information on an F class Coutts hydroplane?

[zul8tr]

Looks good after all those years. Next time out would like to see a fly by at max speed. Interesting sponson chine and bottom planking rear curve shape On the turn fin why builder tucked it in so far that left turn spray will hit the rear chine side plywood, not clean turn spay more drag? I see fin removed in latest pic, unless you want to keep boat original consider moving it out more for clean fin spray ?

Happy safe running

[Ketzer]

Ditto on the fly-by at max speed...while planting butt at the back of the boat.

[Speeditwin]

Looks good after all those years. Next time out would like to see a fly by at max speed. Interesting sponson chine and bottom planking rear curve shape On the turn fin why builder tucked it in so far that left turn spray will hit the rear chine side plywood, not clean turn spay more drag? I see fin removed in latest pic, unless you want to keep boat original consider moving it out more for clean fin spray ?

Happy safe running

Will have a video once I've actually ran at max speed, want to get used to the boat first.

It is an interesting shape, the surface getting smaller at the back probably contributes to the fin being so far inwards. if we wanted it further out we'd likely need a different fin so ill probably leave it for now unless its a problem

[zul8tr]

Good idea to get used to the boat before serious top speed runs.

The fin where it presently is should not be a problem but it will not give clean water off fin blade in a turn. When used to boat at speed make left turns at top speed and see what happens with the water spray off the fin and see how much water the rear chine carries with the fin spray. Ideal is to have minimal left turn fin spray hit the rear chine which is more drag and also tends to lift the boat (rotate CW) to port and forces right side of boat down. Plus clean fin spray looks cool! ;-)

When the fin is remounted measure how deep the blade is below the sponson bottom.

Your present fin could be useable to move out: depends on dimensions and blade hole and other details, in turns how deep the fin is needed in the water, if adequate rear sponson back wood is available to secure fin bracket.

My hydro set up optimum (Avatar) carried no fin in the water in the straights in the turns I would move forward some and lean left some and sink the fin to grab, fin set far outboard. Hydros need to run at speed with sponsons off the water.

Be safe and safety first and have a rescue boat. In the video you have no helmut get a good one.

[Speeditwin]

Didn't realize it would rotate the boat like that, you can sort of feel it doing that though.

The location of the drain plug is the real problem as the fin has a cut out for the plug hole, fin is about 2.5"-3" below the boat. Wow didn't realize all the hydros would run like that haha, seems like a fun ride sponsors out. As it is feeling the lift of the boat and acceleration is already pretty crazy to me.


Will be getting a better jacket and helmet next year as we have only had it running since labor day

[zul8tr]

There is a lot of upward force off that fin spray especially at speed that hits the rear chine and causes some CW boat rotation to dip the right side down influencing turning.

The fin assembly can be made to fit outboard on the sponson back and the 90 degree fin angle bracket can be secured just above the drain hole. Just have to make the bracket and fin to suit your boat. I have it that way on my hydro with the drain hole just below the bottom of the 90 degree bracket and the fin blade is designed to be vertically adjustable with several holes in it to suit the boat drivability in turns and clear of water in the straights. Each boat is different and good testing resolves issues.

Can send sketch if interested.

There needs to be adequate wood thickness on the inside sponson back to secure the fin bracket. Bolts are best with back fender washers if you can get your hands in there if lightening hole is in in port coaming near the dash board?

[Speeditwin]

here is the fin on the boat. it could definitely be moved, i see what you mean about the spray forcing one side up.

[Speeditwin]

Where did you pick the boat up? Did a motor come with it? My Father would have Knowledge on Jim Coutts.

do you have any photos of other coutts boats, or racers with them?

this boat appears to have been all red before the previous owner painted the white on the front.

[Dew1us]

These were some of the Stones Couts Crafts. And they were green not purple as I originally thought.

[zul8tr]

Referring to sponson fin in post #17 you said:
"here is the fin on the boat. it could definitely be moved, i see what you mean about the spray forcing one side up."


Yes the fin can be moved outboard above the drain hole and be adequately clear of the rear chine top edge. Would need to not use that present fin with the clamp style bracket to secure the fin. I used for the bracket a 90 degree radius inside corner 1/4" thick alum (length dependent on boat specific dimensions) with one leg facing inward and secured to the sponson back the other angle leg faces rearward and the fin is secured to the inside face of that angle leg. The fin blade is made of 1/4" alum of proper shape and length.

If interested in I can send a design sketch and pics of what is on my hydro which is essentially same a s described above.