19' c-dory

saltspring":1e2eijcn said:
My 19 has a Honda 90 on it and a 8hp Yamaha (87 pounds). I do have a perma trim and I find that if I am running at 4,000 4,500 rpm I can trim the motor pretty far up and only have the tabs down one or two clicks. Before the permatrim I found I was messing around with the trim tabs a lot, now I rarely adjust usually just to balance right and left ride.

I find the optimal ride is at about 4,000 rpm which puts me running at about 18-20 MPH. I have not done detailed fuel calculations but it does seem that running a long time over 4,000 RPM uses sharply more fuel.

Nice to see a 19' thread going!!!!
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Good notes! Based on my reading of this thread over the past week, I approached trim very differently this weekend. Big differences! I also found that 4000 - 4500 was the point where I was up out of wash and gliding very smoothly. I have the 90 Yamaha and had a little more than 30 gallons of fuel aboard. I noted your thoughts about engine trim... I think that's the one piece I still need to work on. I don't have the permatrim, so sounds like my situation is a bit different?
 
Just some observations on running my 19. Sweet thing that she is. :love

I spent about 12 hours out in the boat this last week. I did a bit of fooling around with the motor trim and trim tab trim. The water on most days was smooth but one day there were lots of boat wakes. The boat is loaded light, and I had between 18 and 30 gals of fuel, and one person on board. So, over all, light. (Suzuki 90 with 6hp kicker. two batteries in the stern)

At 4000 RPM, I could run at about 12 knots, but this is where I needed to use the trim tabs the most to keep the bow down. With the motor all the way down on the "stops" and the tabs down about 1/3, it held the speed nicely. But this speed doesn't seem to be the most efficient. The boat pushed more water, throws a bigger wake, and takes a bit more effort to steer.

With the same set up, I increased the RPM's to 4500. I could get about 16 knots, but if I used no tabs, and raised the motor to a point that I would call neutral (lower unit parallel to transom) the speed increased to 18 knots. This seems to be the beginning of the sweet spot for both the boat and the operator! The boat is very easy to control including a very light steering wheel. Sharp turns are easy, and the boat stays in excellent control. Small waves and wakes are not a problem, as the boat rides smooth with no banging.

At 5000 RPM, motor on stops, no tabs, speed about 18 to 18.5 knots. But if I raised the engine a bit, the speed increased to 20, and about another second on the motor trim button, 21 knots. Again, this remained a very comfortable setting for the boat and operator. If the motor is raised more than about 3 seconds, that is when I can get porpoising to start. I never have this effect when the engine is on the stops.

At 5500 RPM the most speed was with no tabs, and the motor raised about 2 1/2 to 3 seconds. 24 knots. 5900 RPM, 26 and WOT 28 to 29 knots. Anything over 5500, the boat can begin to get a mind of it's own. It may start to pull to one side, porpoise, etc. But if it is flat calm it will hold the speed and course nicely. I do this about 3 times a year just for the fun of it!

I find that I run between 4500 and 4800 90% of the time. I use the trim tabs very little. If the waves and chop start up, I adjust to the comfort of the ride. This of course really depends not on just the size of the waves, but the period and the direction of the boat in relation to the waves. I use the trim tabs much more in these conditions. Mostly to push the bow down at lower speeds.

Robbi

An afterthought on trim tabs. I think that the 19 benefits greatly from having the tabs, even when they are not deployed. They give a bit more lift to the stern in the neutral position. When I say I don't use the tabs, that is different than not having tabs. But you already knew that. :wink:
 
Good information!!! Glad there are some 19' owners on board. I've put 15 hours on my new 19'/ Honda 90 during the past few weeks and am getting acquainted with it's personality. With winds in the 15 to 20 mph range most of the time, I haven't spent any time at WOT. My observations- 1. Doesn't obey well at slow/docking speeds...flat bottom problem. 2. Pounds pretty good in the chop...keep rpms in the 3,500-4,000 range. 3. Have to use the trim tabs (Bennett M-80) to control porpoising. 4. Engine "droning" noise irritating in the pilot house around 3,000 rpms...avoid that range. 5. I like 4,000 to 5,000 rpms if the chop is not too bad... Good speed...comfortable ride. Yesterday was a rough day on Lake George. The Sea Ray owners were complaining that the waves were coming over the bow and up their windshields. I felt very secure rolling around in my C-Dory...and they all thought it was cute(the ladies did).

UPS just delivered my Permatrim this morning. From all the good reports I've read, I expect that it will improve handling and performance.
 
Invaluable info! Thanks... now I have to go out an experiment again... what a cryin' shame. :D You guys are both a couple notches ahead of me and this is really going to help.

When you say droning, are you speaking of a slight kind of vibration? That's what I get around the 3000 mark.

I feel so much better after reading your comment about docking speed. I've dealt with the flat bottom you refer to, but this has taken some getting use to. Learned really quick she continues to slide through the water after cutting power without slowing much. Once it climbs below a certain drift speed, a turn is interesting to handle... when she starts to turn she wants to continue to turn! I've gotten the hang of knowing when the no-return point is!

