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Trim issues after installing Seakeeper

Discussion in 'Stabs, Tabs & Gyros' started by HaveADay, Jun 1, 2016.

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  1. HaveADay

    HaveADay Member

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    Hello all,

    This winter I installed a Seakeeper 9 on my 2003 Carver Voyager 570. The stabilizer is as far back as it can be on the center line in the engine room. This was pretty much the only location available and also seemed like a good location.

    Fast forward to this spring. The boat which has always been a little stern heavy, especially when full of fuel, went into the water with about 1/3 tank of fuel. It sat a little stern low but nothing worse than I'd seen previously.

    This spring I also noticed that I wasn't able to make maximum RPMs on the engines nor was I able to hit the 30ish knots I'd previously been able to achieve. I had my props tuned this winter so that represents another variable. Once the boat went in the water I went about reconfiguring some of the weight on the boat. I added a set of spare props and located them as far forward as possible and on the starboard side to counteract a little bit of port list, likely coming from my dinghy.

    So, this weekend I filled the boat with fuel. That was an addition of about 550 gallons of fuel which is just over two tons of fuel. The fuel tanks are located about two feet forward of the front edge of the Seakeeper, but overall still pretty far back in the boat. With the tanks full the bottom of the swim platform is just touching the water. A protractor shows about 3 degrees stern low.

    The Seakeeper weighs 1,200 pounds, the structure added for it is about 300 pounds and there's probably close to 100 pounds of ancillary gear for it.

    I've added 1200 pounds of sand to the bow to try and figure out what it's going to take to regain the trim on the boat. The sand is located under the front berth in the VIP which is pretty darn far forward. So, the question is, how much more weight do I add? I am nervous about putting too much weight in one specific spot as well as just adding more weight to the boat overall. I'd definitely welcome any insight.

    Thanks
    Ben
  2. Capt J

    Capt J Senior Member

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    First, get the sand out of the bow. I would remove the dinghy (guessing around 800 lbs) which is EASY to do, on the stern, and will get you close to your pre-seakeeper weight with the dinghy on there, seatrial the boat and compare it to before the props were re-done and sea-keeper added. If performance is where it was before

    NEXT I would find weight to either remove from the stern or take away from the stern and move to the bow. Remember, moving 600lbs from the stern to the bow, is a 1200 lb swing.

    I am NOT a fan of adding useless weight (ballast) to a boat unless it is ultimately necessary.
  3. Pascal

    Pascal Senior Member

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    Adding ballast is indeed a last resort. How much speed and rpm have you lost?

    Between the gyro and spare wheels you ve added about 2000 lbs. the boat is definitely going to loose some top speed, the question is how much. Adding weight to trim will only make it worst.

    How about your trim tab, you will need them to add lift. Did you make sure they re working?
  4. HaveADay

    HaveADay Member

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    Thanks for the insight. This morning I removed the dinghy and went for another test run. When I removed the dinghy the stern came up about an inch. The test run yielded the exact same result. 27kts at 2200 RPM. The boat should hit between 29.5 and 30kts at 2300+ RPM. One thing I've noticed is that maximum speed is reached at maximum tab. From this I'm surmising I might be leaving some speed on the table if the tabs effectiveness were increased, either by increasing the surface area or adding drop fins. The current tabs are 54" x 12" so they aren't particularly small.

    I will remove the sand, I've invested $60 in it so it was really only a cheap experiment to see if I could counter balance the weight. That doesn't seem to have worked. And, I also don't have any affinity for adding useless weight. That said, I'm not sure how much weight I'll be able to pull out of the stern. I'll try relocating tools and supplies but I fear that's only a hundred or so pounds and even if moved to the extreme front of the engine room that's only about mid-ship.

    Ben
  5. olderboater

    olderboater Senior Member

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    Does the issue change based on whether the Seakeeper is on or not?
  6. HaveADay

    HaveADay Member

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    The Seakeeper being on and locked, on and unlocked or altogether off doesn't seem to have any impact at all.

    Ben
  7. jet55

    jet55 New Member

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    Do not, I repeat, do not make my cockpit the largest floating sandbox in the harbor.
  8. Sea Gull

    Sea Gull Member

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    Your boat seems To have a dry weight of 44,000 pounds. With fuel and other gear, it weighs maybe 50,000 cruising weight. The gyro added +/- 4% to the overall weight of the boat, so re propping is in order. Your prop shop should be able to get you back the 100-150 RPM that you lost.
  9. RER

    RER Senior Member

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    Was this a DIY install? Was the unit dropped in without any calculation? Where is Seakeeper on this?
  10. Pascal

    Pascal Senior Member

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    So you have added almost 2000 lbs of gyro and related stuff plus 1200lbs of sand.

