Flexofold 2 or 3 blade folding on oversized 50hp FP Lavezzi

[CaptainRivet]

Originally Posted by alamoana

I would choose a 3 blade prop to minimize vibration of a 2 bladed prop.
You do not need more speed under power, but would like better performance while sailing. Are you sure you could gain 2 kts with new props? Did you try sailing with and without props to confirm this? I believe 2 kts is a lot of speed to gain but I am usually wrong!
A feathering prop such as a Max Prop will give you a better hydrodynamic profile and allow you to change pitch if you do not get it right the first time.
I have studied and used Gerr’s Propeller Handbook extensively on my sailing Privilege cat and it is not easy to get it perfect the first or second time, so a feathering prop of the right diameter where you can dial in the pitch is a good idea.
Maybe new sails or less weight (Lithium batteries) or better rudders will get you a larger speed increase than folding props?
I would sail with and without props and confirm I can get close to 2 kts more speed.
Best of luck!

Thank you. Went with the 3-blade 18x13L FOF and found an agreement with MD Keld that i can swap the blades if that doesn't fit.

Yes wanna impove sailing but keep as much speed under power as possible, actually very handy to have a sail and power cat in one cat figured that out later...
Important when I bought it was that absolutely everything in the engine room is new,had 19h, because absolutely nothing fits if you swap a MD2020 to a D2-50F. And for that 67000Euro bill I just paid 5-10k more then one with 3000h on the 2030 engines.

Both props fell off during sea trial when I bought it in may last year because Volvo idiots fitted the props on the 130S saildrive with the old 120 hardware... Thats how i discovered it is around 2kn more and I need a folding or featuring prop. Well original is a 2 Blade fixed 12x11 fitted, now its a 3 blade 17x15
Thats a serious difference in drag and it performs approx 2 kn slower then the polar diagram shows and other owners confirmed it fits quite well.
Also confirmed by the fact that when motoring with 1 engine i have to correct 8-10 degrees while a standard Lavezzi with 12x11 has 0 till 3 degrees correction.
Besides going with FOF folding, i am
Swapping to Lithium at the moment to balance the additional weight of the D2-50F and added round-sail and Parasailor with additional 2 backstays in dynema for Downwind till 90 degrees low wind sailing. Soon to come a reecher on a retractable bowsprit made from storm spinnaker material to improve lightwind sailing from 45 till 90 degrees.
90sqm sail area on 8.5t with slim hulls in standard config, Lavezzi doesn't need much wind and sails well for a production mass catamaran...just compromised due to the huge propeller needed for d2-50F.

[alamoana]

You are doing all the right things to have a turbo cat! I would choose the 3 bladed prop. Fair winds

[CaptainRivet]

Originally Posted by alamoana

You are doing all the right things to have a turbo cat! I would choose the 3 bladed prop. Fair winds

I bit the bullet and ordered 2x the 3 Blade FOF. Thank you all for the suggestion and explanation why, convinced me to spend extra bucks on the 3 blade is well invested money.