SAW Tunnel Design

[Kris Flynn]

I have been following the SAW Hydro thread on the main board and thought i would ask some things about SAW Tunnel design...

First: To do with the boat design, what is designed differently than the 'heat' or 'oval' racing tunnels?

Second: The motor and Prop selection are very important aspects, correct?

Thats all i can think of now, maybe more will come later from others

Kris

 

[_laxmasta2039]

Kris,

i've never owned a tunnel but you guys dont seem to talk much about turning aids or stuff like that, so i wouldnt think that there would be much to change as far as turning....only things i can think of would be smaller fuel tank, less emphasis on turning stability, and no worry about two minute starting time and other boats in the way.

Joe

 

[Slideblues]

Kris,

My experience has been this.

For SAW the biggest concern is speed and to do this you trade off some handeling.

Generally saw boats have flatter sponsons from the transom forward about 10 to 14 inches, that is no rocker that you might find in a oval boat.

Second is you build them simple and lite, cause if you flip one at the top end of the run ya might just get back pieces.

Fuel tank only needs to be big enough for a run through the traps flip a 180 and do the backup run and your done.

With a small margin for launching, warm up, and back to shore.

The hull must turn, but does not have to turn well like in a oval hull, The design must be stable as it accellerates.

Setup does get tricky, as far as CG, engine height, prop and pipe selection.

Gene ;D

 

[_laxmasta2039]

kris,

are you planning on doing a SAW tunnel?

Joe

 

[Kris Flynn]

Joe, I wouldnt mind giving one a go, although i only just finished breaking in my first outboard motor, but still would be fun none the less

I was also thinking that some of these concepts would be nice to try on an electric 12 cell Tunnel which i would only really want for speed...

would building one from balsa, then coating it with some light glass be better/lighter than just making it from ply?

Just to clarify something, what is the fastest recorded speed an outboard tunnel has gone? Is it Tommy's 63 MPH (and a little bit more) or was that done with an outboard rigger?

Kris

 

[Kris Flynn]

Something else i want to ask...do the SAW tunnels have the right sponson a bit seeper thn the left sponson to assist with acting against the torque (something along those lines anyway)?

Do you make any mods to the lower unit (K&B I'm talking about at the moment) like cutting the skeg a little shorter, and taking off some width and also thinning it down some (plus making it real sharp of course...but do you do anything other than this?

Sorry about he questions, im just very curious to how it is all done

Kris

 

[Slideblues]

Kris it is interesting that you brought up electric tunnels, the NAMBA record for SAW 12 cell tunnel is about 43mph with a Graupner Formel-1, A hull I was just talkin about in another post. With a Hacker motor on a K@B lowerunit, by Larry Larson. Read it in the June 2002 issue of RCBM.

For 3.5 Nitro

IMPBA 1/16 mile SAW

Tommy Lee

Record run

3.504 sec.

64.212 mph

LeeCraft Tunnel

NR Outboard

ABC prop

O'Donnel fuel

Futaba radio

Lohring might comment about the sponsons,

Let me see if I can find a pic of my lower unit mods....

Gene ;D

 

[Slideblues]

I do mine like the shape of the older models, polish from the cav plate down and sharpen the edge, however the longer skeg is needed on some hulls,

So test,test,test

If ya check out the shadow of the blade profile, ya might pick up on a secret prop too...... :-X

Billy, I see you lurking, just waiting to pounce!!!!

Ha,Ha,

Gene ;D

 

[topfuel443]

Gener, whats the saying............Dont mess with TEXAS (or i guess you would want to in this case!) what prop is that anyway?

~ James

 

[Slideblues]

Here is what I was talkin on the sponsons, see how they stay flat as they come forward for around 10 inches:

Last years S-1 in pic....

 

[Slideblues]

Keerect, Prather 220 dia. reduced and texas cut, In the first pic you can see the thinned blades. Seems like I added a little cup, and a smidge of tongue relief cut.

Gene ;D

 

[Kris Flynn]

I didnt get the June 2002 issue...I dont think any newsagents had it in their stores ???

Was there any pictures of the OPC tunnels in it? Or very much information about them? like setups?

Thanks for pictures of your lower (old one anyway) i was only thinking of cutting it down a little, maybe 10mm of the depth and 5mm off the width, but add more angle to the front of the skeg, like the real ones.

Have you, or anyone for that matter, done much testing with the didths of the ride pads?

And one more thing...Does Mr. Tommy Lee have an internet connection? If so do you think he would be a good addition to the knowledgeable people who are already coming here and sharing their priceless information??

Kris

 

[Slideblues]

Kris the pic in the mag was very small, you really could not tell to much about it, here is a pic of the kit, and a list of parts that was in the mag.

Driver, L. Larson

MPH, 42.93

Hull, Graupner Formel-1

Motor, Hacker B50-7XL

ESC, Schulze 105

Cells, Fuller 2400

Hardware, K@B

Prop, Octura

Dont know if Tommy Lee is online or not,

The sponson shape and width is Grim's design.

Gene ;D