The significance of trim

[Barry Oliver]

Hi all,

I've recently bought a new polycraft drifter 4.5m. I'm in the process of running it in and sorting out teething problems.

Certainly a learning process- I didn't know the live-bait tank drained into the hull- to me that's a stupid idea but seems not uncommon! Anyway, draining a tank full of water into the hull coincided with taking a mate for a spin up the Brisbane river.  I pooed my pants when getting up on plane the boat heeled significantly to the left. Didn't help with my mate saying 'seems like the hull (it has two skins) is full of water'. Anxiety kicked its ugly head my way.  I turned around and got back to the ramp and onto the trailer and sure enough more water came out the drain plug than I thought was in the bait tank but I expect that's what it was- it was here I found out the bait tank drained into the outer hull.  Anyway, back into the river and I still had a significant heeling problem when the boat got on plane. I did one run without my mate and it seemed better but I was anxiety ridden by then to be in a good mental state...:-)

The only thing I can think of is trimming the motor was the cause. I tried a bit to change trim but was pretty anxious so my trial was a bit chaotic. I'd put the boat in at Jindalee and the current was ripping out so just getting a new boat in and out in such an environment was a stressful challenge in itself!

Anyway I'm just posting here to see if those of you who are more experienced than me (mostly all of you I expect!) would agree that trim can have a significant impact on heeling. I've not experienced such a strong heeling effect on a tinny (my only other experience). And wondering if the polycraft is more sensitive to trim or is it similar to many other boats. I don't have the experience. I googled a bit and it might be the case,

I'll try and get out for more trials in the next few days. And let you know what I find. 

It certainly a heart pumping moment when a boat gets on plane and heels over, especially after having a jetski and know how easy they are to roll over!!!

In the meantime if anyone has any thoughts that would be good.

Cheers

Barry

 

 

 

 

 

[Jimmyjack]

The trim should only change the position of the prow v the stern Baz, not the line of the boat from left to right. That lean to port or starboard normally has something to do with the weight distribution in the hull. For example, if the fuel tank and the battery are on one side it can lead to a definite lean.

[Alex2505]

 

Hi Barry

Is it a centre console or side console?

 

Were is the live bait tank in the rear under the hatch?

 

my Drifter had a slight list to port the reason being the electric motor is mounted on that side.

 

 

 

 

 

 

[Junky]

First of all. Make sure the hull is 100% empty. 

 

 

Side to side listing can be weight, and wind, perhaps trim (rarely) .

Especially if you have a roof. The wind will cause you to ride on a lean. 

The wind is easy to identify. 

Change course. See if the problem goes away or changes sides etc. 

 

If it's leaning the same way all the time then perhaps you need to look at weight positioning as mentioned above. 

This is what I would think is the problem  provided your hull is completely empty of trapped water. 

 

Your trim is more used to adjust bow height (get more of the hull out of the water) when under way and allow you to achieve higher revs/speeds without adjusting the throttle. 

If the trim is right down then you can enhance prop torque but I wouldn't think so. 

Start off with the motor trimmed down. Once on the plain, start to trim the engine up. If you go to far the engine will cavitate (air around prop causing reduction in drive with significantly higher revs.

Don't be scared to adjust the trim on the move. 

 

 

[Barry Oliver]

Thanks all,

For those, like me, who are learners...'Listing' refers to a boat leaning off centre- left or right, due to something within the boat (like cargo distributed more to one side than the other). While 'Heeling' refers to a boat leaning off centre due to some external (like wind).

I found this link helpful (as well as all your comments)

https://www.boatingmag.com/how-to/tips-to-alleviate-lean-list-and-heel/

 

I also note that the electric motor is on the LHS along with the battery. Its a polycraft model with two consoles and so the captain console is on the RHS, which should offset the motor. The bait tank is on the LHS too but was empty when I experienced the List.

Anyway, until I get out and test the trim and weight distribution the discussion is academic but still useful for my learning.

Thanks again.

[Hweebe]

How big is your electric battery? How much does it weigh? Where it the boats starter battery positioned?

I don't think the engine trim would do this and sounds like weight distribution (since it was better with the mate not in the boat)

Which side does it heel to, was this the same heading out and back in to the ramp

[GregOug]

If you bought it new, which you apparently have, you should ask the dealer to look into it. Did he rig it out? He should have done a water test and should have taken you for a run in it prior to handover. 

[Barry Oliver]

Hi all,

The plot thickens!

Today I removed the electric trolling motor from the front and lifted up the large transducer (I thought that may have been acted like a trim tab as it was on the rear RHS).

Alas, as some of you have already alluded to- these things weren't the cause of the port side heel.

The test I did this morning was in calm water, multiple directions, multiple speeds and using a level to measure the heel/list. This is what I found.

