Any engineer/techie types here play around with OpenFOAM?

[soggy_feet]

Im having trouble keeping up with the pinhole leaks in the steel hull of my houseboat this season, the bow is at the end of its working life (the rest has already been re-plated).

She plows a bit more than I think she needs to, and I was thinking about redesigning the bow a bit before I rebuild it.

Was hoping to do some fluid dynamics modeling to see if a few tweaks will make a big difference or not.

My problem is, I have a linux netbook, and only that. Not nearly enough for modeling. I can get away with doing a bit of play on the windows computer at work, but Im sure they wouldn't be happy with me installing a virtual machine, and a linux operating system, and an open source fluid dynamics program on a machine thats supposed to be only used for CAD/CAM work for the mill I run.


Long story short, who wants to play around with some hull designs for me?

 

[oops!]

Re: Any engineer/techie types here play around with OpenFOAM?

post pics of the hull......

there are simple ways to tweak it ....get petter planing and increased floatation of the toons.

but if they are at the end of thier working life.......why not replace them or buy a new boat?

 

[soggy_feet]

Re: Any engineer/techie types here play around with OpenFOAM?

Because I can fabricate a new hull (not pontoons, a steel hull) for probably $700, considering my costs would be the purchase of steel, and beer. I paid $3800 for a 40ft houseboat, and I doubt I will ever again come across a boat that size, for that price.

She is very much, NOT a planing hull. 15,000lbs, with a top speed of about 11 knots.

Everything below deck, from the start of the curve of the bow forward needs to be replaced.

I was actually tossing the idea around of building a bulbous hull (now the need for fluid dynamics modeling), for reasons explained here.

 

[DeepBlue2010]

Re: Any engineer/techie types here play around with OpenFOAM?

Two things I can think of
A) Online program that runs over a web browser. All the real calculations will be done on the server side and you netbook will be for the user interface only.
B) University Labs may allow you access to their CAD systems.

I wish I could be of more help. Best of luck to you

 

[soggy_feet]

Re: Any engineer/techie types here play around with OpenFOAM?

Thats a pretty good start. I bet I could find somebody at the University of Vermont who can give me some ideas, or help. I hadn't thought of that...

thanks!

 

[sasto]

Re: Any engineer/techie types here play around with OpenFOAM?

Bulbous bow on your project? Nah. If she were mine I would get her in good working order...then rethink technology.

Good Luck!

PS: don't overengineer.

 

[MichaelP]

Re: Any engineer/techie types here play around with OpenFOAM?

I agree with sasto here. Don't over think this because you need to look at the design as a whole. That hull was already engineered for that craft and any tinkering could have a detrimental effect. Free engineering is like free advice...You just may get exactly what you pay for.

I always though it would be neat to have one of those boats.

 

[soggy_feet]

Re: Any engineer/techie types here play around with OpenFOAM?

The boat is awesome, its my summer home. I stretch the season a bit in the cooler VT climate, but I can get 7, maybe 8 months out of it if I can get it in the water early enough.

As for engineered hull. I would put money on it that it wasn't engineered at all. The boat is a '73, and houseboats were really climbing in popularity at that time. These were churned out... made to last 10 years, not 40. Little work was put into them at that time.

If I were planning on just adding/modifying the hull, I'd be more inclined to take your advise, but this is where the modeling comes in. A few hours in front of the computer, and I can be fairly confident in what the end result will be, and I'm fully capable of producing the end product.

Another example:
The structure on the hull was 1/2" ply ONLY, stapled at the seams, with a little more reinforcement in the ceiling to hold the roof up.

Since I've owned it, I've gutted half the cabin, and reinforced it with 2x3 framing, insulated the walls, and finished it on the inside with mahogany paneling. I've done a lot, and have a bunch more planned, but the hull is in serious need of attention, and if Im already cutting it off and rebuilding it, I might as well attempt to make it better.

 

[soggy_feet]

Re: Any engineer/techie types here play around with OpenFOAM?

Little update for anyone interested, I've got a good start on a windows based program that doesn't take up much space that I've just started playing around with tonight. So far, fairly intuitive for me, I've wireframed a crude version of my hull without reading the manual for the program. Can't really go much past this point until I can get some exact measurements on the hull to start dropping coordinates into the modeling program.

http://hydronship.net/download.htm
Free!Ship Plus is the program, and once Im set on my model, I'll add on Michlet- http://www.cyberiad.net/michlet.htm or, http://www.boatdesign.net/forums/design-software/michlet-9-20-released-37816.html (where the actual download link is located)

There's a lot of math to this, but I'm hoping that once I'm past the initial learning curve, this will all flow much easier, and I'll start working on other boat designs... Like updating those cheap hydroboat kit plans from the 50's and 60's to where I have a safe design to run twice the HP they were intended for, without getting airborne and breaking my neck.


