How to tune stepped mono for racing?

[Jesse J]

I have several now and would like to see how people set theirs up and what kind of races they are in.

I'll post up mine in subsequent posts, but they include:

H&M 3 step chief 34"
Hopf cyklon 1 big step (I'll check spelling) 32"
And now a syncron 2 steps (thanks Joseph) 28"

If you have a stepped mono please share your experience.

[photohoward1]

In IMPBA and NAMBA. stepped monos are considered hydros. They are not allowed in the mono classes.


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[NativePaul]

Are stepped monos allowed in your Offshore classes? I guess they are as stepped cats are allowed in it. As a Naviga racer I have thought for a while that a Naviga type stepped mono would do well in P ltd Offshore, and maybe one of the bigger ones in P Offshore too. On the other hand I have never seen one with a COG as far forward as you may need it now NAMBA have banned self-righting, maybe they would hook like crazy at 30+%.

[Fluid]

In IMPBA and NAMBA. stepped monos are considered hydros. They are not allowed in the mono classes

NAMBA classifies stepped monos as Offshore hulls.

The preferred CG will depend on the location and depth of the steps. Different makers seem to have different ideas on hull bottoms of stepped hulls.




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[Jesse J]

thanks for replies guys. i fear she will be a journey of adjusment-run-adjustments.
I have copied from video section: yesterday's video... thoughts?

[NativePaul]

Pirosteel on here is Joseph Toth whos company is ToysPort, he designed Syncrons, built them, has fitted out dozens of them to sell ARTR, and has raced them, he will be able to give you the best setup advise for that one.

Different makers did have wildly different ideas on Mono steps, 20 years ago stepped monos ran with riggers and cats in our hydro classes, and when the powers that be realised that was ridiculous and decided they were Monos, many different directions were chosen. Hopf's big single steps were very efficient and ferociously fast in a straight line, but tended to ching around corners, Tenshock's dual stepped hulls turned really well but lost too much in the straights, I think the Chief may as well be unstepped for the size of the steps and I would try setting it up as if it was. With nearly 2 decades of development steps have converged pretty closely around an ideal for the Naviga course, and for the last couple of generations (5+ years) all the race designed stepped monos have had single steps of roughly the same size and in roughly the same location, while hull size, deadrise, lifting strakes, spray rails, ride pads, nose pads and aero change according to the conditions the designer wants the boat to excel in.

Your Chief looks a little wet, but you are running in good conditions alone, in race water it may be perfect. Do you have self righting and if so are you allowed to use it? Are your races long enough to benefit from it? We tend to run our stepped monos at around 27%, but we race for 6 mins and if a self right takes 5 seconds, just 1.4% extra speed makes that up. If however you are running a minute and a half sprint race, you need to go 5.9% faster to make up for a roll over, which is very unlikely just from moving the CoG back a few percent. Even for a 4 minute Offshore race you would need to make up 2.1%. It seems Like you would be better off running wetter and safer and throwing your extra power at it.

[Jesse J]

Thanks Paul, sounds like a different world across the pond. Here I would be pretty much limited to p offshore, therefore will try your suggestion. I have heard mixed reports about the legality of self righting, so will not plan on it.

Do you guys do much tuning with strut depth or angle?
Weight back and behind the front step, is what I'm hearing.

[NativePaul]

I will caveat this with telling you that I was a cat guy, and now race riggers, I am not a Mono guy so I don't know the exact and measurements, I have given it a go in the past, but I wasn't too keen and my own stepped race mono was designed back in '08, I have not raced it for years, and it would be hopelessly uncompetitive if I tried to race it now. They are however the most popular classes here, I see them all the time, and the standard is pretty high. My last club had the current Mono2 (4-6s) world champ in it, and my current club has a former world Mono2 champ in it. I can give you generalisms and rules of thumbs, but if you want to know specifics I would have to ask one of the mono guys.

There is little or no prop depth angle or length tuning, all monos have the motor mounted as low as possible in the step, and the vast majority use a straight alloy, carbon, or alloy and carbon stuffing tube, with a fairly thick for the power (2mm for Mono1 (around 500W) and 2.5mm for mono2 (around 1kw)) piano wire drive, and at least one intermediate bearing in the stuffing tube to reduce the whipping intrinsic to a straight shaft. The prop hub is placed close to the line following the step and transom. If you get the depth or length of the prop wrong you unglue the stuffing tube, oval out the transom hole reglue it and try again. There are exceptions, most notably Rasch makes a carbon fibre angle adjustable stinger that many of his customers use for ease of setup, and his boats have a lot of aero lift so the weight is not as critical. All props are very low lift types and with no ears, usually Tenshock CNC, Graupner Carbon, Dr Prop CNC, TP CNC, not the Octura clones in rages that include them like TP and Doctor Prop.

Sorry, I don't usually take static shots, so these are the best "shaft" shots I have on my PC, 2 typical stepped mono straight shafts, and the Rasch carbon stinger, all on well set up boats despite the aerobatics in the photos but if I post more typical photos you cant see the shafts. the number plates are all about the same size, that is a Mini Mono, a Mono1 and a Mono2, so although it looks like the step size is getting smaller on the lower pictures, it is fairly consistent, it is just proportianally smaller on the bigger boats.

[Jesse J]

Dang, you is a greased weasel!!

Thanks for info. So os you're stinger perpendicular to transom and just gets moved up or down?
Low lift props, and straightest wire drives. Got it.

How do you make them turn well? Mine want to turn flat... is this common?

I got a synchron from Joseph and it likes to hook... my inclination would be to raise strut.. but he told me it won the 1999 races... I was wanting to make it run like it did when he made it win.

[Fluid]

Hmm, I suspect that the speeds in the last millennium were considerably slower than they are today. Maybe slowing it down will help....


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[Jesse J]

Bah! Would Tom Taggart agree to SLOWING down?!? Or adding weight? Or letting up?
Ok, fair enough, slow it down or change the strut depth. Of course I can't argue with the man who wrote the book on FE racing....

[NativePaul]

Stinger/stuffing tube/driveline should be at a slight angle to the transom if the transom is upright (which it may or may not be).

Speeds are definately faster now, but maybe not as much as you expect as they keep adding runtime to our races in order to moderate the speed. If I recall correctly and I am not sure I do, we had swapped to brushless back then so motor efficiencies were similar, batteries were NiMh of about 3300mAh and run time was 4 minutes, now we have about double the capacity but 6 minutes runtime.

The biggest change would be weight in 1999 it would have run 12s sub C weighing about double what a 5000highC or 6600low pack, I would try running 4s2p with both packs on the left to simulate how it would have been with NiMh.

Hooking is often a Cog too far forward, or could be a rudder angled with the bottom further back than the top, A prop with too much lift can make it hook with the power on too.

[Erik Aa]

Would an octura prop (say x437/3) work in a stepped mono if you detounge it?

Best,
Erik

[NativePaul]

I haven't seen it done sucessfully, but maybe if you detounge the hell out of it for efficiency and cup it to reduce lift

[Jesse J]

What prop would be good start? Now I have an x442 and AQ 2050 motor on 4s

Also, do these things turn flat or bank?