One thing I’ve always known about Gaia – she’s no race boat. She always has sailed pretty well on a beam reach (meaning when the wind is perpendicular to the direction we’re pointed), but thats about it. Any other angle of sail and we’d better have plenty of wind (at least 12-15kts) to go anywhere at all.
A day where the wind is blowing 12-15 is just about perfect, but they’re also way outnumbered by the days where it’s only blowing 5-10. On those more numerous light-air days, I always looked jealously on the boats with their sails actually up and not motoring along. We on Gaia, would always be motoring on those days.
Until recently that is! As part of gear-ing up for this voyage, right before we left we decided to shell out some big $$ for a “feathering” propeller. This means that when we’re sailing, the propeller automatically turns it’s blades parallel to the flow of water which dramatically reduces drag.
Meet the MaxProp, it’s fancy:
The MaxProp automatically switches between these two positions with an ingenious system of gears that pivot the blades into motoring mode when the shaft turns and then into feathering/parallel mode with the force of the water when the shaft isn’t turning.
I’d heard really good things about these sort of propellers – that they can increase your sailing speed by up to 1kt (thats about 20%). But I was a hopeful skeptic – I considered it a pretty big gamble – but as soon as we sailed with the new propeller I became a convert. This thing makes Gaia a whole new sailboat! I’ve read estimates that sailing with our old propeller (which always looked like the image on the right) is like dragging a 5 gallon bucket through the water. With so much less drag, we can now get away with sailing on those light air (8-10kt) days.
Sounds wonderful, right? Well it is now – FINALLY… see it’s been a battle to get this &#$@*(&#! propeller working right! Unfortunately, it was a battle entirely of my own making.
As with almost all things on Gaia, I decided to install the propeller myself while we were hauled out in Salem just before heading south. What could possibly go wrong?
The MaxProp on the inside has a lot of complicated gears that let it rotate the blades
from parallel (feathered) to motoring. These gears also allow you to change the angle or steepness of the blades in motoring version, this is called the pitch of the propeller. Normal propellers have a pitch as well, but it’s fixed – the blades are cast at a certain angle, so you need to match the right propeller with the strength of your engine and weight of your boat. The easiest way to understand this is like the gears on a bike (or car) – having a propeller that is too steeply pitched is like riding on a slight uphill in a gear thats too low, your legs suffer to push the pedals down, and the engine struggles to turn the propeller. A propeller pitch that is too shallow is like riding your bike on a slight downhill in too high of a gear, your legs have to spin really fast to speed up the bike – same goes for the engine it has to spin way to fast.
When you install a MaxProp it involves assembling a bunch of parts around your propeller shaft, and as you assemble it you set two different gear positions to determine the resulting pitch of the blades when they’re in motoring mode. The combination of these two internal settings determines the resulting pitch of the blades. The manufacturer recommends a setting based upon your engine and boat, and then if need be you can change it. Once you get it right you shouldn’t ever have to change it again.
MaxProp Hub, before installing gears, casing & blades.
Of course, when first installing this thing, yours truly manages to somehow mess up these two settings and get an invalid combination that results in an extremely steep pitch. And worse, I didn’t spot the fact that the blades were at WAY to steep of an angle. Kirsten & I happily put the boat back in the water in Salem and were ready to get on our merry way – until we put the boat in gear… KERTHUNK KERTHUNK KERTHUNK KERTHUNK, the whole boat vibrated and shook like crazy as we rapidly pulled the transmission back to neutral. Uh oh.
So we hauled back out and tried some stuff (not the right stuff), and then put the boat back in the water … same thing. At this point it was friday late afternoon and the marina was done with us… we could hang out (and pay) at a slip for the weekend and try again monday. So I quickly got on the phone with the manufacturer and talking it through with them figured out the error of my ways… DOH.
Thankfully, it’s possibly (though very tricky) to disassemble the propeller in the water and change the pitch. Thankfully I had newly bought scuba gear on board and was eager to justify it’s purchase.. so into the water I go the next day and manage to re-pitch the prop to a much more correct angle, woo!
This let us leave Salem and get underway, we quickly raised sail and found delightful new sailing performance due to the reduced drag… score! Unfortunately, the pitch was still wrong – like riding the bike in too high a gear up a slight hill. So I’d have to dive again, and also it the whole boat was vibrating some while in forward…
A week or so later I went diving again and re-pitched the prop this time too far in the other direction, now it was really easy for the engine to turn the prop – too easy. Worse, the vibration was still there.
At this point it was time to leave Boston on the way south, so in consultation with the guys I bought the prop from and others, we decided to make due with it as it was until we hauled out in Oriental, NC to inspect the rudder (a whole other story). This was a bad idea, we should have tried to solve the vibration at once.
So we motored our whole way south up to this point with a wobbly prop – not wanting to go too fast as a wobbly propeller is likely to wear out the cutlass bearing, which is the thing that holds the prop shaft in place. The whole time the cause of the vibration was a mystery.
Fast forward to our recent haul-out in Oriental, NC…
First thing we did was to take off the MaxProp and at the distributors recommendation package it up and send it back to Washington State to have them take a look and try rebalancing it. Waste of time… a week later when we got it back, they said it looked fine and they didn’t change a thing. Sigh.
Hacksawing out old cutlass bearing
Removing prop shaft
Once we got it back, as I was reinstalling it I realized the cutlass bearing was indeed pretty worn and would need to be replaced. Sigh again. So I got to it, I’d done this once before but it’s a process that involves removing the entire propeller shaft and hack-sawing out the metal sleeve from inside the strut.. no fun.
Once that was done, I went to finally reassemble the whole thing and we were going to splash into the water the next day. Putting the prop shaft back in I realized.. oh jeez, the shaft alignment is WAAY off. Prop Shaft/Engine alignment on any boat is very important, essentially the propeller shaft has to bolt directly on to the transmission and it has to line up PERFECTLY. If it doesn’t line up, the whole engine needs to be moved to match the position of the propeller shaft. Now in our case this was a little different as we have a V-Drive, which is a gearbox that sits in-between the engine and propeller. So in our case it is the V-Drive that needs to get moved.
This unfortunate discovery starts causing lightbulbs to go off in my head – the alignment being off probably caused the vibration in the first place, but how did the alignment get off? The alignment was perfect with the old propeller… Duh! Of course! The alignment got off due to my original mistake of wrongly pitching the new propeller ridiculously steeply making the whole boat go KERTHUNK KERTHUNK… All that torque caused by the prop probably shifted the V-Drive a little bit and threw off the alignment – so the propeller was fine all along, and we could have solved the problem all along without hauling the boat… So the final solution was get the boat back in the water (you can’t accurately align the shaft on the hard because of slight hull deformation) and realign the shaft to V-Drive, which really just amounts to slightly moving the V-Drive.
Once I did that, we put the boat in gear at the dock and eureka! Finally we have a non-wobbly, correctly-pitched MaxProp… for the first time ever, Gaia sails fast AND motors fast!
If you got this far in my diatribe/essay, you’re a brave soul (or a parent) and let me assure you that none of this was anyone’s fault but my own, and I strongly endorse MaxProp… so much so that I’ll say anyone with a heavy cruising boat with a 3 blade fixed propeller should absolutely start saving up now for some sort of a feathering or folding propeller…. or you can just continue sailing around towing that giant bucket of drag under the boat.. your choice!