Shamanized Topspeed

[lohring]

There has been some discussion about the Topspeed and similar tunnels being a little small for the latest P spec tunnel speeds. The Shaman seemed to be the next step up in size. I took a very abused Topspeed, cut off the sponsons, revised their bottoms, and added a new center section. It keeps the Topspeed look, but is a very different boat. Its 1" longer with a recessed transom and has a 1 3/4' wider tunnel. The sponson bottoms have 17 and 20 degree angles. The result ran very well with a stock 42 x 55 prop.

The tunnel tabs were another idea that works too well. They floated the boat so well that steering inputs barely turned the boat. They also lifted the transom so when the boat did turn it tripped on the left sponson. I couldn't move the CG any more aft, so taking them off was the answer. I think that tunnels like the Leecraft XT-460 that often end up with bow weight could use the tabs.

Lohring Miller

 

[Kris Flynn]

Looks very interesting Lohring!! you have spent some time and effort on this one for sure!

Did you start with a TS3 or TS2 center?

I can see some 'Cant' on the sponsons which is interesting also.

Very deep tunnel which i think is a good idea.

Do you make them progressive deadrise? ie less as it head toward the front of boat?

 

[lohring]

The center section only uses part of the Topspeed 3 nose and canopy from the old cowl on a narrower radio box. It was easy to do and was a light weight solution for a complex shape. The sponson bottoms were built up with 1/2" balsa and had the angles, copied from the Shaman, carefully sanded in. I held the same angle to the stumble blocks. This left the outside edges nearly the same but with the inside edges 1/2" lower. I sheeted the balsa with 1/16" ply and built up the stumble blocks to match. I extended the balsa and plywood sheeting 1" behind the sponson transoms and covered the top for added length. There shouldn't be any cant since I built a jig to hold the tunnel bottom flat and the sponson edges vertical. There was some of the Topspeed wing left on the sponsons so I just glued the 1/16' plywood sheet to it on the top and bottom.

I think the extra tunnel area flies the boat better and makes up for the increased sponson bottom angles. The increased angles should improve rough water handling. We'll see.

Lohring Miller

 

[Ronald van Essen]

A tunnel tab has already been tried by Kevin...forgot his last name at the tunnel WTC in I believe 2007 on a Shaman????.

That seemed to work well. Since the boat was fast and did turn well.

Maybe they are to big.....

Its good someone is trying some new stuff.

 

[properchopper]

Hi Lohring !

Pray tell, what is that piece that sits on top of the O.S. cav plate ?

Thanks,

Tony

 

[Jim Mamaril]

Hi Lohring !

Pray tell, what is that piece that sits on top of the O.S. cav plate ?

Thanks,

Tony

That has to be a K&B lower not an OS.

 

[RodneyPierce]

yes indeed. K&B Lower unit.

 

[lohring]

It's a K&B lower and that's the water cooling tube. It runs behind the cav plate to clear the prop.

Lohring Miller

 

[properchopper]

Thanks. (I'm feeling pretty stupid now :wacko: )

 

[lohring]

Don't feel stupid. It isn't obvious from that angle. I probably would have used the OS lower if my last one hadn't sunk to the bottom of our deep pond after I broke my converted VS-1 when I hit a buoy. Now, that's feeling stupid.

Lohring Miller