pushing the limits struts vs scale drives

[iridebikes247]

I have noticed a lot of guys running the long modelbaupirate drives on the back of their hpr hulls, I imagine to get the prop to sit slightly deeper in the water and of course add some more down force as a result of the vector force generated by a prop/drive pushing and dragging through the water.

If you take an hpr 135 or run an mhz 138 or equivalent with short scale style drives, then compare with long drives or even struts, to what extent will driving characteristics change at 100 mph?

I might add I have a few boats setup and have never run over 95, but shoot for rock solid stability at these speeds WOT and held for long periods of time i really enjoy running like this instead of cutting power down real quick.

Anyway figured this post addresses a topic I'm sure some of us are curious about. I plan to run struts on my next mhz build or long click drives. Basically I'm interested in this because of more stability when crossing my own wake at speed and what not.

Thanks and hope people enjoy discussing this one.

[srislash]

So how about the two piece shaft setups? They put the fulcrum point more rearward by putting the prop pressure on the transom instead of on the motor. Apparently it changes everything. I have not tried one yet buy the nitro/gas guys ran the square shafts for years.

[Ralf]

I built my Mystic138 in the first step with Struts.
Achieved any position, also prop depth variation without changing angle.
Now i drive her with the scale drives.

To be honest: the problems of the cats are in other areas than the drives, so i would build her scale. Simply because it is way more easier to adjust and better look. Has nothing to do with the better setup options with the strut.

Regards
Ralf

[iridebikes247]

http://www.kbbforums.com/viewtopic.php?f=5&t=1358

I posted this on keith's site too last week and have gotten a lot of response. I for one will be trying struts now lol. Definitely a more advanced tuning idea/option but maybe it will prove to be awesome for some of us.

Boyd Marshall commented on how much cheaper struts are, couldn't agree more. I like mtc hardware their struts are fantastic and really cheap.

The idea is to build a boat identical to the one I have, kinda, and compare. One runs low 80s one will have capabilities for over 100. Neu 1521 motors with 8mm shaft 1870kv on 7s with etti 220 esc.

[Ralf]

Sure, more options more fun :)
I wanted to describe: expect not to much.
I also glued a running surface to the stinger drives cause there was a hype anno 2011, that these flat surfaces on the drives would help....i did not recognize a difference or increase in stability on my mystic.
Boat ran 112mph with 10S1P overall and a pair of 2250 after reducing lift in the hull for its low weight (8kg). Because of that the hull was extremly sensitive. Drive-mods did not helped me, maybe other projects had better results.

Regards
Ralf

[iridebikes247]

Interesting it was so sensitive, thats a ridiculous speed with 2250s in a 138 hull lol.. I was at like 11.5-12kg with my mystic on 13s per side with 5850 motor...looks like I went in the opposite direction lol. boat was a nightmare at low speed with turning, was stable as anything at moderate speed, it had to be going very fast to get up and out of the water how I liked.

[Ralf]

Oh, it was everything else than what i had planned...lol.
The idea was having a bigger hull with respect to the 114/115s for a more robust ride in the L10-Class.
But the boat had to be light to control the acceleration power. Then the high lift of the mystic138 was pain in the ass....

Result: forget it :)
You have to load a cat to a proper weight for its lift or cut lift out of the hull.This is one of these "other problems"

[iridebikes247]

idk I like the mhz mystic but like the hpr more for straight line speed it just looks more at home than my mystic. The mystic turns so well its freaky though so I plan to always have one or two in the fleet.