How to tune stepped mono for racing?

[NativePaul]

I didn't really understand that you meant by "what is fun sport class?" and tried indicating that Hydros are more fun classes to me. I was just joking though, stick with it and I am sure you will get there in the end. Where are you at now?

I am now understanding that you think "fun sport" is the name of a race class? If so you are mistaken, all the surface drive mono classes have Mono in the name, there is Mini Mono for <450mm hulls with <110g 2-3s battery, Mono1 with <280g 2-3s battery 6min, Mono2 with <560g 4-6s battery 6min, and their used to be Mono3 with 20 SubCs 6min (but it was killed off when LiPo came in). There are also submerged drive mono classes Eco <280g 2-3s 6min, Mini Eco <110g 2-3s 6min, FSR-E <840g 15min, F1-E speed, and F3-E steering.

While H&M make some great race boats aimed at the Naviga classes they only constitute about 1/3rd of H&Ms hulls. Most are semi scale boats for fun running, sport running, powerboating or whatever you want to call it, running either solo or in a club but maybe without even having buoys out to make a course, and not against a clock. I think they put funsport in the competition class category to indicate that it isn't made to fit a class.

I have never seen a Chief racing and nor do I expect to, it is a good looking fast scale boat, but it is very big for a Mono 2, maybe small Mono 3 size if it was still going, it has a very high deadrise, and has rather a lot of freeboard, all of which could make it a good very rough water boat, but count against it in typical conditions. However the rear overhang is just dead weight, the engine bulges would slow down self-righting considerably, and the 3 steps are too short to be of much use at model size.

[Jesse J]

Dang, me so foolish! Now that you spell it out, all makes sense. I did buy it for its looks... recon I'll keep at it and not try to race it competitively.

Had it out last time, but just as it hit full throttle, me stub broke loose from the wire, so still don't know how vertical turn fin works. Should have another go this next Saturday.

[Jesse J]

I am in contact with randolf and am about to order me a tomcat m2 with flood chamber.

[Jesse J]

Removing lift strakes

Last weekend I think I got the mix closest so far. Hacker 8xl, 4s, m645 prop, strut 1/2" up from keel and down 3-4 degrees. But, was still chine walking severely as every time I've taken her out. I think this is what is causing the problems in the turns and instability in the straight line.

So, I Got me a "lift strake sander" and went to town on the chief.

This Pneumatic sander was just made for this project!
My little 1.5 gal air tank made the process take 4 times as long as it should have.
About an hour of sand until pressure drops and sander stops (5 sec) wait for pressure to build back up (20 sec) then repeat. I'm glad I wore my respirator, ear plugs and safety glasses... that fiber glass is nasty!

[T.S.Davis]

Late to the thread but thought I'd share, If you;ve already figured all this out I apologize.

Stepped monos are defined by both organizations as hydroplanes. NAMBA has an electric offshore class in which steps are allowed. IMPBA has no electric offshore classes at all. We run them. They're just not in the book. Major difference being that most IMPBA venue run offshore as a sprint instead of a timed heat with most laps winning. I've not seen the Chief up close but the website claims 880mm or 34-5/8" Makes it Q.

Great pics Paul. Something I noticed that's different on most of those than what we typically see on step-less mono. Big turn fins and they are square to the water instead of square to the bottom. Interesting...... Maybe this is why I've seen one turn well. It also looks like the prop is very far behind the trailing edge. Farther than the typical stinger strut we tend to use on mono hulls.

[CraigP]

It's been my experience that prop behind the rudder induces understeer. Maybe that keeps them from spinning out?

[NativePaul]

The Fins are almost vertical but you can see in some of the pics that there is a degree or two of hook angle. I don't really know how your boats work with the fins hooked the wrong way at the entry and exit of the turn, do you run a much deeper rudder? The fins are indeed bigger in proportion which is I think due to our course dimensions, the Naviga oval is 60m (66yd) straights with a 5m (5.5yd) radius on each end for a total length of about 1/12 mile, I know your oval is 1/6mile and straights are much longer, but from the videos I have seen your turn radius looks much bigger too (what is your radius?).

