Stabilizers for Blue Angel, engineering question

[BartW]

I'm still a bit worried about heat and would want some technical analysis on that, but I might be over-worrying. I guess i am concerned that the fin area has been restricted to reduce power and heat generation when at anchor, because 1m sq feels right to me (and doesn't even look especially big on an 80 foot boat)
....................
Are you thinking of going ahead with this idea before the start of 2013 season BartW?

at the moment I'm going ahead as if it is a pre 2013 summer project;
- DL is involved, has done a similar project with a SunS
- The former Canados teamboss is tracing the orriginal Canados Engineers and orriginal Canados info (they are old and slow remember ;-) )
- The weekend after next, I will try to make as many measurements as possible, ao stringers, frames, thikness of the hull, (two methods) ;-), underwatership, .....
- Today I had a phone call from that yard in SOF,(he called me coincidently) I made a appointment for next friday to talk about our plans
- got a mail today from CMC, they didn't say no to our pragmatic approach, but nevertheless insist on a good job.
- bottom line, I don't think that a retrofit hydraulic driven system is practically feaseable, leaves one solution, and me getting old.
BUT
if it turns out that there is a serous bumb in the road, I can skip or postpone the project.
nothing signed yet.

If you have some serious arguments against, pls let me know

here is a pic I've got today from a installed system in a "Moonen", which is "in a tank" (not very clear from the pic)
so no extra ventilation

 

[jfm]

Well, neither the gyros nor the hydraulic stabs would run without the genset while at anchor, anyway...

Agreed. All 3 need genset at anchor. I meant underway, when you have 2000hp from the main engines and you're doing 10 hours, it's nice not to have to run a genset too. But maybe that's just my personal preference - lots of IT boats need 230v always when underway. No big deal, and anyway I was wrong becuase BartW can power them off the engine alternators

 

[jfm]

What valves? My Naiads are free floating whenever turned off, with no need to do anything.
I can see why that would require a clutch with electric stabs, anyway.
And I also don't think they use one, though I actually can't tell for sure.

Wih Sleipner you shut all the valves, both cylinders inlet and outlet. The thing is then hydraulically locked, in any position that the software tells it to lock, with a multiple of the locking force that a pin can provide (not that a pin isn't strong enough!)

To achieve that electrically, with no current draw, you must have a clutch. If you have a pin, you can lock but only in one position, not floating centre. If you have no clutch and no pin, I do not see how you can lock at all without current, but I'm curious to find out

 

[MapisM]

Wih Sleipner you shut all the valves, both cylinders inlet and outlet. The thing is then hydraulically locked, in any position that the software tells it to lock

I understand that, but my point is, why bother locking the fins at all?
My question was because you said that they "have a floating centre with no power draw".
If the fins are just free to rotate, that's the best/easiest possible floating center at any given speed, surely?

 

[MapisM]

Agreed. All 3 need genset at anchor. I meant underway...

Yup, all agreed, my post was in answer to Bart, just to remember him that at zero speed the genset is a must anyway, regardless of the system.

 

[jfm]

at the moment I'm going ahead as if it is a pre 2013 summer project;
- DL is involved, has done a similar project with a SunS
- The former Canados teamboss is tracing the orriginal Canados Engineers and orriginal Canados info (they are old and slow remember ;-) )
- The weekend after next, I will try to make as many measurements as possible, ao stringers, frames, thikness of the hull, (two methods) ;-), underwatership, .....
- Today I had a phone call from that yard in SOF,(he called me coincidently) I made a appointment for next friday to talk about our plans
- got a mail today from CMC, they didn't say no to our pragmatic approach, but nevertheless insist on a good job.
- bottom line, I don't think that a retrofit hydraulic driven system is practically feaseable, leaves one solution, and me getting old.
BUT
if it turns out that there is a serous bumb in the road, I can skip or postpone the project.
nothing signed yet.

If you have some serious arguments against, pls let me know

here is a pic I've got today from a installed system in a "Moonen", which is "in a tank" (not very clear from the pic)
so no extra ventilation

Good that DL is involved

I agree that for BA it is CMC or nothing. Retrofit hydraulic is complex and adds big costs

You seem to have enough room - tick

You can use them underway without generator - tick

I'm worried about heat, on basic laws of physics, but I'm in a minority of one - tick

I think the question of fin area needs more work, but only if you care about at-anchor use. Underway a small fin is ok

Therefore you are almost at a point of deciding they are a great product. Then it's down to time and money

 

[jfm]

I understand that, but my point is, why bother locking the fins at all?
My question was because you said that they "have a floating centre with no power draw".
If the fins are just free to rotate, that's the best/easiest possible floating center at any given speed, surely?

Yes, but if your power system fails and you want to reverse the boat in a harbour without smashing the actuator unit, you need to lock them. I suppose you could move very slowly, <1 knot, in a case where you had a failure. In tidal waters you couldn't but in the Med you would be ok

I see your point though that when underway you don't need to lock them, normally. If you were at anchor in a beam swell, and had no stab power, you wouldn't really want them to flap freely as that would bust the actuator mechanism. I suppose in that case you wouldn't anchor in a swell

 

[MapisM]

If you were at anchor in a beam swell, and had no stab power, you wouldn't really want them to flap freely as that would bust the actuator mechanism.

Good point, I never considered that. Though while swimming around the boat, I've rarely seen the fins moving, and even when they did, it was always a very gentle and slow motion.
Yep, I suppose that if the swell would be enough to damage the actuators, it would be the crew who can't stand it anymore and wants to leave, well before that point...

