Boat in build pics (2013 Fairline Squadron 78)

[maverickofpoole]

Loving this thread especially the photos, I don't understand all the techie speak only learn't to read 52 years ago are we due more piccys soon

Martin

 

[jfm]

considering that both engines in a boat spin in the same direction as the wheel in the video, the precession of both crankshafts/flywheels should constantly try to steer the boat to port.

That was a good video MapisM, although he perhaps went quite fast at the crucial bit! Ref your sentence above: yes, except for the following. In the bicycle wheel demo, the torque vector of the forces trying to move the wheel's axis away from horizontal (namely, gravity and the string) was constant. In a boat in a head sea, it oscillates: you have a wave lifting the bow, then gravity pulling it down into the trough. So the "gyro steering" effect on the boat also oscillates port/starboard. Our "perfect helmsman or autopilot" would therefore be tweaking the rudders left-then-right constantly as the bow lifts and falls in the head sea

But I'm only making a fine tuning refinement here to what you said; I basically agree what you said

 

[rafiki_]

That was a good video MapisM, although he perhaps went quite fast at the crucial bit! Ref your sentence above: yes, except for the following. In the bicycle wheel demo, the torque vector of the forces trying to move the wheel's axis away from horizontal (namely, gravity and the string) was constant. In a boat in a head sea, it oscillates: you have a wave lifting the bow, then gravity pulling it down into the trough. So the "gyro steering" effect on the boat also oscillates port/starboard. Our "perfect helmsman or autopilot" would therefore be tweaking the rudders left-then-right constantly as the bow lifts and falls in the head sea

But I'm only making a fine tuning refinement here to what you said; I basically agree what you said

I think we are in violent agreement here. Apologies for confusing the issue with my analogy

 

[John100156]

I really do like the Techie stuff chaps, all very interesting to me, but I suspect (totally unqualified of course) the effects are more important in theory rather than practice, you'll be bringing in corrections to the cosine angle that the boat hits the wave next... Then the height of pitch, roll... JFM will get distracted, and he will not have time to publish more pictures for us all

 

[jfm]

I really do like the Techie stuff chaps, all very interesting to me, but I suspect (totally unqualified of course) the effects are more important in theory rather than practice, you'll be bringing in corrections to the cosine angle that the boat hits the wave next... Then the height of pitch, roll... JFM will get distracted, and he will not have time to publish more pictures for us all

Point taken John I'll try to get to factory soon and get some more pictures

Meantime, here's a geeky pic. It's the ais track 10 mins ago of MSC Arica, on board which is my container containing Match 2's new tender, from Florida. The ship has been anchored, awaiting a berth in Felixstowe, but 30 mins or so ago (ie midnight Friday 28/12/12 it weighed anchor and is now steaming to Felixstowe. I guess my container will be unloaded tonight, and fingers crossed it will be trucked the short distance to Essex Boatyards maybe Monday or Tuesday next week, where I'll go and see it, woohoo

I've never done this contianer shipping lark before but so far it's been dead easy. I just need the last part to work ok, where a truck takes the whole container from the docks and delivers it (to EBY in this case) and a forklift empties it

 

[Portofino]

Here is my 0.002 peny,s worth --the rpm of even Cat 32,s x2 is relativley low and the mass inc crank+ flywheel may seem "high"- but is is not really relative to ---compare /equate this to the inertial mass of the total weight of the boat pitching through a head sea .
Factor in (i do-not think any body has done this )the resistance of the sea pushing the boat back up in the wave +a little water friction and wind resistance .
All this =negligible noticeable effect on the steering.
Thinking of the Ferreti (Mitsubushi) zero speed stabs -F=1/2 Mass x velocity squared ,
V can be up to 40,000 rpm and the M-not sure ,but not far off the crank of a C32 ? ish ?
I suspect(prepared to be corrected) that one can up anchor and "bug out" with the gyros still spinning and steer the boat without noticing?? in a 24M boat.
40,000 Sq is a bigger No than 1750 Sq.
real world -waves coming in at diff height ,angle ,pitch, boat speed changing ,windage altering , boat rolling as well(changing the wet area and hull profile in the water - may effect steering ?).

So the fact the cranks turn in the same direction (engines "handed" for ease of maintenance) then one gear box reverses the direction connected to a suitably "handed" prop to balance the thrust , people think this may effect the steering or the gyro effect the be noticeable?
I do not think so -too many variables cancelling out the effect of two engines spinning the same way even C32,s mainly the combined mass of the boat and the mass of the water it,s displacing
Apologies if if i have missed the point !

