Trimming a Simmons

Discussion in 'Boat Design' started by Sawdust, Aug 16, 2011.

  1. Sawdust
    Joined: Aug 2011
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    Sawdust CEO & sweeper

    I'm doing sea trials on a Simmons Sea Skiff replica. She's probably twice the fully loaded weight of the original 18 footer, and the 40hp EFI Merc outboard is set to maximum trim (except for removing the trim pins altogether).
    With a 10 inch 10 pitch prop at WOT, she plows lots of water at 5900 rpm; with a 10 inch 13 pitch prop, she gets up a little better (but still not planing) but the engine speed falls to 4900 rpm. Question 1: can this boat plane? Question 2: I've read in other threads about adding shingles (effectively fixed trim tabs) to the bottoms adjacent to the well--I'd assume a very long taper is best, but how thick at the butt? Question 3: are trim tabs the best option?

    Thanks!
    Stu Anderson
     

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    Last edited: Aug 16, 2011
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  2. tom28571
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    tom28571 Senior Member

    Your real problem is that this boat has high bottom loading in pounds per square foot. This is not the type hull to overload and expect good planing performance. A Simmons is based on the dory hull form which has a narrow bottom, meaning less bottom area. Simmons put a small hook in the aft bottom to force the bow down and help get past the problem by increasing bottom area, as well as increasing waterline length when getting on plane. All Simmons's and dories tend to go a bit bow high but the weight of yours shows dramatically with big wake in the photo. Without removing weight, the only answer is more power but it will still be reluctant to plane a low speed. The 13" pitch should be about right for the boat and power if it were only lighter weight.

    Weight is the enemy of all planing boats, not only dories.
     
  3. Sawdust
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    Sawdust CEO & sweeper

    Thanks for the input, Tom. The boat is intended for a single passenger--hence the moniker SOLITARY-- so, compared to the trials, it should be 200 pounds lighter in normal use. What do you think about adding trim tabs?

    Stu
     
  4. DCockey
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    DCockey Senior Member

    I notice you call the boat a Simmons Sea Skiff replica. Was it built to Simmons Sea Skiff plans or was it built to look like a Simmons Sea Skiff?

    Reason for the question is there has been previous discussion here about the hook designed into the bottom of the Simmons Sea Skiffs. Do you know that you boat has the exact same bottom shape?
     
  5. tunnels

    tunnels Previous Member

    Not having seen one of those boats out of the water i would say it is meant to be a slow boat !with a rounded bilge and the keel has rocker from end to end so is displacement hull form thats not intended to go fast !!
    Have a look at a planing hull and see why it gets up on top of the water and goes !!
    Then have a look at yours and see why it dosent want to get up on top of the water and plane !!
    Has every thing conceavably wrong to making it Plane .!!
    It could be made to plane given enough time and understanding of the dynamics of a planeing hull ! and some clever little spray strakes set in the right places to shed water and create lift and slightly change the bottom shape all at the same time !There placement and size need to be completely understood as to what you are getting onto !!!
    Stability will be a big issue and at speed it could simply fall over if it goes fast enough to lift the hull !! not chine walking but fall over to one side or the other !! thats even worse than chine walking! Would be fun to watch mind you !
    Being heavy has been a good thing and has possibly save you from getting tossed out and right good dunking !! ! :D
     
  6. Sawdust
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    Sawdust CEO & sweeper

    DCockey:
    The term replica refers to construction methods and arrangement--the lines were lofted from a table of offsets from the Cape Fear museum, so I'm pretty sure they are true to original. I'd been told the Simmons tended to be skittish at speed and added an inch of keel to help keep her on track. As for hook, it is not terribly noticeable, maybe 1/4 to 3/8ths of an inch in the aft 18 inches of the bottom. The keel does rocker about 2 inches.

    Tunnels:
    I've seen numerous Simmons (originals, hull weight around 350 lbs in the 17 foot version) pushed by 40 and 50 hp 2-cycle outboards, and never heard tell of the horrors you describe; maybe those who had such experiences did not live to tell the tale :eek: or declined to discuss the event with others ;) and simply damped down their animal spirits at the helm. That being said, I'm more interested in attaining a proper trim than skimming over the salty with just the prop in the water.

    Perspectives on adding trim tabs would still be appreciated.

    Stu
     
  7. Milehog
    Joined: Aug 2006
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    Milehog Clever Quip

    It seems to me, an illiterate novice, that the high chair and tall console can't help the boat's stability.
     
  8. tom28571
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    tom28571 Senior Member

    Tunnels,

    A Simmons is designed to plane and will do so as well as handle well in the rough water of ocean inlets. Like most dories it is flat bottomed aft and not a lot of deadrise forward either. It's not the best planing boat around but will do so well enough if not overloaded. It is a bit tender and weight high up is not advised.
     
