PDA

View Full Version : Causes & remedies for broaching.



rando
28-11-2009, 04:56 PM
Gday Ausfishers
Coming home from offshore last trip I had a 1.5-2m (maybe more) following see & the 4.5m Clark abalone cc was showing a tendency to broach .
I was hurrying a bit as the swell was building,,, power-plant is a 40 horse 2 stroke, fitted with a foil. I was solo.
The first one caught me by surprise as I had not experienced it before, then i realized what had happened and throttled back a bit. But copped another one before I was back in safer water.
I reasoned that too much throttle is a factor, what else comes into play in these conditions.


What causes the broach,? what are the remedies,? is the foil a contributer? what do i need to do to prevent it happening again,,,, engine trim? weight distribution?
all help gratefully received.

Thanks in advance.

Rob

frankgrimes
28-11-2009, 05:55 PM
Hi Rob,

Trim out to keep the nose up in following sea, and shift some weight to the stern, also be ready on the throttle(More power to gain control over rudder/steering)

Mick

Mister
28-11-2009, 08:27 PM
Cause of broach? Being in a 2m sea in a 4.5 m Clark abalone (what was you thinking?)

Remedies? 4.5m clark abalone's don't like such conditions, best to stay home in such conditions

Easily preventable? Don't go offshore in a 4.5m clark abalone (what was you thinking?)

What else comes into play? best not say :)

rando
29-11-2009, 02:19 AM
G,day Mister
Where I fish, it is only a short trip (couple of ks) to get to some good offshore grounds. With a 2m swell, conditions are not too uncomfortable as the water is pretty deep 30-50m and the swells are long . Well within the capabilities of my vessel. Coming back in is the only problem , as the swell stacks up a bit on the shallower ground, just requires a bit of care and attention really. The entrance is quite wide and deep .
I just ride the back of a swell till I,m inside the reef .
but thanks for the cautionary words,nice to see fishermen looking out for each other.
Cheers
Rob

Vitamin Sea
29-11-2009, 08:11 AM
Hi Rando

As has already been said, you want weight at the back of the boat and as much nose high attitude as you can get without cavitating, but, some boats do have a tendency to broach regardless.

Coming back in is the only problem , as the swell stacks up a bit on the shallower ground, just requires a bit of care and attention really.

This statement does concern me a little though, you should not really put yourself in a situation where anything is knowingly going to be a "problem"

Cheers

VS

deckie
29-11-2009, 08:13 AM
G,day Mister
Where I fish, it is only a short trip (couple of ks) to get to some good offshore grounds. With a 2m swell, conditions are not too uncomfortable as the water is pretty deep 30-50m and the swells are long . Well within the capabilities of my vessel. Coming back in is the only problem , as the swell stacks up a bit on the shallower ground, just requires a bit of care and attention really. The entrance is quite wide and deep .
I just ride the back of a swell till I,m inside the reef .
but thanks for the cautionary words,nice to see fishermen looking out for each other.
Cheers
Rob

You're actually saying it ISNT well within the capabilities of your boat at all...most boats can go into a sea but the real test is with your back to it or rear qtr to it. THAT is what separates a boat from being capable or not...not whether u can skip over chop on the way out.

There are plenty of craft around 4.7-5m which take a small following sea reasonably... some good old hulls and some good new ones...but i doubt any boat under 7-8m would feel safe(ish) in the conditions u describe. Just shouldnt be in that situation...and whilst you are only a cpl of k's from safety that has obviously sponsored u into feeling its a quick run out of trouble.

Best advice is to watch the weather more coz from my experience it at least takes awhile for a 2m+ groundswell to build and you get some warning...or if its tidal influenced and your problem was run out tide on incoming breeze then it is a shorter sharper sea and more understandable that u got caught out... but u still need to know the area and EXPECT it.

If its only a "cpl of k's" as u describe then u either got warning of it and chose to ignore it for awhile or u put to sea in ultra borderline conditions for a tinnie in the first place.

My first thought would be lifejackets for yourself and anyone else just in case...followed by trimming the nose up and trying to ride the backs of them using the throttle..not easy on a 40hp tinnie coz u dont have either weight, power or cut into the water at the back to stabilze you as u come down the face. Lower the centre of gravity by getting rods out of rocket lauchers, dropping bimini's etc. Dont ever just head in the direction that causes broaching simply coz its as the crow flies to saftey...even when its only 2-3k's, plan the way home with the safest way to get there that doesnt compromise safety... coz only you know the feel of the boat with heavy water behind you.

I'd also scan the area and look for anyone else about coming in ...maybe tread water if u have to for a short while into the sea so that u can cover the distance with someone else riding shotgun in that sort of sea in a tinnie.