 

[Piers]

Point taken John I'll try to get to factory soon and get some more pictures

Meantime, here's a geeky pic. It's the ais track 10 mins ago of MSC Arica, on board which is my container containing Match 2's new tender, from Florida. The ship has been anchored, awaiting a berth in Felixstowe, but 30 mins or so ago (ie midnight Friday 28/12/12 it weighed anchor and is now steaming to Felixstowe. I guess my container will be unloaded tonight, and fingers crossed it will be trucked the short distance to Essex Boatyards maybe Monday or Tuesday next week, where I'll go and see it, woohoo

I've never done this contianer shipping lark before but so far it's been dead easy. I just need the last part to work ok, where a truck takes the whole container from the docks and delivers it (to EBY in this case) and a forklift empties it

What make an model tender, John?

 

[MapisM]

Here is my 0.002 peny,s worth...
...too many variables cancelling out the effect of two engines spinning the same way even C32,s mainly the combined mass of the boat and the mass of the water it,s displacing

I really can't see how either the mass of the boat or of the water she's displacing (what's the difference, btw?) can "cancel out" the effect we were debating.
I think we all agreed that it's bound to be negligible, for various reasons, but I can't see anything on a boat (or anything else equipped with a spinning engine, for that matter) which can cancel and/or compensate such effect.
I'd rather think that it's simply ignored by the designer, because someone must have done the maths and understood that it's not worth bothering about it.
Otherwise, why not consider also the gensets, the big stabs AC pump, and... what else?
The washing machine, all the other onboard pumps, and also the winches, maybe?

Geez, this gets my vote as the thread drift of the year!

PS for jfm: yep, all agreed re. your additional remarks on my previous post.
I didn't consider pitching in my train of thoughts, but of course that could reverse the effect.

 

[STEVEDUNSTABLE]

hi jfm..... sorry to ask you to go back afew steps(pages), but id like to ask about the trim tabs !!!!... will you need them to "get over the hump"??...(i would of thought not with all those "stallions"!!!)..... so are they basically for port n starboard leveling etc ?? cheers...... OH n ps. as mentioned any chance of a "picy" update.... regards n HAPPY NEW YEAR TO YOU n YOURS ....frm steve..

 

[jfm]

I really can't see how either the mass of the boat or of the water she's displacing (what's the difference, btw?) can "cancel out" the effect we were debating.
I think we all agreed that it's bound to be negligible, for various reasons, but I can't see anything on a boat (or anything else equipped with a spinning engine, for that matter) which can cancel and/or compensate such effect.
I'd rather think that it's simply ignored by the designer, because someone must have done the maths and understood that it's not worth bothering about it.
Otherwise, why not consider also the gensets, the big stabs AC pump, and... what else?
The washing machine, all the other onboard pumps, and also the winches, maybe?

Geez, this gets my vote as the thread drift of the year!

PS for jfm: yep, all agreed re. your additional remarks on my previous post.
I didn't consider pitching in my train of thoughts, but of course that could reverse the effect.

+1 to all that MapisM. The fact that the gyro effect is small, which Portofino is adding is 0.2c to, has never been in doubt. As you know, I was only ever asking whether the "formula 1 mentality" raceboat guys care about it. I sure don't care about it on Sq78

Portofino your maths was a bit flawed. When you square the speed, you should not square the rpm number. RPM isn't a mathemtically pure measuring scale; it is made up by man, becuase man made up the concept of a minute. Thus your comparison of 40,000 squared and 1750 squared is pretty flawed. You have to use consistent and pure units, eg Si units

 

[jfm]

hi jfm..... sorry to ask you to go back afew steps(pages), but id like to ask about the trim tabs !!!!... will you need them to "get over the hump"??...(i would of thought not with all those "stallions"!!!)..... so are they basically for port n starboard leveling etc ?? cheers...... OH n ps. as mentioned any chance of a "picy" update.... regards n HAPPY NEW YEAR TO YOU n YOURS ....frm steve..

Hi Steve
Actually there isn't a hump, at least not that you can notice. You completely do not notice the trnasition from D - SP - fully P. In fact there is pretty much no hump that you can feel on any boat above say 50 feet - thing of the t60 Aura you were on, I bet you couldn't feel much hump on that?

So the tabs don't help with hump. Also they will not be used for left-right levelling, even though they could, because the fin stabs do that automatically. On a fin stabbed boat, it's importnat to keep the tabs even port-starboard and not have one lower than the other, otherwise the stabs will cancel the twisting effect of the tabs but in doing so will add drag and more fuel

Hence, the only thing they do is adjust bow up/down trim in case that needs to be adjusted for economy and dropping the bow down into a chop

I'll try to get some more pics next week. HNY to you too!

