What causes an F1 tunnel boat to spin out on a turn?

[KnotFast]

I have a new 30” TFL F1 tunnel boat and on the maiden voyage I’m finding it difficult to turn with spinning into a 180. It does it mostly when I turn right. Turning left is drastically reduced. I did some digging around and learned that the reason why it’s spinning out on a right turn is due to the prop direction (ccw) so basically the prop is “walking” and induces this 180 spin out. Does anyone out there have any tips? Maybe reduce servo travel? Add expo?

[BUMBLESPECIMOODA]

It might be the speed at which you are cornering. The hull might not be settled down enough, for the sponsons to be deep enough in the water, for the rudder/outboard to push against. Maybe add some turn fins to the sponson insides, to help cornering at speed. Where exactly to put the turn fins, is something the more experienced will have to chime in on.

[KnotFast]

It might be the speed at which you are cornering. The hull might not be settled down enough, for the sponsons to be deep enough in the water, for the rudder/outboard to push against. Maybe add some turn fins to the sponson insides, to help cornering at speed. Where exactly to put the turn fins, is something the more experienced will have to chime in on.

Awesome info thank you. I’ve been watching lots of f1 races and when they are about to turn I notice how the front just drops and grabs the water carving it. Amazing. I will practice and tune as I go.

As far as adding a turn fin I have no way to access the opposite side of the sponson from inside. Are these just simply glued on?

[BUMBLESPECIMOODA]

Lots of force on a turn fin. Bolt her down good. How? You'll have to figure that one.

[racer504]

I think that is a very cool boat. I have watched a bunch of videos of that boat from different posters. Spinning out in corners seems to be a common theme. I would try some different pops as well as trim and tilt, if that is possible. Also, that is a self-righting boat, so the design principles that enable that may be working against you.

[KnotFast]

I think that is a very cool boat. I have watched a bunch of videos of that boat from different posters. Spinning out in corners seems to be a common theme. I would try some different pops as well as trim and tilt, if that is possible. Also, that is a self-righting boat, so the design principles that enable that may be working against you.

At first I thought it was the self righting version but it’s not. This hull has no chambers. It’s designed not to flip or at least minimize it according to TFL. I bet I can flip it. :)

[JestDanny]

Where is your center of gravity? 30 inch tunnel boat = 30 percent = 9 inches. from rear. That's where I would start CoG. Important. Ride height an thrust angle. Ride height to high cavitation, find that point an stay a hair below it. Thrust angle, to much positive n ya blow over, to much negative n ya spin out. Fine line on some hulls to get all three just right.

[lohring]

Does your hull have "stumble blocks"? These control the amount the sponsons dig in when the boat settles in a turn. Also how sharp are your turns? Tunnels dig in more the sharper the turn. Setup is a balancing act between a boat that's too loose and blows off versus a boat that doesn't turn well. It takes a careful adjustment of CG, prop angle and prop height to get it to run well. Run with a club that has members that run tunnels for help.

Lohring Miller

[lohring]

Does your hull have "stumble blocks"? These control the amount the sponsons dig in when the boat settles in a turn. Also how sharp are your turns? Tunnels dig in more the sharper the turn. Setup is a balancing act between a boat that's too loose and blows off versus a boat that doesn't turn well. It takes a careful adjustment of CG, prop angle and prop height to get it to run well. Run with a club that has members that run tunnels for help.

Lohring Miller

[KnotFast]

Well running the TFL scale outboard on 4s is a no no. The gears failed but good news is I replaced it with a TFL CNC outboard and now it’s running way better. Here’s a video if you’re curious.

https://youtu.be/KIlExHoetl0?si=JPsbdOskO-mIIjAN

[JestDanny]

Watched your vid, looks good, tunnels are me all time favorite. I like that TFL CNC lower have 2 of them. What prop are you running? You stated your ride height is at center of prop shaft = bottom sponson, you can go, try a little higher. Many set the bottom of prop shaft = to the bottom of sponson . Some racers will even go a little higher than that. get that prop to unload, toss the H20 better. Air it out, a loose boat is a fast boat. Good luck an have a blast.

[KnotFast]

Thanks. My shaft Centerline is 1/4” above the sponson bottoms and trim is neutral. The prop I was running in the video was a 4216 2 blade CNC (prop that comes with the Proboat blackjack 24 v2). I now run a 3 blade 4014 CNC.