Ill get pics tomorrow if it's not raining. The pump was built by George over at ARS Marine back in '11, but I haven't opened it up yet. Plan on doing that this winter (among other things) to inspect/freshen it up, although it looks brand new inside. Very low hours

Awesome!! A fellow newbie! 
Great looking ride!

Hi 08chevyguy.
Thanks! It's not perfect,  but pretty darn close, and exactly what I wanted.
It's a shame that I've looked at a lot of jet boats around here and for not much less than I paid for the Sprint,  they're completely molested piles.......

Hi Fordlover!
Thanks!

Is it right to already start thinking about the changes I want to make to it after owning it a week? (If it ain't broke, fix it anyway???... .)

Thanks 08chevyguy,  I appreciate the encouragement and I'll definitely post more as I move forward on the build! 

Hi everyone, Happy New Year!!

Well, I'm on to the next step and I thought I'd provide an update......

I got the chance to clear some space on the floor of the shop (my buddy that shares shop space with me calls it the toy box....  ) and put together a couple sheets of plywood, cut some battens out of a 16' piece of pine and started lofting, or drawing out, the hull full-size to verify the data points in the Linesplan. I was happy with the lines generated in the CAD program and I almost didn't take the time to loft it out. Boy am I glad I decided to do it!

The data points from the Linesplan are pretty darn close, but not perfect, and I've had to make a few very minor adjustments as I've been going through the process to smooth the lines out. The lofting has shown some kinks in the hull lines that I still can't see on the computer screen or on paper.

Sorry that the pics don't show the hull lines very well on the plywood, but standing there looking at the hull lines full-size, I have a much better idea of the size and overall look of the hull and I'm more than ready to start building this little ball of crazy.

Thanks for letting me ramble 

Dave

 

Yeah, it's been a crazy couple of months with work and life getting in the way of the fun, which I'm sure a lot of people have the same problems... 

But the boat is definitely going to happen. I already have too much time and effort into it to just let it go. Heck, I'm probably more excited to see this little ball of crazy run now more than ever, now that the design phase is pretty well done and the building can begin.

Thanks 08chevyguy!
Dave

Sorry Joe, I got a little sidetracked.....

As far as my C of G criteria, I shot for putting the C of G just behind the center of air lift at speed, which ended up being 3.8' forward of the transom, so I didn't end up with too much stern lift and unloading the pump, or too much bow-down moment. Unfortunately, this proved to be as much of a game as the radius keel is.
The problem is that the center of water lift moves forward and back at different speeds. Center of air lift moves even more drastically ( in the case of my design, when it starts lifting, it starts about 7' forward of the transom and moves back to about 4' from the transom by 75 mph, and starts moving forward again by about 80 ). While this is happening, water drag, air drag and other bow-down moments are moving the C of G at the same time, so they actually can pass each other forward and back. A lot of this relates to the shape of the tunnels, the "attack angles" of the tunnel roofs and how close to the water the tunnel roofs are, along with the shapes and surface area of the wetted sponson and center pod surfaces.
Basically, a fast and efficient tunnel hull is running on the edge of being unstable at speed. The trick to making this work is making the lift and drag moments move slow enough to able to control it with throttle and trim when running the edge......

Thanks Joe,
Dave

Hi Joe, thanks for the reply! This is the last detail of the design to hammer out before I start building and it's been driving me to drink more than I already do! 

I do feel more comfortable with this last keel design myself after digging around for info, and your feedback definitely helps.it also became pretty obvious that a good starting point is the best I can hope for, but it's a lot better than what I had before.

To start off, the hull is a one-off that I'll be building in African Mahogany and Okoume marine plywood, so I won't have the issues involved from doing it in glass. The pod does look longer than it really is because of the 3D rendering program I'm using skews the perspective. It's actually extends 12" behind the transom to be able to fit the powertrain in the boat and get a good C of G (I determined the pod length based on where the back of the shoe landed). The Linesplan shows a better view of the dimensions.

