Oz hydrofoils.

[maverick58]

I’m Looking to give my little tohatsu 9.8 2-stroke a bit more get up and go whilst out on the water. I Previously had a SE sport 200 on a 15 a while back and was quite impressed. Oz hydrofoil do one for the tohatsu, I’m wondering if anyone has one or used one and what they are like in terms of performance and value for money etc. Also do they have a European distributer??
many thanks.

[Pikey Dave]

Originally Posted by maverick58

I’m Looking to give my little tohatsu 9.8 2-stroke a bit more get up and go whilst out on the water. I Previously had a SE sport 200 on a 15 a while back and was quite impressed. Oz hydrofoil do one for the tohatsu, I’m wondering if anyone has one or used one and what they are like in terms of performance and value for money etc. Also do they have a European distributer??
many thanks. Attachment 142214

Unless you have a specific issue that requires hydrofoils, then they will reduce your “get up & go”

[Old seahorse]

Hi Maverick. I’ve got a permatrim, which is very similar in design. Mine was fitted to my Suzuki 6; four stroke, to reduce cavitation/ ventilation on my Takacat, which suffered from air being pushed through the tunnel between the two inflatable hulls. It has given the boat improved performance in all conditions and reduced turbulence considerably.
Obviously different boat/ engine combinations work differently, but I’ve been impressed with results.

[maverick58]

Originally Posted by Old seahorse

Hi Maverick. I’ve got a permatrim, which is very similar in design. Mine was fitted to my Suzuki 6; four stroke, to reduce cavitation/ ventilation on my Takacat, which suffered from air being pushed through the tunnel between the two inflatable hulls. It has given the boat improved performance in all conditions and reduced turbulence considerably.
Obviously different boat/ engine combinations work differently, but I’ve been impressed with results.

Hi seahorse. That’s very similar to my set up, I have an Aircat 335 which was doing exactly the same thing yesterday out on the water. 2 up the prop was slipping in the water & A fair bit of splash too coming off the rear end between the outer hulls and hitting the inside leg of the engine. We tried a few different trim holes to see which one worked best, might have to raise the engine up slightly. Is the permatrim a uk based product??

[Old seahorse]

You seem to be suffering similar issues to me. Takacat actually recommend permatrim, but I wasn’t made aware at time of purchase. Since fitting, my boat accelerates better, is more relaxed, and feels more balanced, especially when 2 or more are on the boat. Spray and turbulence have been greatly reduced.
Permatrim are New Xealand based. Mine came via Avon marina in Christchurch Dorset. I think you can buy direct from the makers, and I see Amazon sell a few. There may be other dealers who sell them. Any who sell Takacats would, I’m fairly sure.

[Matt]

Originally Posted by Pikey Dave

Unless you have a specific issue that requires hydrofoils, then they will reduce your “get up & go”

This! So there is a time and place for them, but really it's to fix some other design issue that, if you can, you'd better off addressing directly. But that said, it's not always feasible. (e.g. a low power rig with a rearwards CG - it might not be feasible to add more hp or move the CG)

[Old seahorse]

Should read New Zealand!

[Blankton]

I fitted one to my old 4 stroke engine. It solved a lot of problems (which were due to the engine being too heavy).

I had to order it from Oz. Its a nice touch that you can specify OB type and it comes paint matched, so it looks OE.

[maverick58]

Originally Posted by Old seahorse

You seem to be suffering similar issues to me. Takacat actually recommend permatrim, but I wasn’t made aware at time of purchase. Since fitting, my boat accelerates better, is more relaxed, and feels more balanced, especially when 2 or more are on the boat. Spray and turbulence have been greatly reduced.
Permatrim are New Xealand based. Mine came via Avon marina in Christchurch Dorset. I think you can buy direct from the makers, and I see Amazon sell a few. There may be other dealers who sell them. Any who sell Takacats would, I’m fairly sure.

Ahh, that’s interesting info, I’m just up the road in southbourne. I’ll drop them a call 2mora. So how has your permatrim changed how your takacat behaves out on the water?? Quite a unique looking design too compared to the stingrays and SE sport, would be interesting to hear what significant changes it made you mate.

