Planing at lower speed

K

Kingmann

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Joined
Nov 22, 2016
Messages
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C Dory Year
2000
C Dory Model
22 Cruiser
Vessel Name
Eva
I have a 22’ cd with a 90 hp Honda. I installed a hydrofoil on my shaft that only seem to add drag as it never rides on the water surface as I would think. The boat seems too stern heavy and when I have full fuel tanks it is worse. I would like to be able to plane at a lower speed, 10-12 mph. Any input welcome.
 
When the boat is on a full plane, the Permatrim. (You did put a Permatrim on?) should ride just on the surface of the water. If not, then move the engine up a hole to see if you can achieve this. Also the trim tab (you do have trim tabs also?) can and should be used to get the boat on a plane. 9 to 10 mph is marginal for a full plane for my current 25--once you are at 14 mph definitely on a full plane, despite a very heavy boat. (Although the 25's 100 gallon fuel tank is under the cockpit floor, the water or holding tank, (depending on year) is all of the way aft.

To get on a low speed plane, trim tabs need to be down, and the bow trimmed down with the engine also--once on the plane, then you can slowly bring up the engine--so the Permatrim is parallel to the surface of the water...
 
Kingmann":38o2go4r said:
I have a 22’ cd with a 90 hp Honda. I installed a hydrofoil on my shaft that only seem to add drag as it never rides on the water surface as I would think. The boat seems too stern heavy and when I have full fuel tanks it is worse. I would like to be able to plane at a lower speed, 10-12 mph. Any input welcome.
Click to expand...

As Bob said, yuou are pushing the lower limits of planing speed. It would be helpful to know what else is on board, besides the full fuel tanks. What is affecting the trim? Bow weight, (anchor, chain, V-Birth load)? How about mobile ballast, ( passengers, food or camp gear) and overhead weight, Radar rack, kayak or inflatables) ?

You said you added a "Hydrofoil" Some are more effective than others. As Bob asks, is it a "Permatrim", (a specific brand that has been the most functional on the C-Dory boats)?

Just looking for more info to maybe be more helpful.

Harvey
SleepyC :moon

JC_Lately_SleepyC_Flat_Blue_070.thumb.jpg
 
Beyond what has already been suggested & if you are currently properly pitched for rpm at WOT, I suggest switching to a 4 blade prop 1 to 2 pitch lower then your present prop. A four blade prop should help raise the stern & be more efficient at lower speeds. I’m going to Honda BF 60 twins & they will have permatrims & 4 blade props. The combination will likely slow my top end speed, but that is no concern with 120 hp. With the less slip in a four blade it should lower my mid to lower range rpm compared to a three blade & help compensate for the added 50 lbs total weight of the Honda 60’s compared to my present Honda 40’s. From my research the benefit of the three blade prop over the four comes with being more efficient at high speed. The CD22 & CD 25 rarely run at a speed where this is beneficial. The four blade prop even through usually a smaller diameter has more blade surface area for water contact, so improves low speed handling such as while docking & helps raise the stern while getting more bite when going to a plane. Also the four blade prop at low to mid speed will likely increase all performance including milage if properly pitched.

Jay
 
Thank you thataway, sleepyc and hunkydory. I am now shopping for the Permatrim and will consider the four blade prop. For a inexperienced boater c-brats is my go to source for input.
 
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