Vosper Mini Fins Stabilisers retrofit on MiToS

[jfm]

Awesome work Vas. Huge respect to you. I have no doubt your boat is planning at 20kts+ (ie, +1 to mapism's post 5 above) and it is no surprise that the fins have no material adverse affect, because as you said above everything is in proportion with other boats (including mine) that suffer no material speed loss/lack of planing with fins. There is a lot of highly confused naval architecture/fluids "analysis" written above but life is too short to correct it all point by point.
Best of luck with the next phase - writing the control software.:encouragement:
Staying tuned here :encouragement:

(OT: thanks for email - yes Maretron plastics = weird. The part that has gone brittle isn't even the part in the sun! Anyway I hope you can make one good DSM250 out of the 2 broken ones. It's a nice display if you can get it to work. I'll send you another one in 2 years

 

[jrudge]

Well done. Amazing

Porto. The hull speed will be say 8 knots. At 21 knots it is planing I cannot see any possible debate

 

[MapisM]

View attachment 72272

LOL, Porto, are you also using the old boatbuilder's trick of taking pictures of their boats with a downhill horizon, in order to give the impression that the boat attitude is flatter?
Maybe Itamas are not planing that well, after all...

 

[JerryC]

Massive respect for this project, Vas, as if rebuilding MiTos wasn't enough already! (I followed all of that thread too, wow!). Just a little question, if you have time: I have played around with a raspberry Pi, but didn't really go anywhere constructive with it for boat projects, but I'm interested in the Arduinos. Your post #97 recommends the "teensy 3.5" but I can't find out anything about it. Could you give me a link, please? Thanks in advance.


Edit, cancel my last sentence, I have now found a link.

 

[wakeup]

LOL, Porto, are you also using the old boatbuilder's trick of taking pictures of their boats with a downhill horizon, in order to give the impression that the boat attitude is flatter?
Maybe Itamas are not planing that well, after all...

Yeah, how are Itamas able to plane at all since their dead rise is so high as we keep being told that it would seem impossible to get over the hump. May be they aren't planing that well and are ploughing rather than planing.

 

[Portofino]

Yeah, how are Itamas able to plane at all since their dead rise is so high)

Change of tack
Keep It Simple

One word
HORSEPOWER


View attachment 72309

Zero deadrise, low Hp —- got it “Wakeup,”

Btw vas,s boat has a reasonable above ave deadrise but dispite his boat and mine being a fag paper difference thickness in dims wise .The combined total Hp of both Mitos engines does not equal ONE engine on the same dims Itama .
So you kinda shot yourself in the foot by moving the swingometer to none planing highlighting Mitos deep deadrise and low Hp . As a base hull sub 14 M to “ fin “
Thanks mate

 

[jrudge]

A little lost. But it seems “ my engines are bigger than yours !” And ...

I am not really sure what the debate is about any more.

Vas has done an astonishing job and with the stabilisers takes it to a new level.

This seems to be detracting from his acheviments not building on what is a very interesting topic.

Vas well done and good luck with the next step.

 

[Portofino]

A little lost. But it seems “ my engines are bigger than yours !” And ...

I am not really sure what the debate is about any more.

Vas has done an astonishing job and with the stabilisers takes it to a new level.

This seems to be detracting from his acheviments not building on what is a very interesting topic.

Vas well done and good luck with the next step.

Hey I,am just politely answering the Q from post #125 posed by MapishM and reiterated by Wakeup,.

It’s a given the tremendous work and sharing of the experience by Vas .
His back will be sore with any more back slapping

Would be nice for somebody to put an alternative to my definition to true planing which I highlighted further up .
As I said too above it’s totally academic in the sense Vas is not gonna go anywhere near 21 knots anyhow where he’s running bow high ploughing through , stern digging in or otherwise.

 

[petem]

Porto, the problem is that it looks like you're splitting hairs just to save face (because you said that Vas's boat wouldn't plane with the stabs fitted). Whatever you think, you'd get a lot more respect by just saying "well done Vas, looks like you were right" (which incidentally he is). Continuing to argue the toss is just making you look a bit of an arse!

I hope you'll take this as the friendly advice as intended .

 

[MrB]

A little lost. But it seems “ my engines are bigger than yours !” And ...

I am not really sure what the debate is about any more.

Vas has done an astonishing job and with the stabilisers takes it to a new level.

This seems to be detracting from his acheviments not building on what is a very interesting topic.

Vas well done and good luck with the next step.

Porto, the problem is that it looks like you're splitting hairs just to save face (because you said that Vas's boat wouldn't plane with the stabs fitted). Whatever you think, you'd get a lot more respect by just saying "well done Vas, looks like you were right" (which incidentally he is). Continuing to argue the toss is just making you look a bit of an arse!

