Floppy Folding Prop

[peat]

Hi All

I have a folding 2 blade prop (Gori type) which appears to flop open too much. The blades have a slight rattle but the pins are very tight, the problem looks to be where the base of the blade rests on the body of the prop (hub?) but with the blades at what I would say was the operating angle this gap is about 3mm + ..... could it be there is a part missing? I think I read some props have a cushioning material placed here to reduce "clonk" as the blades open but I guess the prop is 20+ years old so is it time to replace or recondition it?

[captjcook]

It looks to me that there is a sizable ding in the blade shank and deformation in the end of the slot where the shank of the blade contacts the hub. This indicates to me that the prop has been repeatedly slung open at higher than idle speeds...slamming a ding and deforming the hug...that being said, most competent welding/fabricating shops or prop shop could build up with bronze brazing the hub and fill the dings, then cleaning up thus align to the proper angle...probably less than $100... Cheers and remember to shift at idle...

[peat]

An other thought - this prop was on a Sadler29 (new to me) which had a Bukh 20hp engine, when I re-engine with a Sole mini 29 the boat behaved as if over propped, mmm would the angle of flop, due to wear increase the pitch of the prop? The new 27 hp engine only managed 2100 revs with this prop but I know the Bukh 20 is a very different beast and as far is I know the folding prop worked with it .... it would be nice to re-use the folding prop if it was going to allow the engine to rev but saying that, calculations show the Sole engine needs a 15"x 10"(folding prop's 16"x12").

[a64pilot]

Sounds like time for a new prop?

[captjcook]

Although the overtravel on the prop might add a bit of pitch???...I do not know recommended rpm of either engines mentioned. Seems like there is more than can be tweaked. A prop shop is your best bet...

[AD28]

Call Geoff Prior at AB Marine, 401-847-7960

AB Marine is the US Gori dealer. He will probably try to sell you another propeller but he's been good to answer questions nevertheless

[GordMay]

Greetings and welcome aboard the CF, peat.

[ejjawhite]

Originally Posted by AD28

Call Geoff Prior at AB Marine, 401-847-7960

AB Marine is the US Gori dealer. He will probably try to sell you another propeller but he's been good to answer questions nevertheless

I've dealt with Geoff and crew at AB Marine regarding an Autoprop which I bought used and into which I installed their rebuild kit (bearings and races). They are very informative. Replacing the 2 blade fixed with the 3 blade Autoprop made a huge difference . As each blade rotates independently from each other on races of ball bearings, there is no banging and clanging underway, or when shifting forward to reverse etc. Additionally, the prop blades rotate w the motion of the boat, yielding the most efficient profile for demand. In a chop and hitting wakes, I suffer far, far less deceleration than in the past. Sailing I've picked up close to 1/2 knot. It would be more had I been equipped w a 3 blade fixed. In reverse, the prop has the exact same configuration as in forward, providing plenty of stopping power.
My top speed powering at full rpms is hull speed + a little more,,, maybe 0.2 knots, but in the mid-range of rpms I achieve same speeds at 2-300 less rpms. That's where you see the difference. Fuel efficiency on my CAL 35 (14000lbs) (Yanmar 3HM35F, 30 hp) at 2000 rpms is ~ 0.7g/hr. making 6-6.2 kts. At the recommended 1800 rpms, closer to 0.5g/ hr.

[EWOL Props]

I see the hub has been deformed by the bangs of the blades during inversions; this gives you an idea of the shocks that folding props give to your gearbox; everytime you shift from back to forth you have a double hammer banging on the shaft.....interesting isn't it ?

Go to a feathering 3 blades no matter if it's an EWOL or another brand, whatever it is will be better than a folding for many reasons. If you want to know more get in touch with me privately.

Originally Posted by peat

Hi All

I have a folding 2 blade prop (Gori type) which appears to flop open too much. The blades have a slight rattle but the pins are very tight, the problem looks to be where the base of the blade rests on the body of the prop (hub?) but with the blades at what I would say was the operating angle this gap is about 3mm + ..... could it be there is a part missing? I think I read some props have a cushioning material placed here to reduce "clonk" as the blades open but I guess the prop is 20+ years old so is it time to replace or recondition it?