A British FS17

[wegcagle]

Beautiful work Steve. Can't wait to be in your shoes.

Will

[Bluefish2]

Steve, You did a wonderful job. Hope my FS17blooks half as good when complete.
Mark

[Lower]

CONGRATS on the launch!!!! Very, very exciting! I'm a bit jelous. Life has been quite busy with the new little one. It's starting to settle, looking forward to getting back to the boat! You did an excellent job on the build, you should be proud. Must have been quite the feeling to see her in the water for the first time.

Bet you are looking forward to the warm weather this year!

Congrats again and enjoy!

[steve292]

Bit of an update.
Today I had the chance to put the boat in at a local watersports lake.I don't have any photos so you'll all have to take my word for it.
The boat was loaded with a 1/2 load of fuel (6 uk gallons) ,5kg plough anchor, 18ft of 8mm chain & 180ft of 1/2" rode, & me
About 1550lbs all up.
The lake is about 1/4 mile long so I got some decent runs in upwind & down.
Some figures, bear in mind the engine is a 1983 vintage suzi DT60.....speeds from gps.

1000rpm .......5.3mph
2000rpm.......10mph
3000rpm .......17mph....planing
4000rpm........22mph
4500rpm........25mph...nice cruising speed
5000rpm........29mph
5300rpm(WOT)...32.5mph...dead stable, even in a hard turn

The max recommended rev range in the Clymer manual is 4800 to 5400, so I am pretty sure I am close with the prop.
There is a very slight porpoising at WOT, which I am sure a Doelfin or similar will cure.
Virtually no hole shot, straight up & go , No slip in turns, it flies around like its on rails
The only chop I could run it in was my wake bouncing back of the revetment, but no spray or slamming even at WOT, but only the real world will prove the last point.
The best bit of the day?.....the guy at the slip who asked me where the custom build boatyard that built my hull was
I am a happy chap
Any thoughts on a fin for the cavitation plate?

Steve

[sitandfish]

To me it all sounds fantastic. And I am especially impressed in the way you buried your own weight in the "1550 lbs all up".

I'll let the experts recommend a doelfin but, they all seem to be great products to me. I have two. Real impressed with your documentation. Very helpful.

[TomW]

Can't do any better with the prop Steve anything within 100rpms is very good. You'd be playing with fire to try to get anything better an 1" of pitch less would give you 2-250 more rpms but might give less mph, the same if you tried to decup the prop you have. Taking a little cup out would give you some rpm but again it may affect speed and handling. I'd stay with what you have. It sounds like it is tracking and really doing a good job for you. If your not getting any ventilation in hard turns you might try raising the motor up 1 hole and seeing how that works. That will give you some speed and rpm without changing the prop. We ended up with Kurt's FS down in Florida up 1 or 2 notches up with his 60hp Yamaha giving it some improvement each time.

As I recall Cracker Larry put on a Stingray this time but don't remember which one and recommended it to Macs.

The dockmaster's comment's had to make you feel GREAT!

Tom

[BassMunn]

Sounds good Steve, those are pretty good numbers for an old 60, it's obviously old but still good

I know a lot of guys like those dolphin fins, personally I don't. They are mainly designed to help get out of the hole, which you don't have a problem with, but they do help with porpoising but at the expense of a little speed due to the increased drag they cause.
I would try shifting a little weight further aft first before handing out the dough for a fin.
Your prop size sounds perfect, the only way to improve it would be to go stainless, it would give very slightly better performance and help with the porpoising, but you could buy a couple fins for the price of the prop.

So I would say try weight distribution first, if that fails try the fin.

[BassMunn]

The best bit of the day?.....the guy at the slip who asked me where the custom build boatyard that built my hull was
I am a happy chap

Gotta love it

[Cracker Larry]

Those numbers look great with the old zuke

There is a very slight porpoising at WOT, which I am sure a Doelfin or similar will cure.

Does that engine have power trim? If so, can you stop the porpoising by trimming the engine down? A slight porpoise is normal at WOT and high engine trim, but if you can't trim it out, then a hydrofoil will stop it for sure.

I'll let the experts recommend a doelfin but, they all seem to be great products to me. I have two.

They are great products for light and fast boats. I've owned 4 or 5 Doel Fins and they improved the handling of every boat I put them on. I've got a Stingray now, my first one and I'll say that it has more authority than a Doel Fin. Before I put the fin on, the boat would porpoise at high speeds and I couldn't completely correct it by trim, even with 40 gallons of fuel under the casting deck, the bow would bounce. The fin completely stops this and lets me trim the boat to any sea condition. I can trim the bow up high in a head sea or trim it down in a following sea. I can trim it down enough now to actually stuff it. Got to be careful with that This stingray fin is like having trim tabs.

That being said, it's also slowed my top speed down about 4 mph, and lowered my max RPM by about 400. She was perfectly propped before adding the fin. To get right again I need to either raise the engine, or buy a new prop, or both Or not The engine is high now and can't go much more without ventilation. I never go that fast anyway, but I don't want the engine to lug either. I've got a jackplate on order from Joel, that will help some I think. Just a matter of time before I bust this prop and have to replace it anyway

Doel Fins have never given me the large reduction in speed and RPMs that the Stingray has, and has always solved my porpoising problems in light, fast boats, but the Stingray has more power to it. I love it for trim control, but I don't like it for RPM loss. I'm past the statue of limitations with my dealer in swapping props

To sum this up, my opinion only, if you can't stop the porpoising with power trim, then a Doel Fin will solve it at a minimum speed and RPM loss. The Stingray is more extreme and you will probably have to re-prop, and will still loose some speed. It's fairly large and has a lot of drag, but it also has a LOT of lift and will sure get the bow down.

Doel fin on GF16..



Stingray on OD18

They are mainly designed to help get out of the hole,

Not at all, that just one of many benefits

quoting Stingray marketing
The StingRay™ Hydrofoil Stabilizer applies the laws of physics to provide the extra performance every boat needs. It’s aerodynamic design creates a higher water pressure on the underside of the hydrofoil surface, which creates lift to bring the stern up and force the bow down. No other product improves performance so dramatically.

I agree with all that, but the higher pressure decreases prop RPM. They don't tell you that

Unlike other so called foils, the StingRay™ keeps on improving performance once the boat is up and running. In addition to providing a superior hole shot, the StingRay™ lets the boat cruise at lower speeds, stops porpoising, eliminates chinewalking, stabilizes handling, increases top end speed and improves fuel economy.

I agree with everything except higher top end speed. Not on my boat anyway.

[TomW]

Nice report on the fin Larry. Good info to have.

Tom