Advice on balancing the boat please

[oGaryo]

I've noticed that increasingly the boat is listing at rest and becoming harder to handle when on the plane due to instability. When I say instability, I mean I am having to apply a good amount of trim tab to the starboard side to level the boat and she tends to react to wind and tide more adversely than last season where I have to apply steering correction or further trim (drive and / or tabs) correction to bring the boat under control after she 'digs in' at one side or the other when on the plane. I suspect this is due to the large amount of trim I am needing to apply to stbd when underway which makes the boat skittish.

It's probably due to adding a bunch of weight toward the bow of the boat this year resulting in the bow being significantly lower in the water and the list to starboard more pronounced e.g. a microwave oven has been added to the galley area along with other gear stored under the seating in the bow.

I've corrected this last weekend by moving as much gear aft and to port as I can and then 'installing' 3 bags of sand, one under the midships sleeping area on the port side and two within the port most compartment within the swim platform.

It's a little better on the plane and the boat is sitting higher at the bow and level (ish) in the water when not underway although I may have over compensated as it feels she's listing a little to port now when at displacement speed but weirdly, I have to apply a little stbd trim when on the plane still . All in all, she still doesn't feel quite right.

So, all that said, are there any other aspects I should be looking into? my props have been changed this year too (same spec though) so is that a factor to consider? If not, is there a more scientific method of balancing the boat? Have I installed the ballast in sensible places? will installing it at the far extremity of the boat (in the swim platform) cause instability issues? is it better to move further towards the midships adding to the bag that is already there?

hope you can help

cheers Gary

 

[rafiki_]

Gary, our Sunline had a slight list to stbd until I evened out the batteries, 3 per side. The additional 2 to port side of the port engine balanced the list. I think the stbd side galley was the culprit, fridge, microwave, hob, sink and cupboards. I don't think you want too much additional weight at the rear as it will will make your planing hump more pronounced, and she will possibly need a higher minimum planing speed too.

 

[[2068]]

Bags of lead shot are more effective (for a given volume) at trimming.
I wouldn't put any weight at the stern, as you'll need too much trim tab applied to correct, which will de-stabilise things.

I'd strip out the sand bags, and all the movable stuff, and start again.
Add a bit of lead shot or gravel underneath the midships berth, then put back the movable stuff, evenly.
Many S28's have a slight list to starboard anyway ... it's a feature, easily corrected with a degree or so of leg trim

.

 

[P4Paul]

if the skipper weighed the 13 stone he should do then I am sure it would be level...

Hope the final month of training goes well buddy but be careful cycling around in the crappy weather

 

[superheat6k]

Too many stops at the King & Queen I reckon ! I'll get my coat, but before I do ...

When say you trim to Stbd is this the stbd rocker pushing the port tab down, which lowers the stbd side, or the port rocker pushing the stbd tab down.

If the wind is abeam then the boat will tend to lean into it, as well as reacting to uneven loading of the boat.

Having more weight forward will tend to pull the bow down, making it harder to get on the plane, but will make it stay there, effectively doing some of the tabs work.

I wouldn't add weight as this will simply increase your displacement and fuel consumption.

Also are your trim gauges calibrated. If you are inadvertently over trimming perhaps more one leg than the other this could make the boat seem off balance and skittish, but I am no expert on outdrives - the devil's egg whiskers !

This might be of use ...

https://www.dropbox.com/s/ph4l9dzhag9d6tv/Bennett Trim Tabs OM.pdf?dl=0

 

[oGaryo]

if the skipper weighed the 13 stone he should do then I am sure it would be level...

Hope the final month of training goes well buddy but be careful cycling around in the crappy weather

thanks Paul

I've gone to the extent of writing up this thing and sticking it on the fridge to track progress.. it's the project manager in me, can't do anything without a plan to work against

 

[P4Paul]

thanks Paul

I've gone to the extent of writing up this thing and sticking it on the fridge to track progress.. it's the project manager in me, can't do anything without a plan to work against

Does Jamie also have one?

 

[oGaryo]

Too many stops at the King & Queen I reckon ! I'll get my coat, but before I do ...

When say you trim to Stbd is this the stbd rocker pushing the port tab down, which lowers the stbd side, or the port rocker pushing the stbd tab down.

If the wind is abeam then the boat will tend to lean into it, as well as reacting to uneven loading of the boat.

Having more weight forward will tend to pull the bow down, making it harder to get on the plane, but will make it stay there, effectively doing some of the tabs work.

I wouldn't add weight as this will simply increase your displacement and fuel consumption.

Also are your trim gauges calibrated. If you are inadvertently over trimming perhaps more one leg than the other this could make the boat seem off balance and skittish, but I am no expert on outdrives - the devil's egg whiskers !

