Roland Illvesand
Active Member
- Jan 14, 2019
- 140
- Boat Info
- Sea Ray 260 DA 2001 Mercruiser 5.7 EFI and Bravo 3
- Engines
- Mercruiser 5.7 EFI and Bravo 3
The tunnel fits in the holes.
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Roland,
Lookin good. Is the tube glassed to the hull and then trimmed, or trimmed and then glassed to the hull?
What is the aluminum frame under the boat? It looks too complicated to be a trailer.
That is really interesting. Is it something you designed as a custom boat holder, or is it a commercial product in Sweden?
Lookin good! Has the boating season started? You look like you are down to the wire.
I remember reading something at one point, what is the reasoning that the back side of the tube isn't flush with the hull? Does that help prevent cavitation?
Looks good!
The way I read that makes yours look backwards... sorry, probably just me.
This is from the istallation manual.
High-Speed Boats
Tunnel lengths must be increased to protect the propeller from damage when crashing against the water surface during high-speed cruising.
1. A possible problem in sail boats or fast powerboats is that a non-rounded surface can generate drag from the back face of the tunnel, as it creates a“fl at” area facing the fl ow of water (1).
This problem can be solved in two different ways, depending on what is possible or easier to perform.
2. The best solution which generally reduces the most drag is to make a recess in the hull at the back of the tunnel. As the back face is removed water can flow freely past the tunnel entry. The depth and shape of this recess will depend on the boat and the angle facing up/ down aft of the tunnel insert. Normally it is angled slightly down because of the water flow on this area (2).
3. Making a deflector/ spoiler in front and underneath the tunnel can also reduce damage to the thruster and drag. The deflector/ spoiler will push the
water flow out from the hull so water can pass by the back face of the tunnel. The shape and size of this deflector/ spoiler will depend on the hull shape.
The easiest way of making the deflector/ spoiler is to retain a part of the lower forward area of the tunnel while installing the tube. Use this area as support to mould a soft curve/spoiler shape from the hull. (3).