Starting my first build with a jet TNT

About using jet ski motors to power small boats

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Reado
Posts: 22
Joined: Sun Dec 16, 2007 2:47 pm
Location: Agassiz, BC Canada

Re: Starting my first build with a jet TNT

Postby Reado » Sun Aug 06, 2017 4:44 pm

Hey Dave....great dreaming and planning going on here! Maybe you could get a rooster tail like this!
https://www.youtube.com/watch?v=KCDTMIJaIFU

DSR
Posts: 214
Joined: Mon Mar 21, 2016 8:11 pm
Location: Allegan, Michigan

Re: Starting my first build with a jet TNT

Postby DSR » Sun Aug 06, 2017 6:52 pm

:LOL!!
Hi Reado,

I'll be able to rooster it but nuttin like that. Denon's will be able to though..... right Denon?

Thanks :D
Dave
DSR Performance - Home of yet another jet TNT build :D
Codename "Just A Little....."
viewtopic.php?f=23&t=29753

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NAMEngJS
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Joined: Wed May 27, 2015 10:21 am
Location: Metairie, LA

Re: Starting my first build with a jet TNT

Postby NAMEngJS » Mon Aug 07, 2017 7:36 am

love the lines plan, in regards to the battery location and maybe you have considered this already, but what about building a small hatch and fixing it down with the hood pin tie downs like those found on classic drag cars. I dont think it would take much away from the look of the vessel but it would allow access to what is sure to be a cramped compartment.
All men dream, but not equally. Those who dream by night in the recesses of their minds, wake to find that it was vanity: but the dreamers by day are dangerous men, for they may act on their dreams with open eyes, to make them possible.

DSR
Posts: 214
Joined: Mon Mar 21, 2016 8:11 pm
Location: Allegan, Michigan

Re: Starting my first build with a jet TNT

Postby DSR » Mon Aug 07, 2017 3:43 pm

Hi Juan, thanks for stopping by.

I appreciate the ideas. I thought about doing an access hatch in passing, but I just can't see myself putting one into the foredeck in this design.. It just wouldn't look right to me.
I figured, as little as I would need to get my hands on the battery, I think I'd rather suffer the indignity of crawling under the deck 3-4 times a year, at most. The seats will be pretty light and I designed quick- release mounts for the seats so they can be pulled out very easily to gain additional space to boot.

How's your project coming along? You were looking to build a 19' Barrelback if I remember correctly?

Thanks :D
Dave
DSR Performance - Home of yet another jet TNT build :D
Codename "Just A Little....."
viewtopic.php?f=23&t=29753

irie E
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Re: Starting my first build with a jet TNT

Postby irie E » Mon Aug 07, 2017 4:04 pm

I think you should definitely wear your blue man suit first time out! What do you think of free ship? Is it fairly easy to learn? That lines plan looks great. I'm considering trying to tweak the bow of one of the cats and wanted to draw it out before committing to do it. Thanks for any feed back on the program.

DSR
Posts: 214
Joined: Mon Mar 21, 2016 8:11 pm
Location: Allegan, Michigan

Re: Starting my first build with a jet TNT

Postby DSR » Mon Aug 07, 2017 6:18 pm

Hi Dom,

LOL. Sorry about the Blue Man suit deal. Just a random bit of stupidity on my part. I just looked at the drawing after I highlighted it and it struck me as looking pretty funny and it went straight down hill from there..... :lol:

Regarding Freeship, mind you that so far I just have a barely working knowledge of it, but comparing it to some of the CAD programs I've messed with (Solidworks for example) , it is definitely one of the easier programs to learn. Having the original data points that I measured from the TNT patterns that I knew would stay correct gave me a good jumpstart on the mods that I did also. I'm kinda technology-resistant, so there were still several false starts and more than a few moments of banging my head against the wall, but once I got a feel for it, it worked well (especially with it being free...)

I did see your thread on modifying an Aquacat and I'm intrigued. I think it's very doable.

If I can help in any way, feel free to yell at me. :D

Thanks Dom,
Dave
DSR Performance - Home of yet another jet TNT build :D
Codename "Just A Little....."
viewtopic.php?f=23&t=29753

Denon Osterman
Posts: 471
Joined: Thu Jun 22, 2006 8:58 am
Location: toronto, CAN

Re: Starting my first build with a jet TNT

Postby Denon Osterman » Wed Aug 09, 2017 12:59 pm

Oh man, those line drawings are sweet! I've never heard of freeship before - is it good? I might check it out for any future builds, see how far I can push the creativity!

