Straight Turn Fin

[Kid Gurry]

Does anyone know where I can find a straight turn fin for a P Ltd Sport hydro or 1/10th scale hydro, or is that a DIY thing? I see them for sale for larger boats, but I'm only finding hooked fins for LSH. Thanks!

[T.S.Davis]

Why would you need a straight fin for LSH? I haven't used a straight fin on a sport.......ever now that I think about it.

For my scales where a straight fin is required I just bought a piece of stainless and cut what I wanted out of it. We have also made them out of cheap dollar store spatula. Cut the shape, sharpen, drill some holes.

[Kid Gurry]

Thanks for the input TS. I don't know that I need one, but I'm a newbie and I've been told hooked fins can be tricky. Any advice on placement/setup would be appreciated!

[Ryanj]

Hooked fins once set up right perform well on a LSH. Setting the fin to start as neutral as the hook/ curve part of the fin is level/ parallel to the bottom of the boat. A straight fin can be used as well but you would need to angle the fin inboard 12-15 degrees to start with. As placement, mounting and so for will depend on the hull, turning direction and type of fin you plane to use.

[Kid Gurry]

Thanks Ryan. I have the fin that ML Boatworks recommends for my hull, which is the Mojo Sport 20. It has a curved hook rather than angled, so I'm not sure I could get the hook parallel to the bottom of the boat. To this point, my plan has been to mount it so the vertical portion of the fin is perpendicular to the bottom of the hull and in line with the outside edge of the sponson ride surface. Is that a reasonable starting point? Thanks again.

[paulejr]

sounds about right. good place to start and see what gives. There are other tweaks for the fin, but you must find them after you get a good, solid feel for the stock one you have.

[Kid Gurry]

Thanks Paul, that sounds like good advice.

[lohring]

Straight, angled turn fins are easier to set up and are more tolerant of left turns than curved turn fins. They may not be as fast. I make my own straight fins but buy my curved fins from Mike Hughes. I've run both. See below.

Lohring Miller

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[Kid Gurry]

Thanks Lohring. I thought for fun I'd try making a straight fin to compare. I just ordered some 7075, 0.098" thick. Sound about right?

[T.S.Davis]

TMojo Sport 20. It has a curved hook rather than angled, so I'm not sure I could get the hook parallel to the bottom of the boat. To this point, my plan has been to mount it so the vertical portion of the fin is perpendicular to the bottom of the hull and in line with the outside edge of the sponson ride surface. Is that a reasonable starting point? Thanks again.

That's what I use on most of my boats and where I place mine too. Bob (Mojo) uses a jig so that the hook is parallel to the top edge of the fin. That was the original intent back when Kevin started doing them with the laser. Randy Rap makes a nice titanium fin that many have used successfully. Never worked for me. Likely would require me to set up different. Larry Jaques was making some titanium fins too I think. Have not tried that.

Nice thing about the hook is that by twisting it forward or back you can change the way your boat rides. Sometimes you need help airing out on a particular hull going straight. Sometimes you get it flying right with the fin and the minute you correct to the left a little it climbs the fin and blows over. Dang it! Sometimes you can use the fin under pressure in the turns to raise or lower the right sponson. Deeper sponson tends grab more. Sometimes you want that......sometimes that's a bugger. That's probably what someone meant by them being tricky. I think of them as a another tool in the drawer.

Don't be afraid to play with that angle on the fin. Neutral is ideal but subtle changes can really affect the ride. Half a degree and all of a sudden....sweet spot. It's worth the experimentation time. You can always go back to neutral knowing that top edge is parallel to the curve.

[Kid Gurry]

Man, that is some really helpful info; thanks TS! I've been thinking that at first I won't really know if any problems are being caused by the fin adjustment or maybe something else. Now I at least have a starting point. Like you said, another tool in the drawer. Thanks for sharing your knowledge!

[T.S.Davis]

That's why everyone is suggesting a neutral starting point. Thinking being that it's not effecting the ride at speed. That's the dream. Completely neutral and everything behaves.

I haven't done this myself but I've heard it a couple times. Some guys trouble shoot by running no fin at all to see what the boat is doing going straight with no influence from the fin..........wait......finfluence? haha. It wont turn to save yer life with no fin but you might be able to determine if your strut depth and center of gravity are in the ball park.

[Kid Gurry]

Finfluence? That sounds like a dad joke, but I like it. Loosely related, I've seen some fins that only use one fastener holding the fin to the bracket. I assume the idea is if I clobber something, the fin will rotate upward instead of ripping off the sponson transom. How much of a concern is this? Keeping in mind that I still need to learn to drive, should I only use one fastener in the Mojo? Thanks.

[T.S.Davis]

I use two fasteners. I don't want that thing moving for nothing. However, I really reinforce the trans where the fin mounts. On the inside when I build that boat that is. There's additional structure and aluminum plating in there. Your call but I want that thing staying put.

[Randy Rapedius]

P-PL Titanium.
$69 US shipped.
Can make with or without hook.

[Kid Gurry]

Thanks guys. I did add a plate on the inside of the sponson transom, so I try using both fasteners and hope for the best.