Wednesday, July 27, 2011

Stabilizer Performance Report

I've got a couple hundred miles on the stabilizers now and thought I'd report back on how they are working. I'm happy to report I'm still thrilled with the results and the performance. We've been out in a wide variety of seas, the worst being around 4-6 ft. We've had lots of opportunities with head seas, following seas, and quarter seas. With few exceptions, the boat just runs flat - that's all there is to it.

The other day I figured out how to get our roll displayed on the Maretron display and can now actually put some numbers to it. Under most conditions the boat won't roll more than 1-2 deg in either direction. The worst I saw was 5 deg, and that was with a really difficult side sea. With the stabilizers off, I was seeing 12-15 deg rolls. In this worst case situation they are taking around 70% of the roll out, and I'd say under typical conditions they take 95% of the roll out.

Mechanically, things are also going well. There is no sign of leakage, either water or hydraulic fluid. I do have a small ooze from one of the raw water pipe fittings at the oil cooler, but it's almost non-extent so I'm planning to deal with it over the winter.

Speaking of the cooler, the hottest I've seen the hydraulic fluid is 100F, and the starboard engine (the one providing the cooling water and running the hydraulic pump) operates within 1-2 deg of the port engine and so far the max temp I've seen is 172F. From all this I'm comfortable that the extra power load and cooling load are just fine.

Happy Camper and I.

Comments and discussion on this post:

dacust: Awesome.

And thanks so much for the report back. That's a valuable part of the write-up.

askaer: Now I am back to Singapore after a long break to Denmark.

We have not ourselves had enough time to test our Grand Banks 47EU since we had the GB factory to refit Trac Star Stabilizers.

We recognise however your enthusiasm on the effectiveness of the system. We have had a bit of shake at low speed. We have had a few parameters changed which helped. I shall revert later once we have had more time to try.

What is your observation with regards to lost speed and increased fuel consumption?

I added a few photos on our homepage from a wonderful cruising in Copenhagen on a factory new GB47 - look at the blog. Kind regards

Tanglewood: Hello Heine,

Sorry I didn't see your post here until today.

Yes, at very low speed it does occasionally feel like the boat just got a gentle bump. But my fins only go active when the engines are in forward gear which means a minimum of about 4 kts of headway. I noticed the bumps when we were commissioning the system at the dock and the interlocks that halt the system while stationary were disabled. The fins were responding to boat movement, but there was no water flow over the fins so they were not having much effect. But on an otherwise still boat, you could clearly feel them twitching.

You have the stabilization at rest feature which I don't, so if you are experiencing it at low speed or at anchor, it may just be an artifact of that capability.

Also, there is some different feel to the boat while underway, but I've always attributed it to the fins doing their job, and don't even notice it anymore. I liken it the odd feel of any boat that you are operating for the first, but after a few rides it all becomes natural.

As for speed loss, ABT predicted 0.5 kts top speed loss. I don't have very reliable data because

1) There was different loading (as in fuel and water) for the various measurements I've taken

2) My GPS speed readings typically fluctuate +- 0.5 kts to over a kt depending on sea conditions, so I estimate an average.

The result of all this is that I probably can't measure a difference of 0.5 kts which tells you how important a loss it is. But if I had to guess (which I'm happy to do), I'd say I lost between 1/4 and 1/5 kt. Now that's off cruise speed of 20+ kts where the drag will be at it's max. At displacement speeds I'd say there is no loss, and my measurements might even suggest there is a gain.

All the same applies to fuel consumption. The bottom line with both is that I think any losses are insignificant.

Nice pictures from Denmark!

askaer: Great to hear from you. You are absolutely right that the boat acts differently in the sea not least due to the counter balance movements by the fins. I am very impressed on their effectiveness. My observations are however that I am 1-2 kts slower, that the fuel consumption is up by perhaps 0,5 liter per Nm and with more noise in the cabins while activated. They work fantastic at rest and we have succeeded to remove the shake at low speed (5-6 knots). I have not had any other issues and I am very pleased with the result overall.

That let me move on to another question that perhaps you may be able to address. In fact I wanted originally to install the Seakeeper Gyro System without fins. Unfortunately as an after installation it would have ended up too far at the aft (additional 500 KG) that I did not like. Have you any information or comparison between the Seakeeper Gyro Stabiliser system and that of TRAC fins for Grand Banks or similar boats? Any out there who could provide pros and cons! I have watched some videos of Seakeeper stabilizers that looks as effective. Is that the case?

Tanglewood: I don't have any first-hand experience with gyro stabilizers, but can give the reason's I didn't pursue them;

1) Physical size. The only place they would fit in my boat was in the laz, and as you say it would have put a lot of weight far aft, and consumed valuable storage/utility space. The active fins don't consume any space that was otherwise usable. This will of course depend greatly on the details of your boat, configuration, size etc. Other boats will not have this issue at all.

2) Weight. I don't know the exact weight of the fin system, but I'd estimate 500 lbs. Not a huge difference compared to a gyro, but 2x none the less.

3) Power. I run my genset only occasionally when needed. It does not run all the time when I am on board. Gyro's all (at least all I've seen) run off AC, and a lot of it, which would require 24x7 gen set operation. It might be possible to rig up some sort of hybrid with an inverter and batteries, but it's a big load to be doing such a thing. By the way, my unwillingness to run a genset all the time (legacy mentality from my sailing days) effectively precludes any form of stabilization at rest since I don't have a power source. If you have a boat with 24x7 power, this too is not an issue.

4) This is all hear-say, but I've heard enough reports of marginal performance regarding gyro's, where I've never heard anything other than complete satisfaction with active fin performance.

I'd say much of the decision was particular to my own preferences and the specifics of my boat, but the last point I don't think can be ignored.

Regarding lost speed and fuel consumption, that's a significant difference. At the same time, you report almost exactly the same speed @2400 RPM as I get. Perhaps your earlier numbers were with a lightly loaded boat? I do see a clear difference between a light and full (fuel and water) boat.

wolfhound: Thank you, Tanglewood.

This thread, now about a year old, is Cruisers Forum at its best.

Any further experience or evaluations from you will be appreciated, as will be similar commentary from your Singapore counterpart.

Tanglewood: Thanks for the thanks. The stabilizers continue to work flawlessly, and we put over 2800 miles on them this year with about 1/2 of that out in very open water. Unless we are on a river or a lake, they are on all the time.

I haven't heard from Heine, but hopefully he's still reading CF and will chime in.

No comments:

Post a Comment

Make comments here