Capsizing Tinny

[Glen_1981]

Hi,

I have recently just bought my first tinny. A brooker 4.10 fisherman with 30HP tiller steer. I have driven a number of tinnies around the estuaries before with no problem. However, I went out in the new boat with two mates (one sittling on the rear bench seat with me and one up the front) when travelling along, if the person up the front shifts or moves the boat goes bloody close to capsizing. Even the waves from passing boats will make the steering jump and the boat unstable. I was wondering if anyone has experienced similar instability. It just seems way to touchy.

[finga]

Gidday Glen and welcome matey :)
What a bugger eh!!
Can you put a picture of your motor setup on here??
Has the 'new' boat got a foil thingo/gismo on the motor??
I have a funny feeling the motor is too low and it has a foil upsetting the applecart.
Just a feeling....nothing more until some more details.
Cheers Scott :)

[blaze]

wrong trim angle would also have a bearing, but like Finga, more info and pics would be good
cheers
blaze

[bootyinblue]

I am tipping like the 4000 before this one, that the motor has a foil/planing plate thing on it!

They serious have very positive but also very negative attributes.

Will be keen to see...

[Hamish73]

My 3.7 has similar attributes, it has a 15 on it.
At 12-14 knots all is well, but when she really gets up and boogies (18-19knots) the nose drops down and that is when she starts to get sensative. I think the correct name is 'broaching' Especially bad if you have the swell on your rear quarter. I have tried trimming the motor up one notch at a time, but t doesnt seem to get any better, then it wtarts cavitating so I ended up back at hole 3.
I know SFA about boats, but a few people have commented that the hull shape will cause this kind of performance.
Mine will also tip violently if someone moves around too much.

[finga]

Might as well bung some pictures on too then Hamish.

[Hamish73]

Might as well bung some pictures on too then Hamish.
ok, I'll post links as not to take up 1/2 the page
http://i97.photobucket.com/albums/l204/hamish73/Boating/tinny001Large.jpg

http://i97.photobucket.com/albums/l204/hamish73/Boating/Tinny004Medium.jpg

http://i97.photobucket.com/albums/l204/hamish73/Boating/Tinny002Medium.jpg

[finga]

ok, I'll post links as not to take up 1/2 the page
http://i97.photobucket.com/albums/l204/hamish73/Boating/tinny001Large.jpg

http://i97.photobucket.com/albums/l204/hamish73/Boating/Tinny004Medium.jpg

http://i97.photobucket.com/albums/l204/hamish73/Boating/Tinny002Medium.jpg
Can you get a picture looking from behind the motor (motor down) looking directly towards the stem and inline with the keel line??

[Hamish73]

Can you get a picture looking from behind the motor (motor down) looking directly towards the stem and inline with the keel line??
sure, thanks for your help. Any advice appreciated. never really looked at it because I've always blamed the hull. Guess the motor maybe needs to be raised and trimmed down further?
My theory was trim it up to try and hold the nose up, but that didnt really work :-[ trim it up any further and it cavitates
http://i97.photobucket.com/albums/l204/hamish73/Boating/Tinny006Medium.jpg
http://i97.photobucket.com/albums/l204/hamish73/Boating/Tinny010Medium.jpg
http://i97.photobucket.com/albums/l204/hamish73/Boating/Tinny011Medium.jpg

[finga]

Hamish, mate try raising the motor about 2 inches for now and then trim in.
You'll probably find that you tinny will work better with the cav. plate between 1 and 2 inches above the bottom of the hull.

[Chimo]

Hamish

Going on your last photos I'd be inclined to lift the motor maybe an inch, from the photos it does look to be a bit low.

Also if it were me I'd be putting a foil on it. I have found that on the 3.7 and 3 m tinnys of this shape the foil does take the instability out of the hull when it moves over a wave and also when you move the tiller.

Also on boats of that shape, from experience, I found the centre pin position to be OK for most uses and one firther out if you want the nose up and wish to go faster.

The amount of weight and having it well positioned will make a big diference too.

Hows it going otherwise? Getting a few fish?