    And you expect the engines to turn rated RPM with the same top speed??
  11. Perlmudder

    Perlmudder Member

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    I don't know about the 570, however, the same is true with a 530. It takes a lot of tab to get speed out of them, otherwise the bow rides very high. So I would doubt that is just your Carver where that is the case.
  12. Capt Ralph

    Capt Ralph Senior Member

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    Tell us more about the "tune up" on your props.
    Do you have the before & after printout on the wheels?
    Was a cup added or enhanced??
  13. olderboater

    olderboater Senior Member

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    What else was done as part of the winter experience? And what problems were you addressing? Why was all this done? Who told you to do it or advised you? We're getting bits and pieces and they certainly indicate that however this point was reached there's a bunch of sand to remove, there are props to change, there may be trim tab adjustments, and there may be a seakeeper to remove. Have you known other owners of the same boat to install a Seakeeper? If so, talk to them about what they're achieving after.
  14. HaveADay

    HaveADay Member

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    No, not at all. I'm happy to give ground on top speed. I am not willing to give ground on rated RPM as I don't want to overload the engines. That said, I want to make sure that I am not making changes without considering the impact of one change on another.
  15. HaveADay

    HaveADay Member

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    For the work on the props it was only a question of returning them to spec. Camber was way out on the props and it appeared they had been worked on a couple of times before I owned the boat with limited precision. I used a propscan shop who did provide me before and after scans.
  16. HaveADay

    HaveADay Member

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    It wasn't a DIY per se. A naval architect was consulted on structural loads being placed on the boat. I'm not certain how much work was done on fore / aft loading of the boat. Thus far Seakeeper's response has been one of basically viewing this as a problem of adding static weight to the boat and not about their product. Throughout the process of installing the Seakeeper I have found Seakeeper to be pretty stand-offish about providing much in the way of help that they view as having a possibility of coming back to them. They provided very limited guidance during the design and installation of the mounting bracket.
  17. HaveADay

    HaveADay Member

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    There weren't any problems I was addressing other than a couple of family members who aren't comfortable with the boat rocking. The rest of what was done was routine maintenance and continual refreshing of a 13 year old vessel. To that end electronics were upgraded, canvas was replaced, carpet changed, etc. I had the props scanned as upon visual inspection their leading edges didn't look as I would expect them.

    At this point the sand is all out of the boat and I found that to be a valuable experiment for $60 in sand. I learned that 1,200 pounds has a minimal impact on the fore/aft trim of the boat. Interestingly to that point removing the 700 pound dinghy also had a surprisingly small impact which is part of why I'm surprised that the installation of 1600 pounds had the impact it did.

    This was the first 570 in which a Seakeeper was installed. I'm quite happy with the job it is doing of controlling the movement of the boat and at this time I don't view removal of the stabilizer as an option.

    I have spoken to Bennett and they gave me two options, one is increasing my 54" x 12" planes to 60" or 66" depending on available space and the other is adding drop fins. They did give me the caveat that the larger the plane the less effective the drop tabs.

    Lastly, and somewhat intriguingly to me a dock neighbor suggested considering a bow mounted fuel tank. That is an intriguing option to me as the larges trim problems are introduced by filling the tanks.

    Ben
  18. RER

    RER Senior Member

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    That's a lousy idea. It seems to me you need to back off prop pitch to get your WOT loaded RPM back, and get comfortable with a few knots off your top end speed due to the weight and location of the stuff you added.

    Am I reading between the lines that you did not buy this unit from Seakeeper? Otherwise I don't know how you would stand for the lousy support.
    Last edited: Jun 4, 2016
  19. HaveADay

    HaveADay Member

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    I did buy the unit from Seakeeper. I'm not sure I would categorize the support as lousy. I think they are CYA more than I would like to see from them.

    I am entirely fine with losing a few knots of top speed. The boat previously topped out at around 29.5kts. If it sees 27 I'm a happy camper. It currently will, but it won't reach maximum RPM which is my larger concern. I agree that it is likely that removing some pitch is going to get me back to rated RPM with a slightly lower top end. I'm trying to sort out trim before I change the props so that I can minimize the amount of pitch I have to remove from the props. The other concern I'm working against a little bit is that I don't want to lose too much in cruise speed. I'd like to maintain a 23kt-ish cruise speed. Previous to the changes to the boat efficient cruise was from 19-25 kts, so I think maintaining 23 should be doable.

    Just curious, why do you say it's a lousy idea to add a forward tank? The potential downsides I see are cost of modification. Risk of fuel spills, punctures, etc up front and complexity. Just wondering if there's something even more obvious I'm missing.

    Thanks
    Ben
  20. Pascal

    Pascal Senior Member

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    Anytime you had a significant amount of weight, you will need to repitch the wheels, that's pretty normal.

    Adding a tank at the bow can open some structural issues as that s were the biggest forces come into play when running in rougher waters. I woudl definitely check with the builder or a naval architect first.

    Larger tabs woudl be I woudl try first though. I also wonder if adding a spacer to the tab piston bracket to get them to extend a little more may help.