Robbo76
29-11-2009, 09:11 AM
Yeah, we had a 4.5 Quintrex (fishraider), it too hated following sea. I guess shallowish v and a pretty flat bottom is not ment for following sea or rough sea. As mentioned previously, trim out, nose up. Not too much as you can lose steering all together. We had a 60 on it, so power was ok to ride swell/slop. This worked for us, but I couldn't do it anymore, no one wanted to go out in it.

Our solution. Sold it and bought something a bit bigger and safer.;D

Stay safe,
Rob

Flex
29-11-2009, 09:14 AM
As mentioned above, broaching is caused from the front of the boat steering, not from the outboard.

Generally, its weight distribution. but not always.

My old man had a 4m tinny that would broach in a bathtub!. so we cut about 2 foot off his keel (ground it back to flush with the hull) and the boat was brilliant after that.

but check you weight, get the nose up. also foils force your nose down and can cause broaching. Do you really need it?

Jarrah Jack
29-11-2009, 09:14 AM
An interesting thread. My broaching experiences come from sailing days but the dynamics of what is happening to the hull is pretty much the same, you lose steering control and the stern wants to go faster than the bow. A bit like a spin out in a car

I think that you have just given yourself a good reason to get another boat if you want to keep fishing out there with some safety margin as all the best advice on steering etc is not going to stop that flat bottomed boat from wanting to broach.

If you ever get caught in the same conditions again there are two other things you should do that have not been mentioned. One is put on a life jacket and two is either radio or ring someone and let them know the time frame of return so they can organise help if need be.

Bros
29-11-2009, 10:46 AM
There's not a lot you can do as the design is the main cause of broaching. Look a large ships and yacht's they present a small area to the rear which stops the following sea from accelerating the boat.
All tinnies present the largest area to the following sea and in the right conditions broaching is inevitable.
I owned a 11m trawler type boat and it had a tendency to broach in a following sea caused by runout tide into a wind so I avoided those conditions. It wasn't dangerous but to keep it on course was a lot of work but it only occurred in river mouths. I've never been over bars but it would have been pig to handle. It used to veer off course a little at sea but used to come back on its own as the waves and swell were further apart.

Not a nice feeling is it to not have control.

Corsie
29-11-2009, 11:05 AM
This is my first post, and this thread is of great interest to me. Rando, I too have a 4.5 metre tinny – a Brooker – and I have also experienced broaching.
Any boat is a compromise, so purchase cost, how the boat will be used, running costs, etc need to be taken into account. I find my side console brilliant for throwing lures and bait fishing in lakes, rivers and bays, as well as venturing outside on a good day. It is extremely economical and easy to tow with a 4 cylinder car.
I live a couple of hours from the coast, so I rely heavily on the BOM Coastal Weather Forecast, and on occasions it is a bit rougher than predicted. The combination of a metre or so of sea plus a metre or more of swell causes the biggest issues, as it becomes a bit difficult to tell – due to the randomness of the seas – when you are starting to overtake a wave, or falling off the back of it.
I am aware of the remedies of weight to the rear, staying on the back of the wave and bow up, but of interest in the replies are the factors of an external keel and a foil, both of which I have. I also have a 40hp motor, a 4 stroke, but the Permatrim does get it up on the plane fairly quickly. Despite the recommendations of buying a bigger boat and/or bigger motor, many people’s family budget just can’t handle that.
My solution at this stage is to troll while returning, which so far keeps me out of trouble. Also, knowing the limitations of the boat, I sometimes just turn around if the seas are too rough and fish the estuary. However, if anyone can suggest any other methods of avoiding broaching or improving the boat’s set-up to avoid it, I would be very interested.

rando
29-11-2009, 11:34 AM
Thanks for all the replies & advice, I think you've solved it . I had the esky forward and motor trimmed in a bit.

As to conditions, it sometimes is a bit hard to pick exactly what is going to be on offer,especially if, as on this occasion, you go out before its light .At no time did I judge the conditions to be marginal.
.And yes, before I am accused of neglect, I did check forecast etc.logged on....

I am the first to admit that my knowledge of "set-up" in powerboats is basic. I have however been in sailing for 35 years and owned 3 sailers from 17-34 feet.

Again I appreciate all the advice,

Rob

Chimo
29-11-2009, 11:36 AM
Hi Rob

Most tinnys today are built wide for their length which tends to predispose them to broaching. Also very few utilize a "rocker keel" which also reduces the boats tendency to broach and tends to make it run better and generally behave far more predictably.

Keep the bow up and place yourself and boat on the back of a wave set and travel there to reduce the issue.

Buy your next boat recognizing that if you want it really wide for its length (a so called "stable at rest" vessel), as most are these days, it will tend to broach.