Cheers
Chimo

[Hamish73]

thanks guys, I'll try it for this weekend. ;D Will this stop the nose riding so low?
Would be nice to stay a tad dryer.

Chimo, had a few cracks along the chimes (caused by floor flex) , welded them up but still leaks a tad, needs another weld. She is definately isnt built like my old 3M that u have. Have got quite few small fish, just got a new placcie setup for myself on Wanda, so its a bit of a learning curve.

[Hamish73]

Does this look better? I trimmed it back one notch aswell.

http://i97.photobucket.com/albums/l204/hamish73/Boating/Tinny2010Medium.jpg
http://i97.photobucket.com/albums/l204/hamish73/Boating/Tinny2008Medium.jpg

[finga]

Getting better.

Personally, I'd be going another inch up.

I'm sure it's been said before but the ideal height is when the cav. plate is fractionally (2mm or so) above the water level when your hooning across the water. Not below.

This in itself may create a problem....how do you hold the motor on if you take it up another inch?? ie 2 inches from standard.
I had to weld a 2 inch infill in my Edgetracker transom to get the heights right.

[Hamish73]

I'll give it a try as is and report back. As you mentioned, the engine mounting will become a challenge shortly.
Thanks again, and sorry Glen for stealing your thread, but there may be some good info for you here too.

[Hamish73]

stability at speed it no better, WOT heading with the wind it cavitates quite badly, but not into the breeze or dead flat. It must be dropping the nose over the waves (very small waves I might add) and lifting the stern fractionally.

[finga]

Did you happen to notice where the cav. plate was sitting in relation to the water??

[Hamish73]

Did you happen to notice where the cav. plate was sitting in relation to the water??
It's till under the water. Lifting it firther could only make the cavitation problem worse wouldnt it?
Boat seems to fire out the hole a lot better, but is definately 'looser' in the rear end. Might go back to previous setting. Strange how the nose rides so low, will have to get someone to take some pics of it in action and show you. 15knots it sits ok, but get up to 18 and its not happy, nose dropys and becomes very touchy to steer.

[finga]

It's till under the water. Lifting it firther could only make the cavitation problem worse wouldnt it?

Nope, It can greatly improve that problem.
You may be getting turbulence from having the motor too low still.

[blaze]

I wonder how many of these type of problems are made worse by inexperienced boat owners with higher expectations of what a given size boat is safely able to do. A trend I have noticed over time without many hull shape changes is the fitting of higher hp motors. Go back 20 years and the average guy with a 12 foot tinnie had it fitted with a 6 - 9.9 hp motor, I for one has now fitted an 18hp to 20 year old brooker hull. The same boat performed ok with a 9.9 johno and 2 people onboard. Now I must say I am extremely pleased with the added perfermance but I have owned many boats over the last 35 odd years and would consider my self experienced, but the same combanation in the hands of an inexperenced operator would be pertentioally deadly.
just some early morning ramblings
cheers
blaze

[kingtin]

Interesting thread, particularly Blaze's last comment. Do we expect too much or are we simply inexperienced?

I for one, don't feel entirely happy with the handling of my 3.95 stacer and 25 merc.

It came with a 15 as standard but I just had to go one better now didn't I? ::)

I researched the hulls and stacer came out tops for ride although somewhat down in stability at anchor. That said, I expected a better ride, but unfortunately, I don't feel entirely safe when running at speed, particularly with a cross wind. That said, she cuts through the chop better than any tinny I've driven before.

I've watched her on the water and she seems to sit ok.......... cavitation plate is where it should be, but she seems very "light" at speed, despite the steering feeling heavy. The slightest gust of wind and her nose sways from side to side and on some occasions lifts right up. If I back off the revs, she settles down ok. Having been thrown out of her once, I suppose I may just be a little touchy. Do you think that I am simply running her too fast and should settle for that "sweet spot" and accept that I've overpowered her? Am I expecting too much from a small craft based on my handling of larger?

