Bennett trim tab position indicators or custom external cable + potentiometer?

[vas]

hello all,

didn't manage to fit all the Q in the title this time, so bear with me

I want to fit trim tab position indicators on MiToS.
I have some trim tabs by a company called Trim Master which doesn't seem to be trading now, not really an issue as pump, rams work (port needs service again but that's another story)
Due to the loading of MiToS with various things latest being an avon jetrib 250kg, I want to have them working and knowing what they do, I may actually increase slightly their surface area but that's another thing altogether.

I have two options:

Get a set of Bennett indicators and use a pair of old bennett rams that my friend has on his shed and be done with (ofcourse I'll get the N2K kit-cheapest I found is in the US for 170usd delivered ) In this case I could replace my original rams, or run them in parallel slowing down movement but increasing force that the system can sustain (me thinks at least-not sure it's needed or makes sense...)

get some decent cable (single core stainless steel thing) and route it from the tip of the tab to above w/l and through the transom and fit a 12usd Chinese rudder indicator https://www.ebay.co.uk/itm/KUS-12v-24v-Marine-Boat-Stainless-Steel-Rudder-Gauge-Angle-Indicator-Sensor/292504294659?epid=18017392446&hash=item441a9d5503:g:ALUAAOSwl7NavgLR:rk:2f:0 (fully analog) on each side and route the cables to one of my custom boxes and pump the N2K sentences to the bus.

solution A will cost me almost 10 times more than B but that's not the point. I'm happy to get the Bennetts but I've heard locally that the trim indicators wont last more than 3-4years and then I have to replace them???
I've also seen the v.weak top mount (both the ones my mate gave me were broken there...) and I'm slightly worried.

OTOH, I'm not sure how long the single core ss rod (say 3mm?) will last moving through a shield which I've no idea what it's made of and how to seal it...

so, opinions please!

cheers

V.

 

[jfm]

I have the Bennett indicator and they have been trouble free with zero maintenance 6 years. I have Bennett high end all ss rams, not the plastic ones, but the trim indicator parts inside are probably the same.

Teleflex cable, with entry thru hull above w/line, going to the Chinese potentiometer, is a good solution and is widely used on fast boats (with direct mechanical read out, not potentiometer). A problem might be that guests accidentally bend them when swimming!

I have a Maretron N2k black box for talking the trim position onto the bus, and for some reason it had a conflict and I quickly lost patience and gave up with it. If I can find it I will mail it to you as you are more likely than me to get it working. Slight problem is I cant remember where it is, so it might take me some time to find it. It might even be in my rudder compartment, just disconnected from the bus.

 

[BruceK]

I have Bennetts in excess of 25 years that are purely mechanical and cable driven. Fault free and accurate

This sort of thing but for tabs not drives

 

[MapisM]

OTOH, I'm not sure how long the single core ss rod (say 3mm?) will last moving through a shield which I've no idea what it's made of and how to seal it...

I don't know exactly what the shield is made of, but it very much reminds me of push-pull cables which are used for mechanical throttles.
Anyway, fwiw, that type of mechanical indicators were OEM installation on DPs, and on mine they are still working flawlessly after 14 years.
Actually, I believe that they were the ONLY indicators supplied by BCS (the trim tabs builder, now part of Twin Disc), back in their days.
And with good reasons imho, because as also jfm said, you will never find anything else than mechanical indicators in all boats where tabs position is seriously critical, i.e. the very fast ones.
In fact, that's a choice not only driven by reliability, but also accuracy.

I'm not sure I would be very happy with the Chinese stuff for handling the conversion from mechanical cables, though.
The very best systems (again, from both reliability and accuracy standpoints) are 100% mechanical, and that's what you typically find in speedboats: the push/pull cables go straight from the stern to the dashboard, where they are directly connected to linear indicators, as the three ones in the upper right corner of the Fountain dashboard below, for instance.
Pretty much the same logic as the mechanical Bennett stuff posted by BK, and probably easy to home build for yourself, I reckon.

Trouble is, I don't think it's possible (I've never seen it on any boat, at least) to replicate those mechanical indicators in two helm stations, as I guess you would want to have in your boat.
In which case, yes, I suppose you must convert the cable movements in some sort of electrical signal.
Fwiw, in the BCS system that I've got on the DP, the mechanical cable are routed only inside the stern lazarette, where they are connected to a black box (that I never had to open so far - touch wood!), from which an electrical signal is sent to two double gauges, one in each helm.
The other pic below shows the one in the p/house, just to give you an idea of how they look like.
I have no clue about whether that black box could create N2K-compatible signals, but I doubt it - unless they made a newer version in the meantime, 'dunno...

