Stabilizers for Blue Angel, engineering question

[BartW]

No worries B, I did ask to the yard near Rome where we met last year if they could handle also boats with fin stabs, and they confirmed me that it's perfectly feasible.
Btw, you'd better mention the fins also to any yard which should lift the boat with slings, because if a sling grabs a fin, and snatches while pulling, it can make a disaster.

yes agree,
have been looking at pictures from the carriage in Le Chantier Des Beaux
not a real problem as long the yard knows there are fins, and take care for that.

 

[BartW]

On the heat build up issue, I would expect there to be a thermal cut-out, if the motor thinks it is getting too hot. However, I am with JFM on this, best for performance and reliability if the heat is managed. Blowing hot air into a bilge that is 20 odd year old, is likely to stir some impressive odours, not necessarily what you would like in an uncomfortable sea. So I would look at ducting cooling air in and out of the motor area, assuming it is encased for noise etc. I dont think you would need huge hoses, probably 50 mm would suffice.

therefor we should suck out air to the outside,
but not from/to the engineroom compartment, because:
- there is very hot air during navigation
- there is a fireproof bulkhead wall between E/r and owners cabin, which I like to keep intact.

I asked the question at CMC about the cooling of the electric motors,
lets wait their reaction.

 

[rafiki_]

therefor we should suck out air to the outside,
but not from/to the engineroom compartment, because:
- there is very hot air during navigation
- there is a fireproof bulkhead wall between E/r and owners cabin, which I like to keep intact.

I asked the question at CMC about the cooling of the electric motors,
lets wait their reaction.

Without going back into the geography of BA, so this might be stupid, but could you draw air in near the air intakes for the engine room? There will be some form of water separator into the engine room so it would be useful to use this source of cold (relatively) air? You could exhaust anywhere where fumes/odours are not important.

 

[Forty_Two]

One small but important detail Bart, do make sure the installer wires up the gearbox neutral or reverse switches to the stabs to put them in standby/centred, otherwise it can be very expensive going astern!

 

[BartW]

One small but important detail Bart, do make sure the installer wires up the gearbox neutral or reverse switches to the stabs to put them in standby/centred, otherwise it can be very expensive going astern!

there is a connection on the Stab system, for the gearbox, for that,
but my gearbox and controlls are very oldfashion, and no connection, just hydraulic remote controll of a lever on the gearbox.
so 'll probably have to add a mechanical switch to that lever, which will switch the stab controller off as soon she goes out of FWD gear.

switching ON the stabs will alway's be manually from the controll panel (I think)
nothing automatic, no interference during manouvring, or slow speed in port, or ....

 

[Piers]

there is a connection on the Stab system, for the gearbox, for that,
but my gearbox and controlls are very oldfashion, and no connection, just hydraulic remote controll of a lever on the gearbox.
so 'll probably have to add a mechanical switch to that lever, which will switch the stab controller off as soon she goes out of FWD gear.

switching ON the stabs will alway's be manually from the controll panel (I think)
nothing automatic, no interference during manouvring, or slow speed in port, or ....

Hi Bart. On my Fleming, the controls are hydraulic, and there's a small light sensor that senses the movement of the arm on the gear box for when reverse is selected. That tells the system to put the stabs into centre position.

Piers

 

[BartW]

Without going back into the geography of BA, so this might be stupid, but could you draw air in near the air intakes for the engine room? There will be some form of water separator into the engine room so it would be useful to use this source of cold (relatively) air? You could exhaust anywhere where fumes/odours are not important.

the fuel tanks are between the e/r and the cabin,
but a hose could go over them, but again we don't want to push air in, but extract air...(then we would need two hoses on each side)


actually my bilges under the cabins don't smell, (except one occasion, leak in the toilet hose connection in our cabin)
we open them regulary, they are used for storage:
- luggage from guests
- watersport gear, fins and glasses for kids, (not used a lot, but need them on board)
- one box with engine and generator spares, (set of spare filters and belts)
- outside furniture covers

 

[BartW]

Hi Bart. On my Fleming, the controls are hydraulic, and there's a small light sensor that senses the movement of the arm on the gear box for when reverse is selected. That tells the system to put the stabs into centre position.

Piers

good idea Piers an optical switch,
choice depends on geometry and dimensions of the gear lever, etc..
and needs a power supply wire.

 

[BartW]

because in such enclosed/restricted space, even a relatively small amount of heat would tend to constantly build up, and in a long passage (maybe in a rough sea, where the motors must work hard) that has to be considered.

power consumption of the system at anchor is far more bigger then at sea

Surely they must have taken that into account somehow, 'cause obviously that's not a BA-specific issue.

thats my point !
the system specced for BA is their smallest system,
their other systems are all gradually bigger, but all of them seem to have just one electric motor,
so surely they should have experience from the bigger systems, on heavyer boats, with much more power at anchor

 

[jfm]

One small but important detail Bart, do make sure the installer wires up the gearbox neutral or reverse switches to the stabs to put them in standby/centred, otherwise it can be very expensive going astern!

