Question for the experts..
 

I have a Thunder Tiger Pro .46 I'll be putting on a Outrigger Hydrofoil Airboat w/ a Jett Stream tuned pipe. The engine will be inverted. This is just the base engine I'm going to use - I know I'll want a better engine once I figure out how to run the darn thing. I'm considering future engine choices; Jett Fire .50 or Sportjett .46, and a Rossi of the same size range. I want some opinions on which choice would be better. I'm not in a big rush to get one as I will need to flog the TT .46 a bunch to get it dialed in and learn to drive it. Here's a link to my build thread of this boat: http://www.rcuniverse.com/forum/m_10045251/tm.htm

I'm open to other options as well - What I'm really looking for is more RPM's. The TT .46 on a MAS 10x6 tached 14800rpm peaked on the stock muffler. I'm sure with an APC It'd be at 15000rpm or so but I wouldn't mind having the option to turn 18-20k. I want to keep the engine in the .45-.50 range because I dont want to run bigger than a 10" prop. (I always run my engines a tad rich of peak anyway so I'll lose a few rpm's when running the boat.

Thanks in advance for the help and wisdom.

RE: Question for the experts..
 

Hi

Might have to look a little, but OS and K&B made Ducted Fan motors in the 45 range. There are a few other makers as well, but they are rare. I am sure they are still out there. They are tweeky motors, and lean runs will kill them quick.


Vince

RE: Question for the experts..
 

""The TT .46 on a MAS 10x6 tached 14800rpm peaked on the stock muffler""

are you sure about those nembers, sounds high, but then again you didn't say what Nitro percentage..


if not a Ducted Fan Engine I would find a used 50 size Heli Engine (Heli Engines have side Exhaust)

Jim

RE: Question for the experts..
 

I broke the engine in on 10% nitro 20% oil Sig fuel (oil blend is 50/50). I am pretty sure I got those numbers on 15% fuel. I ran about 4oz of 15% nitro after the break-in on 10%. I heat cycled the engine 12 times slightly rich (220* temp at the base of the head each run). I thought it sounded high but I peaked it twice and got near-identical numbers. I'll run it again and take a picture when it warms back up a little.

This engine was new/never ran when I got it but its at least 10 years old. According to the (blue) box, its ABC not ABN like the newer ones. (also - has straight needles, not angled) I did note one odd thing with the engine though - It didnt have the kind of pinch that I figured it would have. With no glow plug in it turning it over didnt seem all that tight. I took it apart, cleaned it, oiled it, sealed it, and reassembled it and with the plug in had very good compression.

I am not particular on side exhaust or rear exhaust though I would rather run a rear exhaust engine and a full-wave tuned pipe. Thats just my thought for now.

RE: Question for the experts..
 

Jett SJ60LX - spec'd to run 18,000 on a 10/6 prop..

www.jettengineering.com

RE: Question for the experts..
 

The small case Jett .60 is probably your best bet for high RPMs. But a Rossi would do pretty good too.
The new Evolution .60 NX looks most promising as well as it fits where the 45's would go.

My problem with the airboats was when I had too much power on them, they would go airborne, flop around and crash. I should have tried some air control surfaces, but at the time, I learned to not overpower them so much. But nowadays, I think putting on some elevons would be a good idea for when you get it to go airborne.

RE: Question for the experts..
 

Since Nelson is gone, IMHO there's no one left besides Dub Jett. I've seen some of his 40 size stuff spinning over 23,000. The sound of that'll raise the hair on the back of your neck. When you get ready, call Dub and splain what your goal is; see what he has to say. Power wise I don't think his stuff can be beat and his carbs are second to none. Be prepared to open the wallet though, the best don't come cheap.

RE: Question for the experts..
 

These engines are insane, the scream they produce at 20,000 + rpm is literally just that, a scream. I can not imagine one on a boat. If you do it,please get a video. http://www3.towerhobbies.com/cgi-bin...?&I=LXBY99&P=0

RE: Question for the experts..
 