The boat was quite level when stopped. The Level was zero. As speed increased it stayed level until about 33kph when it began to heel. Top speed was about 46kph. It had heeled to port about 5-8 degrees. Reducing speed didn't make much difference until I got below 33kph when the level returned to zero.  The boat came onto plane about 22kph. Coming onto plane didn't seem to cause any heel.  As soon as I got to about 33kph it would heel to about 5-8 degrees and basically remain there as speed went to maximum. I didn't try it with the elect motor installed but that's only going to make it worse if anything. I did the test going upriver and down river on multiple runs. It was very calm with an outgoing tide.

Trim did not make any noticeable difference (as I had thought previously). It may have been that previously as the motor was trimmed out it increased speed and I thought trim was the cause. Today I kept all variables constant, except speed and the heel was remarkably persistent above about 33kph. It may have increased a little from 33kph to 46kph but the level never went above about 8 degrees and variable between 5 and 8.

What was also interesting was that below 33kph the level was remarkably stable around zero.

I can't do anything else and have no idea what might be causing it. I guess there are only two things left- the motor/propeller and the hull. 

Emails have gone to Brisbane Yamaha and Polycraft.

As I mentioned in the email to them, its very disappointing as apart from this problem and another minor one, I really like the boat.

Brisbane Yamaha have replied saying they've forwarded my email to their workshop and will get back to me.

I expect they will need the boat returned.

Anyway, that's where things are currently at and since we are in lockdown here in Brissy now, there's nothing else I can do. 

 

cheers

b

 

 

[ellicat]

This is very intriguing. I hope you can get an answer and get the problem rectified.

[GregOug]

I would say it has to be water related. Something of weight is moving around, and I can’t think of anything else it could be. Without knowing the design of the boat, I would hazard a guess that there’s water in the hull and it’s moving forwards and backwards as you increase speed and decrease speed. However, there’s probably a blockage in one of the central sidewards drain holes at either the aft or the stern, so that when the water runs either forward or backwards, it can’t equalise side to side and level the boat, but once it runs back it can once again equalise. Just an idea.

[Angry51]

or the keel's not square/ inline/ to the hull.

Just a thought.

[Tracker]

have a look under the hull ,you may have some hook near the stern.

[Neil Stratford]

Sounds like prop torque , trim it up before you hit warp speed. Try putting some more weight down each of the rear sides.

regards

neil

[Drop Bear]

if the trim was way out it will lean to one side. 

[Kenne]

I have a 4.2 runabout with a 40 H Mercury 2stroke. I've found at times it will lean over to port side at times but over come it with the trim. Some days does it some days don't. Has never done it off shore tho only going in the broad water or rivers. Can do 30knts/55ks without leaning but at times it does. I put it down to a combination of weather conditions, tide, prop torq ,trim and how you drive to those conditions.

[Drop Bear]

9 hours ago, Kenne said:

I have a 4.2 runabout with a 40 H Mercury 2stroke. I've found at times it will lean over to port side at times but over come it with the trim. Some days does it some days don't. Has never done it off shore tho only going in the broad water or rivers. Can do 30knts/55ks without leaning but at times it does. I put it down to a combination of weather conditions, tide, prop torq ,trim and how you drive to those conditions.

Yep I have experienced this as well. 

I also think wind is a big factor in this as if you have a wind on your beam, you will need to turn into the wind to keep the boat traveling straight. This effectively means the boat is turning, to keep straight and is why I think boats lean into the wind. 

One day, I shouldn't have been out there, I was heading to Green Island in 25 knots in a 4.2m tinny. it happened 3 times... Im a slow learner. I was just off the plain and as I went over a large lump the wind span the boat around nearly 180o... Thankfully I made it. I did have a life jacket on and had the EPIRB in my hand. 

[shakey55]

I can’t see what motor you are using. Has anyone considered the TRIM TAB

 

https://continuouswave.com/ubb/Forum1/HTML/021079.html

[Ed.]

Not all motors have that trim tab on the leg, I know my 2013 Optimax 150 doesn't and can't remember seeing it on the 2005 Evinrude 225 I used to have either. They are now just flat flush anodes, it might only be on some motors.

[Kenne]

Another strange thing is that it only happens when the missus is in the boat.

Only saying

[dmck]

14 minutes ago, Kenne said:

Another strange thing is that it only happens when the missus is in the boat.

Only saying

OHhhhhh Kenne...........   I trust your health insurance has maximum coverage and is up to date.  

Yer a BRAVE man........

[Barry Oliver]

Hi guys,

Thanks for all the thoughts, although I suggested the 'missus' issue to her and I'm now writing this from my hospital bed...;-)....I don't think that was so helpful...:-)

I did the testing both up and down the river in very calm conditions to exclude water/environment.

The motor is a new 60hp Yamaha. It does have a sacrificial trim tab which is offset to the RHS about 8 degrees- this is the recommended setting afaik. Also afaik the trim tab impacts the steering rather than any list/heel.

I undid the bungs after the test and there was no water in hulls.

I've heard back from Brisbane Yamaha and they want the boat back to do their own tests- bring on the unlockdown....given the boat is new not much I want to fiddle with. Anyway will let you all know one day...

[Junky]

Watching with interest. 

I going to have a stab at prop torque.