 

[vas]

thank you all for the ideas.

out of all that I take John's experience with bennett indicators that are not failing as I was told. That's good thanks!
now guys, I'm not going to get mechanical cable driven things to the helm.
Bruce, you get a couple of such things all the way to the helm? Nice and smooth without fancy bends? Not easy job routing them for sure...
P., I understand that mechanical is king for high speed craft, but we are talking 18-20kn, trying to improve balance and maybe gain .2kn or most importantly gain .1l/nm by trimming right
Speed of response is not of paramount importance.
Accuracy neither.
J. Interesting fact that swimmers may bend the steel rods/wires, I've got the pipework that holds the swim platform around and I don't think it's easy to get your legs in there. I may improvise the position to be shielded

Obviously if I go the chinese rudder sensor route I'll get a couple more just in case and keep them as spares
Black box is nothing difficult, have already done this job to convert an old CETREK rudder sensor to N2K, getting two more of these potentiometers pumping the trim tab N2K PGN is nothing to worry about.

So, if we can refocus the discussion:

WHAT cable/teleflex/gland would I need to do so?
any pointers?
I can easily drill a hole at an angle on the 20mm (or 25mm don't remember now) transom.
What teleflex is available with a gland that would be possible to fit at say 20-30deg angle to transom? I could built a wedge and get a decent vertical meet, dunno.

Anyway, just trying to see what options I have as whatever I do will be around Easter when MiToS will come out for the annual maintenance.

cheers

V.

PS. John, regarding the Maretron, I'll happily have a look and see what's wrong with it if you wish, but I struggle to think of any conflict issues unless you were running out of power on the bus or something. Shouldn't be reporting anything else but Trimtab position on PGN130576.
I notice that they may be reporting on Engine Param Rapid PGN127488, in which case it may be conflicting with engine RPM, boost or engine ID even.
We had a similar issue with NoLand analogue engine -> N2K and the fuel flow meters were both sending the same PGN (which has a gazilion of variables in it, only different variables each) and because of a silly mistake on my part it was interfering as in zeroing the values reported by the NoLand. Changing from 0 to NA or something like that, solved it.
However Maretron are no newcomers to the game and I doubt they'd do something like that...

 

[BruceK]

To answer your question, yes. The same route as gear cables, then gear and throttle and finally gear, throttle and steering cables. Its an easy run. If its not for you thats fine but no mere complex than rods, bits and DIY and decidedly less so.

 

[jfm]

Vas, thanks for the PGN info - I cant remember what the problem was and a (good) guy did the install for me so I don't recall it first hand. I know I gave up too easily, so I will check. If it can be made to work the nice thing about Garmin is that the trim angle appears as a pop up when the value changes, then the screen goes back to "normal" after 10 seconds as the pop up sinks back down.

Ref your question, Teleflex offer this hull entry thing https://www.jamestowndistributors.c...at-ControlCables(v4_0)Panel_Cables.pdf(bottom of page) but it relies on the nuts at the end of the cable and does not offer a seal halfway along the cable, so will not be much use. I think you need to use one of the many glands supplied by index marine (or similar) eg the DR1 or the bottom row on this page https://www.force4.co.uk/department/brands/index-marine.html Obviously we are talking about above w/line cable entry here.

 

[MapisM]

P., I understand that mechanical is king for high speed craft, but we are talking 18-20kn, trying to improve balance and maybe gain .2kn or most importantly gain .1l/nm by trimming right
Speed of response is not of paramount importance. Accuracy neither.

Yeah Vas, I fully understand that you don't need the half degree accuracy of mechanical indicators (they ARE that accurate, I kid you not).
Neither do I on the DP of course, as opposed to the Fountain. But it's still nice to have a reliable system that seems to be withstanding the time very well, anyway.

Anyhow, if what you are interested in is the engine load/fuel burn optimization at any given RPM, actually in my experience you don't need any indicators at all.
I mean, what I do once reached the desired cruise speed is fine tune the trim tabs till the SOG is maximized without touching the throttles, nothing else.
Sure, I know by now that the optimal setting is in the 8 to 6 degrees range, at my typical cruising speed between 18 and 22kts respectively.
Above that, the boat requires progressively less tabs, up to her fast cruising speed of 26/27, when the speed is optimized with neutral tabs (0 deg).
And the fully raised position (2 deg negative) only makes sense above 30.
Therefore, I do look at the gauge, to set an approximately correct tabs position. But when I have a longish leg ahead, I don't mind spending a couple of minutes more to fiddle with the tabs a bit, because a 0.2 kts improvement is definitely achievable, with a bit of practice.
The indicators are irrelevant in this respect, though.
Let's say that one day I set the throttles for 20kts with 7 deg of tabs, and then after fiddling a bit I find a position where the boat makes 20.2kts.
Let also say that according to the indicators the resulting tabs position happens to be 1 degree less, i.e. 6.
All well and good, but if the next day I go out after refilling water and/or fuel, it's quite possible that the boat goes faster with one degree more than "normal", not less.
And for this last bit of fine tuning, the only instrument I actually look at is the GPS, because that's far easier than trying to build a table with the optimal settings for all the possible combinations of speed and load.
Btw, I also found that my cellphone is even better than the Raymarine onboard stuff in this respect, because on top of giving the speed with two decimals accuracy, it also reacts faster - but this is another story.

