Squadron 55 suggestions about flaps use

[hkikis]

Hello!

I have flaps gauge from 0 to 25...
Generally I have them to 0!

-I don't have any ballance difference to use one to put the bow down..
-My boat can plan very easy..

So I don't feel any reason to use flaps. When I have waves I put them on 5 to handle better. But I am not sure if I can feel any difference..

When you are talking about fuel consumption most of you also refer to flap position. And in low speed you have them full down. At wot full up.

Can anyone help me about that? I was thinking that with the flaps down the fuel consumption going worse.

Give me some suggestions please. This boat isn't like my previous 30ft boat that I used the flaps either to handle better or to make it plan easier or to balance it. But if with flaps I can earn in better fuel consumption or in something else tell me your suggestions..

I attached how is my trim flap meters...

 

[jrudge]

It’s about running angle. Generally in flat water you trim to get the nose down and speed will increase / consumption decrease. Rpm is not a reliable indicator if engines are electronically controlled which yours are.

I have a s58. I cruise at 18 kts and it is more efficient with full tabs. Generally the faster you go the flatter the boat will be so less tab but this will depend on hull and sea conditions.

If going into the waves you trim down to limit the rise so it does not slam back down. But not so much you take water over the bow.

In a large following sea keep bow up as you don’t want it to surf into the next wave and bury the bow.

Even better just go out when the weather is nice !

 

[MapisM]

I have flaps gauge from 0 to 25...

Do you mean in the upper part of the display, which should show the flaps angle in degrees?
If so, that's a helluva inclination, makes me think that the plates are too small for the boat.

Anyway, checking the optimal setting at any given speed is not difficult.
Just pick a day with a dead calm sea, throttle the boat to your typical cruising speed, and keep her on a straight line.
Then play with the flaps a bit: after lowering or raising both, just give a moment to the boat for stabilizing in the new attitude, and check how the speed is affected (without touching the throttles, of course).
You should see at the very least a change of a few decimals of knot, depending only on flaps position.
The excursion from the worst to the best position, at any given speed, could even be in excess of one knot, but every boat is different.
If you see zero difference between flaps full down/full up and anything in between, either the flaps aren't working or (as I guessed at the beginning) they are way too small for the boat.
Mind, the result could be slightly different depending also on load distribution, so it's worth checking the behaviour with full vs. empty tanks.

Lastly, don't trust blindly those junk Bennett indicators.
On the next occasion when you will have the boat on the hard, check the consistency between them and the actual plates position.
You might well be in for a surprise.

 

[Hurricane]

I tend to put the tabs down when we go on the plane.
But, as the OP suggests, they don't seem to mak a lot of difference.

That said, on the plane, if you get a cross wind, the boat tips away from the wind.
By trimming the tabs more on one side than the other does make a BIG difference.

Mine are Lenco tabs - the procedure is to look at the bow.
If the port side is higher than the starboard, I press DOWN on the port side.
I usually start planing with about 80% tabs on both sides and adjust accordingly to keep the boat on an even keel.

As I say, fore/aft trim doesn't appear to do much but it must do otherwise it wouldn't work to trim left/right.

 

[Portofino]

MapisM is correct , if your flaps are effective you should see a speed change If you adjust them .
You have not said the speed you cruise .
J rudge has and that 18 knots seems low to me .

Not wanting to drift , but bear with me .Since we are talking planing boats one of the most consistent definitions of planing a common denominator is this definition .I have been working on the subject .

Forgive me for this it’s a bit long .but I have been reading around and keeping stuff like this in note .
just before you read it , think what MapishM has written , your flaps are either too small or ( my contribution) you are not going fast enough for your hull to properly plane , hence it does not react as expected .

That’s the reason for the ineffectiveness of the flaps reported .


Enjoy .....


Planing
A planing hull is simply one so shaped that a degree of dynamic lift is added to its natural buoyancy during the time when its speed of advance exceeds that rate at which solid water can close in abaft of it .

I think we all first need to agree that there is no one binary point of planing. It is not either on or off. It is a transitional regime, and therefore, any attempt to define a point of planing is somewhat nonsensical.
What actually defines planing using the most widely accepted definition is —-

The fact that if the speed increases the trim angle will decrease.

If you aren't planing, increasing speed in the sub planing regime results in an increase in trim angle, for a planing hull. Again, for a semi-planing hull that might not happen at all, but for a true planing hull, the speed where it attains planing status is the point where the trim angle decreases as the speed increases.

Look guys this is pretty simple.
Think about an airplane wing. To supply a given amount of lift at a given speed you need a specific angle of attack. If the speed increases you have to decrease the angle of attack or you will get an increase in lift. As you approach planing speed the trim angle doesn't decrease and indeed, the lift is increasing since you are supporting an ever increasing portion of the hull with hydrodynamic lift.

But once you are on the plane, even though the hull may be heavy and still have a significant portion of displacement lift, if &the trim angle drops as speed increases, it has attained planing status.