I hope you'll take this as the friendly advice as intended .

BIG +100 on both accounts.:encouragement:

 

[MapisM]

Hey I,am just politely answering the Q from post #125 posed by MapishM and reiterated by Wakeup.

Well, if it's my post #123 you're referring to, I suppose you are formally correct in qualifying it as a question, since my statement ended with a question mark.
Otoh, wasn't it crystal clear that "joke" would be a much more appropriate definition for what I wrote...?

 

[wakeup]

Well, if it's my post #123 you're referring to, I suppose you are formally correct in qualifying it as a question, since my statement ended with a question mark.
Otoh, wasn't it crystal clear that "joke" would be a much more appropriate definition for what I wrote...?

My apologies to VAS for thread drift. I was Porto baiting, which is now banned in several departments of France.

VAS, huge respect to your latest project and going with your gut feel and keen eye. I am in awe that you adapted these fins to look right for your boat. I am sure if they look right that you will get the whole project to work. Looking forward to seeing your pics and video of a swing test and real world tests if you ever get on the plane that is :encouragement:

 

[vas]

guys,

thanks for all the comments, I've been working way too much to get the boat ready for the first week or so onboard, so way too tired to even read carefully and reply.
Will do in 10days when I'm back home and have fully recovered.
Should have enough time to try the fins out and report.

cheers

V.

 

[MapisM]

Tired? Need to recover?
In my mind, I always assumed that you are actually a bionic being, who eats work for breakfast, and then keeps going with boat reconstruction at night - all while posting on the forum through voice dictation...

 

[Lloydroberts]

And he eats 3 Shredded Wheat for breakfast?

@Vas
Good luck with your testin g and enjoy your well earned break.

 

[vas]

hello all,

back from two weeks onboard (with a week in between for change of crew and some more work...) and catching up!

Now then,

boat is still afloat, clocked around 300nm with no issues other than the Mase generator control panel dying on me and ending up wiring an old DD barrel for it...

First week was rather windy (ideal for testing fins) but the whole control box was on a prototyping board and I wasn't at all happy running with it just like that in case it would fail (as in a resistor or whatnot popping off!) and I'd end up with fins in funny positions and trying to figure out what to do.
So one morning managed to transfer everything to a proper board and solder them in place using my dremel gas soldering gun. Happily wired it in, nada wouldn't wake up
no time to play, so just left it and on returning from the first week took it home and under stronger light and better glasses noticed a dry solder on a ground hence not firing up as there was no 5V supply to the arduino...

So all up and ready for next trip.

Next trip though I spent a lot of time trying to sort out fuelling to the new to me rib so first test was done with a nice quartering sea last Friday. Speeds 7.5-8kn me hanging over the rails to see the fins moving, was ecstatic, really was, just spent time looking at them moving back and forth, could hardly believe it! Noticed that there was too much delay on the movement from the actual tilt of the boat which effectively amplified the roll instead of removing it, nice
Conclusion fins work for sure!
Pump is strong enough, things don't squeak, no water coming in, nothing cracked, fins move properly, boat responds to movement nicely. All fine hardware wise.
So now down to s/w to sort.

Forgot to mention that just in case and while I was wiring the Detroit diesels barrel to start the generator I bought a 2euro 1KΩ pot (with on-off switch) and wired it so that I could alter the travel of the fins for testing. So basically full whack and fins move the whole travel, turn it down and movement is reduced gradually down to 30% under which fins just park in the middle position. Off and the inverter is turned off, pump stops and whole system is shut down.


So, next morning I altered some values and got them a bit more responsive.
Unfortunately the last day returning to Volos sea was dead flat, so couldn't really test it but I did manage to take a video of fins induced roll on flat seas, not quite the aim of the project, but proof I'm on track as if fins can induce roll on a flat sea they are capable of eliminating roll on a a rolly one (if you know what you're doing s/w wise that is )

Back home and on checking my code again I note a few things:

A. I used the accelerometer of the MPU9250 3euro chip. Don't get me wrong chip's good one, just cannot believe how cheap it is
Reason was that when I was testing this was giving me nice + and - values when tilting one way or another.
TBH, don't remember if I tested the gyro values, on hindsight should have done!
WRONG! should really use the gyroscope as now values change from + to - when boat passes the centre position, so by the time the fins move to correct roll it's way too late.
I could change my code so that the movement of fins is introduced when the + or - value stops increasing and starts decreasing (implying a change of roll direction) but I'm not sure that this is the right approach tbh, so will try that as well as the gyro values.
Gyro will allow me to program and respond when the rate of turn changes direction and gain enough time to move them where they should.