Gotta say... it's a lot different than any I've piloted, but I am loving it!
 
I have found that this knob has really helped me with docking and getting into the boathouse. If you don't have one, I think you will find it a nice addition to your boat.
boat_steering_wheel_knob.jpg
Thanks Fred!

Robbi
 
This is an interesting subject. I'm running the 75Yamaha with an 8hp Yamaha kicker. I found it very easy to porpoise once i started to trim the engine up. This spring I added a Stingray XR111 hydrofoil and the change was very dramatic. It no longer wants to porpoise. At Wot (5100 rpm - I lost 300Rpm off the top) I can run about 3.5 on my motor trim and depending on wave size about nuetral on my trim tabs. it is a bit of a balancing act to get it just right. I've got 215 hrs on the boat now and am just getting the hang of it. I'm usually running pretty heavy 2 adults , gear for overnighting, extra fuel etc. so the top end is just over 21 knots.The boat is definitely ass heavy. I wonder if saddle tanks wouldn't help the balance out? Maybe something C-Dory could look into.

Glen
 
Tsargent, The droning sound is engine noise that is "captured" in the enclosed, hard wall cabin...happens around 3,000 rpms. I now keep ear plugs on the boat. Also, an update, had her out on the Hudson River the other evening...calm water to a ripple. I was able to try out the upper end of the rpm range. Performs well at speed with proper trim settings. The engine trimmed all the way down keeps the bow down but adversely affects performance. As the engine comes up, the rpms and speed increase. It will take time to figure it all out. Very comfortable and manageable up to 5,400 rpms...above that control becomes a bit touchy...almost feels overpowered. Also, my Honda EFI 90 "surges" in the 3,000 to 4,000 range. With the throttle set, it will move up and down about 200 rpms in 3 or 4 second intervals. Otherwise it runs good. I don't think it's gas. I'll talk to Honda service about the problem at the 20 hour checkup.
 
Thanks for the info. I was afraid I had a loose engine mount! I could see it happens at a certain rpm range.

With all the input about permatrim, I am wondering about adding that. It sounds like this addition takes a lot of the touchiness out of this. I have no problems learning to adjust as needed, and I suppose I'll become an old hat at it. But if such a simple thing decreases adjustments for waves and wind, maybe it's worth the cost?

Is it a simple project? Seems to just bolt on? Will do a lot of looking this weekend in Oriental!
 
Sea Wolf":3snx53m3 said:
ghone":3snx53m3 said:
<Some things edited>

I had the engine trimmed right down as far as possible and no tabs on. I got a porpoise going that was not stopping.

The porpoising was interesting as I've not seen much about that in any thread. Next time out I'll start with bring the engine up in increments till I find the sweet spot. Anyone else experience the bow hooping/porpoising?

:D
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The 19 is the same hull as the 22 with three feet removed from the rear, and a different interior arrangement.

Early on, it was found that the shorter hulled 19 porpoised a lot, and needed trim tabs to hold the bow down.

Trim tabs were then added as standard equipment.

The generally accepted view is that the shorter hull is the cause of the instability that makes the boat popoise.

A Permatrim hydrofoil woulod also work to reduce porpoising because of it's leverage at the back of the hull.

Trim tabs also work, and give you lateral trim as well. Some 19's have them both!

Enjoy your new boat!

Joe. :teeth :thup
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Keeping in mind the above, if I had a 19, I'd add the biggest Permatrim and set of trim tabs I could put on the boat .

The Permatrim is long shaped, not wing shaped like the Doel Fin, and adds pitch stability to the boat with it's extra length. (I might even make my own, both longer and wider than the standard, but keeping in mind the anti-cavitation plate will only take so much stress. A strut could be added from the top rear of the Permatrim to the motor shaft above to support a longer version.)

Bigger, longer tabs will also help restore some of the lost length and stability.

The bigger and longer they are, the less angular trim will be required to reach a given trim adjustment. The less angular the surface of the tab, the less drag will be produced, and the better will be your mpg.

Plus, of course, you've have more planing surface with larger trim tabs and the Permatrim too.

Just something to think about.

Oh, by the way, my physics background thinks the drone sound is probably a resonance effect, like found in musical instruments and tuned exhaust and intake systems (and lots of other places) where a certain frequency sound matches the size of the chamber such that the reflected sound reinforces itself and makes the whole chamber vibrate in synchronous time. Not much you can do about it except to add a deflector like a canvas bulkhead, and even that won't be entirely effective as it wouldn't be strong enough to stop the sound from penetrating into the cabin.

Joe. :teeth :thup
 
PhilR

The Loose Nut has a Honda 90 (2007), we went thru the same "surge" thing. :( With a bit if info from the membership here, + Marc @ Wefings, we told our local Honda shop about replacing the fuel control module (its a small electronics thing). He contacted Honda, got the part, installed (warentee), and PERFECT. No more surge :D
 
Sea Wolf did a much better job than I did explaining the droning noise. My canvas bulkhead reduces the noise level slightly.