Yup. The stabs computer will also sense reverse by its own the GPS

 

[jfm]

surely they should have experience from the bigger systems,

Yup, and just maybe that experience is that heat build up is quite a problem. Of course they wont want to say that, and will prefer to say "it's ok" which is why imho you need to keep your antennae tuned and look them in the eye/read their claims carefully and check they conform to the laws of physics.

 

[MapisM]

Re. centering fins when reversing

Light sensor, GPS... Eat your heart out, folks.
On my boat, the fins are automatically centered whenever I'm entering a marina, together with the fenders deployment!
In fact, I've only got the stabs control panel inside the p/house, and since typically in summertime I'm helming from the f/b, I instructed swmbo to center the stabs while she prepares the fender and the lines.
Tried and tested, works a treat!

 

[Forty_Two]

Light sensor, GPS... Eat your heart out, folks.
On my boat, the fins are automatically centered whenever I'm entering a marina, together with the fenders deployment!
In fact, I've only got the stabs control panel inside the p/house, and since typically in summertime I'm helming from the f/b, I instructed swmbo to center the stabs while she prepares the fender and the lines.
Tried and tested, works a treat!

Love it so it can never be your fault....

 

[MapisM]

Precisely.
Besides, if and when the automated system fails, it only takes some screaming to repair it.

 

[BartW]

On my boat, the fins are automatically centered whenever I'm entering a marina, together with the fenders deployment!

not talking from experience, but had a similar aproach in mind; just switch them manually on (and off) during steady cruising,
but with a planing boat, it makes sense to have a automatic Stab Stop or lock function,
for whenever you have to stop or switch out gear unexpectedly ?
(has happened to me in a few occasions)

 

[Forty_Two]

not talking from experience, but had a similar aproach in mind; just switch them manually on (and off) during steady cruising,
but with a planing boat, it makes sense to have a automatic Stab Stop or lock function,
for whenever you have to stop or switch out gear unexpectedly ?
(has happened to me in a few occasions)

I really believe in the auto off setup. After a trying trip you arrive in a strange harbour with a wind doing the wrong things & the last thing you are able to remember before going hard astern, to maybe rescue a tricky situation, is to put the stabs in standby.

I have come across people who have bent their stab shafts & it's not a cheap option especially part way through a holl

 

[MapisM]

but with a planing boat, it makes sense to have a automatic Stab Stop or lock function, for whenever you have to stop or switch out gear unexpectedly ?

If you're talking of an emergency stop to avoid hitting something, or just of disengaging the gear because you've seen a floating line/pot etc., the fins self centering is the last of your problems.
I mean, yes, they can affect the handling while maneuvering, when you need a predictable boat behaviour to move within restricted spaces.
But in the above conditions, the fins effect is neither here nor there. I wouldn't be worried one bit.

 

[BartW]

just got an e-mail from CMC with an answer to my questions,
second point was about using the system on a invertor
particularly the last tick is interesting

- The system is equipped with an electro-magnetic brake, in case of energy loss the system automatically engage the brake when the fins are close to their neutral position.
- As long as the system supplied the right power I don’t see any problems.
- Due to the high mechanical efficiency , the power losses and therefore the heat generating is very low. We don’t need any cooling system even at anchor.-
- The standard delivery time is approx. 6 weeks.

 

[jfm]

just got an e-mail from CMC with an answer to my questions,
second point was about using the system on a invertor
particularly the last tick is interesting

- The system is equipped with an electro-magnetic brake, in case of energy loss the system automatically engage the brake when the fins are close to their neutral position.
- As long as the system supplied the right power I don’t see any problems.
- Due to the high mechanical efficiency , the power losses and therefore the heat generating is very low. We don’t need any cooling system even at anchor.-
- The standard delivery time is approx. 6 weeks.

This is what i meant when I said above that you have to look at their response and decide if it is engineeringly correct or marketing BS. So, everyone else in the world makes electric motors that generate heat, but one tiny company called CMC has cracked it and their 1-2-3 Kw motors convert nealry all the electricity into kinetic energy and stay cool. And the reason for that is "mechanical efficiency". Yeah, right.

I'd be interested to know more about the brake (I called it a clutch above, but same thing). Does it lock when power is off? How much current does it draw when unlocked? How is it that with no power it refrains from locking until the fin is nearly central? Etc

 

[Deleted User YDKXO]

This is what i meant when I said above that you have to look at their response and decide if it is engineeringly correct or marketing BS. So, everyone else in the world makes electric motors that generate heat, but one tiny company called CMC has cracked it and their 1-2-3 Kw motors convert nealry all the electricity into kinetic energy and stay cool. And the reason for that is "mechanical efficiency". Yeah, right.

I tend to agree with you. I suspect that what they are actually saying is that they are using brushless motors which are indeed more efficient than brushed motors but I don't see that this necessarily means that heat will not be a problem. The brake seems to be electromagnetic which I would assume means that it only works with power on? I think what BartW can take out of this statement is only that so far they haven't encountered any heat problems but of course with the small number of installations, that's not necessarily reassuring