[maverick58]

Originally Posted by Blankton

I fitted one to my old 4 stroke engine. It solved a lot of problems (which were due to the engine being too heavy).

I had to order it from Oz. Its a nice touch that you can specify OB type and it comes paint matched, so it looks OE.

I must admit that does look nice and sleek. Love the colour match too.

[paintman]

Permatrim on my 17' Dory.
Fitted it years ago.
On plane sooner, stays on plane at lower speed. Improved fuel economy as a result.

I've had no issues with it & no corrosion at all so the finish is robust.
Straightforward to fit.

Side bonus when I caught the rope off a set of crab pots at speed - blue polypropylene, yards of it floating just in the surface so the first I knew about it was when the boat started slowing.
Stayed on top of the plate & didn't slide down to get caught by the prop.

[chipko]

Although not a massive fan of hydrofoils per se I feel they are a worthy tool to consider in addressing ventilation issues on small cats.
Personally my first option, if adjusting trim/motor height all fails, would be to try a cupped propeller. This has worked on a few combinations I know of.

If going hydrofoil then my choice would also be the Permatrim (or the similar OzProps) and I’d probably Sikaflex it on like the guys at TrueKit show, although imagine will be difficult to remove!

https://youtu.be/AAxiXea58PE

Interesting to note Tacakat lowered their transoms a few years back to help combat the dreaded ventilation and I also recently saw they now do a strap on (Ooer!) central speed tube to help smooth water flow over prop.

Good luck with your quest.

[maverick58]

I think I’ve found what the biggest issue here is, short shaft engine on a 15” transom and it’s sat too low in the water. There’s a lot of great info on here regarding similar issues and it would seem not every engine is suited to every transom. Locozodiac’s thread was an interesting read.

So, In order to get my cheap Chinese aircat married up nicely with my tohatsu, step one, raise the engine up on a 20mm block, step 2 install the recommended permatrim for that hull to bring better stability at speed, better holeshot and sort ventilation issues. And step 3, take it all down to the river to test it out.

Yesterdays test, a little cold, but says engine is still sat too low despite the raise in height with Lots of Backsplash still present, water hitting the rounded edge just below the ventilation plate so not slicing through the water cleanly enough. Permatrim has made a huge difference to both the holshot and stability at speed so kinda making baby steps.

Back on dry land for more testing this morning, measuring different heights and set ups with a few pics for illustration. Fellow sibbers can I ask for your opinion on which of these pics looks to be near enough to being correct in terms of where the cavitation plate should sit. Pics 1 through 3 show standard seating of engine, up 20mm on block, and then up 40mm which is yet to be tested.

[maverick58]

[maverick58]

[maverick58]

[Steve509926]

Hi Maverick, all the pictures show the cav plate being lower than the keel, but the last pic (40mm) is closest to where the cav plate should theoretically be. However, it looks like that doesn't give much "land" on the outboard mounting plate for the clamps to grip on to. If that is the best height I'd want to bolt the OB onto the transom, better safe than sorry.

[Steve509926]

Just realised you run a cat and my comments above #17 don't really apply, I thought it was a sib you had. Thinking out loud (metaphorically speaking) should the cav plate not be level with the bottom of the tubes?

[maverick58]

Originally Posted by Steve509926

Hi Maverick, all the pictures show the cav plate being lower than the keel, but the last pic (40mm) is closest to where the cav plate should theoretically be. However, it looks like that doesn't give much "land" on the outboard mounting plate for the clamps to grip on to. If that is the best height I'd want to bolt the OB onto the transom, better safe than sorry.

Good observation Steve. No you’re right it isnt. The 40mm raiser is 45mm in width to match the transom and mounting plates combined, hopefully creating a half on half off tight grip for the OB to sit on. It’s still in testing stage at mo, 26kgs is a bit of fat monkey to get off your back, but more importantly is getting all of those 10 horses safely clamped to the ground without losing the outboard.

[maverick58]

Originally Posted by Steve509926

Just realised you run a cat and my comments above #17 don't really apply, I thought it was a sib you had. Thinking out loud (metaphorically speaking) should the cav plate not be level with the bottom of the tubes?

It’s a Sib Cat, all inflatable with HP floor.