM160 Harmonie
Fort Lauderdale, FL

---In amelyachtowners@..., <lokiyawl2@...> wrote :

Bill,

   A great post!  Your points about the problem of load matching a particular prop to various conditions is on point I think.  I was thinking about what you said about the fixed bollard test and prop walk possibly being almost useless data and am wondering if that is always correct?  I thinking this because generally when I shift into reverse, the boat will usually have little or no forward motion so there will be a period of time where there is almost no flow over the hull in either direction.  So in effect would this period of reversing when the boat is reversing direction not be quite similar to being tied to a bollard?   

   Can you tell me if there is a significant difference in the amount of prop walk (sideways) between a prop shaft that is angled such as on my Maramu versus the shaft on the SM which appears to be in line with the WL?  

   Again, interesting discourse, thanks!

Best,

James
SV Sueno,  Maramu #220


 


 


Re: [Amel Yacht Owners] Mast Deck Flood Lights

eric freedman
 

Mark,

If you are talking about the foredeck light half way up the mast. I bought one last year at Budget Marine in St Maarten. It is a stock item.

24 volts just means you have to change the lamps from 12 to 24 volts.

Easy install with ¼ inch pop rivets.

Fair Winds

Eric

Kimberlite Amel Super Maramu #376

 

 

From: amelyachtowners@... [mailto:amelyachtowners@...]
Sent: Monday, November 27, 2017 8:01 PM
To: amelyachtowners@...
Subject: Re: [Amel Yacht Owners] Mast Deck Flood Lights

 

 

I believe that Barry's email is referring to a light fixture not merely a bulb.  In my case, the fixture had lost the retaining ring/cap and was otherwise in poor shape.  I could not find a replacement fixture for a 24 volt Aqua-Signal incandescent fixture anywhere online in Europe. I am not sure that one can find them in the US.  Only the 12 volt versions of the incandescent fixture seem to be available.  So if you want to stay with Aqua-Signal ("stay close to the original" as Barry said) and require 24 volts, as we do, then the pricey Aqua-Signal Series 43 LED combi light seems to be the only way to go. It's a "drop in" replacement.

   Mark

  Sabbatical III, SM#419, Spain

 

On 11/27/2017 7:06 PM, 'Mark Erdos' mcerdos@... [amelyachtowners] wrote:

OMG – You paid $610 for a light bulb?

 

 

With best regards,

 

Mark

 

Skipper

Sailing Vessel - Cream Puff - SM2K - #275

Currently cruising – St Lucia, the crime island

www.creampuff.us

 

From: amelyachtowners@... [mailto:amelyachtowners@...]
Sent: Monday, November 27, 2017 4:51 PM
To: amelyachtowners@...
Subject: Re: [Amel Yacht Owners] Mast Deck Flood Lights

 

 

Hi Barry & Robyn,

   I recently installed the Aqua Signal Series 43 LED Masthead / Foredeck Combi-Light.  Fits exactly where the original incandescent Aqua-Signal light was.  Runs at 12 and 24 volts.  You can buy it everywhere.  I got mine at svb24.com in Germany but defender has it for $610 in the US.

  Best regards,

   Mark Pitt

  Sabbatical III, SM#419,  currently in Spain

 

On 11/27/2017 3:35 PM, seagasm@... [amelyachtowners] wrote:

Good morning crew, I would like to replace the Main Mast Deck Flood Light, preferably an LED. Has anyone got a contact where to obtain these and in 24Volt. There is such an array of options available, it's exhausting and I would like to stick with something close to the original.

 

Best Regards

Barry & Robyn

Tradewinds III SM #171

 

 


Re: [Amel Yacht Owners] Mast Deck Flood Lights

Ryan Meador
 

I replaced my mizzen/cockpit lightbulb with this one: https://www.amazon.com/gp/product/B06XWWB5LM

It has served me well since August, and is probably the least expensive boat maintenance I've ever done.  They also make a spotlight version which I intend to install on the mainmast first thing in the spring.