B. I assumed that fins must move to either one end or the other and never park in the middle (as my original code did)
Rationale was that I'd rather improve response by going straight to the other end and not having a small stop in the middle.
Wrong! If it's not really rolly, what happens is that with the delay to move them about you start introducing roll...
This is how I managed to do the next video. Fins move to one end to eliminate roll, then to the other (again with a delay) and whole thing amplifies roll.
Improved it by reducing the fin travel but got to sort A first.
Then I have to re-introduce parking fins again, or based on speed and roll amplitude start reducing the travel of the fins until parking them when there's no need for them to move. We shall see.

[starts with fins active and inducing roll, at 10sec I turn them to park moreorless when son turns up, roll disappears, at approx 30sec I start them up again]

Other observations:

interesting that I have a small list to stbrd amplified with the new heavy rib as well as a not fully extending stbrd trim tab that I noticed snorkelling around on Sat. Not much I can do about the latter now, got to wait and check them both on the hard in the winter.
So boat is slightly listing to stbrd, by turning the stabs on it automatically straightens, turn them off lists again. This I understand is the right response.

Although you cannot physically move the fins when system is off and hydraulics/pump etc are off, travelling through water seems to create more force than what I can do with bare hands on the hard, as they do move according to swell and wind direction. So not a park and forget job. Means I'll have to add the pump/clutch/etc assembly on the port engine during the winter so that they run off the motor when moving (and free my geny in order to produce water when going from one anchorage to the other)

Problem is that I'm about to leave for a week to Denmark on a conf so I'll be able to test my ideas beginning of Sept.

May have a go at testing the handbrake turn of the cat liner on Wed without taking the boat out if I'm lucky and have finished some work work to be done by then.

cheers

V.

 

[jrudge]

Well done.

From what little I know about stabilisation the software takes the upset and then starts to eliminate the predicted roll , presumably then monitoring the actual roll and then modifying the inputs accordingly so that more roll is not induced as the wake for example fades away.

I doubt that any mechanical system could act fast enough tho counteract a roll that has already started.

This then gives a requirement for some sort if appropriate initial response given the nature of the upset and a learning module that accepts the boat is rolling and then decides how an active roll is best managed.

Just my thoughts.

 

[MapisM]

I doubt that any mechanical system could act fast enough tho counteract a roll that has already started.

I understand your doubt, but that's exactly how old school fins stabilizers actually worked.
The so called HMG controller built by Naiad, which drove the stabs in my old boat, didn't rely on any kind of predictive algorithm or other sophistications, quite simply because it didn't have any onboard "intelligence". As soon as the gyroscope sensed a rolling motion, the fins were rotated as quickly and as much as necessary to correct it - as simple as that.

Actually, already back in those days (I'm talking of more than a quarter of a century ago...), Naiad was already selling a more advanced controller, called MultiSea II and computer driven.
It could also be retrofitted, and according to their brochure it granted a "vastly improved performance", but I never considered it.
In fact, aside from being bloody expensive, I never bought the idea of "vastly improving" something which was already as close to perfection as it could be.
Otoh, this is all related to non-STAR stabs.
I suppose that a well designed software capable of considering several different parameters and act predictively is much more crucial for an effective zero speed stabilization.

All that aside, excellent job, Vas. The proof of concept is definitely a go, I reckon.
Ref. the centered fins position, I have no clue about if and how to handle that, but as the theory goes, the "neutral" fins position is NOT fixed (i.e. longitudinally parallel with the keel, as intuition suggests), and depends on speed instead.
If you have any way to measure the fins position accurately, by leaving them free to rotate and cruising in dead calm sea at different speeds, you should be able to check how much inward the fins tend to stay at any speed. And those are, in principle, the correct central/neutral positions, which minimize drag at any speed.
Fwiw, my old Naiad only had three positions: OFF, ON, and centered. The latter was strictly meant to lock the fins to avoid interferences while maneuvering, and I suppose that they were just locked parallel (never bothered checking that). In the ON position, they moved as much as required depending on the hull roll, and I really don't think they were aware of any central position at all, let alone dynamic ones.
Otoh, it stands to reason that the relevance of dynamic center is neither here nor there, in a pure D boat.
It could make more sense on P boats, though even for them, I wouldn't hold my breath about any measurable efficiency improvements granted by these sophistications...

 

[rafiki_]

Great progress Vas, and huge congratulations for getting this operating. Plenty of time to refine, but good to hear that the mechanical side works without detriment to MiToS. Your list will probably be down to a loading issue, and you might need to move batteries to level up. Had to do this on previous Rafiki.

 

[BartW]

huge respect to you Vas, for reaching this stage !
many congrats,