Turbine Dilemma
 

I am currently rigging a 38’kV scarab with a one 1600hp French turbine driving a splitter box then out onto 2 arneson asd8 drop boxes to give counter rotation.
Is it possible this boat could have run with a single drive? Doing away with the splitter box, or would this have created a boat with bad handling?

Engine output shaft speed 6400rpm@100%
1.5-1 Asd8 giving a prop speed @100% of 4266rpm

As much info as possible would be appreciated as I am based in the UK and there are no other guys out here rigging boats with turbines.

Re: Turbine Dilemma
 

Howard Arneson has a cat outfitted with one turbine... I don't see why you can't drive the boat with one drive... the only problem would be the possiblity of some chine walking from the prop torque.

Re: Turbine Dilemma
 

I would think that getting on plane with a 38' boat and a single prop would be challenging at the least! Especially a single surface drive.

Re: Turbine Dilemma
 

Hmmmm... might not have as much trouble with the single as you would think. The higher hp and torque from the engine will compensate quite a bit for the loss of the second source of thrust.

Chine walking and paddle-wheeling (The tendancy for the stern to walk in the direction of rotation of the prop) might be of concern especially with the slightly more agressive prop you are going to want to run in order to help with the hole shot.

Are you custom building the splitter, or buying one stock?

Re: Turbine Dilemma
 

We want pics! :D :D :D

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Prop would have to be off a tug boat!

Re: Turbine Dilemma
 

Going with a single drive will save a ton of money. I am sure that splitter box cost many$$$$$

Re: Turbine Dilemma
 

i tend to think if he's messing around wit turbines he's not overly worried about saving $.

contact rik wimp at twin disc, they biuld all the ASD drive and rik knows just abtou everythin there is no know abotu ASD Drives and setting them up.

Re: Turbine Dilemma
 

and yeah we want some pics of his bad boy!

Re: Turbine Dilemma
 

Here are a few shots of the engine and box I made
The engine is about 1600mm long the splitter box is home made with 50mm wide gears which were made by a British company all bearings are pressure fed, gears have oil injection between teeth,dry sumped
This is just a hobby of mine and costs need to be kept low, as I have done most of the work myself in the garage.
The engines were picked up from Europe I have 4 in stock for spares
Overspeed is controlled mechanically and electronically+ shatter blanket just in case!
I have had problems with my user name so please respond to this reply

Jason

Re: Turbine Dilemma
 

Sorry about that this forum thing is new to me,more used to getting thick of oil
Try again
J

Re: Turbine Dilemma
 

Nice!! :D Make sure you get us some more pics when you get it in the boat :D

Re: Turbine Dilemma
 

Sorry the engines I am useing are very hard to come by so I will not be selling, if you in the states the best idea is to souce some T53s
J

Re: Turbine Dilemma
 

impressive set up :cool:

Re: Turbine Dilemma
 

very cool rig!

Re: Turbine Dilemma
 

That splitter box will have a tad of torque running thru it, and I would keep the lid closed in case it lets go...

Getting a single prop to bite to get on plane with a pitch descent enough for good top end might prove challenging pushing a Scarab and the fuel you need to turn that monster.

The Gentry Eagle is setup with a monster single Arneson Drive behind an even more grotesque Turbine but it has twin diesel jet-drive to help get on plane and some serious weight and length to offset the torque.

On a Kevlar Scarab 38 however even if you get on plane in a single drive configuration, taking into account the torque I would run tabs the size of Scotland behind it to feel safe. 1600hp is not a ton but your boat will be very lite compared to a classic boat, you won't have the big block's weight in the rear end weighting it down.

Just expressing common sense in my eyes I am by far no expert.

Re: Turbine Dilemma
 

Sweet set up! :D

Re: Turbine Dilemma
 

I think you will need to put some mounts on that splitter box to stop "flexing" and keep drive shaft alignment proper. What kind of reduction are you running?

Wannabe

Re: Turbine Dilemma
 

That turbine only turns 6400 rpm at 100% ?

Re: Turbine Dilemma
 

Says "output shaft" might be reduced before the output shaft.

Re: Turbine Dilemma
 

The main mounts are going to be located on the splitter box allowing the engine to expand forward 3-5mm during max temp,the front engine mount is a sliding assembly to allow for this.
Shaft speed from the turbine gearbox is 6400 rpm @100% reduced down to 4200 rpms at the props.
I let you lads do the maths and work out the theoretical top speed.

Re: Turbine Dilemma
 

89 mph

Re: Turbine Dilemma
 

If you are asking what you should do, stick with the original plan!

The boat will be a pig at best with a single propeller as you would be putting 2,000 lbs of torque to a single prop. Too much and the propeller will be to big.

Splitting as you have done will make the boat far better with counter rotating propellers.

You need to check the reduction ratio in the drop box drives as well as check the weight of the boat.

I'd suggest a 1:1 in the drives as you have the proper propeller rpm and the torque from the engine is sufficent to run at what you have built. You might change the output shaft on the splitter box so that you can couple a drive line or better yet a transmission to them. Then you will have a boat you can dock.

What is the center distace of the splitter box? If it is built to last then you should have a reliable boat.

Re: Turbine Dilemma
 

Rik
The centres on the splitter box are 40" I was planing on doing the counter rotation in the drop box, one box as a chain drive and one as gear drive.
The dry boat weight is 6000lbs and the engine and splitter box weigh another 1000lbs.
Fuel consumption around 140gph @ 100%
We spoke a couple of years ago when I visited your workshop in California around Christmas time. Since then I have tried many different turbines to find the right European engine to use in a boat.
When you build turbine boats using the T53 or T55 do you alter the N2
Fuel govner to react faster in boat or do you leave as its standard setting?
The splitter box should be well up to the job the only question I could do with some advice on is what oil to run in it the bearings are pressure fed with a dry sump and filter.
Cheers

Re: Turbine Dilemma
 

My hats off to ya!! The exhaust tower looks bigger than we usually see on Lycoming boats..why is that?

Re: Turbine Dilemma
 

The exhaust on the T55's is only 18" in diameter. On the French turbine they had to make the exhaust form around the hot shaft and thus they made the exhaust more oval than round making it look larger but the oval is not that wide for/aft.

What is the fuel control like in the engine? Sepeate N1 - N2?

Re: Turbine Dilemma
 

att image of the ext two tailpipes need to go into one

Re: Turbine Dilemma
 

86 the splitter box and run 2 of the turbines... you'll still have 3 spares and 3200hp to boot.
i know a guy with a 800hp single surface drive and it is one scary mufa . its all over the place. the splitter box looks like problems waiting to happen. follow the route taken by the other turbine guys. run a pair witha pair of anrnesons. it works. cool azz project. keep the pics comin as is progresses. ratman

Re: Turbine Dilemma
 

Very cool, is there a book or database that you would recommend to help learn more about turbines.

Re: Turbine Dilemma
 

I'm at a loss of what to say here....NICE PICS!!!

Re: Turbine Dilemma
 

Sorry... I know the question was posed to Rik, but for what it is worth... Id run the same turbine oil in the splitter as you run in the engine. That's what gets done in the helicopter world...

We leave the N2 Governor wired full open. (T-53's) and it's response is quite reasonable. Mind you we have a computer control system for the engine as well that has a much quicker reaction time.

Looks good. Good luck with the install.

Re: Turbine Dilemma
 

keep in mind by adding the french turbine your boat will become a coward with homosexual tendencies and try to avoid competition! it will avoid bathing whenever possible and like to be used by muslims. be careful and always watch your 6 when your around it :evilb: