Robert, thanks for the input. While wrestling to unscrew the fins today, I suddenly had a brain fart. Why not just cut them shorter? So that is exactly what I did-- I cut about 6 inches off on each side, so that they now extend about two inches out farther on each side than the cavitation plate(about the width of my 15 inch propeller). This is just a gut thing, but it sure "looks right". Hopefully I will have the best of all worlds-- no drag, safe turns, safe ballast dumping, and improved bow down, easy planing. Because of storms and mountain skiing planned for this week, test result reports may be delayed..
Rolf
Dolefins
-
Mark Prouty
- Admiral
- Posts: 1723
- Joined: Mon Jan 19, 2004 8:52 am
- Location: Madison, WI Former MacGregor 26X Owner
-
Duane Dunn, Allegro
- Admiral
- Posts: 2459
- Joined: Fri Jan 02, 2004 6:41 pm
- Sailboat: MacGregor 26X
- Location: Bellevue, Wa '96 26x, Tohatsu 90 TLDI and Plug In Hybrid Electric drive
- Contact:
Report back if they have any effect with your 90 hp. I would have tried them full size first.
Mark, that looks like the StingRay version of the fins.
I had mine on for over a year with my 50 hp. They were standard black Doel-Fins, $29.99 at West Marine. There is no quick rise to plane. They do not have any effect on trim. They do not affect the ability to dump ballast. They do not change how the boat turns. With the lower power of the 50 they don't affect the boat handling at all.
I kept waiting for any and all of the effects warned against by MacGregor, but they never happened. Finally I concluded since nothing good was induced by them they must just be more drag and I took them off.
Mark, that looks like the StingRay version of the fins.
I had mine on for over a year with my 50 hp. They were standard black Doel-Fins, $29.99 at West Marine. There is no quick rise to plane. They do not have any effect on trim. They do not affect the ability to dump ballast. They do not change how the boat turns. With the lower power of the 50 they don't affect the boat handling at all.
I kept waiting for any and all of the effects warned against by MacGregor, but they never happened. Finally I concluded since nothing good was induced by them they must just be more drag and I took them off.
Hmmm, probably should have tried them out before cutting, but paranoia got the best of me. I was also afraid of any possible excessive added upwards thrust/tension on the transom. Bad news around here is with all these crazy SoCal storms (worst I've ever seen, almost 3 weeks straight now), still no sailing, speedboat racing 
. Good news is I got the best two CLEAR (between storms) days of skiing in my life up at Mammoth mountain! Been at least 10 years since my last ski foray into mountains, and these new skis they have now are awsome(I'm going to forget about snowboarding, even tho I surf). Also I had my 4 year old and the wife ski for first time as well, and they loved it! Finally, a new family activity we can all enjoy. But it will never compete with the mac when it comes to VALUE and fun -- skiing is EXPENSIVE(and that was with a free place to stay).
Rolf
. Good news is I got the best two CLEAR (between storms) days of skiing in my life up at Mammoth mountain! Been at least 10 years since my last ski foray into mountains, and these new skis they have now are awsome(I'm going to forget about snowboarding, even tho I surf). Also I had my 4 year old and the wife ski for first time as well, and they loved it! Finally, a new family activity we can all enjoy. But it will never compete with the mac when it comes to VALUE and fun -- skiing is EXPENSIVE(and that was with a free place to stay).Rolf
We have been on hold for our ski trip to Utah for 3 weeks now and looks like another week of bad weather is with us. First Florida with hurricanes and now us. I read every five years is a bad weather year. Good thing we can pull our boats out of the water and work on them at home when the weather is bad.
BTW, those new parabolic ski's are great. My skiing went up a whole notch. We can no longer afford Mammoth at $63 a day. Utah is half that and has 19 different ski areas all about 30 to 60 minutes away from Salt Lake City.
BTW, those new parabolic ski's are great. My skiing went up a whole notch. We can no longer afford Mammoth at $63 a day. Utah is half that and has 19 different ski areas all about 30 to 60 minutes away from Salt Lake City.