Ryan
SM 233 Iteration
Boston, MA, USA

On Mon, Nov 27, 2017 at 8:01 PM, Mark Pitt mark_pitt@... [amelyachtowners] <amelyachtowners@...> wrote:
 

I believe that Barry's email is referring to a light fixture not merely a bulb.  In my case, the fixture had lost the retaining ring/cap and was otherwise in poor shape.  I could not find a replacement fixture for a 24 volt Aqua-Signal incandescent fixture anywhere online in Europe. I am not sure that one can find them in the US.  Only the 12 volt versions of the incandescent fixture seem to be available.  So if you want to stay with Aqua-Signal ("stay close to the original" as Barry said) and require 24 volts, as we do, then the pricey Aqua-Signal Series 43 LED combi light seems to be the only way to go. It's a "drop in" replacement.

   Mark

  Sabbatical III, SM#419, Spain


On 11/27/2017 7:06 PM, 'Mark Erdos' mcerdos@... [amelyachtowners] wrote:

OMG – You paid $610 for a light bulb?

 

 

With best regards,

 

Mark

 

Skipper

Sailing Vessel - Cream Puff - SM2K - #275

Currently cruising – St Lucia, the crime island

www.creampuff.us

 

From: amelyachtowners@yahoogroups.com [mailto:amelyachtowners@yahoogroups.com]
Sent: Monday, November 27, 2017 4:51 PM
To: amelyachtowners@yahoogroups.com
Subject: Re: [Amel Yacht Owners] Mast Deck Flood Lights

 

 

Hi Barry & Robyn,

   I recently installed the Aqua Signal Series 43 LED Masthead / Foredeck Combi-Light.  Fits exactly where the original incandescent Aqua-Signal light was.  Runs at 12 and 24 volts.  You can buy it everywhere.  I got mine at svb24.com in Germany but defender has it for $610 in the US.

  Best regards,

   Mark Pitt

  Sabbatical III, SM#419,  currently in Spain

 

On 11/27/2017 3:35 PM, seagasm@... [amelyachtowners] wrote:

Good morning crew, I would like to replace the Main Mast Deck Flood Light, preferably an LED. Has anyone got a contact where to obtain these and in 24Volt. There is such an array of options available, it's exhausting and I would like to stick with something close to the original.

 

Best Regards

Barry & Robyn

Tradewinds III SM #171

 




Re: [Amel Yacht Owners] Mast Deck Flood Lights

Mark Pitt
 

I believe that Barry's email is referring to a light fixture not merely a bulb.  In my case, the fixture had lost the retaining ring/cap and was otherwise in poor shape.  I could not find a replacement fixture for a 24 volt Aqua-Signal incandescent fixture anywhere online in Europe. I am not sure that one can find them in the US.  Only the 12 volt versions of the incandescent fixture seem to be available.  So if you want to stay with Aqua-Signal ("stay close to the original" as Barry said) and require 24 volts, as we do, then the pricey Aqua-Signal Series 43 LED combi light seems to be the only way to go. It's a "drop in" replacement.

   Mark

  Sabbatical III, SM#419, Spain


On 11/27/2017 7:06 PM, 'Mark Erdos' mcerdos@... [amelyachtowners] wrote:

OMG – You paid $610 for a light bulb?

 

 

With best regards,

 

Mark

 

Skipper

Sailing Vessel - Cream Puff - SM2K - #275

Currently cruising – St Lucia, the crime island

www.creampuff.us

 

From: amelyachtowners@... [mailto:amelyachtowners@...]
Sent: Monday, November 27, 2017 4:51 PM
To: amelyachtowners@...
Subject: Re: [Amel Yacht Owners] Mast Deck Flood Lights

 

 

Hi Barry & Robyn,

   I recently installed the Aqua Signal Series 43 LED Masthead / Foredeck Combi-Light.  Fits exactly where the original incandescent Aqua-Signal light was.  Runs at 12 and 24 volts.  You can buy it everywhere.  I got mine at svb24.com in Germany but defender has it for $610 in the US.

  Best regards,

   Mark Pitt

  Sabbatical III, SM#419,  currently in Spain

 

On 11/27/2017 3:35 PM, seagasm@... [amelyachtowners] wrote:

Good morning crew, I would like to replace the Main Mast Deck Flood Light, preferably an LED. Has anyone got a contact where to obtain these and in 24Volt. There is such an array of options available, it's exhausting and I would like to stick with something close to the original.

