Sunday, February 5, 2017

FlexoFold Props

Original Fixed Blade Props
LUX has had the stock two-blade fixed props that are outfitted on the charter fleet.
We had spent some time buddy boating with Dave on 5thQuarter and he was able to make better speeds at lower RPM, even though he had the 30HP Volvo MD2030 engines (LUX has the 40HP MD2040 engines). We recorded measurements of the performance at different points in time, shown in the table below, including 5Q’s performance, just for reference.
It was clear that Flexofold props were better. But they make a two blade prop and a three blade prop. Which one should we get?


Description (both engines running) RPM Speed (kn)
Before 2014 Haulout 2500 6.5
2800 7.1
After 2014 Haulout 2500 6.9

2800 7.3
Three months after 2015 Haulout 2500 7.1

2800 7.4
After 2016 Haulout (Flexofold props) 2500 7.4

2800 7.7

3000 7.9

3400 8.3
5th Quarter 2500 7.3

2800 7.6

Flexofold with PropSpeed
We asked Flexofold what they recommended for the MD2040 engines with the 130SR saildrdives (gear ratio 1:2.47). They responded that the three-blade 16x13 props would perform best. We agonized over the decision for a while and queried them about three-blade vs two-blade props, which 5Q and other Leopards we knew had. They told us that the extra blade helps with powering into seas and headwinds. The additional blade also provides better reverse performance. The pair of three blade props was $1000 USD more than the two blade props. We finally decided that the additional power was worth the money and ordered the three blade 16x13 props. They arrived within two weeks, nicely packaged. There was a small nominal charge from the shipper for entry into the US.

We have never had good luck with prop anti-fouling. It always seems to only last half the year. So we decided to try PropSpeed this year. It is an expensive anti-fouling for running gear. It has a tight timeline for application of multiple coats, so we had to be prepared and work quickly. We noted a number of boats being hauled had PropSpeed applied to the running gear and it seemed to be working for them. We’ll see…


We are happy with the performance of the Flexofolds. We can now motor on one engine at the same speed (in flat water) that we previously attained when motoring with two engines (6.6kn @ 2500rpm, 7.3kn @ 2700rpm). The motoring speed with two engines is improved (shown in the table above). Reverse performance seems about as good as with the fixed blade props. We did an informal quick stop test, similar to the one in the Yachting Monthly Folding and feathering propeller test magazine article of March 2015. The Yachting Monthly article reported stopping in 9.5 seconds, or 48 ft. In our test, we were able to go from 6kn to stopped in approximately one boat length (about 40ft). This is quite acceptable to us. Sailing performance also seems better, which we attribute to the folding props. The better motoring performance on one engine is also due to elimination of drag from the idle engine/prop. In summary, we’re quite happy with the Flexofold props.

6 comments:

Gregg Billman said...

Great writeup! Thanks for the info. We are looking to reprop our Leopard 40 and were looking for just such assistance (we have the md2030 engines like 5Q).
Question: did 5Q use the same size props as Lux?
Thanks again. Gregg

Terry said...

Gregg,

5Q has two-blade props while we have the three-blade props. I'll check on the diameter and pitch for 5Q.
Flexofold recommended the three-blade props for LUX. We did some research on two-blade vs three-blade and decided to go with their recommendation. It may be that the 2-blades are better for the MD2030 (30hp) engines. Check with Flexofold for a recommendation. They will need to know the transmission gearing too.

-Terry

Gregg Billman said...

Thanks Terry. I misread your post...thought you went to 3 blade because 5Q's performance was better with them vs your 2 blade factory setup. I have emailed flexfold but havent heard back from them in a week. May call when i get back from our current keys cruise.
Gregg
SV Cruzan Rhumb II

Gregg Billman said...

Terry. Im being quoted $2370 per prop. Does that sound right? Thanks. Gregg

Terry said...

We paid about $4300 for both props a year ago. Post-Brexit, the price you're quoting sounds about right. It is expensive, but it is something we should have done as soon as we bought LUX.
You'll also need to decide if you're going to paint them or try Propspeed.
-Terry

Gregg Billman said...

Terry-
We just brought CR II back from the yard with her new 3 bladed flex-o-folds on. THANK YOU for all of your guidance. Doing a bit of power setting vs speed research enroute to and enroute from the yard, we are seeing about a 1.25 kt increase (on average). Haven't had the opportunity to check under sail, with props stowed, but I suspect we will be just as happy.
Thanks again.
Gregg
SV Cruzan Rhumb II