Broaching

[jaybee]

Have a 16 ft sportsman craft runnabout been converted to a quarter cuddy 70hp johnoson fitted with a stingray. In the following sea on the weekend (first trip in slop with it) it broached both left and right. I have taken the stingray off it in case it might be this but havent had a chance to see.No cavitation, or excessive revs but couldnt run anymore then 10knots while my bro in his steber craft left me behind my bro suggested also to get the prop doubled cupped..anyone know where there is a prop specialist in brisbane. thanks.

[dnej]

Did you have the motor trimmed out to get the bow up?
Some boats are worse than others, but trimming helps.
Rule of thumb, bow down to a head, bow up for following sea.

Also weight distribution sometimes helps. Some boats are a real worry.
Regards David

[jaybee]

With the motor trimmed out the bow seemed to dig in more. Took it for a run today without the stingray and the bow rides a lot higher now pushing water a lot further back. Seems a lot better but still thinking of having the prop doubled cupped.

[clutter]

Jaybee, A mate had the same problem a few years ago after fitting a Stingray to his Haines. I think with the ray on, the boat was pushed too far out of the water and he had to change the height of his motor on the transom to suit. Might pay to check with a dealer. Hope this may have helped. Clutter.

[jaybee]

Hi clutter sussed that out as well and the motor is as low as it can go..it appears to ride higher in the bow now without the stingray and the motor trimmed but really need a following sea to see it the problem is solved before I go any further. Would like to have a talk to a prop specialist to see if a double cupped prop will help but the only one I know off is somewhere in southport.
cheers.

[Flynny]

Broaching is a real bummer and dangerous too. the biggest cause of broaching to my knowledge is when a boat is either overloaded,or unevenly loaded(towards the bow) and the engine does not have enough power to maintain forward motion into the back of a wave.The action happens when the bow of the boat becomes the pivot point and the wider end pushes the boat around forcing it to steer on it's bow.In other words the propellor no longer is in control of the steering of the boat.
Check your load,because normally a 70 running well is o.k. for your boat.
Cheers Sumaset

[jaybee]

Hi flynny
the prop was submerged tried shifting wieght around but no difference the steering didnt move in my hand it just dug in to the port and then to the starboard as soon as i hit more then 10 knots. My bro was watching and said i looked like a trawler pushing heaps of water with the bow and rocking from side to side. What I really would like to do now is talk to a prop specialist about double cupping the prop..n e one know of one in brisbane.
cheers.

[Flynny]

Yeah Mate
Try Steve at just propellors in Maroochydore he does mine nearly while I wait,Don't know the phone no. off hand but he is in newspaper place.
Cheers Flynny

[jaybee]

thanks flynny will endeavour to chase him up from here

[jaybee]

Thanks for the replies guys I think i have found the problem after talking to a prop specialist and found this on the stingray web site
The Sting Ray Hydrofoil Stabilizer, through its advanced design, creates upward thrust on its under side to provide lift, bringing the stern up and forcing the bow down. Even at low speeds, the boat is brought up on plane and out of the "hole" in less than ½ the normal time. So i would say in a following sea with the stern up and bow down the boat is going to broach.

[Flynny]

Good Luck with that one mate,
Cheers pete

[SNELLY]

Jaybee,

Over twenty years ago we owned a 15ft Sportsmancraft and it was a great boat. Friends of ours purchased the same boat a couple of years later and it was a real bastard for broaching in that all it wanted to do was follow the troughs of the waves. It was sceary even in small seas. The only difference betwen the two boats was the height of the floor. I think our floor was lower than the other. I do not know why they lifed the floor but it made a detremential difference.

[jaybee]

Thanks snelly on the weekend down the pin i purposly got into the wake of a couple of big cruisers and surfed down the front of the wash and back over the top and did this right up to the white water towards the stern with no probs so at this stage until i can get out in the ocean again i think the problem was the foil..riding bow high now
cheers n thanks.

[jaybee]

Well I finally got the boat into a bit of slop today down the mouth of the brisbane river and koopa channel..the wind around 20 knots with both outgoing and incoming tide the boat didnt even hint at broaching even at 21 knots in the cross chop at the juntion of koopa and the river..and with a following sea..i am stoked..very comfortable and dry ride..thanks to everyone for their feedback. I guess i really cant recommend a hydrofoil to anyone after this.

[krazyfisher]

jaybee
I am looking for something the same for my boat but what brand was yours I dont know which sort to go for but they are not cheap so will have to be the right one hopfully it would do this to me as my boat ride high.