 

Best Regards

Barry & Robyn

Tradewinds III SM #171

 



48galley

james Hosford
 

Is the Maramu 48 galley functional? Looks like it’s just open to the salon and doesn’t have a good place for bracing?


Re: [Amel Yacht Owners] Re: Mast Deck Flood Lights

Paul LaFrance <pflafrance@...>
 

Barry Robyn

We replaced our bulbs with this light that fit in the recepticle that housed the GE bulb. Worked great. Really bright. http://www.grote.com/products/63821-trilliant-36-led-work-white-light-with-spade-screw-terminals/?industrycat=&prodcat=work-lighting

Cost was about 90 -100 USD

Paul & Sue LaFrance

Former owners of SV NOMAD SM #362

www.grote.com
Grote Industries - Part: #63821 - Trilliant® 36 LED Work White Light, Spade/Screw Terminals. UV Coated And Hard Coated Lens For Durability.




From: amelyachtowners@... on behalf of greatketch@... [amelyachtowners]
Sent: Monday, November 27, 2017 5:02 PM
To: amelyachtowners@...
Subject: [Amel Yacht Owners] Re: Mast Deck Flood Lights
 
 




---In amelyachtowners@..., wrote :

Good morning crew, I would like to replace the Main Mast Deck Flood Light, preferably an LED. Has anyone got a contact where to obtain these and in 24Volt. There is such an array of options available, it's exhausting and I would like to stick with something close to the original.


Best Regards

Barry & Robyn

Tradewinds III SM #171


Re: [Amel Yacht Owners] Re: Flexofold Prop

greatketch@...
 

Pat,

For a boat with an effective bow thruster, I agree, prop walk is rather minor consideration.

I don't entirely dismiss the independent testing, it tells me that the performance of the props are all essentially the same, and that is useful information.

Once I get to the point that all the props are pretty similar in performance, then I would check to be sure they would fit my boat.

After that, it's tough. Which one is easier to work with?  Do I feel I will need to be able to adjust the pitch underwater easily?  What kind of support is available?  Do any of them look better built than the others?  

For someone with an Amel, using an Autoprop or a MaxProp can cut several corners.  You can find out exactly the model, size, pitch settings, etc that work for other people with your exact boat and engine.  That's significant but not overwhelming value.

Otherwise, I don't have a magic answer for picking the "best" other than saying I have never heard anybody voice really serious  valid complaints about any of them, with the possible exception of the smaller two blade Varifold models, but they aren't suitable for an Amel anyway.


Bill Kinney
SM160, Harmonie
Fort Lauderdale, FL


Re: [Amel Yacht Owners] Mast Deck Flood Lights

rossirossix4
 

I think several Amel owners have had good luck with MarineBeam.  They sell dedicated spreader lights and have a Par 36 replacement in narrow and wide beam in 5, 9, and 13 watt.  I use the 5 watt because in certain situations I will leave it on overrnight.  The "narrow" beam seems to cover the entire deck.  http://store.marinebeam.com/4-1-2-par36-led-sealed-beam-replacement-bulb-sb-par/
Bob, KAIMI SM429


Re: Mast Deck Flood Lights

greatketch@...
 

The exact match for the light used as a deck flood light on our boat is an Aquasignal light, model "KIEL" it is now available in both conventional lamp and LED models.

It is in current production, but as far as I could find is not is not available anywhere in the USA.  We ordered ours from an eBay vendor in Lithuania.  It is also available from several of the larger European online chandleries.

The original was riveted to the mast, I'd suggest drilling out the rivets and tapping for machine screws.

On our boat the deck light and the steaming light were in separate fixtures several meters apart on the mast.  It was far easier to replace the deck light in kind, than to re-route wires and install a combined fixture.

Bill Kinney
SM160, Harmonie
Fort Lauderdale, FL


Re: [Amel Yacht Owners] Mast Deck Flood Lights

Mark Erdos
 

OMG – You paid $610 for a light bulb?

