Servicing a Varifold Folding Sailboat Propeller
In this post we will run through how you service your Varifold folding sailboat propeller during your yearly haul out. It is possible to perform some of this work underwater should it not be possible to haul out, however the service is best done when the sailboat is on the hard.
The primary purpose of the yearly service is to protect the Varifold propeller from galvanic corrosion by replacing the anode (Zinc / Aluminum / Magnesium) and also to ensure the blades and buffer pads are in good working order and the blades move freely.
Which Varifold Propeller do you have?
To ensure you get the correct spare parts for your Varifold folding propeller it is important to know which model you have. Obviously the first indicator is the blade number which will be either 2, 3 or 4 blades. The 2 blade model Varifold come in a shaft or sail drive option with diameters up to 17″, the shaft model does not have an anode (you must use a shaft anode), and the sail drive version has the anode recessed. The 3 and 4 blade models all have cone mounted anodes that sit on an anode holder over the gear teeth. For a good article on sizing the right anode click here – Anode Guide.
Finally all of the propellers need small pads to cushion the blades when they open – known as buffer pads. All of the pads were updated about 5 years ago to a harder more robust material (rubber to hard nylon). The basic difference is that the old style are black and the new style are white. For a good article on identifying the right buffer pads click here – 2 blade buffer pads, 3 blade buffer pads, 4 blade buffer pads
Removing the Propeller Blades
The first part in removing the blades is to remove the anode holder (3 & 4 blade models). This is an important part and one that some yards who are not familiar with Varifold sometimes discard. It is a bronze plate held in position over the blades with 3 or 4 screws depending upon the propeller model. Removal of the old anode can be achieved using a pipe wrench revealing the threaded shaft of the anode holder.
Once the anode holder is removed, the propeller gears will be revealed. Each blade rotate around a pivot pin, which are held in with stainless steel fasteners. Again depending upon the model there will be 1 sometimes 2 bolts holding each side of the pivot pin in place. A detailed set of instructions for the propeller can be found here. Propeller Assembly Instructions.
Once the fasteners are removed the pivot pins can be pushed out from the hub and each of the blades will come away easily. Be sure to mark the blades and their corresponding bays (1,2,3, etc) so that the blades can be returned to their correct position. All of the Varifolds are dynamically balanced and there can be slight weight differences between the blades, which if put back in in the wrong order can lead to noise and vibration. At this time the bay where the blade sits should also be inspected. This area should be paint free and not show any excessive wear.
Removing the Buffer Pads
The next step is to replace the buffer pads. If the pads are the old style, it is simply a case of prying out the old pad and sticking in a new one. Each new pad has a self adhesive back so it is simply a case of getting it clean and sticking them on.
For the new pads things are a little more tricky. The pads are longer lasting and much harder to replace. The white nylon pads should be carefully drilled out from the hub. It is a good idea to pilot drill the pad first and then use a 5/8″ drill bit or similar to remove the pad. The pads can wear very thin and in some instances can cause the blades to stick open if not properly maintained at the yearly service. Typically they should be replaced every other haul out, with the anodes being replaced every haul out.
Once the area has been cleaned up the new pad is tapped back into place using a soft mallet. They are tapered to start and are significantly easier to get in than to remove!
Changing the Anode
The anode on any propeller should typically be changed once it reaches 50% of its original size, beyond this its effectiveness diminishes and risk to the propeller increases significantly. The anode has been sized to allow a years ‘typical’ operation between haul-outs and the wear rate depends on many factors including where the boat is moored (steel piers) and so on.
To replace the anode the remains of the old one must first be removed. All Varifold anodes are held in place on a bronze anode carrier that sits in front of the propeller blade teeth as mentioned above. Once the old anode is removed the contact area of the of the hub and anode should be lightly sanded to remove oxidation. A good contact between the two dissimilar metals is necessary to make the anode work. The anode is screwed onto the carrier and depending upon the model (typically the larger diameter propellers) held in place with a stainless steel bolt. It is also possible to use some loctite on the threads to help as well as nipping the anode up with a pipe wrench.
Wrapping it up
Finally it is time to put the propeller back together. Re-assembly is, as they say, the reverse of what we just did. Remember to put the blades back together in the order that they were removed. Some customers do grease the teeth at this stage. The propeller is water lubricated so there is no need but with the blade removal the grease can help bed the blades back in. Once the pivot pins are in and the blades mesh correctly the fasteners should be fitted. Tightening torque is 15 Nm for the bolts and all of them should be treated with red loctite. Finally when you are satisfied that the blades are installed correctly, the anode holder can be bolted onto the propeller; again the fasteners should all be treated with loctite.
A video showing all the steps in servicing a Varifold folding propeller is given below.