This is why using arbitrary measures like % of weight or amount of lift, are not appropriate, a heavy hull might have a different lifted height when compared to the same hull when lightly loaded. But in both cases, when the trim angle decreases, planing has been realized.
How much of the displacement volumn must be above the surface to be "on plane"? all of it, most of it, half of it, any of it? What % if any ?
Since planing begins to occur when hydraulic forces lift the hull, how much until it is actualy "planing"? Any lift replaces displacement forces with dynamic ones, so some say the begining of planing occures when there is any lift not associated with displacement.
Therefore to some they see no reason for any of the qualifiers at all. Many shapes can plane to one degree or another, no reason to put those conditions on it. I also do not see why 50 percent is the magic number either, if any portion of the weight is lifted out of the water by hydrodynamic lift you will reduce the drag and increse speed.

Some say that planing occures if any of the weight is suppored by the dynamic forces on the hull from the water. A little or a lot of the weight being supported is illrelevant, the fact that the hull is not fully in displacement mode means that lift forces on the hull are partially supporting the weight of the boat.

I think the real problem is the word "planing" itself is obsolete and based on archaic ideas about fluid mechanics. The origin of the word assumes it is even possible to be above or "on" the plane of the surface. We know a lot more about the process and forces involved but are stuck with these obsolete terms.


Getting back to the topic some suggest taking into account the “subjective feeling “ of the persons on board, I believe that anyone who has been on board a planing vessel can witness that it's movements became "stiffer" and more jerky when encountering waves at high speeds than it was during low-speed navigation. A mathematical explanation for this behavior is that the perturbation of hydrostatic lift component is in linear relationship to the vertical speed of the incoming wave disturbance, while the dynamic lift component increases as a square function of the vertical speed of the perturbation. Hence, the vertical accelerations become much more severe in high-speed regime.

It makes me think that perhaps it can lead us to a completely different criterion for the definition (by convention) of the planing, based on the vertical acceleration response of the vessel to incoming waves, or to a single standardized perturbation which could be reproduced in towing tanks. The planing regime would then be indicated during sea trials by the on-board accelerometers, rather than through the GPS readout .


Just some food for the few creative minds on here .


I think that at the end, it is a matter of semantics and not physics or engineering. It would be better to say, for example, "this vessel at a speed of 54 knots has 93% dynamic lift to displacement ratio", rather than argue whether it is planing or not

I think we can all agree that, when looking trim angle it becomes pretty clear where planing starts.

The more you think about it one soon realises this becomes different for every hull, and for every load condition, every thrust angle, and for every offset of the thrust vector from the line of the planing surface, as well as things like prop rake. It's possible to significantly change the onset of planing by modifying those variables.


When all things are considered, it is far more complex than a simple % of lift. For lightly loaded short, wide hulls, the change in trim angle happens much more quickly with increasing speed. For much larger hulls with heavier bottom loading, the curve will likely be more of a gentle hump, but the reality is, when you are past the peak of the trim angle curve the hull is now in the planing regime. Since there a any number of variables that can push the actual speed at which the trim angle starts to decrease - that's not a bad thing to use for a rule of thumb .


Maybe planing is like time: we all know what it is, until we think about it

 

[Portofino]

Take a peek at the speed opening shot and flap position 0.07 and the wake shot near the end .
The AoA reduces with speed , not flaps because I believe we are truly planning as per what I posted above .

The flaps are there for what Jrudge says to adjust the bow depending on sea state and wave Dir.
In the vid the sea state is such the flaps are almost redundant , the boat is heavily fouled btw ( missed a haul out C19 etc this season Vid last month ) With a clean bum + sterngear the flap would be 0 , its -1 if you look .
The fouling loosing a tad of stern lift .

 

[Deleted User YDKXO]

Anyway, checking the optimal setting at any given speed is not difficult.
Just pick a day with a dead calm sea, throttle the boat to your typical cruising speed, and keep her on a straight line.
Then play with the flaps a bit: after lowering or raising both, just give a moment to the boat for stabilizing in the new attitude, and check how the speed is affected (without touching the throttles, of course).

Agreed. Its not rocket science but just to say that different boats behave differently. I have had 3 Ferrettis in a row and they definitely need plenty of down tab to reach their optimum planing speed at any speed upto around 25kts. My current boat can plane at 13-14kts but it needs max down tab to do that. As the speed increases I gradually take off the tab angle until at about 25kts they're fully up. Above 25kts, having any down tab actually decreases the speed

I would say to the OP, do some trial runs in flat calm water without any tidal current at various rpm and play with the tabs until you get max speed at each rpm stage and then make a note of those tab positions. Best to use the GPS speed rather than the log speed as log speeds are not usually dead accurate as they can have different errors at different speeds. Allow a few seconds between changes in tab angle because it takes a few seconds for the boat to settle at its new angle. For the future be aware that changing loads such as fuel, water and crew may affect the optimum tab angle so always be prepared to play with the tabs at any given cruising speed to optimise the speed

And Mapism is right. Its also worth checking that you are actually getting the full range of tab movement on both sides and that tab movement corresponds approximately to what your angle indicator is saying. Also make sure there is no fouling on the cylinders which actuate the tabs as this can restrict or even stop movement. On this last point, when you get the boat lifted for hull cleaning, leave the tabs fully extended so the yard cleans the maximum extended length of the cylinders

 

[MapisM]

On this last point, when you get the boat lifted for hull cleaning, leave the tabs fully extended so the yard cleans the maximum extended length of the cylinders

Correct.
And just in case the OP doesn't already do that, it's worth remembering to do the opposite while the boat is docked - i.e. leave the tabs fully retracted.