 

 

With best regards,

 

Mark

 

Skipper

Sailing Vessel - Cream Puff - SM2K - #275

Currently cruising – St Lucia, the crime island

www.creampuff.us

 

From: amelyachtowners@... [mailto:amelyachtowners@...]
Sent: Monday, November 27, 2017 4:51 PM
To: amelyachtowners@...
Subject: Re: [Amel Yacht Owners] Mast Deck Flood Lights

 

 

Hi Barry & Robyn,

   I recently installed the Aqua Signal Series 43 LED Masthead / Foredeck Combi-Light.  Fits exactly where the original incandescent Aqua-Signal light was.  Runs at 12 and 24 volts.  You can buy it everywhere.  I got mine at svb24.com in Germany but defender has it for $610 in the US.

  Best regards,

   Mark Pitt

  Sabbatical III, SM#419,  currently in Spain

 

On 11/27/2017 3:35 PM, seagasm@... [amelyachtowners] wrote:

Good morning crew, I would like to replace the Main Mast Deck Flood Light, preferably an LED. Has anyone got a contact where to obtain these and in 24Volt. There is such an array of options available, it's exhausting and I would like to stick with something close to the original.

 

Best Regards

Barry & Robyn

Tradewinds III SM #171

 


Re: Mast Deck Flood Lights

greatketch@...
 




---In amelyachtowners@..., <seagasm@...> wrote :

Good morning crew, I would like to replace the Main Mast Deck Flood Light, preferably an LED. Has anyone got a contact where to obtain these and in 24Volt. There is such an array of options available, it's exhausting and I would like to stick with something close to the original.


Best Regards

Barry & Robyn

Tradewinds III SM #171


Re: [Amel Yacht Owners] Re: Flexofold Prop

Patrick McAneny
 

Bill , Prop walk is probably less importance to me than drag and thrust. The test concluded that drag is greatly reduced , to the point of a non issue compared to a fixed prop , with folding props virtually zero drag and feathering only up to 5 % of a fixed prop. So then that leaves thrust and maybe emergency stopping. Assuming that all 15 props tested were pitched for the test boat , and they test them at the same RPM , then cannot one draw a conclusion about  the amount of thrust produced by various props. 
When one spends 3k - 4k on a prop , you of course want the best overall prop for your money. Its only logical to assume that all props are not created equal . So the question is , if you disregard independent testing / evaluation , what do you base your choice on ? Ask TOM , Dick & Harry and they will all tell you their prop is the best . I guess you can always throw a dart . Back to prop walk , your explanation helped me understand what causes it , I had a theory and it was wrong.
Thanks,
Pat 
SM#123


-----Original Message-----
From: greatketch@... [amelyachtowners]
To: amelyachtowners
Sent: Mon, Nov 27, 2017 3:08 pm
Subject: Re: [Amel Yacht Owners] Re: Flexofold Prop

 
There have been many explanations for prop walk written over the years.  The best that can be said about most of them is that they are "creative."

The idea that it was caused by the angle of the prop shaft was a popular one that has appeared in a number of popular sailing books and instructional materials. If that was the reason for why we have prop walk then an Amel SM, with its horizontal prop shaft, would have none.  But of course it does.  Not a lot compared to some boats, but enough to prove that explanation is just plain wrong or, at the very least, incomplete.

Here is how I explained it to my students when I was teaching big boat maneuvering:
An ideal propeller in a perfect universe would move through the water like a screw moves into a wood plank. A propeller with a 14" pitch would move a boat forward 14&qu ot; for every turn.  But there are no perfect propellers, we do not live in a perfect universe, and water is not wood, so propellers "slip".  A propeller with a 14" pitch will move a boat (very roughly) 10" forward for every turn, and some water will be thrown in the opposite direction.  This is the "slipstream."

Because a propeller is spinning, its slipstream is also rotating as it move away from the prop.  Now comes the hard part without drawing on the napkin...  

Imagine you are behind a boat in reverse. the prop is spinning counterclockwise as you look forward. The slipstream is moving forward, and while it moves forward, it also is spinning counterclockwise.

The top of the slipstream is moving from your right to your left while moving forward.  It hits the hull and/or keel. Very close to 100% of its horizontal momentum is transferred to the boat, pushing the stern to your left (the boat's port).

