Here's some.
Mark N
And now doing some changes to the tunnel shape.
Here's some.
Mark N
And now doing some changes to the tunnel shape.
Jimboat liked this post
I like your sponson shape. It's different and you are now changing the profile of your aerofoil. I guess to create more lift and move the center of pressure forward .....
Are you tunnel side canted inwards? Are there any benefits do that. Read somewhere it help hold better during turns....
My Bunky Bowerman hydro has a similar curve where the bottom meets the sponsons forward
Not as radical as the tunnel.
Yes, I am trying to have the lift move forward so I can move weight in the boat forward. The original design was super on the straights but needed a lot of work in the corners and dock starts. There was so much boat out of the water it didn't want to turn. It rides super high, not bow high but the whole boat. Jim's program worked great for such a radical design as my boat. It was just the operator of the program that needed to be more conservative.
When I went to build the boat I did it (exactly) as what the program showed. Even the wing shape. Notice it comes back to about 1/8" at the rear! Tough to do but I wanted to go by the program to the very last detail.
The changes I've made this time are not from Jim's program but from some experience with working on other tunnel boats. It's somewhat based on the design used in SST 60, just smaller. The S bottom is used in many of the small hydros and inboard hydros and in the slower tunnel classes. It's been tried in SST 120 with not so good luck, they go to fast for the design.
The canted tunnel walls have been around for a while. Mine are, in the new design, a C shape. Will it work? Don't know yet, but it will interesting to find out.
Mark N
Yeah, Hall Kelly's 3 point hydro Ben Hur has very similar bottom profile as your hydro. Not as pronounce as Mark's tunnel but similar. Read somewhere this helps lower the pressure differential at the bow and keep it from blow-over while increasing the lift at the aft......
It did great on the Ben Hur and I am sure too on your Bunky Bowerman.
Sounds like you are on the right track. Moving more weight forward, shifting the centre of presssure to the bow and with the S bottom, negating the lift a little at the bow. This should give you some control of the directionality in turns. How much weight have you added to the hull thru this re-design?
Mark N,
Nice boat, any dimension eg: tunnel width X long
Thanks in advance
Wfred
Well, I added 31" to the length of the tunnel at the front. Sounds like a lot but believe it or not my wing section was only 7 feet long before. It's pretty amazing that Jim's program worked on such a radical design.
So, I put thicker plywood on the tunnel bottom, added the pod, added extensions behind the sponsons (for flotation), cut access holes in the decks for adding weight in the sponsons (we were 75 lbs. light before) and cut the back of the capsule for moving the gas tank forward.
I will take off the aluminum on the transom too. Hard to tell, maybe 15 to 20 lbs. more than before.
Mark N
I'll be at the shop tomorrow and check again. I don't have that design on the computer anymore. Working on a new one The new one is going to be based on F1 designs, deep sponsons and deep pod. And in a kit form. Hopefully it will be ready for next summer or fall. Depends on work schedule.
Mark N
There are currently 1 users browsing this thread. (0 members and 1 guests)
Bookmarks