-
Mark Prouty
- Admiral
- Posts: 1723
- Joined: Mon Jan 19, 2004 8:52 am
- Location: Madison, WI Former MacGregor 26X Owner
Enjoy the slopes till sailing season starts up again!! I've taken up snowboarding and have gotten pretty good at it. We finally got some real snow!BK wrote:We have been on hold for our ski trip to Utah for 3 weeks now and looks like another week of bad weather is with us. First Florida with hurricanes and now us. I read every five years is a bad weather year. Good thing we can pull our boats out of the water and work on them at home when the weather is bad.
BTW, those new parabolic ski's are great. My skiing went up a whole notch. We can no longer afford Mammoth at $63 a day. Utah is half that and has 19 different ski areas all about 30 to 60 minutes away from Salt Lake City.
The kids are out on the snowmobile trails. Hope you surviving your nasty weather. 
-
Randy Smith
- First Officer
- Posts: 254
- Joined: Mon Oct 11, 2004 11:31 am
- Location: "Breezy" 26X Boardman,Or
Moe and Dimitri
A quiet place, a cocktail and talk of the boat........why don't you guys fly in and meet half way between where ya'all live, shake hands, look each other in the eyes and fricken chill.....heh, we are all Mac Bros!!!!
Randy
Randy-
NYharleyrider
- Deckhand
- Posts: 34
- Joined: Tue Oct 12, 2004 3:57 am
- Location: Rochester, NY 05 26M, 70 HP TLDI
- Contact:
I've been reading about the dolefins and everyone's opinion
I'm convinced their not a good idea and not worth putting on.
Has anyone ever heard of or tried the powerthruster.
http://shop.macgregorowners.com/detail. ... &group=294
I'm putting a 70 hp tldi on my 26m and was wondering if this device is a good
idea or pretty much a waste of time like the dolefin.
I'm convinced their not a good idea and not worth putting on.
Has anyone ever heard of or tried the powerthruster.
http://shop.macgregorowners.com/detail. ... &group=294
I'm putting a 70 hp tldi on my 26m and was wondering if this device is a good
idea or pretty much a waste of time like the dolefin.
-
waternwaves
- Admiral
- Posts: 1499
- Joined: Wed Oct 13, 2004 8:18 pm
- Location: X less in North Puget Sound -have to sail other boats for a while
apples and oranges
NYHarley,
what you're comparing here ...are items selected for two different applications.....
The doel fin and its likes are designed to provide additional vertical lift to the transom of the boat at speed. this lift allows you to change the trim angle of the boat and perform better......for some boats.. especially those not balanced optimally, or with lots of horsepower they can produce tremendouse results....
however....
the item you are looking at...the powerthruster.is of a different ilk. and caged props have been around a long time...... in fact the only reason I can find that every propeller does not have a slip ring around it is manufacturing cost.... for high load low speed applications....anything that reduces slip will have considerable effect on acceleration and top speed....
this is the same reason that a 4 horsepower bow thruster can push the front of a vessel often times better than a 8 hp outboard mounted on the front of the boat ( that, and it is a larger prop)....almost all of the water is pushed in the same direction.. slip is minimized.
caged drive systems can be organized into two families
shrouded prop and ringed prop....
the difference being whether or not the prop spins with the shroud...
bow and stern thrusters are typically shrouded...
several manufacturers have started commerically producing ringed props (mostly composite) where the shroud is integral with the screw....
It is difficult to compare the two styles directly since there is little overlap in horsepower range.... but the shrouded solution is much cheaper..
Secondly, as the velocity of the water stream increases.( boat goes faster)....the benefits of a shrouded prop decrease as the drag from the device increases...and the amount of benefit ( which can never exceed the the missing amount of the original hp rating ) diminishes.....
for most engine configurations...this seems to be about 20 mph... beyond this range the drag component of the ring or shroud becomes too high.....for the pitch of most props..
Many in the houseboat pasture put the number at about 15 mph,
but ultimately, the two kinds of devices ( fins and shrouds) are designed for different purposes...one to provide greater transom lift....the other to minimize slip.