Make sure you've got someone small handy for that battery. I was ~14 when I did my TNT and crawling under the dash to wire the front light, etc, was tight for me back then! It's damn uncomfortable on the Stem too :(

Denon's will be able to though..... right Denon?
Yes, yes it will :D

DSR
Posts: 214
Joined: Mon Mar 21, 2016 8:11 pm
Location: Allegan, Michigan

Re: Starting my first build with a jet TNT

Postby DSR » Wed Aug 09, 2017 4:46 pm

Hi Denon,

Yeah, Freeship was really useful for relocating all the data points and fairing the design with all the changes I made. It's a free source program that you can download right off the net and it's geared to boat design. It's kinda amazing how far some of the data points move when you start putting things, such as frame 1 on the TNT, out of proportion within the design
Along with the Linesplan, it can also generate and export a file that has all the data points for the design grouped by station, which will be a lot of help when I start building, but it shows the measurements in decimals of feet (like 2.15'). Nothing a little work in Excel can't fix, but it is one more step......
I wasn't able to figure out how to render the model in Freeship though (I don't think it can), so I exported it into Blender (another free source program) which I used to render the white on blue pictures from. Blender was a lot harder to figure out, but it can do a ton of stuff. Even CG animation.
Very cool, but I don't think I have the patience to go that far with it......

"It's damn uncomfortable on the stern too"? Is that kind of like saying it was a PITA? :lol:

Thanks Denon,
Dave
DSR Performance - Home of yet another jet TNT build :D
Codename "Just A Little....."
viewtopic.php?f=23&t=29753

Denon Osterman
Posts: 471
Joined: Thu Jun 22, 2006 8:58 am
Location: toronto, CAN

Re: Starting my first build with a jet TNT

Postby Denon Osterman » Wed Aug 09, 2017 5:29 pm

Hey Dave - Sounds very cool, I'll have to check it out. I've heard of blender but don't have much animation / rendering experience myself...just stuff like Solidworks / Autodesk (Inventor, Fusion, etc). I'll give Freeship a look for sure!

It's uncomfertable on the steM - the curvy part of the keel at the front - when you're lying on it's hard edge instead of a flat sheet, trying to do work under the bow. The frames aren't very comfy either...PITA sounds about right :wink:

DSR
Posts: 214
Joined: Mon Mar 21, 2016 8:11 pm
Location: Allegan, Michigan

Re: Starting my first build with a jet TNT

Postby DSR » Wed Aug 09, 2017 5:59 pm

LOL!!.......Oooohhhhh, now I get it.......... :lol:
DSR Performance - Home of yet another jet TNT build :D
Codename "Just A Little....."
viewtopic.php?f=23&t=29753

DSR
Posts: 214
Joined: Mon Mar 21, 2016 8:11 pm
Location: Allegan, Michigan

Re: Starting my first build with a jet TNT

Postby DSR » Thu Aug 24, 2017 8:29 pm

FINALLY!!!!

After almost 2 months screwing around with the keel and pump intake design on my little bit of insanity (and many thanks to a couple great people that I was fortunate enough to converse with on it), it looks like I have a solution and I can start building!!

I was surprised by the design that works the best, but it actually made a lot of sense when I researched it. I also thought I would share it in case it may be of value or interest to anyone else here on the site that may be able to use this info without having to put all the lumps on their forehead from smacking it against the nearest wall in frustration.....

The fix is what the jet drive hot boat community calls a "radius drop keel"

Basically, I'm adding a radius keel section to the bottom planking on the hull that's the same width as the front of the pump intake (6.5" in my case) and extends forward 4.5-5' from the front of the intake before very subtly blending into the original hull bottom (thereby minimizing any additional water drag) and using a radius of 10 13/16", ends up with the center of the radius arc dropping about 1/2" below the original keel, then it gently curves and blends into the lead-in at the front of the pump intake.

