Rebuilding a 30 year old Dumas DV 40!
06-29-2009, 03:42 PM
#26
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RE: Rebuilding a 30 year old Dumas DV 40!
Performance report:
I had the boat out at the lake for a week and got a lot of good runs.
I had not commented on engine temp, and the marine conversion because I did not want to give misleading info until I had verified this on the water.
Initial temps on land once went as high as 255F with the water bottle about 2 feet above the engine. I was pretty concerned, but in the end all worked out OK as this was a fresh engine (less than 5 aircraft flights in its previous life) and after a few sloppy-rich break-in runs on the water I believe it now runs with reasonable temp. After a run, with a 30 second lag to get to my temp gun I never got a reading over 200F. Mostly 160 to 170F. I ran 15% aircraft fuel and an OS #8 plug after break-in.
So I can say that a modern aircraft engine can still be converted to make a good general-purpose non-racing marine engine.
I bent the Octura kool-clamp to conform to the square shape of the OS 46 AX cylinder head and also put thermal conducting grease between the kool-clamp and the cylinder head. The flywheel was a Dumas from the original DV-40 kit and the collet was an Octura Flex Coupler for 1/4-28. I kept the original aircraft style muffler (reversed in direction) and used a muffler pressure on the fuel tank. The pressure nipple is on the lower side of the muffler, so I may re-locate the nipple to the top side of the muffler, now that I am pretty sure I'm keeping this engine in the boat.
BTW the boat is faster than the old 1975 Fox 45 with tuned pipe that the boat had before. The OS 46 AX has more advanced porting and a much larger carb. So, even with the aircraft muffler, it makes more power than the old engine did with the pipe.
I had the boat out at the lake for a week and got a lot of good runs.
I had not commented on engine temp, and the marine conversion because I did not want to give misleading info until I had verified this on the water.
Initial temps on land once went as high as 255F with the water bottle about 2 feet above the engine. I was pretty concerned, but in the end all worked out OK as this was a fresh engine (less than 5 aircraft flights in its previous life) and after a few sloppy-rich break-in runs on the water I believe it now runs with reasonable temp. After a run, with a 30 second lag to get to my temp gun I never got a reading over 200F. Mostly 160 to 170F. I ran 15% aircraft fuel and an OS #8 plug after break-in.
So I can say that a modern aircraft engine can still be converted to make a good general-purpose non-racing marine engine.
I bent the Octura kool-clamp to conform to the square shape of the OS 46 AX cylinder head and also put thermal conducting grease between the kool-clamp and the cylinder head. The flywheel was a Dumas from the original DV-40 kit and the collet was an Octura Flex Coupler for 1/4-28. I kept the original aircraft style muffler (reversed in direction) and used a muffler pressure on the fuel tank. The pressure nipple is on the lower side of the muffler, so I may re-locate the nipple to the top side of the muffler, now that I am pretty sure I'm keeping this engine in the boat.
BTW the boat is faster than the old 1975 Fox 45 with tuned pipe that the boat had before. The OS 46 AX has more advanced porting and a much larger carb. So, even with the aircraft muffler, it makes more power than the old engine did with the pipe.
06-29-2009, 04:51 PM
#27
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RE: Rebuilding a 30 year old Dumas DV 40!
ORIGINAL: ic-racer
Here is the radio box. It looks like a lot of wire because I am re-using a very, very long ''Y'' cable from a plane. When I get a shorter one, it will clean things up a lot.
As you can see I had a lot of those 'standard' servos to use up, so I linked two of them together for steering.
I'm still deciding on a good way to mount the switch. The 'access plug' for the finger hole in the radio box cover sticks down about one inch, so I can't mount the switch too high, otherwise the plug will hit it.
The steering control rod is at an angle because it needed to avoid the mounting screws for the strut. The ''ideal'' route for the control rod would have been right through the mounting hole.
Here is the radio box. It looks like a lot of wire because I am re-using a very, very long ''Y'' cable from a plane. When I get a shorter one, it will clean things up a lot.
As you can see I had a lot of those 'standard' servos to use up, so I linked two of them together for steering.
I'm still deciding on a good way to mount the switch. The 'access plug' for the finger hole in the radio box cover sticks down about one inch, so I can't mount the switch too high, otherwise the plug will hit it.
The steering control rod is at an angle because it needed to avoid the mounting screws for the strut. The ''ideal'' route for the control rod would have been right through the mounting hole.
I see the two standard servos working together for the rudder. How do you connect the two servos to one receiver plug. Is that the Y-cable you had mentioned or is something more needed?
Thanks
06-21-2010, 06:48 PM
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RE: Rebuilding a 30 year old Dumas DV 40!
Ok, an update to this thread. So, in 2009 the motor mount screws stripped out of the old wood in the hull. I drilled out the holes and put in some fresh dowel rod, and then re-drilled the mounting holes. I took the boat up to the lake I use when I went on vacation and forgot the controller (6 hour drive). So, this year I just got back from a week of running and can say that the boat is extremely fast. Way faster than the old Fox .45 with the tuned pipe. The trim wedge added to the outdrive was perfect! It had very good stability blasting over waves and flying through the air.
The only downside is that the engine does run hot. Maybe too hot but if I can get five years of running this for one-week each year I'll be happy.
The only downside is that the engine does run hot. Maybe too hot but if I can get five years of running this for one-week each year I'll be happy.