Back to your main question, sorry but I can't tell you much more than I already did.
Just in case looking at an actual cable might be meaningful for you, I'm attaching below the best detail which I found in my pics archive.
Don't look at the unusual reversed position of the cylinder - that is due to a rather peculiar stern shape, which surely doesn't apply to your boat.
Btw, the cable entry is waterproof in this installation, because it's just below the (static) w/line.

 

[MapisM]

So, if we can refocus the discussion:
WHAT cable/teleflex/gland would I need to do so?
any pointers?

Hi again, V.
I googled around a bit because the indicators posted by BK made me curious, not having ever seen them mated to any Bennett tabs.
And they are built (as the pic suggests!) by Stainless Marine, a US producer of custom accessories for high performance boats.
Mostly suggested for K-planes trim tabs - the ones built by Mercury Racing. BK, were they retrofitted in your boat, maybe?
Anyway, they are designed to be installed with Morse 33C cables, if that helps.

 

[BruceK]

I am not sure Mapism. They, the indicators, are OEM to the boat and the boat is old at 1992. The tabs look identical to other examples of my boat so I presume they are OEM too. I dont have in my stock any clear photos but these 2 I do. On them unit there is no maker's mark

on the left by the CP

 

[BruceK]

Had a look in the original brochure it says Aeromarine K-Planes w/trim indicators. K-Planes (tab) are now part of Mercury racing and look nothing like what I have which look exactly like Bennett. That's the problem with boats built before the internet.

http://www.mercuryracing.com/sterndrives/accessories/k-plane-trim-tabs/

 

[vas]

evening all,

had a search around the boatyard and spotted 2 boats with external trim tab indicators, so on top of MapisM setup (P, I see your rams are steel, right?) I have another two examples of a similar setup on plastic rams

Broom 36 (or something like that). FWIW, the rams on the broom are same brand and type as mine (TrimMaster):

Azi 55 f/b:

Now, the broom has solid ss core and some flexthing on top two clamps to hold the lot on the ram.

The azi otoh is a simple multicore like an old school pushbike brake cable only thicker.

So seems that it's done extensively and since mine is too easy to route a cable like that above w/l and behind the cross brace for the rudders, I'm most likely going to go for that option.
Got to find a teleflex or similar dealer in Athens and see what they have as far as cable with teflon/pvc/whatever lining and get a couple of metres of the thing!

cheers

V.

 

[Portofino]

View attachment 74963
View attachment 74964

FWIW we have a similar set up a boden type cable that runs through above the WL .
Inside it’s attached to a control box ( looks like a rudder indicator) then wires to the helm .
At the helm is a pair of analog gauges with -2 to + 6 .
The pics are with them @ +6 to facilitate easy an jet wash off when it was lifted .

Buy I don’t know what make it’s all is unfortunately.
I think it’s the same hydraulic set up as MapisM - bcm or b ** ??

 

[vas]

thanks Porto,

all these pics persuaded me that dipping a bowden cable (learned the right name for it thanks ) in the sea is not a bad idea as I originally thought.
I'll order 3-4 chinese rudder indicators once I find suitable ss cable

cheers

V.

 

[Portofino]

BCS is the Co name they do marine hydraulics .
The flaps , steering ram and Passerelle all operate from one 24 v electro hydraulic unit .
Here’s there diagram for flaps

View attachment 74965

If you get stuck you could try them for the relevant parts .

 

[MapisM]

P, I see your rams are steel, right?

Well, there's zero plastic anywhere in their construction, if that's what you mean.
I believe that only the rod is in actually s/steel, while the cylinder body and the connecting blocks are in bronze.
Pretty substantial stuff.

 

[MapisM]

I think it’s the same hydraulic set up as MapisM

The cylinder actually looks very different. Am I right in understanding from your pics that yours have external hoses?
In mine, both the hydraulic flows (up/down) are completely inside the connecting block, and there are no exposed hoses anywhere.

 

[MapisM]

Had a look in the original brochure it says Aeromarine K-Planes w/trim indicators. K-Planes (tab) are now part of Mercury racing and look nothing like what I have which look exactly like Bennett. That's the problem with boats built before the internet.

Aha, interesting.
Aeromarine is one of the legendary marine companies in the US, founded by Carl Kiekhaefer and later taken over by Mercury/Brunswick.
And K-planes are indeed, also nowadays, a very popular speedboat installation - that's what I had on the Fountain, in fact.
What exactly makes you believe that your components have anything to see with Bennett?
If it's the flaps shape that is similar, I suspect it's a case of Bennett copying from Aeromarine, rather than the other way round...

 

[BruceK]

Possibly. My boat if you remember is a Thunderbird Formula but at the time of it'd build Formula was more invested in racing and racing craft. I assume they are Bennet because that is what they look like.

 

[MapisM]

I assume they are Bennet because that is what they look like.

I fully understand your assumption, looking at the things with 2018 eyes.
But unless you have any other evidence that Bennett had something to see with them (I mean, a manual, the name stamped somewhere, whatever), I believe that the similarity is just incidental.

By chance, did anyone else ever come across Bennett trim tabs with cables going straight to a mechanical indicator on the dashboard?
I wasn't aware of any, so far.