This accomplishes two things to provide the intake with good solid water flow at speed.
1) The radius drop keel subtly splits and "steers" the aerated boundary layer present on the top of the water that causes pump cavitation, to either side of the keel, leaving solid water headed towards the intake and as it was explained to me...
2) The gentle curve into the front of the intake operates on what is called the Coanda Effect. This is the effect when water passes over the curved surface at the back of the radiused keel, it creates a low-pressure area leading into the intake. Combined with the viscosity of the water, this actually "bends" the water flow into the intake as it tries to follow the surface of the keel.

An example that I found on Youtube:

https://www.youtube.com/watch?v=1JWjLly6xNE

From what I've found, this is THE setup for high speed jet drive hulls, including low-deadrise warped bottom hulls and V-bottom hulls also.
The caveat in this deal is that the proper dimensions for the radius keel varies quite a bit and is very dependent on the type of hull, horsepower and speeds targeted for the boat, so this is definitely a "trial and error" situation. From what I've been told is that what I have is a solid baseline to start with and I'll have to play with it from there, so I think it's high time to try it out and see what happens..... :D

DSR Jet TNT radius keel1.jpg


DSR Jet TNT radius keel2.jpg


DSR Jet TNT radius keel3.jpg


If anybody has any thoughts or questions on this, just yell!

Thanks.
Dave
DSR Performance - Home of yet another jet TNT build :D
Codename "Just A Little....."
viewtopic.php?f=23&t=29753

DSR
Posts: 214
Joined: Mon Mar 21, 2016 8:11 pm
Location: Allegan, Michigan

Re: Starting my first build with a jet TNT

Postby DSR » Sun Oct 22, 2017 2:32 pm

Hi everyone,

Just another mini update......

It's been slow going lately with a change in job status at the shop and learning the new position has taken a bit of time, along with other side projects getting in the way (spent the last few weekends restoring and modifying a LeMans carburetor for a friend's '67 Shelby GT350 Mustang and started on porting another set of cylinder heads....).

But I decided enough was enough and blocked this weekend off to finally get the engine and pump pulled out of the ski and it actually worked!!

You have to partially disassemble the engine (pull the intake, intercooler, exhaust and turbo) to pull the engine out of the hull and I just finished putting it back together. Now that it's out and sitting in the cradle I'm really chompin' at the bit to get the build going.....
Attachments
R12X engine rear view.jpg
R12X engine intake view.jpg
R12X engine exhaust view.jpg
DSR Performance - Home of yet another jet TNT build :D
Codename "Just A Little....."
viewtopic.php?f=23&t=29753

DSR
Posts: 214
Joined: Mon Mar 21, 2016 8:11 pm
Location: Allegan, Michigan

Re: Starting my first build with a jet TNT

Postby DSR » Sun Oct 22, 2017 2:37 pm

........One more pic of the engine and a pic of the pump and the driveshaft on the bench in front of the Yamaha GP1200 pump intake.......
Looks like I have some work to do to the intake to make it work....... :D

Thanks!
Dave
Attachments
R12X engine top view.jpg
TNT jet pump and intake.jpg
DSR Performance - Home of yet another jet TNT build :D
Codename "Just A Little....."
viewtopic.php?f=23&t=29753

Denon Osterman
Posts: 471
Joined: Thu Jun 22, 2006 8:58 am
Location: toronto, CAN

Re: Starting my first build with a jet TNT

Postby Denon Osterman » Thu Nov 30, 2017 7:28 pm

Dave, that looks like it would be more suited for my Rampage than your TNT...*nice* :D

Can't wait to see this build progress, it's going to be awesome. Even if we never end up having a "north east" gathering, I'd love to see that thing in action when it's done!

Denon

DSR
Posts: 214
Joined: Mon Mar 21, 2016 8:11 pm
Location: Allegan, Michigan

Re: Starting my first build with a jet TNT

Postby DSR » Sat Dec 02, 2017 10:19 pm

Hi Denon,

Yeah, I'm really excited to get this little under-powered TNT going!

You're not that far away from me, being in the Ontario area. I'm sure we can set something up once the boats are running.

I wanted to do a little traveling with the TNT to some various locations (I'd definitely like to hit at least one Glen-L gathering with it) just for the pleasure of seeing and enjoying some different scenery in the boat (probably at high speed..... :lol: ) and I definitely want to see that beautiful Rampage in action!!

Thanks Denon
Dave
DSR Performance - Home of yet another jet TNT build :D
Codename "Just A Little....."
viewtopic.php?f=23&t=29753


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