 

[jfm]

Good point, I never considered that. Though while swimming around the boat, I've rarely seen the fins moving, and even when they did, it was always a very gentle and slow motion.
Yep, I suppose that if the swell would be enough to damage the actuators, it would be the crew who can't stand it anymore and wants to leave, well before that point...

The slow motion is because of damping in the hydraulic fluid, or a small swell. In a big swell with unlocked electric actuators, apart from damping due to the reduction gearbox (which could be considerable; I dont know the gearbox spec) they will flap around. It might only take one stroke to bust the mechanism - depends on the design. On the other hand the electric ones may be able to spin 360 degrees with no damage - I don't know

 

[MapisM]

I'm worried about heat, on basic laws of physics, but I'm in a minority of one

Actually, after you mentioned, I also wondered about how that's addressed, 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.
Surely they must have taken that into account somehow, 'cause obviously that's not a BA-specific issue.
At a guess, I would think that also the water flow on the fins should cool down the main shaft, and in turn also the motor.
But maybe they have also some more clever way to deal with heat dissipation, 'dunno...

 

[MapisM]

In a big swell with unlocked electric actuators

Oh yes, I was actually talking of my stabs, which don't work at anchor, hence I should keep one engine on and the stabs centered (they have hydr center lock, with a pin only for emergency), just to keep them from flapping around, which would be crazy.
For the electric ones, afaik all of them are designed to work also at anchor, therefore I suppose that in a big swell you would want to turn them on anyway....

 

[jfm]

Actually, after you mentioned, I also wondered about how that's addressed, 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.
Surely they must have taken that into account somehow, 'cause obviously that's not a BA-specific issue.
At a guess, I would think that also the water flow on the fins should cool down the main shaft, and in turn also the motor.
But maybe they have also some more clever way to deal with heat dissipation, 'dunno...

I honestly wouldn't believe the waterflow cools the motor. Far too remote. Most of the shaft outside the boat is covered by FRP fin, and the heat transfer from the motor winding would have to go thru the gears. Nah, no way!

 

[vas]

Is it only me thinking that these el.motors are rather small???
how come?
I guess they need to produce some serious power, no?

Also, on the clutch issue, couldn't they employ an electromagnetic pin thing that needs power to pull, as in when el. fails, it locks in place, when they turn on, it pulls off the axle/motor/gears/whatever and the system is operational.

To JFM and MM: do your hydraulic systems let the fins do a full spin? Since I very much doubt, what sort of angle off centre do they allow?

Bart, once you fit them, no more traditional old fashioned lifting allowed! Only slings Really liked the wooden ladder sort of thing and massive winch

cheers

V.

 

[jfm]

Is it only me thinking that these el.motors are rather small???
how come?
I guess they need to produce some serious power, no?

Also, on the clutch issue, couldn't they employ an electromagnetic pin thing that needs power to pull, as in when el. fails, it locks in place, when they turn on, it pulls off the axle/motor/gears/whatever and the system is operational.

To JFM and MM: do your hydraulic systems let the fins do a full spin? Since I very much doubt, what sort of angle off centre do they allow?

Bart, once you fit them, no more traditional old fashioned lifting allowed! Only slings Really liked the wooden ladder sort of thing and massive winch

cheers

V.

They're modern brushless. Lots of power from small body

The pin thing works, but only locks the fin if you can move the fin to the place where the pin pops in. That is easier said than done - ask ellesar who had to do it on a failed Trac BAT stab on a Nordhavn in Bay of Biscay 2 yrs ago

Yup, mine and MapisM's will not do 360. I don't have the exact figure but it's like +/- 45deg from the centre position only.

 

[vas]

They're modern brushless. Lots of power from small body

The pin thing works, but only locks the fin if you can move the fin to the place where the pin pops in. That is easier said than done - ask ellesar who had to do it on a failed Trac BAT stab on a Nordhavn in Bay of Biscay 2 yrs ago

Yup, mine and MapisM's will not do 360. I don't have the exact figure but it's like +/- 45deg from the centre position only.

thanks for the replies, but wtf are you doing up at 3AM? OK, it's 5AM here but I've spent the last couple of days in bed with a bad cold and cannot sleep anymore, but you??
Got to work hard to pay for all the toys, not faff about in forums!
shame on you

V.

 

[BartW]

I think the question of fin area needs more work, but only if you care about at-anchor use. Underway a small fin is ok

Therefore you are almost at a point of deciding they are a great product. Then it's down to time and money

The specced drive model / shaft, can have 3 types of fins, 0.6m2, 0.8m2 or 1m2, so I'm not so much wurried, option for a bigger fin is still open,

About heat of the electric engine, will asc CMC about this, but a simple fan, and circulating the air in the bilge, using the "heat capacity" in there, and the cooling from the surrounding water ? not enough ?

main issue will be timing I think,
from all party's involved,
and delivery time of the system, (don't knwo yet)
and my time, can be flexible but there are limits

 

[BartW]

Bart, once you fit them, no more traditional old fashioned lifting allowed! Only slings Really liked the wooden ladder sort of thing and massive winch

good point Vas, didn't think of that,
the yard I have in mind doesn't have a crane, they have a similar old system but wiith a big carriage on rails,
point to discuss with the yard next week friday.

great ! thanks !

 

[MapisM]

Yup, mine and MapisM's will not do 360. I don't have the exact figure but it's like +/- 45deg from the centre position only.

Yes, of course any hydr system has an excursion limit.
I also dunno exactly, but your guess sounds reasonable - in fact, I wouldn't see the logic of a higher angle, particularly when cruising.

 

[MapisM]

good point Vas, didn't think of that,
the yard I have in mind doesn't have a crane, they have a similar old system but wiith a big carriage on rails,
point to discuss with the yard next week friday.

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.

 

[rafiki_]

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.