The bottom of the slipstream hits your boat hull and/or keel moving from left to right.  Less than 100% of its momentum gets transferred to the boat because some of it escapes by going under the hull and/of keel.  It does push the boat somewhat to the right (starboard) but it is less efficient, so the stern of the boat experiences a net push to port.
There are probably other things going on here too, but this model seems to explain all the variations I see.  For example, when  you first shift into reverse, the boa t is not moving.  Slip is close to 100%, and prop walk can be dramatic. As soon as the boat begins to move, slip decreases, and prop walk decreases even if you don't correct at all with the rudder.  Maybe you could argue that this is the time you are most concerned with and the YM test is a reasonable model.  I would argue I prefer to know if the boat can be steered once it starts moving, because that is more important to me.  So...  maybe I was a bit harsh to say "almost useless" :-)  At least I didn't write "totally useless!"

In a typical sailboat propeller installation the slip is about 30%.  Yes, it will be higher in reverse, but close enough for argument.  The way YM ran their tests the boat was tied down and could not move.  So the slip must be 100%.  The slipstream is roughly 2 to 3 times stronger than it would normally be.  The difference between t he amount of propwalk in the real world (where boats actually move)  with different props is caused by the changing ratio of thrust to slip. The test they ran takes that completely out of the equation. In the test as they ran it the prop that moves more water will always show more propwalk.  

There are so many variables, that I would hesitate to ever predict the differences in prop walk magnitude between two different boats. But I'll say this, if there is a difference between a Maramu and a Super Maramu, it is not because of the angle of the prop shaft.

Bill Kinney
SM160 Harmonie
Fort Lauderdale, FL

---In amelyachtowners@..., wrote :

Bill,

   A great post!  Your points about the problem of load matching a particular prop to various conditions is on point I think.  I was thinking about what you said about the fixed bollard test and prop walk possibly being almost useless data and am wondering if that is always correct?  I thinking this because generally when I shift into reverse, the boat will usually have little or no forward motion so there will be a period of time where there is almost no flow over the hull in either direction.  So in effect would this period of reversing when the boat is reversing direction not be quite similar to being tied to a bollard?   

   Can you tell me if there is a significant difference in the amount of prop walk (sideways) between a prop shaft that is angled such as on my Maramu versus the shaft on the SM which appears to be in line with the WL?  

   Again, interesting discourse, thanks!

Best,

James
SV Sueno,  Maramu #220



Re: [Amel Yacht Owners] Mast Deck Flood Lights

eric freedman
 

 

 

From: amelyachtowners@... [mailto:amelyachtowners@...]
Sent: Monday, November 27, 2017 5:23 PM
To: amelyachtowners@...
Subject: RE: [Amel Yacht Owners] Mast Deck Flood Lights

 

 

This might be the lamp.

http://www.lunasealighting.com/products/detail/spreader-foredeck-led-light-bulb/led-flood-lights

If it is not ot looks like this.

Fair Winds

Eric

Kimberlite Amel Super Maramu #376

 

 

From: amelyachtowners@... [mailto:amelyachtowners@...]
Sent: Monday, November 27, 2017 5:09 PM
To: amelyachtowners@...
Subject: RE: [Amel Yacht Owners] Mast Deck Flood Lights

 

 

Hi,

I believe Alexandre posted the model of a very effective LED deck light.

Unfortunately I do not remember where I bought it. I bought the narrow beam one for the foredeck, and the wide beam for the cockpit.

It fits into the Aqua Signal deck light fixtures. They are heavier than the glass light bulb. I would strongly suggest reinforcing the fixture or put silicone around the LED due to its weight.

They are amazingly bright.

Fair Winds

Eric

Kimberlite Amel Super Maramu #376

 

 

From: amelyachtowners@... [mailto:amelyachtowners@...]
Sent: Monday, November 27, 2017 3:36 PM
To: amelyachtowners@...
Subject: [Amel Yacht Owners] Mast Deck Flood Lights

 

 

Good morning crew, I would like to replace the Main Mast Deck Flood Light, preferably an LED. Has anyone got a contact where to obtain these and in 24Volt. There is such an array of options available, it's exhausting and I would like to stick with something close to the original.

 

Best Regards

Barry & Robyn

Tradewinds III SM #171


Re: [Amel Yacht Owners] Mast Deck Flood Lights

eric freedman
 

This might be the lamp.

http://www.lunasealighting.com/products/detail/spreader-foredeck-led-light-bulb/led-flood-lights

If it is not ot looks like this.

