Tunnel strut angle

[BHChieftain]

I'm setting up a woodstuff tunnel with an OS lower. I've got the strut height with the prop shaft level with the bottom of the sponsons.

On the strut angle, I'm striving for level. If I had to be a hair off, am I better with the prop shaft canted up (which would lift the nose) or down?

It seems the OS lower is biased with the prop canted down--that is, if the motor were // to the transom, the prop shaft would be angled down.

Thanks,
Chief

[siberianhusky]

No valid info on the woodstuff tunnel, never even seen one run, but have you made a setup board yet? Handy for all boats but I find it almost an essential for tunnel hulls. Gives you a reference to measure from, much easier than trying to measure off the hull.

[BHChieftain]

I've seen a setup board, but I don't have the specifiecs on how to make one. If it is just a piece of wood with a notch cut out then I'm thinking my eyeball off the table would be close 'nuff....
Chief

[properchopper]

I am by no means a tunnel expert () but I have lots of experience burning up motors on my current tunnel. What I've found is that many tunnels (like my Herb Stewart 30" spec powered tunnel) runs nose high as do the Woodstuffs (IIRC). Consequently while running at that attitude (nose high, stern low) the prop gets fairly submerged, thus really loading the motor.
My particular solution has been to run the drive vertically higher than what's normal for other tunnels; eg. the ML295 which runs way more level. Also the drive angle is adjusted to compensate for this. A setup board is a no-brainer and is a good way to keep track of this.

DSC03185.JPG DSC03186.JPG DSC03187.JPG

[BHChieftain]

So is the general idea to have the prop shaft run // vs the waterline *given* the natural lift of the nose, as opposed to trying to adjust the shaft angle to dial in the nose lift?

Note, my particular hull runs fairly flat as is, just some slight lift. I can either get the shaft just above the sponson bottom centerline, or just below --- I actually don't have easy adjustability across that range given where the transom holes were set (I can either set it slightly low to excessively low, or I can take the lower off the bracket, flip the bracket around, then I can set it slightly high to excessively high). If I set it slightly high ( which is the lowest possible setting with that bracket configuration), then I can get the prop midline if it is angled down a bit.

But if the objective on the shaft angle is to be level after the nose is lifting ( implies i would want it slightly angled up) then this isn't going to work too well.

I would be able to set it up exactly like your last picture, however. I'll give that a go.

Thanks
Chief

[siberianhusky]

The back part of the VS-1 instruction manual actually has a very good section on general tunnel hull setup with a nice breakdown of individual adjustments effect on the hull. You can download the pdf of it, worth the read.

[BHChieftain]

Thanks!

[properchopper]

Chief, I too belonged to the "it's either too high or too low club" until I elongated the heck out of the mounting slots to get me where I needed to be. I've found (remember, I don't claim to be a tunnel expert) that keeping the prop above the sponson bottom lets the motor run free'er and wind out to it's max, given the prop load. I also found that shifting the cg forward a good bit and using some up-angle on the outdrive lets the hull air out under full throttle but backing off the throttle a tad going into the turns lets the hull settle and corner way more smoothly. Doug P (here on OSE) has a nice running Woodstuff (until his annual t-boning by Pete W at WW's) and might be solicited for tuning.

[BHChieftain]

Thanks Properchopper

[AlanN]

Tunnels are funny in nature. It depends on the hull, outdrive, location of cg, prop wind and water conditions. Some tunnels like a positive angle and some lie negative angle. I have been told by some older nitro runners that they preferred a negative angle on their woodstuffs and some say completely opposite. So, as the gentlemen have suggested....get a flat board and spend a good amount of time changing angles and depths to get it running comfortably for you. Make your adjustments in small increments and note what the changes do.

[BHChieftain]

Yeah, that's what it looks like. Funny thing is, when I got it with the strut set 1 full inch below the sponsons, it actually ran great... super stable, and only moderate nose lift. Motor was cool, but ESC and connectors were pretty hot-- thinking that "submerged" prop was really pulling a lot of amps and also costing speed. I've got enough ideas from this thread to keep me busy for awhile. Thanks everyone!

Chief

[AlanN]

1" is way too low.

[BHChieftain]

Yes, I know...