There are guys at my field that fly this engine, it is fast and the rear exhaust / rear intake shouldn't give you a problem for your application. Of course, Jett prices give you a warranty for similar performance. Konrad pointed out the lack of warranty on these OS engines. Something to consider when you're over $300.

RE: Question for the experts..
 

Quote:

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ORIGINAL: Phoenixangel

These engines are insane, the scream they produce at 20,000+ RPM is literally just that, a scream. I can not imagine one on a boat. If you do it, please get a video. http://www3.towerhobbies.com/cgi-bin...?&I=LXBY99&P=0

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PA,


Using a prop on this engine limits the choices considerably...

Finding one that at this RPM (20,000), would actually produce enough effective thrust; at speeds typical of a prop-powered boat, is impossible.


To the OP; for your application, just stay with a 10" prop and don't assume that using a lower pitch would keep the speed that you want to see...

A 10x4 prop would not be spun at 20K, because it requires 2.16 HP, which is more than this engine is actually capable of producing, with a full-length tuned-pipe.
The JettStream is not a tuned-pipe, but a tuned-muffler. It is less capable than a full-length tuned-pipe, in getting top performance out of an engine; but is much better at being usable and getting usable performance out of it.

A 10x3 prop is too small (insufficient load; just 1.66 HP @ 20K) and would make your boat appear like it is running 'full-throttle in neutral'.

Both props cannot be spun safely at this RPM!

An MA black prop offers considerably sell load than an APC of the same size; and its manufacturer limits its safe RPM even further, stating its limit is 16,500.


If you ask experts, don't expect to hear what you want to hear... Those that state what you do expect, are more often vendors...

RE: Question for the experts..
 

It was the easiest link to find. :)

Please get something with a warranty.

RE: Question for the experts..
 

Hi!
Some advise from a pylon racing guy that has been in this hobby for a long time!
First of all get rid of that 10x6 MA prop! It's more or less useless! It's noisy and does not produce equal performance compared to other props of the same size.The best props on the market for a .40-46 engine is a RAM or Graupner Cam-prop (not the old blunt tipped prop though) followed by APC.
10x6 RAM and Graupner Cam-props are the ones we (I) use over here in Sweden for our Q-500 racing class.

Second! That TT .46 pro engine of yours is one of the best engines produced, certainly better (and lighter) than the Rossi .40, so don,t considder changing it for a Rossi. The Nelson or a JETT is another thing! Those are much more powerfull! Though the Nelson is no longer produced.

For best performance using the TT.46 see o that you either use a Uniflow tank or ...better, a Tettra "bubble-less" tank. The Tettra tank is used world wide by all pylon fliers!

0-15% nitro fuel is all it takes to have thhe TT engine run perfectly well!

RE: Question for the experts..
 

I didnt want to deviate from a 10" prop, so no problem there. Pitch speed is thrown out the window when propping airboats only because there arent many airboats that can actually go pitch speed. Only one comes to mind that might. Ducted fan engines are out. Ideally, I want a front intake/rear exhaust airplane engine on a full-wave tuned pipe. I have no specific RPM "goal" to meet, I just want more oomph than the TT is capable of. I know the Jettstream pipe is a tuned muffler / 1/4 wave pipe. This was going to be used on the TT for some extra grunt until I get the fancy go-fast engine. I read around and some Tach readings with this engine have been more promising on the Jett pipe vs. the ultra thrust or tower muffler.

The MA prop was only used for break-in. I have an APC for running on the boat. While on the bench, I was very much impressed with how the engine ran. It is by far the least persnickity engine to break in I've ever ran. Most of my engines are car engines, but my other airboat has a K&B Sportster .65 Drone engine on it. Break-in and running of this engine are not as good as the TT (by a long shot). The Drone engine is a far-off subject but both of mine need carb parts to run right.

Since the TT will be inverted and the tank is going to be located directly underneath it in a sealed compartment, I'm expecting to use a perry pulse pump on it, and find the right size tank. I'd like to run an 8-10oz tank that will fit the compartment size of 5.75"Lx2.5"Wx1.625"D. I have a 8oz sullivan tank on the K&B boat and havent had too many bubble problems but I dont like how the tank lids seal. It seems no batter how tight the screw is the tank always leaks just a teeny bit - I would like to not have any leaks if possible. I run a high castor content fuel and the less sticky crap the better.