Working a ton of overtime right now, and all the extra hours putting my brain to use has knocked a few cobwebs loose, I've brainstormed a way to plate the curve of the bow without the use of a very large slip roll that I dont' really have any access too, and minute after that lightbulb lit, I think I came up with a way to build a bow thruster without that pesky/expensive right angle drive for the impeller.

My brain is in gear on this... watch out, because the brakes are kinda sketchy... ha!

 

[orlandoclippertim]

Re: Any engineer/techie types here play around with OpenFOAM?

All I can say is that people sure are negative when you want to build something new aern't they ?
How about putting a prop in the nose of the torpedoe ? or would the part of the fattening cross section just behind it make a big drag/fluid resistance on the water that the prop is pumping ?
Or maybe a tunnel inlet in the nose ( like an F-86 ) with that water feeding a prop or jet drive at the back end ?
But I know less than nothing about hull design ........ didn't even play one on TV

 

[JDA1975]

Re: Any engineer/techie types here play around with OpenFOAM?

If ya know what your doing and have the knowledge and will to design and engineer it, go for it. worse that can happen is she sinks. My buddy designs and builds experimental aircraft and aint nobody gonna tell him it wont fly lol

 

[Sleeper-6]

Re: Any engineer/techie types here play around with OpenFOAM?

From what I have read bulbous bows are usually used on boats over 50 ft that spend most of their time near their maximum speed.

It is possible that with all the work you have done has added a some weight and that's what is causing you to plow more water. If you could get more displacement out of the new hull design maybe that would help reduce the overall draft and therefore plow less.

 

[justchecking]

Re: Any engineer/techie types here play around with OpenFOAM?

Nice boat. Has the bow lost all structural integrity? If not, how about sand blasting off the paint/rust, then doing rust converter to get to any pits. Then build up a slightly bigger bow out of foam and fiberglass. That will be strong and increase your flotation and be way faster/cheaper than forming a new metal bow. Also a lot easier to form. I wouldn't do they bulb, I don't think that would help anything. If you increased the entire hull with foam/fiberglass by 2" to 4" how much extra flotation would that give you??

 

[orlandoclippertim]

Re: Any engineer/techie types here play around with OpenFOAM?

I saw a 60 to 80 foot long aluminum pontoon ship from WW2 in a marina. All aluminum. Fellow said it was some kind of tender used durring the war. That should be plenty of hull for you if you could find one of those !
Tim

 

[oops!]

Re: Any engineer/techie types here play around with OpenFOAM?

hi bud....

welcome back.....

im gonna throw a few things in here.....

first.....im kinda concerned that you are not going in the right direction with the bulb on the bow.
the reason for this......is that they are designed for a much deeper v hull than you are working with.
the hulls that use the bulb have a far deeper draft than you...... yes you are a displacement hull.......but you are almost a flat bottom.

to mod that hull to a bulb ....in my opinion.....would just cause you drag.
i mean you arent a speed demon....so i would think that your best advantage would be to decrease the weight of the hull, or decrease the drag by increasing the keel and chines, giving you more stability, and even a chance of plaining with the right power

with a bulb, even though there would be more displacement.....the bulb would have to be bang on in design....too much port or starboard and you will list as well as making the bow ride higher, and the stern lower. this is huge drag.

can you post a pic of the mock up? or even a ms paint of the new hull design you are think of?

btw....someone posted about being negative about new ideas........sorry.....not here....im the last one to tell you not to do something with your boat......its your boat and you can do with it what ever you want.
trust me......i took a chain saw to mine and made it 5 feet longer.

we all just want to make sure of the best way to get the results you want

 

[chriscraft254]

Re: Any engineer/techie types here play around with OpenFOAM?

I can attest to remodeling houseboats, I have done many of them. Even new houseboats are not build with longevity in mind. The pin holes you get in the hull are most likely from electrolisis. You can get pin holes in 3 year old hulls. It depends alot on where you dock. Most marinas have the water tested annually for this.


