The question of available space and tip clearance is a bit complex, and requires some additional information, and ultimately a judgment call.
Minimal tip clearance has little effect on the performance of a propeller.
The real reason for tip clearance is to reduce noise and vibration created when the vortices coming off the blade tip reach the hull.
Due to the shape & efficiency of Flexofold blades, we have lower tip vortices than any other low drag propeller to begin with.
There are 3 factors that come into play in deciding how much tip clearance to leave:
- What is the hull shape? A flat hull above the prop will create more resonance (like a drum skin), while a V-shape or rounded hull form will reflect more of the tip vortice
- What is the hull construction? A modern, light laminate will resonate more than an older, heavier laminate. A cored hull may increase or decrease resonance, depending on the core material.
- How tolerant are the boat owners of noise and vibration under power? If you’re used to a relatively vibration prone 1 or 2 cylinder diesel, you may not notice the noise created by low tip clearance.
Yes, all Flexofold propellers are shipped with pre-applied underwater Loctite, which allows for underwater applicaton. This Loctite is different from that which can be purchased in a hardware store, which will not cure underwater.
Once a screw with pre-applied Loctite has been used it won't work a second time underwater. Find new screws with pre-applied underwater Loctite in our Spare Parts Section.
Prop walk, which is produced by all propellers, is exacerbated by extreme down shaft angles and small tip clearance. Many people don’t realize there is prop walk in both forward and reverse. However, in forward the prop is pushing a moving column of water over the rudder’s surface, and you have steering control right away to counter the walk. In reverse, you can control walk only by getting the boat moving backward, thereby creating water flow over the rudder. The Flexofold’s superior reverse performance should overcome most all prop walk concerns.
(e.g. after installing of a new engine)
Yes. New blades can be bought separately and are easily mountable on the existing hub (the existing hub must be with shock absorbers – feel free to send us a photo if there is any doubt).
Yes! The pitch can be changed by mounting new blades with different size/pitch in the existing hub, unless you have a very old propeller.
Yes! Bronze and stainless steel are very close in the galvanic series and will corrode very slowly in the absence of an anode. With a properly installed anode on the shaft, you should be protected against any slight galvanic corrosion that might exist.
You can buy a Flexofold direct from our manufacturing plant in Denmark. Leadtime is short and we ship worldwide by UPS. Simply make your an inquiry on our Inquiry Page and we´ll send you our recommendation and offer.
The only maintenance required is to keep the propeller clean. The Pivot pins and gears are water lubricated, but adding waterproof grease to the moving parts will help the folding and unfolding.
- When handling the assembled propeller, avoid being pinched by the opening or closing blades.
- Do not operate the propeller when close to people or animals in the water.
- Stop the engine immediately if you notice any strange sounds or vibrations coming from the propeller.
- Check that the propeller functions in both forward and reverse before each voyage.
- Shift gears at idling RPMs only.
- When sailing, the propeller must be stopped for the blades to fold/close.
- With a mechanical transmission; stop the engine and put the transmission in reverse gear to prevent the propeller from turning.
- With hydraulic transmission; while boat is moving forward under sail or due to momentum and engine is still running, engage reverse gear and shut down the engine.