I've ran it on 10% and 15% and it ran very very well. I was told by many fellows on this forum that it is the best .46 I'll ever own and I can see that possible. When I peaked the engine after break in, I was surprised to see the temp not get any higher than 270*.

Is 15% the limit for nitro content on these little guys?
I bought this engine specifically for this project and since it only cost me $45, and add a $60 jett muffler I figured I'd have a good base-engine setup for 105$. I figured I couldn't go wrong with the deal.

On the original subject: Whatever I end up using, I want it to keep the .46 size radial engine mount (do all .40/.46 engines use the same mount pattern?). I need it to run inverted and perform better than the TT combo by a decent margin to make it worth the extra cost.

RE: Question for the experts..
 

Anyone have any input to my last post? If not, thats cool... I have a pretty good idea of which direction I need to go..

RE: Question for the experts..
 

1QwkSport2.5r,


Break-in of tapered-bore engines, is covered in detail in [link=http://www.rcuniverse.com/forum/m_1850473/tm.htm]my thread from 2004[/link].

There is discussion on whether the Jett/Nelson/MVVS tuned-mufflers are 1/4 wave tuned-pipes, or simply 'Helmholz resonators'.
The Tower Hobbies .46 muffler has no internal pipe ("inner tube..."), so it is probably not much more than a large volume muffler.

In summary, all are effective power boosters; and it would be pretty stupid to disagree with factual results; the Tower being the least effective by a large margin.


The only real option that you have, to replace the TT; is to get [link=http://jettengineering.com/engines/bse40.html]a Jett[/link].
Shelling out $20 more will get you the .50 and 500 more RPM.
The availability of the YS .45 seems rather dubious (besides it needing higher nitro fuel) and the [link=http://shop.vendio.com/RossiEnginesUSA/item/2061313519/index.html]Rossi .45[/link]; albeit very powerful, weighs nearly as much bare, as does the (slightly stronger) Jett .50 with its JettStream tuned-muffler.


You got most of the things and issues right. ...Except for the temperature issue, that is.

You can regard this statement as an axiom; if a glow engine is running right, with good power; it is at the proper temperature.
It's numerical value is totally irrelevant!

So that remote IR thermometer is irrelevant and it is just a cash trap for newbies...
...So forget about chasing your own tail; trying to reach a target temperature...

RE: Question for the experts..
 

I don't run my engines at a specific temp. I do like to keep an eye on it, but my philosophy is if its running out nice and theres smoke coming from the exhaust, its good to go. I've had some car engines run close to 300* but they ran fine and restarted hot just fine so I just let it go and had some fun.

I kinda figured a Jett 50 would be the way to go. They sure are spiffy lookin'..

Thanks for your input. I'll look through your tapered-bore thread.

RE: Question for the experts..
 

Quote:

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ORIGINAL: 1QwkSport2.5r

I don't run my engines at a specific temp. I do like to keep an eye on it, but my philosophy is if its running out nice and theres smoke coming from the exhaust, its good to go. I've had some car engines run close to 300°F but they ran fine and restarted hot just fine, so I just let it go and had some fun.

---

1QwkSport2.5r,


As I wrote, in an airplane engine, the numerical value of the temperature is irrelevant; as long as the engine is running fine.

So, why bother to buy the IR thermometer and why bother taking a reading?

I do understand that for car and heli engines, this might not be the case... It is not a simple matter to simulate full-load with the prop-wash cooling capacity in these engines.

But you've got a propped plane engine mounted in your boat.


And, BTW, a good smoke trail is hardly an indication that your engine is running rich enough... It could still be too lean.
Its being slightly rich of peak RPM is a much better indication.

RE: Question for the experts..
 

Certain lubes when run lean and hot can make white smoke creating the illusion of being rich.

RE: Question for the experts..
 

Sounds like you are on the right track. what you have is a pretty user freindly, stable setup, that will give you good performance (TT .46 and Jett stream).

