Sub-Surface Drives and Hull Design??

[Darin Jordan]

I was wondering if anyone out there could shed some light on some of the technical details of hull design when using a sub-surface drive setup?

I've been doing some research, and there appears to be a couple of ways to go. I noticed that NAVIGA uses a lot of "Eco" style hulls, with the propeller way forward up under the hull, and the hulls appear to be designed with a "planing" section in the back half... almost flat back there... I've posted a pic as an example.

Then I've seen other applications where the prop and strut are located more simliarly to a surface drive setup, the strut is just pushed down much deeper and the driveline exists the hull up under the keel...

Can someone point me to some reasonable tech information or maybe join in the discussion here to shed some light on what it takes to make a good sub-surface drive application?

I'd appreciate any information you may be able to provide.

Thanks,

 

[carlnoki]

your pic of the boat in the example is the style the rest of the world uses (for the most part) called FSR-V.

they are set up for counter clock-wise running for VERY LONG periods of time. (20 min. and up)

the rear section is basically pretty flat and the owners and or designers use R/C adjustable trim tabs for planing and turn attitude as well as little permanent mounted non-adjustable tabs along the hull line to help in the ride attitude.

the props used are of the threaded spin on type for super fast replacement in case of damage during races.

they are not designed like those we use here in the states (ABC, Octura, ect.), they have ALOT of what i refer to as reflex in that the props usually are curved rearwards as you get closer and closer out to the tips. (which also helps prevent TORQUE roll during boat operation). we tried one of these when we were stationed in europe back in the 80's with a couple of Octura props and boat NEARLY torqued over on it's top when the motor was run up.......................

our style of sub surface (like you stated ) is the strut is lowered below the keel line and the prop is still out back of the boat.

most people used this method on the boats back in the days (Demon, Prather, Sightler, Witch Craft, Ect.)

if anyone else would like to chime in, please do so. can't remember what all was involved in setting one of those up. (been WAY too long)

carl

 

[marker]

Darin

Here are some drawings for a FSR 3.5cc and 6.5cc hull for some information on their setup .What size hull were you looking at.

Mark

http://www.chinahobby.com/motu/drawing_dld01/fsrv35.jpg

http://www.chinahobby.com/motu/drawing_dld01/fsrv65.jpg

 

[Darin Jordan]

DarinHere are some drawings for a FSR 3.5cc and 6.5cc hull for some information on their setup .What size hull were you looking at.

Mark

http://www.chinahobby.com/motu/drawing_dld01/fsrv35.jpg

http://www.chinahobby.com/motu/drawing_dld01/fsrv65.jpg

Thanks Mark and Carl,

This is all very helpful...

Size?? I'm looking at something that would be in the 20-22" range... It looks like I'm on the right path... all of these look to be Eco style boats. I have an H&M Eco on the way to give a try.

Thanks again for the info.

 

[Ian Webster]

For the FSR-V stuff take a look at Dave Marles site, loads of setup info for his boats here.

On the ECO style of boat he has a setup for the Sloopy, which is similar I think here, hull is around 18".