Take a look at the shape and design of surf boats and then look at what we have offered to us and you can see why many tend to broach.

Good luck with it...........

Cheers
Chimo

banshee
29-11-2009, 12:40 PM
Lose the foil and your boat will be a different beast (for the better) offshore.I owned a clark of similar size and fished outside often in it,I also wated to fit a foil but the bussiness I deal with told me it was common knowledge that they are leathel offshore.

Chimo
29-11-2009, 01:26 PM
FYI

Patented Non Broaching Hull US Patent designed in Melb Vic.

Power boat hull - Patent D408347 (http://www.dogpile.com/clickserver/_iceUrlFlag=1?rawURL=http%3A%2F%2Fwww.freepatentso nline.com%2FD408347.html&0=&1=0&4=124.189.197.87&5=124.189.197.87&9=76bc18fff4f54589b1c885c80070ca01&10=1&11=info.dogpl&13=search&14=239138&15=main-title&17=20&18=6&19=0&20=8&21=12&22=xw%2Bf%2BD%2BWKFY%3D&23=0&40=sdxxrXOx6By9O%2BU5TNOHlg%3D%3D&_IceUrl=true)
Non-broaching boat hull. Yost - April, 1978 - 4083320. Planing boat hull ... The ornamental design for a power boat hull, as shown and described. ...
www.freepatentsonline.com/D408347.html • Found exclusively on: Google



Cheers
Chimo

borryking
29-11-2009, 02:11 PM
Pull the foil off and chuck it in the bin, dangerous things on the wrong boat. My old boat had one and it used to broach in 0.5m following seas. Once the foil was removed she was like a completely different (and much safer) boat.

Horse
29-11-2009, 05:33 PM
The best advice in a small vessel in a following sea is:-
1/ move weight aft
2/ trim bow slightly high
3/ travel slowly on the back of the wave. Be ready to give it a squirt if needed if the following sea is catching you. The old saying "speak softly and carry a big stick" fits the situation. If you dont have the grunt to keep the tinny manouverable then you should not be out there.
My old 4.9 Abalone had a foil and it made it a much better and safer boat. It was great in a following sea but a bone shaker into one

Bros
29-11-2009, 06:02 PM
My old 4.9 Abalone had a foil and it made it a much better and safer boat. It was great in a following sea but a bone shaker into one

Those old abalone's sure were solid. They reminded me of a boat that they forgot to put a sharp end on as they had a very short curved section for a bow.

ozscott
30-11-2009, 05:59 AM
Rob - the above advice all fits with my (limited compared to many) experience of large following seas. As for the foil - ditto. My uncle was a very experienced fisherman in Townsville. He had a Haines V163 runabout and had a 150 on the back. He fitted a foil to his motor one day for the usual reasons on a deep v narrow boat - lower planing speed and better economy. It all went well until he was in a large following sea one day and he swears it nearly killed him - and he was used to big following seas and went out in all sorts of crazy (to me) conditions...he went straight home and ripped it off and never had a problem again (he was in his late 60's when he fitted it and had been boating constantly since he was a kid - went out all the time).

Cheers

GBC
30-11-2009, 01:06 PM
Foils are great on a flat or flat ish ocean.

In a following sea the engine is trimmed out, so the foil is no longer in the same plane as the keel.

Then when running down swells, the foil can submerge rather than plane, generally at the bottom of a swell when there isn't enough h.p. to get up the next one, causing the arse to 'bog' - obviously unpreferred.

Something to look out for because it doesn't happen on all boats - depends on the individual setup.

ozscott
30-11-2009, 02:27 PM
Good call GBC - I had one on my Haines 163C/16C with a 60 merc and it improved it in every way...except that I didnt test it in a big following sea and I didnt have tabs.

Cheers

Guido
30-11-2009, 02:27 PM
Also, knowing the limitations of the boat, I sometimes just turn around if the seas are too rough and fish the estuary.

Welcome Corsie, and good advice here. I can't count the number of times we've got to the mouth and turned around because it's too rough. This is something I don't tend to see much these days. Lots of people can't accept heading home to put up with the wife, so they bash their way out and back in poor conditions. Fair enough, you might get out there and back, but I really don't understand the joy of slopping around for an hour just to realise it's too uncomfortable. Not to mention the added risk if conditions get worse.

Guido

revs57
18-12-2009, 06:16 AM
Hey Rob,

Get a Riptide!

Problem solved;)

hope you and yours have a great Christmas

Cheers

Rhys

Vitamin Sea
18-12-2009, 07:49 PM
Hey Rob,

Get a Riptide!

Problem solved;)

hope you and yours have a great Christmas

Cheers

Rhys

Or a Haines Rhys;D

Have a good one

Cheers