Sorry to hijack the thread but I think Blaze's point may be quite relevant, particularly in my case.

kev

[finga]

Yep, Blaze's and Kev's points are very relevant.
My little 3.7 tinny had a 25hp on her first up. Really quick in good conditions...deadly in any other conditions.
Grossly overpowered.
Funnily enough the same 25hp motor on my little 3.7m glass boat is a totally different kettle of fish.
The glass and tinny have the same top end performance with the 25hp but the little glass boat is in another class when handling is concerned.
I now have a 15hp Honda on the tinny and I couldn't be happier.

It takes a lot to get a boat set up correctly.

A little boat seems to take more to set up then a larger boat. Mainly due to the power trim most bigger motors have on them and the speed in which a tiller can go from lock to lock in the steering compared to a boat with forward controls. It takes time for a forward control to go from lock to lock and with a tiller it's nearly instantaneous. (Just watch the rubber ducky's race and see how they turn)

I've spent many, many hours just trying something else to try and get the tinny to go well and be less of a handfull.
Maybe I have too much time on my hands but it's a pleasure for myself or anybody else to grab the tinny and have a safe, low stress fishing trip.

Don't forget to set the tinny up with everything you tend to take fishing as the balance/performance/handling is easily upset.
For me, if I take 1 extra person all the time spent setting the tinny up turns to poo.
Then I wished I still had the 25 on it.

Another point Blaze made is also very valid. Experience. Got to crawl before you can walk. :)

[Hamish73]

There is no doubt that I am inexperienced, bought my first boat about 2 months ago. My complaints, if you call them that, are related to how this boat handles compared to my first boat (a 3m stessl) and other boats I have seen on the water. Most other similar sized boats , when scooting along at high speed, sit with their first 1/4 out of the water shipping over small waves, where as mine is more of a nose down style, deflecting when the nose ploughs into the wave.

We are planning on getting a bigger boat soon so I'm not concerned if I cant 'fix' it, but I was intrested to see if there was some settings that could improve it, or if it was just the nature of the beast.

[finga]

Try trimming the motor out a hole to raise the front as well as raising the motor.

[Chimo]

Hi Hamish

When you are describing the boats behaviour are you talking about having the three of you in it with an estimated weight of what say about 250kg or just yourself at about 110? With all of you on board you are looking at smooth water only I hope?

Because of the shape of boat ie narrow bow section there is not a great deal of weight carrying capacity right up the front. It will push thru water well with that style of bow. Remember the boat did have a 9.9 Mariner with a foil and it went well if not slower with thre people in it on smooth water.
Have you tried two in the middle and on in the back? You may get better performance and ride that way esp with the 15 HP you have on the boat.

Having the motor up an inch is probably enough and while you fiddle with load trimming it may be worthwhile to put the motor into its central position

You may also get a satisfacory outcome if you operate at 1/2 to 2/3rd throttle rather than flat out. The last couple of knots are probably where the most accidents happen in all small boats.

Good luck with your adjustments and given the size of your family a larger boat will certainly get you out to more places. There is a great low priced soft riding Al 5 m machine on the market not that far from you I'd look at if I was in the market for another machine. The 15 would make a good auxillary and trolling motor on it to and the 3.7 can be the tender!

Cheers
Chimo

[Hamish73]

Chimo,
I do 'testing' by myself. When we all go out together it's me down the back and the mrs and kid up the front. Suprisingly, the ride and handling is similar with 1 or 3 of us in there.
When I say 'small wave' I really mean ripple, 6" or so. Anything bigger than that and it's down to sub-planing spped.

[Luc]

In my boat's case, I have to agree with Chimo's lines
"You may also get a satisfacory outcome if you operate at 1/2 to 2/3rd throttle rather than flat out. The last couple of knots are probably where the most accidents happen in all small boats."

My tinny is a 4M Seajay pointy punt with a 25/4 Yammy. Other than flat or almost flat water with just me or plus 1 or 2 crew, there's no point going past 2/3 to 3/4 throttle.

Sure, at full bore I get a couple of extra knots but the boat becomes really twitchy and I have to be really attentive to the handling. A little bit slower makes the ride more pleasant and relaxing.

The electric trim N tilt makes it easy to find the sweet spot depending on speed & weight.

Luc