Arniehuff, Thanks for the input...you may have saved me some time and aggravation getting this issue resolved.

Tsargent, I have my Permatrim. As soon as my new prop comes in, I'll be installing it. The directions that come with it are OK, but there is more detail with pictures on the dealers web page, Shipyard Island Marina, Washington Island, WI. From all the good things I read about the Permatrim, I expect handling/ performance improvements across the board.
 
I just read the review of the Permatrim by Darren. The information that he offered concerning the Permatrim seemed to be good information. But I can't figure out the part about the Bennett Trim Tabs. He said the only way that he could run the boat at speed (before he got the Permatrim) was with the tabs full down. Plus he said that one of his major reasons for getting the Permatrim was because of porpoising.

Is there that huge of a difference in the set up of 19's??? I could never run mine with the trim tabs fully down, at any kind of speed. I realize that there are different sized tabs, and probably different amounts of travel, but.... And to have them full down and have a porpoising problem? I would be running at periscope depth!

Robbi
 
I'd agree with you, even with my limited experience. I began my tests of trim tabs by using both extremes. Took but seconds of full trim to tell me they'd rarely be used fully extended!

Another question on permatrim... what's the risk of this thing breaking off part of my Yamaha?? There must be tremendous torque there! Can't help but think Yamaha didn't design those wings to support such pressures.
 
tsargent":3dlinukv said:
<some discussion clipped>

Another question on permatrim... what's the risk of this thing breaking off part of my Yamaha?? There must be tremendous torque there! Can't help but think Yamaha didn't design those wings to support such pressures.
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email Tony Murano at Shipyard Island Marina (the sole U.S. importer and supplier of Permatrims, which are made in New Zealand) with this question.

He's one of the most helpful, truthful, and reliable service representatives in the marine industry, and can give you a straight-up answer on this.
 
Sorry... I should have been more specific in my question. I do see in the archives the info for Tony and have emailed him. Thanks for reposting that! And, our thread here has had some good discussion of the physics. I guess what I was seeking were real observations... experiences any of you have witnessed or experienced (with any hydrofoil product). I've come to rely more heavily on advice from first-hand experience over the years than that from sellers and theory. Learned too many lessons the hard way by relying on those!!

Anyone who has the time, sure would appreciate your experience. Feel free to email off post if this topic doesn't fit in this thread.
 
I just returned from the Lake Powell C-Brats Sept. Cruise. I believe that Lake Powell was designed and built for 19' C-Dorys with 90 hp, no kicker, trim tabs, PERMATRIM :D, fuel tanks 90% full a launch, heavier stuff forward, one person and 35 lb doggie :wink:. The builders did a fantastic job.
I cruised with 22's and 25's. They can carry a lot more weight and they do! :( . This past season Tee Ten went to San Fran Bay Cruise, Catalina Cruise and Lake Powell and put a bunch of hours on Lake Tahoe.
Tee Ten cruises best, crisp at a nice plane, at 4000-4250 bow med. engine tilt just below hull level angle 20% and no trim tab. Bow down with Permatrim. 8) 20-23 mph over ground.
Last year I did Lake Powell in Gizmo 16' C-Dory with almost the same set up no trim tabs. Permatrim a must on 16'er.
My cruising speed was faster buy 3-5 mph than the other faster boats so I most often was running ahead on off to the side. Last year the 16'er power was 50 hp this year the 19'er is 90 hp. Run a little over 200 miles last years on 36 gal. Believe it or not :lol: More miles this year and maybe 40 gals.
Conclusion, 19' C-Dory is a great little cruiser. Needs more power than not. At least Permatrim if not also tabs. Fuel weight costs ya. Take what you need stay lighter.
I agree the 16 and 19 are in a different class then the 22 and 25.
It is what it is :smileo
 
Having a new Yamaha 75 I didn't feel like doing all the hole drilling the Permatrim requires so I fitted the Stingray XrIII like Lucky 7's has.
What an amazing change. I was out today in the rain on the same lake I was on 2 weeks ago with similar conditions of wind and wave. I trimmed the engine first up to 2 on the gauge about level on the cowl top. This is about where I expect the prop is square to the waterline. First run was tabs neutral. Time to plane was right now as I'm still running very light 1/2 fuel aboard, solo and only safety gear aboard. The boat ran flat, I could see the horizon at all times from start to wot. I got the same 5200 rpm I got before the tab install. I ran through my wake to see if I could start the porpoise. Nada, bow goes up bow goes down then stabilizes. I ran several different runs at between 1 and 3.5 on the engine trim gauge similar results. The tabs I only needed to lift my side going downwind, the rest it was tabs neutral. The handling was very sporty and predictable. One run from stopped to wot with some aggressive turns was easy and fun. I think the boat really benefits from the long axis directing prop wash, the stabilizer installs in about 10 minutes and requires no bolts. I had to stop a few times and lift the motor just to be sure it was all still tight down there. It seems way to easy. Looking forward to getting more experience with it. Sweet ride :D
 
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