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Old 10-14-2015, 09:54 PM   #1
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2005 Mainship 30 Pilot II tim tab mod

In case you did not see it on the Yahoo Group, I had what I consider good success in adding a Bennett drop fin kit from Defender to my Bennett 12X12 flat trim planes. Instead of drilling 16 holes in the existing planes in order to bolt the drop fin kit to them or just ordering new 12X12 planes with the drop fin integrated, I welded the fin kit to my existing fins.

The result is a much better view forward at my chosen RPM of 2900-3000 (315 HP Yanmar) and a bit more speed, now up to 18.5 knots.

Now I don't have to figure out a way to raise the chair height.
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Old 10-15-2015, 10:58 AM   #2
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Rich:

I did see your post on Yahoo and I am glad that you also posted here because I wanted to ask you a few questions. I am considering doing the same thing for my Pilot 34. The trim tabs drop the bow ok, but I would like to pick up a bit of speed and I think that the fins may help.

You obviously had to remove the existing tabs to weld on the fins. How difficult was that? My boat will be on the hard for the winter, so I have access and time to do it.

I am not going to weld them on, but maybe pop rivet. Will that work? Even if the back of the rivet keeps the tab from closing flush to the hull, that is ok if they stick open an inch or so. Seems like rivets will be much more secure than screws and nuts.

The Defender price is even cheaper now- $30 for a set of four.

David
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Old 10-15-2015, 11:54 AM   #3
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I'm interested in this as well, I'd like a little better performance out of the tabs on my 400T.

I wonder if Mainship used the same tabs on all the 2005 models?
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Old 10-15-2015, 01:09 PM   #4
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When I read the Bennett installation instructions for my trim tabs I noted they said to stick the ends of the screws which hold the backing and hinge plates in place into some Epoxy before screwing them in. I was glad to find that had not been done on my boat, and that the screws backed right out with evidence of 5200 on their threads. I had previously acid cleaned the protruding threads of the two machine thread screws which connect the trim tab to the rams; so they came right out too. I was sitting in a rowboat under the boat in its lift and had no trouble getting the trim tabs off and back on.

Pop riveting the fins in place with rivet material compatible with the 304 stainless Bennett trim planes would probably be ok, and I cannot see where any properly installed rivet would interfere with the full travel on the trim plane.

I don't know that drop fins would necessarily increase boat speed at a given boat trim. What they did in my case was provide greater lift and thus more trim by the bow or flattening out the boat which resulted in a tad more speed, nothing dramatic though.

I have no idea what different trim tabs MS may have used on different models of its 2005 boats.
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Old 10-15-2015, 02:40 PM   #5
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Quote:
Originally Posted by rgano View Post
The result is a much better view forward at my chosen RPM of 2900-3000 (315 HP Yanmar) and a bit more speed, now up to 18.5 knots.

Now I don't have to figure out a way to raise the chair height.
Hmmm, I'm only getting around 16-17 knots at 3000 rpm (315 Yanmar also). And, as you noted, visibility over the bow is an issue. I might have to look into this kit. Is your boat in Southport on a lift? I'd like to see your installation in person (I'm in Panama City). I don't have access to the Yahoo group. Can you provide more details here?
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Old 10-15-2015, 05:48 PM   #6
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Call me at 850-596-3824. I am here at home in Southport most days. If you want to visit by boat, we have extra slips here too.
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Old 10-15-2015, 05:49 PM   #7
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Oh no, I mistyped! It was 18.5 MPH not knots. Sounds like we are close.
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Old 10-15-2015, 07:44 PM   #8
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The "drop fins" capture water that would normally slip out the side increasing the efficiency of the tabs by about 25-30%. The edges of the tabs must be parallel with the keel to use these.

Bennett doesn't weld because it changes the properties of the stainless and could increase the rate of corrosion. There are a few manufacturers that insist on welding on tabs and in those cases Bennett does weld but then passivates the tabs.

Most Bennett Tabs can easily be removed for the "drop fin" mod by disconnecting the actuator and loosening the hinge screws into the transom. At some point the tabs will clear the locking tab and just slide out the side without removing the hinge entirely.

A little known fact is that on many Bennett tabs sold to Mainship the Actuators were restricted in their travel. Mainship did this to avoid bow steering and along with the minimum sized tabs on the Pilots this restricted the performance of the tabs. A standard Bennett Actuator travels 2.5". The modified Actuators travel 1.75". If you have a modified actuator there will be a label on the bottom of the lower hinge (where it attaches to the tab.)

Another easy fix for a little more performance is an actuator spacer. Bennet will give these to you for free for the asking. They are triangular and the same footprint as the upper hinge where it attaches to the hull. It is notched to fit around the brass nipple that carries the fluid and is easy to install, even in the water for most boats. You just back off the 3 screws in the transom, slip the spacer between the actuator and the hull, goop it all up, and re tighten the screws. Gives .5" additional travel down but does away with the - angle Bennett recommends.

