bushings instead of ball bearings in furler

[markxengineerin]

There seem to be two or more ball bearings per furler, one at the bottom and one on top. Some are sealed, some open (Torlon), but are there any that are just plain bushings, maybe teflon, torlon, nylon, even brass? The entire length of the foil is supported by bushings anyway, and I suspect the friction difference would be negligible if the two ball bearings disappeared. This would eliminate a whole pile of parts, reduce cost, and keep things simple, which is usually a good thing.

[wholybee]

The weight of the foil (and sail) is supported by the bearings on the bottom. None of the bushings along it's length carry any weight. It would almost certainly not work if you omitted the bearings.

[markxengineerin]

I can imagine a plain (non-ball) thrust bearing having more friction since that load is so concentrated. Doesn't the halyard take the weight of the sail, though? The sail comes down when the halyard is released, at least when unloaded. I've never tried this while actively sailing, but would friction hold it up if the sail is loaded? If either of these things factor in, there might be less axial load on the bearing than otherwise expected.

[SV_Sweet_Ruca]

Sorry, couldn't resist when I saw the thread title!

[JC Reefer]

I agree with the other person, the bushings don’t hold the load. And I think there’d be too much friction without something rolling.

I’ve often wondered if there were torlon replacement bearings that would come in the same packaging as the steel ones do. If that exists then the last part are the Circlips. Might find those in titanium.

Get a harken and then you only need to deal with the cheap drum covers that break off. ☹️

Off topic but maybe helpful. I don’t see the little steel ball in your image above. You need to take that little guy out so that assembly can happen properly. An ice pick from the inside gets the old one out.

[RaymondR]

The two roller furlers I have had experience with both had shallow groove ball bearings in them. The problem with this arrangement is that when you place a high axial loas on this type of bearing the rolling friction greatly increases, which is why halyard tension has a large effect of how hard it is to furl.

There are a number of arrangements which would improve this situation, including bushes for transverse positioning with a roller thrust bearing for resistance to the axial load.

Another bearing arrangement which would provide concurrent, transverse positioning and axial load resistance is opposed conical roller bearings such as those in the front wheel of your motor car.

There are roller bearings which are designed for greater axial load resistance but they were not utilized in the two unit types I am familiar with.

[markxengineerin]

@raymondr, I agree with all that you said. Profurl uses deep groove ball bearings, though. Here is invoice from 123bearing (great place to buy bearings and seals, by the way):


I'm not sure which would have lower friction- a well designed plain thrust bearing, or a deep groove ball bearing, for a given axial load.

Does a tight halyard generally make it more or less difficult to furl? The way I am thinking about it it, the top bearing would become more highly loaded, but the bottom bearing might be less, as halyard tension increases, at least up to the point where the mass of the sail is fully supported. Then the net axial force on the bottom bearing might start pointing up, not down?

[markxengineerin]

@JC Reefer- that photo was from the forum archives, not mine, but I don't remember seeing any steel balls other than plugging some holes in the "housing" part of the furler. It looked to me like they might have been access points for re-greasing, maybe blocked when someone decided it wasn't necessary. But that was a guess. Could you explain more about what they're for and how they are related to re-assembly?

[wholybee]

I have a Schaefer furler. It's probably 20 years old, and had minimal maintenance. It uses quite large torlon ball bearings (3/8"?) . Low friction, and relatively easy to rinse out. Easier on the newer models than the old one I have.

When I completed my circumnavigation, without a single bit of furler trouble the whole time, I decided a teardown and rebuild was a good idea as a preventative measure. I had to drill out a whole lot of rivets holding the foil together, and damaged some minor parts in the process. (Schaefer warned me beforehand that it was nearly impossible to take apart without at least a little damage.) After the teardown and inspection, I concluded it probably hadn't been necessary. Except the foil joiners and bushings that were damaged by me, everything was still in great shape, even after 20 years and 35,000 miles.

Anyway, my conclusion is that large torlon ball bearings are a fine arrangement. I'm skeptical of smaller stainless bearings as shown in the picture.

I know that on several friends boats (I don't recall what furler they have) they need to have a very tight halyard to furl smoothly, even though they often ease for better shape.

[Rumrace]

I’m a newb on furlers absolute pro amateur on bearings
Take a standard Chevy small block and ship it to Merc or Volvo. Both remove the cam bushings and replace them with needle bearings. The bushing simply is not designed to handle the load. The standard rockers are from 1959 and pretty much car just. So a roller bearing bearing is added to the tip of a performance car or marine engine to reduce cam load and valve guide offset loads.
A LS3 at 7500 RPM doesn’t quite get 500hp
Marinize this much improved Chevy and @ 4300 rpm - 500hp.
Nylon is not you grandpas nylon. I know I’m a grandpa. Nylon has long past average bearing race now made in China. PA11-CF needle bearing might be the ticket. It’s a form of nylon very hard to make things from due to warping. The new blend is stabilized with Carbon Fibre. It’s also know as Carbon Black. Expect to see masts made from it on overpriced boats. It’s like $120.00 USD a kilo.
That babbling aside. Bearings fail because they were poorly made. Base metals really count and when you toss floor sweeping back in the smelter you get false metals. SAE UL CE imprints fake.

[wholybee]

The requirements of bearings in an engine, and bearings in a furler are entirely different. Steel requires lubrication, and oil/grease isn't a good option for a furler which may at times be submerged in salt water. They can(will) fail not because they were poorly made, but because of the environment. So, IMHO, plastics which don't need any lubrication, but just a rinse with water are best. Note that I have 20 years and 35,000 ocean miles on my plastic (torlon) bearings, and they are still fine and I see no reason to change them now.

I know that some major manufactures use other arrangements. But I am sold on the use of torlon ball bearings.

[Rumrace]

Until the day plastic takes the lead I’d still pick a roller with some flexibility to handle the whacky loads.
My pick....

[Rumrace]

You’re absolutely right. Explains why plastic is popular. There are lubes for plastic rollers. I bought some. It’s water resistance dry. A salt water wash would sure wreck a bearing.
Is this also true for the upper bearing

[RaymondR]

Having pondered upon it a bit more I have decided that from an engineering viewpoint bushes for axial alignment and roller thrust bearings would be the best arrangements for furlers.

As a first iteration, because of it's high load capacity and low friction qualities, I would consider bronze filled teflon for the bushes, bearing upon SS shafts for the axial bearings and one of the plastics or ceramics for the thrust bearing rollers bearing upon SS seats for the thrust bearing components.

[markxengineerin]

Warren- i understand your thinking, and after tearing down my furler, I do have some regret, because it involved drilling out multiple specialized titanium bolts that I'm too cheap to replace, and overall I may be as likely to make things worse as I am to make things better. But I did discover that the previous owner/installer had used the wrong foil section on the bottom, and the result was some set screws only holding the foils up by friction rather than by positive penetration into the foil. This is very dangerous because if the foils slip down, the furler can jam, and there are several posts on this forum describing that happening. I would never have discovered the error unless I had decided to take everything apart. There's a fine line in between "it ain't broke, don't fix it" and an appropriate level of being a control freak with understanding all the boat's equipment.
The Shaefer product looks better to me than ProFurl. I'm not impressed with Profurl's use of plastic for critical pieces, poor selection of fasteners, cheap decorative instead of hardcoat anodize, etc. It has been "functional" for 10 years, but could be a lot better for little or no extra cost. Maybe they have improved on more recent models.