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  9. Sawdust
    Joined: Aug 2011
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    Sawdust CEO & sweeper

    "A bit tender" is a generous assessment; one quickly learns two things--hang on when walking around the center console, and stay calm because she rolls only to a point and then becomes quite stable. This can all be quite disconcerting with two aboard, as the roll is quite startling if not anticipated.

    The trim tab kit is shipping. Will update after next test.

    Stu
     
  10. Sawdust
    Joined: Aug 2011
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    Sawdust CEO & sweeper

    Tabs installed

    After recovering from recent rains and floods (the NYS boat launch on Canadarago Lake had 4 feet of water in the parking lot!) and shipping the tabs back to Florida to have the hinges reversed (to accommodate the rake of the transom--Bennett Marine did this for free, and quite quickly), I finally got to try them out. Just flat, their added bottom length improved the boat's trim, and with them extended about an inch, she trimmed fine. Of course handling and speed were greatly improved by getting the bow down. As predicted by earlier posters, the boat does have a tendency to roll onto a chine at high speed, but this was only a problem when approaching wide open throttle. Thanks for the warning!

    Regarding propeller selection, I started with a 10 inch diameter/13 inch pitch prop and got good performance but a top engine speed of only 5150 rpm, well below Mercury's recommended range. Then I switched to a 10 inch diameter/ 10 inch pitch prop; handling and performance were significantly improved, but engine speed at WOT pegged the tach at 6000 rpm. Have instructed the dealer to order something in between. I'm assuming the pitches are available in 1 inch increments, but the dealer was talking about a 4-blade prop. Any recommendations?

    Thanks to all. I'll keep you posted.
     

    Attached Files:

  11. tunnels

    tunnels Previous Member

    a four blad could give you the bit in between and has better get up an go and less wake and noticably smoother as well :eek:
     
  12. Sawdust
    Joined: Aug 2011
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    Sawdust CEO & sweeper

    Chine enhancement

    While I'm waiting for the next prop to ship in, I've been reading (endlessly, it seems) various threads regarding strakes, chine flats, and spray rails. As the boat is far beyond the design phase (already on the water), I'm simply toying with ideas to fine-tune performance and possibly even discourage a tendency to chine walking. I'm considering adding a small strip on the bottom, following the curve of the chine, possibly centered fore-and-aft. The strip in mind is:

    http://www.jamestowndistributors.co...milyName=Stainless Steel Solid Back Half Oval

    It's a half-inch wide stainless steel half-oval strip, 6 feet long, prepped for screws every six inches (I'll bed it in epoxy, just to be sure it stays attached.)

    More options at: http://www.fisheriessupply.com/productgroupdetail.aspx?cid=214321&keywords=rub rail

    Am I on a potentially productive course, or should I just ease back on the throttle? Opinions requested...

    Stu
     
    Last edited: Oct 17, 2011
  13. Sawdust
    Joined: Aug 2011
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    Sawdust CEO & sweeper

    Another prop test

    Got out on the lake today, despite the State of NY having removed the docks at the boat launch, and the mid-40's air temp. Winds were blowing steady at about 18 knots from the north, and the chop was running about nine inches. Put on a 10 inch diameter/11 inch pitch prop and went looking for some leeward waters that were a little smoother. Must have gotten the trim tabs perfect, because when I went to wide open throttle, the boat trimmed up and skittered over the water like a competition racer--it felt like greased lightning! As I broke out of the lee and into the heavier chop, it was like going too fast on an icy road and directional control became a little iffy:eek:. As I was the only boat on the lake (so there was no one to fish me out) I eased up and put her back on the trailer. Unfortunately, at WOT she again pegged the tach above 6000 rpm, so we're back to order either 12 pitch 3 blade or an 11 pitch 4 blade. The saga continues....

    I'm finding it difficult to believe that no one has dared venture an opinion regarding my previous post on lifting strakes/chine flats....on the other hand, today's test had me going faster than I would choose to go in this boat under even ideal circumstances, so maybe further refinements are unwarranted.

    Stu
     
  14. tunnels

    tunnels Previous Member

    my chioce from past exsperiances !

    My choice from past exsperiances would be carry your 13. =3 blade but use your 11 = 4 blade .
    The four blade will give you more push and a smoother wake at high speed ,a little less bite in the lower parts but middle to high rpms should better also smoother !!. and getting out of a hole should be a breeze .

    My old boat i went from a 13x 16 to a 11 x 21 and oh dear the range from 3000rpms up is great . The lower is also good as was harder to maintain a slow speed comfortably Now its no problem !! :D
     

  15. Sawdust
    Joined: Aug 2011
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    Location: New York, USA

    Sawdust CEO & sweeper

    Still waiting for the Merc dealer to get another prop...hoping I won't have to weave between the ice fishing shanties to test it. In the meantime, I've started working on a marketing campaign:

    :) It runs almost ten minutes, if you have time to kill...

    Stu
     
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