MossRoad
Super Moderator
- Joined
- Aug 31, 2001
- Messages
- 57,989
- Location
- South Bend, Indiana (near)
- Tractor
- Power Trac PT425 2001 Model Year
I did, and IMO as an automotove engineer and a boat guy, it was way off base. Boats commonly have exhausts that exit below the water. In the case of these ducks, what they have done is bring the exhaust out through the hull high, and then pipe it down to the waterline, likely to keep the engine a bit quieter for passengers. The exhaust flow coming out is far more powerful than any wave action trying to follow backwards against the direction of travel and up into those exhaust outlets.
Wave action isn't going to stall the motor. It'll keep chugging happily along, just like my little Mercruiser, which runs happily with the exhaust exit well below the water line, and more than 4' below if I come to an abrupt stop. Heck, at that point, the top of the engine is better than a foot under, and it still runs happily. Same with my Jeep, which certainly isn't at risk of stalling simply because the tailpipe is underwater.
It may also be relevant to point out that although these ducks are based on the DUKW from WW2, they have been extensively modified. My understanding is that they are longer, and that the payload has been increased over the WW2 version. It also appears that they may have less freeboard, though that may simply be due to seeing DUKW's operated with light loads, while ducks are commonly operated very near capacity.
In the picture that BCP posted, you can clearly see the hood that I was talking about being propped up. In heavy seas, that's a water scoop. I still suspect that may have been a large part of the problem, especially since one boat negotiated the same heavy seas without sinking, or even taking on water as far as we know...
It is interesting to note that the thing that got the original DUKW program approved was using a prototype to rescue stranded sailors in very heavy seas.
Boat exhaust from inboard gas engines generally have an upturn in them at least a foot above the waterline, and the exhaust then exits at the waterline, not below the waterline. Did the DUKW that sank have this?