View Full Version : Broaching

29-07-2002, 11:30 AM
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.

30-07-2002, 06:23 AM
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

30-07-2002, 12:28 PM
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.

30-07-2002, 03:34 PM
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.

30-07-2002, 04:02 PM
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.

31-07-2002, 10:52 AM
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

31-07-2002, 01:12 PM
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.

31-07-2002, 05:04 PM
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

01-08-2002, 03:07 AM
thanks flynny will endeavour to chase him up from here

01-08-2002, 05:08 AM
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 the normal time. So i would say in a following sea with the stern up and bow down the boat is going to broach.

03-08-2002, 06:08 PM
Good Luck with that one mate,
Cheers pete

15-08-2002, 10:52 AM

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.

15-08-2002, 11:01 AM
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.

05-09-2002, 03:40 PM
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.

05-09-2002, 03:44 PM
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.

05-09-2002, 03:53 PM
I had the stingray it was on the motor when I bought it .. I see your profile is mackay was going to suggest you could borrow it to try and if it worked prob sell it for $40.. mine was designed to bring the bow down..try this site http://www.familyboats.com.au/accesory/stingray.html #they were very helpful and suggested a few things but most important was a reputable dealer who knows the products..the stingray comes in 3 distinct shapes from memory.

06-09-2002, 08:34 AM
Do you think a Permatrim would help or hinder ???

06-09-2002, 09:12 AM
All I can say is trial and error Mick..i was advised to see a propellor specialist and have a talk to them first..some not all know of the hydrofoils and can recommend which one to use. i was advised
1. Foil Change
2. Wedging
3. Engine height adjustment
4. New prop

However it all costs money my third phone call i spoke to a prop specialist he said take the foil off if you still have problems then come and see..but I dont think you will have too. My foil is designed to bow down which left the stern too high in a following sea..on a good day it was great, going into the sea trimmed out wasnt too bad..but get the sea up ya stern and look out ..

16-09-2002, 11:07 AM
Hi Jaybee,

After reading this post I decided to take the foil off my Sportsmanscraft today. Yesterday we went about 10km north of Tweed with the foil on and we did the same trip today.

I was amazed at the diference - can't believe I haven't tried it before. The boat handled far better when cornering in flatwater and felt heaps better going through the 1 metre seas outside today with the south easterly on it.

It's really cool to get new ideas from a site like this and get an improvement in your experience.


16-09-2002, 12:35 PM
Thanks for the reply steve..its good to hear from other people that have been having the same problem and they give positive feedback.

17-09-2002, 09:40 AM
The best prop man in Brisbane is Colin Lough at Performance Propellers, Bulimba. Ph 3899 1501
Personally I think those stingray type hydrofoils work well on some boats, especially when it comes to improving the ride in a head sea. The trade off comes with diminished performance in a choppy following sea, with broaching occuring more easily. It seems that even with the engine trimmed further out, the effect of the hydrofoil is to still make the bow ride too low in a following sea which sounds like what you have been experiencing.
Anyhow only an expert like Col will be able to tell you whether the double cupping will be worthwhile. Please keep me informed.

Bill Corten

17-09-2002, 02:28 PM
Thanks bill have made a note of the name and phone..my problem was solved the minute i took the foil off..was out in the mouth of the river in 20 plus knots a few weeks ago..conditions were very much if not worse then when i was off mooloolaba..tried everything to get the boat on its side.. my deckie was not happy jan..didnt happen..feedback from stingray suggest there are 3 foils for different jobs..i can live without one after the experience i had..however i have noticed an increase in fuel comsumption without it..thats life eh.

17-09-2002, 03:39 PM
Really foils can be down right dangerous on some boats (and especially cats).

There appears simply too much hoohah from some foil manufacturers in that these things are supposed to fix all problems, which of course they don't.

Cheers, Kerry.