1/8 Miller sponson depth

[Eugene Lyle]

Hello Everybody !

Currently building Dumas 1/8Miller American hydro. Have substituted kit wood with ply to make new parts. Frames from sponson transoms rearward are 1/16 and I've added the requisite lightening holes throughout the framework. I'm nearly ready to assemble the ride pads at this point. Without the pads, the air trap depth at the inner sponson transoms is 7/8". The ride pads will add 3/4" at the sponsom transom inside which I suspect will be too deep. The sponson dihedral is basically zero for about 50% of the sponson length measured forward from the sponson transom without adding the pads so obviously, I'm gonna have to do something there. I'm thinking of trimming down the pad keels. My question is this: What air trap height (sponson depth) should I end up with at the sponson transom insides ?? Or should I try a different approach ?? I did view the pics on the Dumas/ML hybrid Miller build thread but cant really tell how much depth there is with the ML kit. Thanks in advance for any and all input ! ---Gene

 

[Hydro Junkie]

This might help. I found a video about the Atlas/Miller and, in the first 21 seconds, it shows that the sponson bottoms are even with the bottom of the air traps and only the ride pad is lower. The video is here:

 

[Eugene Lyle]

Okay Sir, Thanks! That is the way the build has worked out with the sponson bottoms being even with air trap bottom. ( FYI: Also forgot to mention in my original post that I have widened air trap by approx 1" to 12".). At any rate, extra 3/4" inches added by the pads seemed like a lot to me as ride surface to top of trap would become 1 5/8" at the sponson transom inside. If these measurements are reasonable, maybe I should just go with the pad dimensions stated on the plans. I know with the 1/8 Dumas Atlas, guys are told they should ditch the extras on the sponsons which decreases the measurement to the top of the trap approx 5/16 ". Maybe thats where I'm getting this. And, they are two different hulls so one doesnt necessarily work out the same as the other. Additionally, the Dumas Atlas sponson depth is substantially greater to begin with. I've not really ever heard of anyone modding the Dumas Miller dimentions but I wanted to check with others in case someone out there might know better on this. I am also still curious as to the ML 1985 Miller measurement.