It also popped to my mind another comment about the following:

in low speed you have them full down

This is only true if by "low speed" you are NOT talking of true displacement speed - which for a 55 footer means 8 knots or so.
If and when pootling around at D speed, it's pointless to lower the tabs.
Not that they make any meaningful difference, but no matter how low the additional drag can be, it's in any case a useless drag.
In fact, at that speed, they boat AoA is flat anyhow - and as soon as it isn't anymore, you are above true D speed.

 

[Deleted User YDKXO]

This is only true if by "low speed" you are NOT talking of true displacement speed - which for a 55 footer means 8 knots or so.
If and when pootling around at D speed, it's pointless to lower the tabs.
Not that they make any meaningful difference, but no matter how low the additional drag can be, it's in any case a useless drag.
In fact, at that speed, they boat AoA is flat anyhow - and as soon as it isn't anymore, you are above true D speed.

Only to say that on some outdrive powered boats having the tabs fully down at D speeds can help the hull track straighter. That was certainly the case with a Sealine S37 I used to own

 

[jrudge]

When I had a squadron 65 they did nothing. The 58 they make a difference. Porto I can cruise at any speed I wish. I have time to spare and me the boat and pax are all very happy at 18 kts

 

[vas]

When I had a squadron 65 they did nothing. The 58 they make a difference. Porto I can cruise at any speed I wish. I have time to spare and me the boat and pax are all very happy at 18 kts

nah, mine are happier at 6 (they sleep) not so happy at 8 (moves more on head seas, they wake up )

 

[Portofino]

When I had a squadron 65 they did nothing. The 58 they make a difference. Porto I can cruise at any speed I wish. I have time to spare and me the boat and pax are all very happy at 18 kts

Agree .
Glad you used the word “ cruise “ though not plane .

 

[rafiki_]

With my Azi 39 I never felt inclined to change the tab setting. She rose sweetly up onto the plane and would plane happily at 14/15 knots. Normal cruising was 20 kn and flat out 29 kn. I did try adjusting the trim when I was learning the ropes with her, but once I found a sensible setting, and in reality the tabs were set to a neutral position, I left well alone. And before anyone asks, yes they did work, but the hull appeared to not be sensitive to tab position.

 

[MapisM]

Glad you used the word “ cruise “ though not plane.

Plane would have been equally correct, Porto.
Any flybridge boat, bar none, is steadily planing at 18 kts.

Don't focus too much on the definition of "plane" as the attitude when the AoA decreases with speed increase.
That's a very sound theoretical concept, but the stress is on the latter of these two adjectives.
If you apply that principle to the Squadron 58, she should only be planning above 24 knots, because that's where her AoA reaches the maximum (5 degrees), and starts going down (up to 4 deg at 33kts).
BUT, at 20kts the AoA is just half a degree less than at 24kts, and at 15kts is one degree less - i.e. 4 deg, exactly as much as at WOT.
In other words, a difference which is neither here nor there, for all intents and purposes.
In fact, also with my similar size/type boat, the only speed range at which I'm not so happy to cruise is from 10 to 16 knots.
South or North of that, anything goes, depending just on mood and sea conditions.

I know that there are boats where the AoA can be all over the place, from almost flat to being unable to see forward due to the bow pointing to the sky.
But that just doesn't happen, with any half decent flybridge boat.
If I should base my comments just on the experiences I made with a 72mph Fountain 27, I should suggest that also your high 20s cruise speed is way too low to be called a planing speed...

 

[Portofino]

@mapishm what "plane at any speed"
Swop plane for cruise and see .
I somehow don't think so

My first post clearly sets out what planning means .
Covers I think every aspect .

 

[Hooligan]

When I had a squadron 65 they did nothing. The 58 they make a difference. Porto I can cruise at any speed I wish. I have time to spare and me the boat and pax are all very happy at 18 kts

I think 18 knots is the perfect optimum speed on the s58 as a generalisation unless you intend to cruise at 10 knots where fuel usage is minimal and flaps irrelevant. The s58 has great flaps and full down in most seas except following or big nose on, increase speed and decrease fuel burn noticeably, at least for me.

 

[Hurricane]

On the P67 it settles comfortably at 24.5 knots.
Not 25 and not 24.
And 10 is a good displacement speed - just a bit faster than the theoretical max displacement speed and easier to calculate ETA etc.