 

[jfm]

Otherwise, why not consider also the gensets,

Hey MapisM, remember most gensets have a "front" and "back" to the box they are placed in, and on my boat the gensets are outboard of the main engines with the front panels on view obviously. See pic below (of e/room, awaiting engines to be dropped in). Wayhay, that means one genset is spinning CW and the other CCW, so they do cancel out (if I run them both!). No wonder I never noticed the gyro steer before now!

 

[jfm]

What make an model tender, John?

Piers it is a Novurania 430DL, 4.3m loa, which is the absolute max for Sq78 in order to clear the passerelle. It has been custom made then put in a container by the excellent Novurania in Florida, using a contact kindly provided by MYAG off this forum. Cold white tubes to match the hull; white caulked decks, step plates, other detailed mods, and best of all it has the new ultra light Yamaha 70hp. (Like you, I no longer have any interest in jet drives; yamaha outboard is where it's at, as far as I'm concerned). When it gets here I have some mods to organise - probably a new dash moulding to house a garmin touch screen and VHF, and maybe better upholstery, Lumishore lights, etc. I have never actually seen one of these close up, so I'll only be able to figure out the mods when I get it

 

[STEVEDUNSTABLE]

Hi Steve
Actually there isn't a hump, at least not that you can notice. You completely do not notice the trnasition from D - SP - fully P. In fact there is pretty much no hump that you can feel on any boat above say 50 feet - thing of the t60 Aura you were on, I bet you couldn't feel much hump on that?

So the tabs don't help with hump. Also they will not be used for left-right levelling, even though they could, because the fin stabs do that automatically. On a fin stabbed boat, it's importnat to keep the tabs even port-starboard and not have one lower than the other, otherwise the stabs will cancel the twisting effect of the tabs but in doing so will add drag and more fuel

Hence, the only thing they do is adjust bow up/down trim in case that needs to be adjusted for economy and dropping the bow down into a chop

I'll try to get some more pics next week. HNY to you too!

thanks for the info JFM..strangley enough, you are right about the T60 in that we could,nt "feel" the hump but we could certainly "see it"!!.. we would get about 7/10 secs of restrichted viss when at the lower helm but being so calm over your patch of the med the tabs were,nt bothered with... just for your info, we did one of those trips the other way, (Nice to Palmer) crossing the gulf de lyon in a F5/6 right on the nose tween 10 oclock n 2 oclock on the compass (hugging the coast) we were using the tabs then forsure!!!!!!!!!... went round cap la dage, WORSE!!! and gave up..a quick 180 into cap la dage harbour but not before the french coastguard wanted to board OUTSIDE the harbour!!!! alass all before the vidcam was purchased !!!..... PM me if you want chapter n verse, was a giggle with HINDSIGHT!!!!!!

 

[Whopper]

JFM, the tender looks nice. One mod that would be a worthwhile consideration would be a ski pole or removable one at least. Not sure if the space is there but you never know.

 

[taz]

Loving the thread but more photos please.


Yours faithfully

A techno-Dunce.

 

[Portofino]

+1 to all that MapisM. The fact that the gyro effect is small, which Portofino is adding is 0.2c to, has never been in doubt. As you know, I was only ever asking whether the "formula 1 metality" raceboat guys care about it. I sure don't care about it on Sq78

Portofino your maths was a bit flawed. When you square the speed, you should not square the rpm number. RPM isn't a mathemtically pure measuring scale; it is made up by man, becuase man made up the concept of a minute. Thus your comparison of 40,000 squared and 1750 squared is pretty flawed. You have to use consistent and pure units, eg Si units

i used rpm to keep it simple - if we use M/sec as V it actually works better making the diff larger,because one has to factor the radius in.
stabs mass is approx at 1/2 M radius spinning compared to C32 crank bearing radius ?6cm,in the journals
assuming 12cm diameter (well around that size) the add ons conrods pistons except- crank balance wieghts are all ineffective on gyro force don,t count here they move vertically -balanced so,s not to shake the engine to bits
using M/s makes the gyro force even more negligible on C32,s
Basically i was illustrating that its the spinning speed that counts V and a large M is only partially useful -compared to the M of the boat re inertial movement and any water it has to move out of the way to effect a turn water is dense .Hope this answers Mapish M Q ?-
Think helicopter - blades spinning big radius = (high V and enough M) attached to a light "hull" enough gyro effect to hover in strong winds
But unlike water ,air provides little resistance in fact needs a counter rotating device - the tail in single rotors
75 tons of boat semi submerged will resist the rotational force of the spinning dare i use it 1750 rpm engines and any other spinning device with regards to steering,
FI possibly with super light hull say 25 ft er powered by a pair of petrols 7000 rpm when airbourne (not really a useful atribute to forward motion?) may torque twist , but for how long 0,3, sec before it lands in to water ,only to be pushed off course by a wave? hull profile as its slightly rotated ?
If its in the air more than its competitors it will not win .