Your idea about a bulb on the front to me will just add to much weight forward on that shallow hull. If you were to get rid of the 1/4 inch plate front rail section and lighten the bow it would probably help. I think the last thing you want up there is more weight. I just don't think you will be able to provide enough extra floatation to allow for the extra weight. .02

What you could do is extend the front of the bow hull like 5 feet and gain yourself a longer hull and more planing surface. This to me would give you better control than adding a bulb under the boat which would also not be good in shallow waters. Many houseboats are heavy in the front because of the extra helm station atop and other build outs inside the boat towards the bow. Yes, the motors in the stern add weight to balance but it just depends on the weight distribution. Shallower hulls usually will have more issues pushing water..

By the way, what engine or engines does this boat have? Single screw or twins?

 

[soggy_feet]

Re: Any engineer/techie types here play around with OpenFOAM?

From what I have read bulbous bows are usually used on boats over 50 ft that spend most of their time near their maximum speed.

It is possible that with all the work you have done has added a some weight and that's what is causing you to plow more water. If you could get more displacement out of the new hull design maybe that would help reduce the overall draft and therefore plow less.

I've also read that the benefits of a bulbous bow trail off below 50ft, but that doesn't mean the benefits will drop to 0 for the length of my boat. This is why I'm going thru the work of modeling beforehand. If its really nothing, then it won't be done. I still may be able to make improvements without a bulb. its a wide flat bow that really pounds the waves. There may be benefits to bringing it to a point. Think oversized canoe, very flat bottom, very sharp bow.Also she's handled about the same since the day I bought her, with the original interior. I've added lumber, but in the grand scope of things, it really wasn't that much weight.

Has the bow lost all structural integrity?

Unfortuately, yes. Right now, I have a 16" long crack running parallel to the weld seam along the centerline of the bow. Years of severe oil-canning of the bow plates has caused a stress crack. I went over the boat fairly thoroughly last fall, and added a few patches, but missed what started as a couple pinholes that weeped this spring. It really just gave in over the course of the summer, and the few weeping pinholes grew into this crack.
She continues to float only because of a big tub of plumbers putty, and a big pile of industrial magnets. Putty keeps the water out, magnets firmly sandwich the putty to the hull. Impressive that it actually completely stopped the water.

If you were to get rid of the 1/4 inch plate front rail section and lighten the bow it would probably help.

Believe it or not, there isn't a piece of steel on this boat thicker than 1/8"!

decrease the drag by increasing the keel and chines.

I haven't made it to the simulation stages yet, and I'm learning this as I go, so can you tell me how this decreases drag? I can understand trying to move toward more of a planing design to get it up out of the water, but without a complete redesign of the ENTIRE hull, I don't see this happening.

By the way, what engine or engines does this boat have? Single screw or twins?

GM 250cu/in I-6, 2bbl carb, single I/O

All I can say is that people sure are negative when you want to build something new aern't they ?

It's easy enough to separate the comments telling me any modification is a bad idea without offering any real help, and the comments that point out that one direction may be better than another. I can take constructive criticism, and I'm generally open to new ideas, provided that the end result is a BETTER boat than what I started with. Restoring to it's original 'glory' is no better than putting a nice shiny wax on a turd. There's always room for improvement!

 

[chriscraft254]

Re: Any engineer/techie types here play around with OpenFOAM?

GM 250cu/in I-6, 2bbl carb, single I/O

^^^^This Combined with the forward weight and the shallow hull are all some of the issues you are battling. You are under powered to start with and the lack of having two motors isn't helping because the stern is light.

 

[soggy_feet]

Re: Any engineer/techie types here play around with OpenFOAM?

She sits pretty level in the water when stationary somehow...


Regardless of that, the main reason for the hull redesign is that theres nothing left up in the bow to hold it together. Focus will have to stay on that, and not on re-powering. (although it would be cool to find a ~250hp jetboat that someone ran aground, and swap in that powerplant). One project at a time though

 

[oops!]

Re: Any engineer/techie types here play around with OpenFOAM?

cool trick with the putty !

if you increase the v of the hull.....and increase the shaprness of the chines.... you will add more surface area to the hull....this will increase the amount of water displaced with out adding much weight....so you will ride higher in the water...there for decreasing drag.

but with the 250...single screw..it wont matter much....

i would seriously consider a toon type hull........triple toon on there.....would be very stable.....and you would be quite a bit faster (not that speed is the goal, but the reduction of operating costs)