getting onto the plane

[johnchristie]

I've seen a few posts which talk about getting the boat on the plane for optimal performance, both speed and fuel economy.

the posts suggest to get on the plane you tuck the drive legs in using the power trim to bring the bow down and by doing this it uses the V of the hull to cut through the water and then you trim out as you pick up speed which raises the bow.

Is that correct because when I tried it in the solent today after my PB2 course (albeit it was choppy) I noticed the revs dropped when I trimmed out from -2 to +2 and the only way to maintain speed was to leave it on 0

We didn't really change the power trim on the instructors boat, he just had the trim set to +2 which raised the bow.

 

[whisper]

Hi and a belated welcome.
We actually don't bother to use the leg trim to assist in getting on the plane, we use our trim tabs instead.
It sounds to me that in your case you've either got an engine with borderline power or possibly have too much weight in the bow.
Using our tabs to drop the nose a bit and adding in the power, lifts the boat nicely out of semi-displacement into planing mode. We then bring the tabs back up and our leg will have remained in the 0 to -2 range depending on the sea state. We will raise this perhaps as far up as +2 in flat water when we are well on the plane and are fine tuning the most efficient angle of attack/comfort level etc.
What boat do you have?

 

[epervier]

As whisper asks, what boat do you have? The more info you give the better answers you'll get back from those with same or similar boats with their experience.

Boat, engine type and size, legs VP dp, Merc alpha, etc.

 

[johnchristie]

its a 2005 sealine s25 with a single diesel volvo penta engine. It was owned by a couple on the broads so it's never been opened up at sea until recently. She handles completely different to the rib I did my rya powerboat 2 course on over the past two days.

 

[Solitaire]

its a 2005 sealine s25 with a single diesel volvo penta engine. It was owned by a couple on the broads so it's never been opened up at sea until recently. She handles completely different to the rib I did my rya powerboat 2 course on over the past two days.

It would do. May I ask why you didn't do the course on your own boat? What you have and doing the course on a rib (what size was the rib) would be very different. Not least becuase of the effects of the wind on the S25.

I always recommend doing the course on your own boat. It is after all what you are going to use!

 

[Spi D]

It is no wonder that an S25 performs differently than a RIB. All boat models have their own best practise and multiplied by the ways they are used, advice can only be accurate if based on as much info as you can get.

As epervier suggests please tell:
What diesel engine do you have? If it is a Volvo KAD32 you should have 2.4 litre and 170 hp.
What drive is fitted (gear ratio)? DP-S and 1.95?
What propeller (pitch) is fitted?
What is the boat's total weight - including all and every bit & person? May weigh some 2690 kgs dry so that should be your starting point for adding...

 

[Kawasaki]

its a 2005 sealine s25 with a volvo penta engine. It was owned by a couple on the broads so it's never been opened up at sea until recently. She handles completely different to the rib I did my rya powerboat 2 course on over the past two days.

To get on 'The Plane'
Always best to to to Port and get into First Class
Sorry couldn't resist
However
Yes. it will handle slightly differently to the R.I.B you did your PB2 on
The 'principles'. are the same though.
To get on the plane you ask
Keep the 'leg/ outdrive' trimmed in
Hit the throttle
Don't be tentative
Full hit on the throttle
The boat will 'chase off' them you can back off a little
Don't back off too quickly
Minute throttle movements are the best way
When She is planing (which will begin at about 16/18 kts ish) just get Her steady and try a small amount of leg trim 'out' -- not much, about 1 or 2 seconds of trim will suffice.
Getting used to 'trim' needs to be done best on flat water, so you can see how the hull reacts
Trying to experiment in a chop with a boat yer aint used to will only confuse
So
Trim in, and 'Hit It'!
Tabs can be used to help
Especially on a 25 footer if peeps move about
Some may
Like whisper says
You need to leave the 'leg' trimmed in
Just use the trim tabs to adjust the ride accordingly
Thing is, the boaty world has no 'definitive' answer ref each mobo
Smallish planing mobos with outdrives and to a certain extent with outboards are quirkey in their own right
Propeller pitch and diameter will also affect the vessel's performance.
Maybe if the boat has been use on the Broads the it may not be 'prpped' correctly for planing use?
You mention She handles differently to the rib you did your PB2 on
She may
The Principals are the same however, as said
'Steer and Gear ' etc etc
For close quarters manouverin or all slow bits
'Hit it' to get on the Plane and then back off for an easy ride and deploy a bit of trim or tabs
Some peeps make the mistake of 'Trimming' whilst 'Getting Up There' ie buggerin the boats handling, before they are planing

 

[johnchristie]

cheaper to do it on one of their ribs than my own boat. It was almost double. Probably would have been better doing it on my own boat but with buying a chartplotter, vhf, safety gear, ropes, fenders it all adds up and I had a budget to work with. Course was good, won't knock it.

 

[epervier]

its a 2005 sealine s25 with a single diesel volvo penta engine. It was owned by a couple on the broads so it's never been opened up at sea until recently. She handles completely different to the rib I did my rya powerboat 2 course on over the past two days.

Ah yes, lots of people I know are PB2 qualified and did it on a 4.5mtr rib with outboard power, then go and buy a twin engined cruiser and are shocked at the difference in boat behaviour, don't try and use the ribs settings to yours, the only thing they have in common is that they both float, after that they are two different animals, that aside, I would unload the boat of all the extra stuff that we all put into our boats, fill the tanks water and fuel,put the tabs to neutral set the legs to max in, get the boat up on the plane see if she rides level, if not adjust tabs to rectify.