Fair Winds

Eric

Kimberlite Amel Super Maramu #376

 

 

From: amelyachtowners@... [mailto:amelyachtowners@...]
Sent: Monday, November 27, 2017 5:09 PM
To: amelyachtowners@...
Subject: RE: [Amel Yacht Owners] Mast Deck Flood Lights

 

 

Hi,

I believe Alexandre posted the model of a very effective LED deck light.

Unfortunately I do not remember where I bought it. I bought the narrow beam one for the foredeck, and the wide beam for the cockpit.

It fits into the Aqua Signal deck light fixtures. They are heavier than the glass light bulb. I would strongly suggest reinforcing the fixture or put silicone around the LED due to its weight.

They are amazingly bright.

Fair Winds

Eric

Kimberlite Amel Super Maramu #376

 

 

From: amelyachtowners@... [mailto:amelyachtowners@...]
Sent: Monday, November 27, 2017 3:36 PM
To: amelyachtowners@...
Subject: [Amel Yacht Owners] Mast Deck Flood Lights

 

 

Good morning crew, I would like to replace the Main Mast Deck Flood Light, preferably an LED. Has anyone got a contact where to obtain these and in 24Volt. There is such an array of options available, it's exhausting and I would like to stick with something close to the original.

 

Best Regards

Barry & Robyn

Tradewinds III SM #171


Re: [Amel Yacht Owners] Mast Deck Flood Lights

eric freedman
 

Hi,

I believe Alexandre posted the model of a very effective LED deck light.

Unfortunately I do not remember where I bought it. I bought the narrow beam one for the foredeck, and the wide beam for the cockpit.

It fits into the Aqua Signal deck light fixtures. They are heavier than the glass light bulb. I would strongly suggest reinforcing the fixture or put silicone around the LED due to its weight.

They are amazingly bright.

Fair Winds

Eric

Kimberlite Amel Super Maramu #376

 

 

From: amelyachtowners@... [mailto:amelyachtowners@...]
Sent: Monday, November 27, 2017 3:36 PM
To: amelyachtowners@...
Subject: [Amel Yacht Owners] Mast Deck Flood Lights

 

 

Good morning crew, I would like to replace the Main Mast Deck Flood Light, preferably an LED. Has anyone got a contact where to obtain these and in 24Volt. There is such an array of options available, it's exhausting and I would like to stick with something close to the original.

 

Best Regards

Barry & Robyn

Tradewinds III SM #171


Re: [Amel Yacht Owners] Mast Deck Flood Lights

Mark Pitt
 

Hi Barry & Robyn,

   I recently installed the Aqua Signal Series 43 LED Masthead / Foredeck Combi-Light.  Fits exactly where the original incandescent Aqua-Signal light was.  Runs at 12 and 24 volts.  You can buy it everywhere.  I got mine at svb24.com in Germany but defender has it for $610 in the US.

  Best regards,

   Mark Pitt

  Sabbatical III, SM#419,  currently in Spain


On 11/27/2017 3:35 PM, seagasm@... [amelyachtowners] wrote:

Good morning crew, I would like to replace the Main Mast Deck Flood Light, preferably an LED. Has anyone got a contact where to obtain these and in 24Volt. There is such an array of options available, it's exhausting and I would like to stick with something close to the original.


Best Regards

Barry & Robyn

Tradewinds III SM #171



Re: [Amel Yacht Owners] Re: Flexofold Prop

James Alton
 

Bill,

  That is the most reasonable explanation that I have ever heard for why props walk.    You have knack for explaining things in an understandable form.  So if i have processed the information correctly, the only way to have a single prop that does not walk is to have infinite draft so that the two slip streams fully cancel?  If I am on the right track, does this also explain  the reason that the more shallow draft boats that I have handled seem to have more prop walk than the deeper keeled ones?  I always just thought that this was due to difference in the force required to move more lateral plane sideways but now you have me rethinking this…   

Best,

James
SV Sueno,  Maramu #220

On Nov 27, 2017, at 4:07 PM, greatketch@... [amelyachtowners] <amelyachtowners@...> wrote:

There have been many explanations for prop walk written over the years.  The best that can be said about most of them is that they are "creative."