The bottom of the hull.has a 2° deadrise at the transom, so the outside edges of the center pod are 1/4" higher than the keel, and the bottom inside edges of the sponsons are 9/16" higher than the keel, so a little more than a 1/4" difference (I was planning to test it as-is and if I ended up with chine walk or other weirdness, I was going to try the aluminum angle air entrapment mod on the sponsons). With the radius keel at 6.5" wide on the 12" wide center pod, I'd have 2 3/4" of hull on either side.
The very front of the intake lead-in (about 2" before the front edge of the grate mount in the intake pics) is 8" in front of the transom and 6.5" wide and tapers down to 5" at the start of the shoe radius. The center of the front edge of the shoe is 15" behind the lead-in, so 7" behind the transom. With the intake being flat front to rear and side to side, I was looking to mount the intake flush with the bottom of the center pod with the surrounding mount flange CNCed to match the deadrise angle, and have the radius keel end where it blends Into the intake. Does that sound appropriate?
I did actually design the fins to be bolt-in and changeable for testing, I'm also fabbing an adjustable ride plate (currently planning on 6.5" wide by 12" long.....)

I actually worked with Jim up at Aeromarine Research on developing the design, and running a performance analysis on it, this thing starts trapping air at about 50 mph,.and by 70 it shows that the outer sponsons are clear of the water and it's generating 27-28% of it's lift aerodynamically (which Jim stated as being a pretty high percentage). The analysis also shows that with the stock 165 hp and a conservative 39% thrust efficiency from the pump (sounds pretty low to me), it's showing speeds over 80 mph.

I really appreciate the help Joe and please let me know what you think, or if you need more info.

Thanks!
Dave

Six-Oh-Nine, I also took some pics of the pump intake to give you an idea what that looks like.

The intake is flat both front-to-back and side-to-side and is 23" x 7". With a 1.5" wide aluminum flange I'm fabbing to surround the intake and mount it into the keel, the outside dimensions are 27" x 10'. The front of the lead-in to the intake will be about 5" from the front edge of the flange.

I've messed with the idea of doing a radius drop keel previously but i'm having a hard time visualizing how to do it with this intake and also the transition from the original keel to a radiused drop keel both at the front of the drop keel and transitioning into the intake to properly load the pump. One thing I can easily do with the mount flange being CNC'ed out of 1" thick 6061 stock is that I can form a radius from the edge of the intake to the outside edge of the mount flange on the sides, if that makes sense?

Thanks again.
Dave

The second design is, what I guess I would call, a more traditional looking drop keel. 6' long with the same drop and 11" wide where it attaches to the hull and the side walls angle in to 9" wide at the bottom surface of the drop keel. It runs level for 3' 3" forward and then gently tapers and slopes again to a point on the keel, but with much softer, more "bulbous" shape.

At this point, I'm leaning more towards design #2 as a better design for the job, maybe even incorporating the vertical side walls from design #1 to create sharp chines for the drop keel?

Again, any help with this problem would be greatly appreciated!

Thanks
Dave

Hi Dan'l
yeah, the Honda turbos evidently run pretty good from what I've heard. My donor was a wrecked one with 66 hrs on it that I got a good deal on. The ski is 842 lbs and has a pretty deep V hull so it should run REALLY well as a 650 lb tunnel hull.   
And if, for some ungodly reason, it's not enough, I can tweak the boost 5 lbs, add water / meth injection and go from 165 hp to 240+...... 

Unfortunately, the pump intakes on these are molded as part of the ski hull so I'm adapting the pump to a aluminum intake duct from a Yamaha GP1200 ski (which has a flat intake).
The river minis are pretty frickin cool for sure, but the hull design is completely different from the tunnel I'm building and I'm not sure if the flat Delta's that they use would work well on it, unless someone can tell me differently?

Hi seapat and Blue2184, thanks for stopping by.

Yeah, some of those river minis are pretty badass for sure!

This is the ski I picked up to power my mini. 1235cc of DOHC EFI dry-sump 4-cylinder Honda with a turbo and air-to-water intercooler. I think it should be a pretty cool little setup when it's done 

Thanks!
Dave

Sorry guys, I should provide a few more details to give everyone a better idea what i'm messin' with.....

The hull is 12' 6" long with a 5' 0" beam and set up for the powertrain from a 2004 Honda R12X PWC donor. The center pod is 12" wide and extends 12" beyond the transom as a drive extension pod (similar to a Southwind TD or Kachina Condor hull). The keel centerline sits 9/16" below the bottom edges of the sponsons at the transom. The pump intake is 15" from the lead in to the front of the shoe assy. The lead in on the intake is also 21" from the back edge of the extension pod.

Any ideas on this would be great.

Thanks again
Dave