Good luck
and as general note, Which I am not referring to the above mentioned or any particular company in specific (so my attorneys dont have to answer too many letters here) Many of these "improvements come from very creative craftsmen and their shops/garages, who develop them for a particular vessel or problem they have experience with.
In talking with many of these individuals over the years it is very obvious that when presented with a problem, there first solution is to get out the sheet metal brake, english wheel and bandsaw..... Because of this shotgun approach, many creative and interesting devices evolve, with many corresponding claims.. and while they do help performance in some situations,,oftentimes the explanations the manufacturers give are a bit......shall we say "light" on the analyiss or truth..or the actual reasons for the improvement. Most of the design work for these types of props and shrouds were fully fleshed out prior to WWII, and available for all to review still, albeit a little hard to find.
I do not wish to belittle anyones efforts on improving Performance for a mac.....But I just remember speaking with some of the development staff at Mercury visiting when I was working with brunswick to try and get a contract at bayliner......
But I mentioned that there really needed to be more work for for getting full hp out of an outboard engine at 25 mph........ and the guys laughed at me and said.....and I quote "why would anyone want to go that slow?"
enjoy All
what you're comparing here ...are items selected for two different applications.....
The doel fin and its likes are designed to provide additional vertical lift to the transom of the boat at speed. this lift allows you to change the trim angle of the boat and perform better......for some boats.. especially those not balanced optimally, or with lots of horsepower they can produce tremendouse results....
however....
the item you are looking at...the powerthruster.is of a different ilk. and caged props have been around a long time...... in fact the only reason I can find that every propeller does not have a slip ring around it is manufacturing cost.... for high load low speed applications....anything that reduces slip will have considerable effect on acceleration and top speed....
this is the same reason that a 4 horsepower bow thruster can push the front of a vessel often times better than a 8 hp outboard mounted on the front of the boat ( that, and it is a larger prop)....almost all of the water is pushed in the same direction.. slip is minimized.
caged drive systems can be organized into two families
shrouded prop and ringed prop....
the difference being whether or not the prop spins with the shroud...
bow and stern thrusters are typically shrouded...
several manufacturers have started commerically producing ringed props (mostly composite) where the shroud is integral with the screw....
It is difficult to compare the two styles directly since there is little overlap in horsepower range.... but the shrouded solution is much cheaper..
Secondly, as the velocity of the water stream increases.( boat goes faster)....the benefits of a shrouded prop decrease as the drag from the device increases...and the amount of benefit ( which can never exceed the the missing amount of the original hp rating ) diminishes.....
for most engine configurations...this seems to be about 20 mph... beyond this range the drag component of the ring or shroud becomes too high.....for the pitch of most props..
Many in the houseboat pasture put the number at about 15 mph,
but ultimately, the two kinds of devices ( fins and shrouds) are designed for different purposes...one to provide greater transom lift....the other to minimize slip.
Good luck
and as general note, Which I am not referring to the above mentioned or any particular company in specific (so my attorneys dont have to answer too many letters here) Many of these "improvements come from very creative craftsmen and their shops/garages, who develop them for a particular vessel or problem they have experience with.
In talking with many of these individuals over the years it is very obvious that when presented with a problem, there first solution is to get out the sheet metal brake, english wheel and bandsaw..... Because of this shotgun approach, many creative and interesting devices evolve, with many corresponding claims.. and while they do help performance in some situations,,oftentimes the explanations the manufacturers give are a bit......shall we say "light" on the analyiss or truth..or the actual reasons for the improvement. Most of the design work for these types of props and shrouds were fully fleshed out prior to WWII, and available for all to review still, albeit a little hard to find.
I do not wish to belittle anyones efforts on improving Performance for a mac.....But I just remember speaking with some of the development staff at Mercury visiting when I was working with brunswick to try and get a contract at bayliner......
But I mentioned that there really needed to be more work for for getting full hp out of an outboard engine at 25 mph........ and the guys laughed at me and said.....and I quote "why would anyone want to go that slow?"
enjoy All