Moving up to anything other than a Jett would probably not satisfy you as any gains would be minimal. The Jett .60 is in a 40 sized case, so it would not be physically larger than your TT, just bored out more. Also, don't assume you need the more expensive CNC cut Bar Stock case (although they are beautifull), there is no performance gain in regards to those versus their cast case counterparts that Dubb sells also.

Give Dubb a call and tell him your intentions and he will make an honest evaluation. He does one off and special motors for people based on their needs. He is a great guy.

I would suggest a bladder tank (Jett or Tettra) versus using a pump if you go to a jett, its just good to keep the air out of the tank and then tend to generate enough backpressure for less than perfect installations.

Also, I'm not to far away, and very experienced with these types of motors. If you want any help, let me know and I can buzz up to the cities. I have lots of family up there and would love to see a water boat (although I assume you using it on snow now).

RE: Question for the experts..
 

"If you ask experts, don't expect to hear what you want to hear... Those that state what you do expect, are more often vendors..." Dar Zeelon.


Excellently put, Dar. Best I've seen yet.


Ed Cregger

RE: Question for the experts..
 

Thank you, Ed and thanks for noticing.

Cheers!

RE: Question for the experts..
 

I understand the whole point about engine temperatures not being relevant. Personally, I like to "just know" where its at. Up until August I hadn't ran any airplane engines - only Car engines. I have 4 r/c cars. In these cases, temps are far more important than airplane engines being that the load is far different. I don't use an IR temp gun, only a failsafe with temp gauge.

I set my airplane engines the same way everyone else does. Tune to peak and richen 500rpm. I set my car engines in much the same way except when peak power is achieved, I richen 1/8th turn on the main needle since there aren't any needle retainers on car engines. (at least none that I've seen or used)

I've been in the hobby for almost 14 years with most of my experience being with cars/trucks. All I've ever had is glow-powered models and I am one of those types of people that will ask a hundred people how they break-in, tune, and run their engines just to know. I'm always looking to learn new tips, tricks, and the like. I respect everyone's opinion even if I don't necessarily agree. I have my way that I feel is the right way but if there is someone down the way that shows me a better way, I'll heed that advice.
I think that is a fantastic quote, but oddly enough I don't think you guys are vendors :)

RE: Question for the experts..
 

I've heard nothing but good things about the TT, and I expect it to perform well. I just know there is a limit to what it will be able to do and the craft will have the ability to handle more. I like the idea of overpowering - gives a person more motivation to learn how to drive properly. There is a limit to this, however. I don't really care how the case is made - I am mainly looking at a rear exhaust engine being easier to run inverted and (generally) make more efficient power because of the port design. When the engine is completely upside down the CoG is lower but a side exhaust engine wont balance evenly completely upside down - The TT will need to be at a slight angle so the muffler will clear the engine stand and balance. A rear exhaust system would tuck under the engine stand nicely and not require much work to balance the engine to the hull.

The reason I was going to use a pump is based on advice given to me in this thread: http://www.rcuniverse.com/forum/m_10162562/tm.htm
Like I stated in my previous post, I'm always looking for a better way to do things. If there is a fuel system that will work with both engines as well as if the tank was right behind the engine, then I am all for it. I'll look at Jett's tanks as well as the tettra tanks.

Thanks for the offer to come help. I think I got it under control for now but if that changes, I will let you know. Two brains are definitely better than one. You're more than welcome to come see the thing run in the spring. Its either gonna go like mad or be a couple hundred hours worth of sunken/broken work.

RE: Question for the experts..
 

get a Jett 56 rear exhaust, with short marine pipe set up. run an APC 10x6 prop around 18,500...............

RE: Question for the experts..
 

I didn't see a 56 on their website. The rear exhaust 50 is 17,500rpm on a 10x6, and the 60lx turns 18,000rpm on a 10x6. It appears the Side exhaust and Rear exhaust engines run the same RPM's. That surprises me a bit. I've always been told rear exhaust engines turn higher rpms and are more efficient than their side exhaust counterparts. (Then again, I've never seen an engine line that had the same identical engine come in both side and rear exhaust variations.)