The idea that it was caused by the angle of the prop shaft was a popular one that has appeared in a number of popular sailing books and instructional materials. If that was the reason for why we have prop walk then an Amel SM, with its horizontal prop shaft, would have none.  But of course it does.  Not a lot compared to some boats, but enough to prove that explanation is just plain wrong or, at the very least, incomplete.

Here is how I explained it to my students when I was teaching big boat maneuvering:
An ideal propeller in a perfect universe would move through the water like a screw moves into a wood plank. A propeller with a 14" pitch would move a boat forward 14&qu ot; for every turn.  But there are no perfect propellers, we do not live in a perfect universe, and water is not wood, so propellers "slip".  A propeller with a 14" pitch will move a boat (very roughly) 10" forward for every turn, and some water will be thrown in the opposite direction.  This is the "slipstream."

Because a propeller is spinning, its slipstream is also rotating as it move away from the prop.  Now comes the hard part without drawing on the napkin...  

Imagine you are behind a boat in reverse. the prop is spinning counterclockwise as you look forward. The slipstream is moving forward, and while it moves forward, it also is spinning counterclockwise.

The top of the slipstream is moving from your right to your left while moving forward.  It hits the hull and/or keel. Very close to 100% of its horizontal momentum is transferred to the boat, pushing the stern to your left (the boat's port).

The bottom of the slipstream hits your boat hull and/or keel moving from left to right.  Less than 100% of its momentum gets transferred to the boat because some of it escapes by going under the hull and/of keel.  It does push the boat somewhat to the right (starboard) but it is less efficient, so the stern of the boat experiences a net push to port.
There are probably other things going on here too, but this model seems to explain all the variations I see.  For example, when  you first shift into reverse, the boa t is not moving.  Slip is close to 100%, and prop walk can be dramatic. As soon as the boat begins to move, slip decreases, and prop walk decreases even if you don't correct at all with the rudder.  Maybe you could argue that this is the time you are most concerned with and the YM test is a reasonable model.  I would argue I prefer to know if the boat can be steered once it starts moving, because that is more important to me.  So...  maybe I was a bit harsh to say "almost useless" :-)  At least I didn't write "totally useless!"

In a typical sailboat propeller installation the slip is about 30%.  Yes, it will be higher in reverse, but close enough for argument.  The way YM ran their tests the boat was tied down and could not move.  So the slip must be 100%.  The slipstream is roughly 2 to 3 times stronger than it would normally be.  The difference between t he amount of propwalk in the real world (where boats actually move)  with different props is caused by the changing ratio of thrust to slip. The test they ran takes that completely out of the equation. In the test as they ran it the prop that moves more water will always show more propwalk.  

There are so many variables, that I would hesitate to ever predict the differences in prop walk magnitude between two different boats. But I'll say this, if there is a difference between a Maramu and a Super Maramu, it is not because of the angle of the prop shaft.

Bill Kinney
SM160 Harmonie
Fort Lauderdale, FL

---In amelyachtowners@..., wrote :

Bill,

   A great post!  Your points about the problem of load matching a particular prop to various conditions is on point I think.  I was thinking about what you said about the fixed bollard test and prop walk possibly being almost useless data and am wondering if that is always correct?  I thinking this because generally when I shift into reverse, the boat will usually have little or no forward motion so there will be a period of time where there is almost no flow over the hull in either direction.  So in effect would this period of reversing when the boat is reversing direction not be quite similar to being tied to a bollard?   

   Can you tell me if there is a significant difference in the amount of prop walk (sideways) between a prop shaft that is angled such as on my Maramu versus the shaft on the SM which appears to be in line with the WL?  

   Again, interesting discourse, thanks!

Best,

James
SV Sueno,  Maramu #220





Mast Deck Flood Lights

seagasm
 

Good morning crew, I would like to replace the Main Mast Deck Flood Light, preferably an LED. Has anyone got a contact where to obtain these and in 24Volt. There is such an array of options available, it's exhausting and I would like to stick with something close to the original.


Best Regards

Barry & Robyn

Tradewinds III SM #171