Dumas 3.5 Hot Shot

[greenman407]

My first glow boat . It comes as a kit made up of birch and mahogany plywood. I tried some unusual things back then. I didnt like to see the wood grain on the surface of the boat so I tried painting on CA onto the skin and let it soak in and then sand. After this treatment 6 heavy coats of POLY-U polyurethane. It came out looking like a piece of glass. You could comb your hair in it. That was way back when I had hair.

[greenman407]

This was when I was new to the hobby, and I was just amazed how you could just sit the boat right down in the water and it wouldnt go!!! You could see the prop spinning madly and the motor reving and it would just sit there. What , did someone sell me a broke engine??? CAVITATION is a cruel thing to pull on a newbe. But at least I knew how to start it. Wow! Look! Back then I had hair and was skinny.

[greenman407]

I learned a lot from this boat. For one thing dont count on the manufacturers instructions to always be correct. In this case Dumas insisted that the fuel tank had to be located forward of the center of the boat. That doesnt work! The engine cannot draw fuel from that far away. Shows a lack of testing on Dumas part. The Fuel tank has to be located as far in the rear as possible and as high as possible in relation to the carburater otherwise the engine will start and run but will die out as soon as it hits the water. Here you are, new to the hobby and you dont know what the problem is. Also I learned how important it is to keep the radio componants dry. DUH!!! Wrap the reciever in a ballon and seal it well and dont mount it on the floor of the radio box but up off the floor so that any water coming in for whatever reason will not soak your rx. Use push rod seals where the pushrods exit the radio box and check your reciever batteries after each run and replace as needed.

[greenman407]

The boat was designed by Jerry Dunlap and the boats that he has come up with since then have shown continual improvement in hydroplane design. The kit itself is a high quality design with die cut parts and the instructions are good. But keeping up with everything else the kit is pricey. Its 3 times more than what I paid for mine back in the late 80s. Is that progress???

[greenman407]

Tragic circumstances led to the loss of this boat. Almost like the" Bermuda Triangle". I had modified the boat with a tuned pipe and was tuning it at a new body of water that I had found. It was a large lake that had a canal on the far other side that emptied into another smaller pond. As I had previously mentioned water had gotten into the radio box on several occasions but not a huge amount and I assumed everything would be OK as it was working fine at the present. I was having trouble getting the needle set the way I wanted and I figured I would have one more go at it. I launched it and it seemed fine. Then all of the sudden it took off like someone else was controling it. Murphys law had interferred and believe it or not it was heading for that canal!! The bad thing about the canal is that it would then leave my line of sight. If I could see where it went aground then I could make a recovery. Well as I watched it disappeared for a few seconds into the canal and then I could hear the engine race and then slowly die. I got in my car and drove over to the other side of the lake. All of the banks were heavily overgrown with thick brush and foilage. I came back the next day with a canoe and plied the area but could find nothing. The problems were many but one of them was that the boat was black (just like the water, black as ink)......................and it was never seen by mortal man again. On my next boat I painted it red and used a radio with a failsafe. Also I made sure that the radio gear stayed high and dry. That was the last time that I used that lake.I went looking and found a much more suitable location and I never lost a boat(permanantly) again. The End

[He Who Shall Not Be Named]

Not cavitation. Air binding. Two different mechanisms, Mark.

David

[greenman407]

So cavitation is the extraction of air molecules from the water caused by low pressure areas in front of the blade and air binding is the pulling of air from above the surface of the water down into the prop...........right?

[ManOwaR]

Believe it or not, those bubbles in cavitation are actually steam. Those low pressure areas drastically reduce the boiling point temperature of the water thereby giving us this effect.

[greenman407]

Joel, Nice Facebook page. I stole a few of your pictures if you dont mind. So your going to do a Astute next. COOL!!

[ManOwaR]

Thanks Mark! Yep, go ahead, whatever you need.

Joel

[ManOwaR]

Yesser Astute it is. she has some very nice lines and they need to be recaptured in 1/72!