Another difference is that you won't see a trim tab on a Naviga Mono, but you guys seem to fit them right off the bat, before you have even run the setup to see if it has any naughty handling defects that need them fitting to rectify.

I hadn't noticed the "stinger" length difference, maybe that extra leverage helps to explain why we need lower lift props (as well as the straighter shafts), and why we run higher KV than you despite using a lot less power (to use much smaller props that walk less). I am however not mono knowledgable enough to say why the longer shaft. As they are prop riding it is effectively extra boat length that is almost free of weight and drag penalty, but I suspect that there is more to it than that.

[NativePaul]

Some are prop behind rudder some are side by side and some are in front, all have close to vertical fins.

If you are getting understeer you can fix it by: moving the rudder back giving it more leverage, increasing the size of the rudder or reducing the size of the turn fin, which you should do depends on what course conditions you want to run in, other handling traits the boat has, and how hard it can turn compared to the radius of your course. As far as I know, moving the prop forwards won't help (if you maintain the same CoG).

[T.S.Davis]

Paul, course size depends on the venue. It can vary. There is some fudge room on the dimensions as long as each lap is 1/6th mile but for many courses I've setup the radius was 35ft. Our home pond is 35'. Pretty sure the idea was to allow ponds that were short and fat or long and narrow to still place a legal course.

The turn fins on our mono aren't in the water typically when going straight. At least mine don't. It they do it's just the very tip. The only time they really touch is when we turn. So we place them perpendicular to the running surface while turning. Looking at the naviga setups it appears you use the fin to help keep the boat traveling straight. Is that accurate?

On the tabs. Speculation on my part here too. Your boats are riding thrust where as we are using the bottom more. If your stepped boats do weird things you wont know since they run like hydro planes with multiple wetted surfaces. If you capsize, you wait, self-right, and continue. If we capsize we're done. So we tend to run a wetter setup. Hence, using the bottom of the boat more. I like to setup my mono so that they fly flat if they come out of the water and then use the tabs to decide how much I let them fly. 30% plus CG from the transome. What do you guys shoot for with CG on the steps?

Truth, I've not spent much time with stepped mono. They seem such different animals with the steps. I was watching this thread. That Chief is such a beautiful boat. I was hoping someone would figure it out.

[Jesse J]

Thanks for all the great input, yes she is a looker. I'm really optimistic about delifting her and bringing her more like our wetter monos. Having three steps, each lower toward the transom, she is kinda hybrid; stuck between the big euro steps and our nonsteps. Hope to get her out this weekend for a test. I have also gone another inch on rudder since she never has hooked up in the corners yet. As Paul has recommended, I have a vertical square turn fin and have added another reinforcement and sturdied up the bracket.

[Jesse J]

New to the fleet

H&m skyper 1 Kevlar carbon ❤️
Ordered June 1... got it today from rocket city in Orlando- Brian be safe brother!

26.5" x 7.5" at transom
4" chamber behind and 3" in front of step.

Odd lil guy. Gonna set him up for mono 1, then race in N2 offshore with HOTMBC crew. Here are some shots of our chihuahua with a boat for scale.

I'll be referring to earlier posts on this...

Not giving up on chief, just with all the bull Harvey, I can't feel too good about playing until I help out some flooded folks.

[NativePaul]

I would be putting on waders and running in the main street.

[Jesse J]

Skyper mono 1 almost ready for test

Got her set up with some euro help...

[Jesse J]

Help me figure out elegant turn fin bracket...
Please?

[NativePaul]

On riggers and monos without much transom depth we generally cut a vertical slot on the transom, and glue in a piece of carbon instead of using a bracket.

Not a mono, and not a turn fin, but you can get the idea from the start of this video.