 

[jfm]

JFM, the tender looks nice. One mod that would be a worthwhile consideration would be a ski pole or removable one at least. Not sure if the space is there but you never know.

Yup whopper, there is space. Novurania offer a removeable one as an option. Thing is, to clear the Yam70 it has to be quite tall and hence needs quite a lot of platework at the bottom to attach well to the hull. It's kinda 25kg territory and I'd use it so little that I've decided to make do with a bridle and the pair of transom U bolts for now and see how that goes. I'm th.e only one in my general group who monoskis hard and I don't pull as hard as I did 20 years ago, so I kind think the bridle will be fine... I know you are more of a purist!

 

[jfm]

i used rpm to keep it simple - if we use M/sec as V it actually works better making the diff larger,because one has to factor the radius in.
stabs mass is approx at 1/2 M radius spinning compared to C32 crank bearing radius ?6cm,in the journals
assuming 12cm diameter (well around that size) the add ons conrods pistons except- crank balance wieghts are all ineffective on gyro force don,t count here they move vertically -balanced so,s not to shake the engine to bits
using M/s makes the gyro force even more negligible on C32,s
Basically i was illustrating that its the spinning speed that counts V and a large M is only partially useful -compared to the M of the boat re inertial movement and any water it has to move out of the way to effect a turn water is dense .Hope this answers Mapish M Q ?-
Think helicopter - blades spinning big radius = (high V and enough M) attached to a light "hull" enough gyro effect to hover in strong winds
But unlike water ,air provides little resistance in fact needs a counter rotating device - the tail in single rotors
75 tons of boat semi submerged will resist the rotational force of the spinning dare i use it 1750 rpm engines and any other spinning device with regards to steering,
FI possibly with super light hull say 25 ft er powered by a pair of petrols 7000 rpm when airbourne (not really a useful atribute to forward motion?) may torque twist , but for how long 0,3, sec before it lands in to water ,only to be pushed off course by a wave? hull profile as its slightly rotated ?
If its in the air more than its competitors it will not win .

Yup, all ok. I think you're covering old ground: since the very start of this discussion no-one has said the gyro-steer effect on a fat thing like a sq78 with C32s is significant. The question was only whether it could be significant in a race boat with formula 1 type mentality and a desire to save a second per hour. Again we're in agreement that the effect is small even in a raceboat but everything in "F1" thinking is small. It needs maths not gut feel to answer the Q for a raceboat, and/or knowledge of whether raceboat builders have ever tried to factor it in

 

[scubaman]

Rafiki, I think you're mixed up on gyro forces. Your mention of two engines bolted to the hull "cancelling out" very much misses the point. The along-the-keel-line torque you are referring to is NOT precession. It is the action=reaction (Newton's first law) force that MapisM refers to 4 posts above. As the crankshafts/flywheels accelerate (not rotate, but accelerate, whether +ve or -ve) clockwise there is an anticlockwise torque on the hull, and vv. Having two engines both spinning say CCW creates this force as the throttleman does his thing, and having two engines counter rotational eliminates it. But this is not precession; this is merely Newton's first law. ( BTW, I'm talking about engines being counter rotational, not merely prop shafts).

Also, gyro forces have nothing to do with out of balance-car-tyres. Out-of-balance spinning objects also behave in accordance with Newton, and create harmonics because of the rotation. But that too is not precession

Precession is a different thing altogether. Suppose you have two crankshaft/flywheels both spinning the same way along a keel line axis in a boat. Then the bow hits a wave and rises - this means the hull rotates about an athwartships axis. Absence anything else you will then get precession - precession here means that (a) the boat will rotate about a vertical axis, in other words if you are above the boat in a helicopter you will see the boat turn left or right without the helmsman doing anything - THAT is precession; and (b) the bow will lift less than it would if the crankshafts were not spinning (being the gyro stab effect)

Alternatively you can stop the precession, eg by having a perfect helmsman or a/pilot who perfectly adjusts the rudders to eliminate it, but that creates drag (and allows the bow to lift fully with the wave because the absence of precessions means there is no gyro stabilisation anymore).

There is no doubt about the forces and effects i'm describing. All I was asking at the beginning of this discussion was whether their magnitude is so tiny that even the hard-core racing guys who care about 1 second in an hour don't even worry about it. If they did worry about it, it would be a reason, in addition to MapisM's Newton-1st-law reason, to have counter rotating engines in the ultimate race boat. As I said above, I guess the effects are too small to worry about

Both crankshafts/flywheels will have the same gyro forces with the same effects from precession regardless of the direction they are spinning, surely? Or am I missing something here?

Edit: to be clearer on this: spinning in different directions wouldn't cancel out each others gyroscopic forces but each would have their one.