This might be of use ...

https://www.dropbox.com/s/ph4l9dzhag9d6tv/Bennett%20Trim%20Tabs%20OM.pdf?dl=0

it's the stbd trim tab down Trev to bring that side of the boat up. both tab appeared to be fully up when she was lifted a couple of days ago so I don't think it's a calibration thing for the tabs and both legs appear to be level when fully down but you have got me thinking. the stbd goes to -4 when fully down and the port to -3 but I set them both to equal numbers when on the plane. I don't think it'll affect it that much but will look to getting them both to -4 when next down the boat adjusting the syncro in the engine bay to do so

 

[oGaryo]

Does Jamie also have one?

He's young, fit and cycles to work 10 miles a day so I think he's going to put me to shame

 

[oGaryo]

Gary, our Sunline had a slight list to stbd until I evened out the batteries, 3 per side. The additional 2 to port side of the port engine balanced the list. I think the stbd side galley was the culprit, fridge, microwave, hob, sink and cupboards. I don't think you want too much additional weight at the rear as it will will make your planing hump more pronounced, and she will possibly need a higher minimum planing speed too.

Thanks Paul, my thinking is that I've added weight to the bow which alters the balance from that which Sealine setup the boat so it made sense to me to balance that out with more weight to the rear of the boat to bring it back to the original setup. I don't think I've added so much that the bow is now higher then the norm when first launched but may be wrong

 

[oGaryo]

Bags of lead shot are more effective (for a given volume) at trimming.
I wouldn't put any weight at the stern, as you'll need too much trim tab applied to correct, which will de-stabilise things.

I'd strip out the sand bags, and all the movable stuff, and start again.
Add a bit of lead shot or gravel underneath the midships berth, then put back the movable stuff, evenly.
Many S28's have a slight list to starboard anyway ... it's a feature, easily corrected with a degree or so of leg trim

.

thanks David, lead shot is an expense too far so sand will have to do I'm afraid. I've taken everything I can of any significant weight and either positioned it to the port side or taken it off the boat altogether e.g. the 5 litre can of coolant is now in the garage and has been replaced by a 1 litre bottle.

The biggest constraint I have is trying to gauge whether the boat is level at the berth, the mooring lines affect the way the boat sits and when away from the berth, I can't see the waterline against the lines of the hull. i wonder if taking a spirit level with me when next out on a calm day is the answer

 

[SLC]

If you have an iPhone you can use that as a level, found in the compass app.

 

[rafiki_]

thanks David, lead shot is an expense too far so sand will have to do I'm afraid. I've taken everything I can of any significant weight and either positioned it to the port side or taken it off the boat altogether e.g. the 5 litre can of coolant is now in the garage and has been replaced by a 1 litre bottle.

The biggest constraint I have is trying to gauge whether the boat is level at the berth, the mooring lines affect the way the boat sits and when away from the berth, I can't see the waterline against the lines of the hull. i wonder if taking a spirit level with me when next out on a calm day is the answer

Gary, if you can't see it by line of sight, then it is not a significant list.

 

[LionsDen]

Gary - How much booze & sweets % have you on board in relationship to your overall boat build

 

[Spi D]

The boat berthed next to mine at the marina has it's water tank to one side, fuel tank to the other. Rarely sits level, simply an erorr by design. Guess that is not the case with yours?

Despite the double effect of moving weight (as in removing from one side and at the same time adding to the other), something sounds weird and I agree to the suggested 'strip out and start over'.
Normally planing boats avoid adding weight as it is a major factor in reducing mpg and speed. Has your top speed been affected?

Levels come in various designs, both apps and devices, designed for boats, RV's and caravans. Google 'clinometer' or 'inclinometer' or go for the traditional spirit type

 

[enterprise]

An easy way to check your trim/list is to look at the boats compass and how it sits at rest alongside and at anchor when away from the berth.

 

[STEVEDUNSTABLE]

Gary - How much booze & sweets % have you on board in relationship to your overall boat build

I have a "sweets removal service" if required. ...... "hazardous" sweets at extra cost .................... I,ll get me coat !

 

[Firefly625]

I have a "sweets removal service" if required. ...... "hazardous" sweets at extra cost .................... I,ll get me coat !

perhaps its the haphazard way the sweets are loaded...?

 

[omega2]

neutralise both trim tabs, bring both legs in, then try it, if she is bow down then trim the legs out equally until she is fairly flat to the water (best planing attitude), if you list then shift the passengers about, and when right nail them into position, the trim tabs only need come into play for sea conditions.

 

[Winchy51]

Gary. Am I right in thinking you have just fitted an automatic boat trim. I have read the position of the internal sensor and the calibration have to be spot on Do you have to re calibrate if you add weight to one side Somebody will have the answer to that one are both tabs working ok no fluid leak. A trim tab problem rather than a weight problem microwave etc. as already suggested if you add weight performance will suffer have you tried turning off trim tabs and trimming the boat using the legs only