Distance between props on twin drive

[ray schrauwen]

How close can a pair of counter rotating props be ?

I've seen some as close as 6mm. Can they be closer?

Since the rudder will be in the middle is there a certain distance the rudder needs to be away from prop wash?

I was going to tinker with an old cat hull and some spare parts.

Ken Joye built a Drifter with props close together back in the NIMH days.

[Fluid]

This is the closest set of big props I could find. No idea how it runs.

[ray schrauwen]

Nice pic. They look very close. I should be fine. Going to hack up an old Geico 29 for giggles. Most put motors in the sponsons but, I want to try something different. Might use a MM hull I've got around.

Thanks Jay.

[dasboata]

the closer the better just save enough room for bigger diameter props ,,,Da ? LOL

[fweasel]

I love seeing twin screw offshore boats where they stagger the engines in order to get the drive shafts and props as close together as possible. It just looks so damn efficient in those engine bays.

[ray schrauwen]

Cool.

[boredom.is.me]

My largest prop will most likely be a 50mm so I did that plus 5mm. HPR Mono 45"

[RunningBeer]

...About 2mm on my pirateIMGP0766.jpg

[Ralf]

1mm on my 50" lizzard with x447.
With finalized sync gear -9mm with x457

[ray schrauwen]

Wow, those are tight! Thanks.

[ray schrauwen]

https://www.rcgroups.com/forums/showthread.php?270445-FS-H-M-Twin-DRIFTER-L-FE-Cat-ARTR

This is still awesome in my books. Finally found it in RCG from 2004.

This is what I want to do to my GEICO, well, similar.

[ray schrauwen]

...About 2mm on my pirate[ATTACH=CONFIG]146097[/ATTACH]

Looking closely, I see your trim tabs are just home made angle aluminum. Is there any adjustment?

Where did you learn this?

[RunningBeer]

...yeh a bit of guess work and I put out a call for help on OSE forum of course! I asked how high from the planing surface everyones tabs were on their pirates and ended up at @1.5mm. Then for width on the transom I tried them out wider (outside the props more) but it didn't hold the nose down in the straights. Getting the boat flatter in the corners was not too hard with rudder and strut angles, although a tiny adjustment on either had a large effect. I then moved them in close ( it didn't affect the amp draw at all) and the boat stays on the straight and narrow.....most of the time. Incidently now I'm running 44mm props, they're really close and I'm at my happy amp spot. I'd have to place the props further apart and go 5 or 6 s and lower KV if I wanted more prop depth. Cheers RB

[don ferrette]

The closer together you place the props the less need you will have to counter rotate. I have been racing big motor nitro outrigger twins for years and never needed to counter rotate (and they spin some big blades). I did do some counter rotation testing and actually found the boats ran better non counter rotating with the props close together. The Smokin' Joe's FE twin cat I have on the for sale page also does not counter rotate, tracks and turns beautifully.

[fweasel]

The closer together you place the props the less need you will have to counter rotate.

Very interesting