Then trim out leg while watching rpm and leg indicator when you reach optimum performance log it into your on board human interface, and remember it, Then you have to learn when you can tab more to make the ride comfortable in lumpy conditions, less when flat conditions, with more experience you'll probably find that with more people/load, the leg trim will stay hard in to be able to get out of the hole shot and stay there, and so on, experience is the only way you're going to find the fine tuning of the set up for your boat, experience is only got by using your boat. I've only touched on a little of what you need to learn. best of luck and first and foremost, enjoy your boat.

All of course is only IMHO

 

[Csail]

This is same as mine and how we do it.
http://www.youtube.com/watch?v=af4tPoGgFGM

 

[Solitaire]

cheaper to do it on one of their ribs than my own boat. It was almost double. Probably would have been better doing it on my own boat but with buying a chartplotter, vhf, safety gear, ropes, fenders it all adds up and I had a budget to work with. Course was good, won't knock it.

Not suggesting the course was not good, but you are using a very different boat to doing a PB2 on a rib! All you have is a PB2 certificate - you now have to learn to drive your boat.
Others are giving you all sorts of advise about tabs and trim, I'm not going to add to it, but I have taught on more S25's than most.

You don't say if the boat is powered by KAD 32 or D3. I suspect that given the age is the last of the KAD 32 or earlier D3 which had problems with power and the boat in fact did struggle to get on the plane. There is loads of advice about trimming the legs to +2 and using the trim gauge - fine, but things are different every time and will vary by sea state and the number of people onboard. Don't get into boating by numbers, do it by feel.

The boat is very sensitive to the use of the trim tabs, so only use them a bit at a time other wise you can feel the boat heal over and it will scare the what's it out of you and all aboard. You will not have used trim tabs on the course as most ribs don't have them, certainly not on a rib used for PB2 training.

The S25 is also susceptible to wind on the bow and if you are not careful you will end up going sideways and you won't know why!

Get out and use the boat, and get real understanding of how it works - but don't rely on the PB2 giving you the answers based on being taught on a rib.

 

[Scubadoo]

Not going to add much as all the others have covered it, however I have a S24 which is an earlier model to the S25. Mine has a AD31 150hp and when fully loaded from full water/fuel tank, holiday gear, people etc, it is then feeling slightly underpowered. To get it on the plane I have to on some occansions use the trim tabs down with the leg pulled in. Planing on mine is around 13/14 knots.

I do mine all by feel based on the conditions which are never the same and not by the numbers game (gauges).

 

[duncan]

the posts suggest to get on the plane you tuck the drive legs in using the power trim to bring the bow down and by doing this it uses the V of the hull to cut through the water and then you trim out as you pick up speed which raises the bow.

Is that correct because when I tried it in the solent today after my PB2 course (albeit it was choppy) I noticed the revs dropped when I trimmed out from -2 to +2 and the only way to maintain speed was to leave it on 0

John

I quote these comments because when considering what you need to be thinking about the why in order to understand what you should actually be doing!

1. You trim the legs fully in so that the drive from the legs doesn't act to simply raise the bow initially from the hydrodynamic lift as you accelerate. You want the drive/force acting to accelerate and push you forwards over the bow wave onto the plane.
2. When you are fully on the plane, about 14 knots on your boat, if you left the legs fully down you would no longer have the drive pushing you forwards as the stern will have lift and the bows will now be unsuppported as you continue to accelerate, and you will be pushing them into the water rather than forwards (this can be useful at slower planning speeds into a head sea, or dangerous at higher speeds with a following sea...). So you trim the drives out to achieve the right balance - this balance for a single prop single engine boat will also include steering balance from a propeller rotating at anything other than 90 degrees to the water surface. You maximum trim up should be limited to that necessary to correctly trim the boat at max speed in perfect conditions - for some boats they remain sensitive to trim through a wide range of speeds - for others it's more of a binary thing with trimmed in up to about 14 knots and out above this.

Finally you shouldn't need to trim in before accelerating onto the plane as it should already be there....it becomes a habit to trim back in as you deaccelerate over time

 

[U4]

FWIW I always have the legs on my boat all the way in as no matter what speed I am cruising at, the speed drops as soon as I trim them out...

Is that wrong?

 

[Spi D]

Well, something is.

Please tell

-your rpm at Wide Open Throttle (WOT)
-if your rpm go up when the speed drops
-if your prop is damaged
-your boat's total weight and -distribution?
-your engines' hp?
-if your hull is clean?

 

[duncan]

FWIW I always have the legs on my boat all the way in as no matter what speed I am cruising at, the speed drops as soon as I trim them out...

Is that wrong?

Well there are certainly some (generally) larger, heavier craft where they sit at the same attitude through the rev range quite consistently - and the need for leg trim isn't there.

However, I agree with Spi that something isn't right if you always get a reduction in speed if you make the slightest move to trim out at any (planning) speed. The obvious implication is that you might even gain if you could trim in further!

What's the boat?

OK - Sealine SC29? I'm not surprised that it requires little in the way of trim as it's a beautifully balanced boat/hull but I am surprised that it doesn't benefit at all; back to the implication above. There should certainly be a difference with, and without, your tender on weaver davits for example.

 

[U4]

This has actually got me thinking and I as I am planning a few days afloat next week I am going to conduct some tests...

 

[Spi D]

One thing to look for is the props 'grip'. If a prop is not in order or of an unsuitable type/design, it simply draws air (ventilate) or cavitate when should generate thrust.

If the problem gets worse while turning the props are definately up for closer inspection.

 

[johnchristie]

thanks..... im at the boat this weekend so will get some practice in the solent at somr point.

 

[johnchristie]

so much for giving it a try today, arrived at teh boat this morning and the EVC says 'electrical problem - call Volvo dealer for service'. Seems its a common occurance on S25 with EVC and D3 - 190