Shaft line cutters

FullMonty

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I picked up a new to me 26 General Marine last past fall. I want to get a shaft line cutter for it. After doing a bit of research I decided to get a spur from New England Propeller. Than after talking to them it was determined that is most likely not possible because of the fiberglass shaft tube. There would be no place to drill and tap to mount the stationary part of the spur. I’ve seen the shaft mounted ones that look like ninga stars. How well do these work. Anyone have first hand experience? Thanks.
 

Genius

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i don't run line cutters. The only time I had problems is when I backed into a lobster buoy (it was a tight spot in a tide with heavy mooring hanging off my stern). Otherwise, never a problem. Why do you want line cutters?

I had a DE boat with a shaft mounted line cutter. I took it off to put something more useful, a zinc.
 

FullMonty

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Running in the dark through Boston harbor and down around scituate. There are a lot of traps. I obviously would prefer to avoid them but sometimes they don’t have enough scope and are just below the water at high tide.
 

andy65

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I have a fiberglass tube and am having Spurs installed as we speak. Spurs on glass tubes are common in Maine. My installer has done many. What they do is cut a thread into the fiberglass using a flat head tap then fill the hole with a special epoxy like product, put the screw in effectively bonding the screw into the fiberglass. The screw can be removed by applying heat to release the agent. A lip of epoxy can be made horizontally below the wedge block to take some force so the screws aren’t taking it all.

Spurs has a method in their instructions for fiberglass: Use a router to make a recessed area in the fiberglass. Tap holes in a metal plate, then bond the plate into recessed area. This solution may be a problem if the glass is thin. Also, a flat plate can be difficult to fit against a small diameter tube. May need a curved plate.

I have a Shark 1.75 shaft line cutter for sale if interested.
 

Dyer29HoldFast

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If you stick to the channel you will have less chance of getting gear in your wheel. There are guys that might set near the channel. which Is dumb in my eyes. Why set gear so close to the channel and possibly losing gear.
I've ran into the same problem as Genius but with a crab pot/bouy. Not at mooring but at a marina.
 

traditions

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I have mounted many spurs to a fiberglass tube. I just split a piece of stainless pipe, and drill and tap a series of holes in the tube. I used to weld the holding block to the pipe, but have been attaching it with bolts like they say in the instructions, because it allows the holding block to shearboff if you get something to latte for the spur to handle
 

Tuna Pursuit

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I had a set on my last boat which was a twin screw. They were a double row of saw teeth. They are in half so just clamp on the shaft like a zinc. With a twin inboard running at night you run over everything. These cut off everything I ran over. Except the telephone pole that was a bad day
 

FullMonty

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I have a fiberglass tube and am having Spurs installed as we speak. Spurs on glass tubes are common in Maine. My installer has done many. What they do is cut a thread into the fiberglass using a flat head tap then fill the hole with a special epoxy like product, put the screw in effectively bonding the screw into the fiberglass. The screw can be removed by applying heat to release the agent. A lip of epoxy can be made horizontally below the wedge block to take some force so the screws aren’t taking it all.

Spurs has a method in their instructions for fiberglass: Use a router to make a recessed area in the fiberglass. Tap holes in a metal plate, then bond the plate into recessed area. This solution may be a problem if the glass is thin. Also, a flat plate can be difficult to fit against a small diameter tube. May need a curved plate.

I have a Shark 1.75 shaft line cutter for sale if interested.
Thanks for the info. I’ll look into that.
Unfortunately my shaft is 1.5 so that cutter is to big.
 

andy65

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I have mounted many spurs to a fiberglass tube. I just split a piece of stainless pipe, and drill and tap a series of holes in the tube. I used to weld the holding block to the pipe, but have been attaching it with bolts like they say in the instructions, because it allows the holding block to shearboff if you get something to latte for the spur to handle
Can you tell us more about attaching the half pipe to the tube? Was the half pipe glassed to the surface with mat over it or recessed some into the tube? Any photos? If there is a boat on the hard, I would like to come take a look.
 

traditions

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I have done it both ways, with glass over , apiece of flat bar was used , and the shaft tube was ground down flat to accept the flat bar, drilled a series of holes in the flat bar, and drilled and tapped into the shaft tube. Then glassed over the whole mess, using hull and deck to fair it up before glassing , to assure all the air can be rolled out. You need a bottoming tap to get the threads all the way thru the Tube,sometimes it’s even into the cutlass bearing. The problem with glassing over everything is if you need to change the bearing, some times you have to remove the stationary holder. I will see if I can get a picture for you. As for the ninja star type, They will cut rope as long as there is a strain on the line, but they are nothing like a spur. My father used to say , “ you must not want to lose that, you have it tied on” about the star cutters, because they always had rope wrapped around them. They also cause the propeller to be less efficient.
 
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capt38

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Has anyone used these ?
I tried one on my 31' Eastern two years ago. I thought it was a great idea, and have very limited space for an zinc & cutter. I hit a submerged mooring buoy early in the season, and the line cutter portion bent badly, causing vibration. I had a diver remove the whole thing. If it just tangled up with line it might have been ok, but didn't fare well with something more solid.
 

andy65

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I have mounted many spurs to a fiberglass tube. I just split a piece of stainless pipe, and drill and tap a series of holes in the tube. I used to weld the holding block to the pipe, but have been attaching it with bolts like they say in the instructions, because it allows the holding block to shearboff if you get something to latte for the spur to handle
I’m thinking about the split a piece of pipe and attaching a 60 deg section to the surface of the shaft tube. The problem is the shaft tube is 3.13” diameter. Therefore a piece of pipe segment needs to have an ID of 3.13” to mate with the curve. Suppose a larger could be used but that will leave voids to be filled. Seems like a piece of angle might work easier.
 

El Mar

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traditions

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I’m thinking about the split a piece of pipe and attaching a 60 deg section to the surface of the shaft tube. The problem is the shaft tube is 3.13” diameter. Therefore a piece of pipe segment needs to have an ID of 3.13” to mate with the curve. Suppose a larger could be used but that will leave voids to be filled. Seems like a piece of angle might work easier.
Just take a smaller piece of pipe, lay it on the bench and flatten it out with a hammer, till it fits . Thats why its called fabricate. You just make it work. Like I said before, you can use flatbar , and grind the tube flat. I will see if there are any in the yard today with a tube.
 

Soundownsam

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We (Soundown/Evolution) manufacture the Shaft Razor. In all honesty I have never been on a boat that was running them when it had to do its job, but, reports from users have all been favorable. They are available in solid or split models with ODs to match most shaft sizes.

To get the correct size you will need to know the diameter of your prop hub as well as the shaft size. Most shaft sizes have a couple of options for cutter diameter to make sure that there is exposed cutting surface, but, not so much you will interfere with water flow to the prop.
Split Iso png 6x5 no shadow.jpg
These are not currently on the Soundown website, but, we will be creating an Evolution web site in the near future. If you would like more info send me a PM with your email address and I will send it over.

sam
 
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