Folding props

[Schnick]

I have a Ranger 29. Would like to upgrade to a 2 blade folding prop.

I know prop companies like to size these, but I have got wildly different answers from a couple different companies.

I was thinking there must be a fairly standard size and pitch that works for most 28-29 foot boats. Friends of mine had a C&C29 that motored great with a folder, but they've sold the boat so I don't know what they had.

Ranger 29:
28'6" LOA
23' LWL increasing to 25 or so at speed.
6500 lbs
9'4" beam
Current prop is 12" x 6" fixed 3-blade

Has anyone tried a Campbell sailor fixed prop rather than a folder?

Previous owner had the CDI A4 prop and threw it out, didn't like it.

[pugetsails]

I have a 1979 Cat 30 - LWL 25'

When I was racing it, I put on a Martec folder 12x7, per Martec recommendation. The A4 would only turn up to 1200 rpm. I had the prop cut down and repitched to 11.5x6 which gave me 1500 rpm and 5.2 kts. I should have been less chicken and gone to 11x5.

Three seasons back I changed to the CDI 12x7 (2 blade, fixed) and I get 1800 rpm and 6.2 kts. Also, I no longer have problems with barnacles fouling the prop.

That's the extent of my experience prop-wise, hope it helps.

Dave.

[MikeB.330]

Dave,

Are you talking about a cruise RPM of 1800 or is that what you are seeing at WOT? I have that same prop in the box waiting to go on. When I ordered it they were talking RPM numbers of 2400 at WOT. I need a cruise RPM of 1800 min. to power through chop and turn a 120 amp altinator. At 1800 RPM it is kicking out around 70 amps and using almost 3 hp.


Thanks

Mike

[pugetsails]

I cruise at 1800. At WOT I don't get much more rpm or kts, just a lot more noise. The CDI punches through a heavy chop MUCH better than the old folder.

Dave.

[MikeB.330]

Thanks Dave.

I will be installing this on my 1965 Pearson Vanguard. The "book" says she is about 10k.pounds dry. After 42 yrs. and being loaded for cruising I'm guessing she is closer to 13.5k pound.

How does that compare with the weight of your boat? I've been told that weight and LWL will have an effect on max RPM at WOT.

thanks again

Mike

[pugetsails]

Mike,

If I remember rightly, the old Cat 30 was advertised as 10,500 lb. I read of one being weighed at about 11,500 and I suspect mine fully loaded is upwards of 12,500.

I agree that weight probably doesn't affect WOT rpm much, but I suspect if you have a longer LWL and are operating lower down the drag curve, then the engine is not so heavily loaded and it should up the RPM at WOT a bit.

Dave.