Dougcole, Mainship used 12" x 48" tabs with dual actuators and 1' upfins for the entire run of 400's. You might check if you have restricted stroke actuators which would be the best way for you to improve performance.

Most of the above are "fixes." There's nothing better than a bigger tab, I had 12" x 42" on my olde '78 MSI and they were the difference between planing or not. There are ways to install bigger tabs on most boats, and the single actuator is standard up to 12" x 42" tabs.

Good luck,

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Old 10-19-2015, 12:12 PM   #9
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rgano,
Can you post a picture of your Mod? I have 2006 rag top with 6LPA-STP 315 and would be interested in seeing if this modification would drop the bow more than the existing tabs do fully extended. I run about 3200 RPM's at 17.5 to 18.5 knots, depending on conditions. I'm really interested in dropping the bow.
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Old 10-19-2015, 02:19 PM   #10
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My MS Pilot 30 II would do almost 17 knots at 3000rpm with the 4LHA@240hp. I'm a little surprised y'all don't do better??? I cruised at 2800rpm which yielded a solid 15 knots.
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Old 10-19-2015, 06:30 PM   #11
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I have no clue why you can get such speed at such a low RPM from a four banger. Maybe our lack of speed has something to do with a significantly heavier boat due to a bigger engine? You also have the hardtop?
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Old 10-19-2015, 06:40 PM   #12
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Photos before and after drop fin kit installation.
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Old 10-20-2015, 06:31 AM   #13
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Rich,
Thanks for the Pictures.
I did notice that the hard top was listed at 1000 pounds more in the specs while shopping the boat. 18.5 is a good speed. I think Bakers boat year had a slightly different hull design? At 2800 RPM I would be closer to 14 knots.
I did try wide open throttle once to see what the boat would do and it was around 22.5 WOT
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Old 10-20-2015, 09:16 AM   #14
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We had the same problem on our Mainship of the helm chair pedestal being too short. We found a company that makes a pedestal extender that slips over the existing pedestal and raises the chair about 10" inches, a real quick fix. Cost about $60.00, Arrigonidesign.com.


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Old 10-20-2015, 09:34 AM   #15
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Rich:

Thanks for your pictures. The installation of the trim tabs is entirely different from my Pilot 34. On that boat the tabs are recessed into the hull and do not extend past the transom, thus my question about ease of removal and whether pop rivets will interfere with closure.

So, I guess I will have to take a hard look at them to see if the fins can be easily added.

David
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Old 10-20-2015, 09:53 AM   #16
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The seat extender looks like a great idea. I have to get the admiral out on the boat and driving with the new fins doing their thing to see if we might need the seat pedestal extended. The Arrigoni site says it extends the pedestal 6 inches, which I already know is too much, but I can always cut incremental bits off the existing pedestal and then try the extended until it is correct.

As to using pop rivets to add the drop fin kit on a boat with the tabs tucked into a hull recess, I would say no problem if your rivet tool is applied from the bottom side leaving the flush part of the rivet top next to the hull and the slightly extended part down.
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Old 10-20-2015, 09:53 AM   #17
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Quote:
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Rich,
Thanks for the Pictures.
I did notice that the hard top was listed at 1000 pounds more in the specs while shopping the boat. 18.5 is a good speed. I think Bakers boat year had a slightly different hull design? At 2800 RPM I would be closer to 14 knots.
I did try wide open throttle once to see what the boat would do and it was around 22.5 WOT
It might be the hard top and the slightly bigger engine causing added weight. I think the hull shapes are the same. 5 bladed prop??? My prop was even under propped as I could reach almost 3600rpm on a 3300rpm engine. I have seen 24.7 knots at WOT when the boat was new to me and before I loaded it up with crap. Still 23 knots at WOT loaded at any given time. Crazy!! At the very least I would imagine the six banger is a lot smoother running. That four banger would vibrate at low idle.
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Old 10-20-2015, 10:32 AM   #18
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I get 24.5 statute MPG at WOT with full tanks and all the crap aboard. That's 21.3 knots.
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Old 10-20-2015, 10:37 AM   #19
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Damn. I wish I would have had this knowledge when I was selling my boat. A few passed on it due to the motor as it relates to speed.
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Old 10-20-2015, 11:07 AM   #20
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I get 24.5 statute MPG at WOT with full tanks and all the crap aboard. That's 21.3 knots.
If I remember correctly, I'm getting a few knots better than that. I'll have to check it again next time I'm out. But, I'm pretty sure your boat is a little heavier than mine (more equipment).

Thanks for the pics of the tabs. This may be a good project next time I have my boat hauled.
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