RC project

[Vaulter]

Here is a sneak peak at my RC boat project. The engine is running well, and I have good control of the needle valve using an RC servo. I just need to try it on the small propane tanks and integrate it all onto the boat.

[James D]

That a great looking project vaulter.

It will be the perfect application for water injection, just pump it up from under the hull and blow it down the tailpipe.

[Eric]

How are you going to get the tanks to provide enough fuel flow?

If you look in harbor frieght there are these brass refil adapters that allow you to refil a 1 pound propane tank from a 20 lb cylinder. I have a feeling that will be very valuable to you, and if you dont have anything else you could make a system that screws onto the tank side plug of the adapter, that way you get a high volume of fuel flow from the little tanks.

Are you going to put those tanks inside the hull?

Eric

[hagent]

Are you going to put something between the engine and tanks to keep them from exploding?

The tanks probably won't explode because of their temp drop durring operation. In addition the PJ heat source should help keep the tanks pressure up. You will just have to experiment with the placement to get max benifit and safty.

Looks great by the way!

[Anders Troberg]

Looks like you need a somewhat bigger pond.

Perhaps you should put some rudders in the air, to help counteract the centrifugal force and keep it stable in high speed turns. It looks like the centre of gravity is fairly high.

Make sure you get a video of it running, I'd love to see that beast in action.

[Vaulter]

So I got the engine running on a single mini tank. It ideals fine, but I can't get much thrust out of it. Last night I tried again with two tanks, and did get a little higher power setting, but still not full juice. I tried inverting on of the little tanks with shaky results. The engine would really surge and then back off a lot. I think I need to make a different injector to run liquid propane.
For the time being I am trying to put together a liquid fuel setup. This is my first attempt at liquid fuel so we will see how it goes.

Eric, I read your post about using water injection to find the sweet spot, and then switching to fuel. Do think I could use the same idea with the addition of a bladder, or would I need to make more of an injector? Is throttling the same with a liquid or is it harder then propane?

I don't plan to put the tanks in the hull until I find a fueling system that works well. I am thinking of making new mounts for the engine to keep thing placed better.

[larry cottrill]

Vaulter -

Basically, cool - BUT, I must agree that the present geometry will give you a CG that is much too high, especially in the turns. Another CG problem is that you will have a hard time getting both cylinders to drain at the same rate, shifting the centre of mass to one side or the other. This could be eliminated with a high-pressure manifold between the two cylinders, but that is a pretty heavy solution, and a source of increased damage vulnerability in the case of a crash.

There is another SERIOUS potential problem that you MUST address: fuel slosh. In the case of propane, it means that you will get little blobs of liquid fuel going up the line. In the case of liquid fuels, it means you will get small bubbles in your fuel line that will kill your engine. Contrary to popular belief, pressurized systems do NOT eliminate these problems. For propane, I'm convinced that the solution is to deliver fuel vapor at atmospheric pressure and use a line big enough to act as an evaporator for small "cells" of liquid flow. For liquid fuels, the thing to do is equip your fuel tank with serious internal baffling (I like to use a nylon "kitchen scrubber pad" or two gently packed into the tank before sealing it up). Before I did this, I could hardly ever get my Dyanjet-powered "Buzz Bomb Trainer" off the ground, since a tiny bubble would flow up and kill the engine sometime during almost every takeoff run. Of course, a "bladder tank" will accomplish the same objective.

Nice looking hydro! Good luck!

L Cottrill

[Vaulter]

I am in a hurry, but I thought I would post a quick video of the progress. I traded pontoons for tires, but I am still not getting a full thrust setting out of small tanks. I’m not giving up just yet though.

[larry cottrill]

Well, that ties it up - Vaulter, you must get the award for the first FWE used for an actual propulsion application, EVER. Can anyone on the forums dispute this claim?

My sincere congratulations (for whatever that's worth)!

Are you sure there's no restriction left in the way at the tank valves? If that little passage isn't opened up (to something generous but safe and reasonable ;-), you're not going to get what you need. Are you seeing any frost on the tanks from a reasonable length run?

L Cottrill

[Eric]

I put a fwe on a "free flight" boat with about 15 seconds of fuel. The boat weighted about 9 pounds so it was a pretty lame show, as planned. lol

Use the normal water test to find the best position that will draw fuel without pressure, and a spot where it wont all blow out of the engine. Once you find that spot make a radial injector with some very very tiny holes, and use a pressurized fuel system.

Finding the spot that will draw fuel normally and take it into the engine is important, since you wont really be able to tell when the water is getting squited into the engine by itself from a bladder.

Once you get it set up you will need a throttle system, and if you have the combination of a pressure bladder and the venturi effect you will be able to throttle it just fine over a very large range.

Most of my early jet powered rc vehicles did not end well. Make sure you have an automatic fuel shutoff valve if the car gets out of range or loses signal. I had a 4 lb stripped down tuned dynajet powered spec car with a cheap radio that took off like a bat out of hell and went into some trees / rocks. Futaba seems to be pretty reliable but still make an automatic cutoff system!

Eric

[larry cottrill]

Eric -

Ooh - OK - my apologies. I knew you were talking about some kind of boat one time, but I didn't remember you saying you had actually "sailed" it. What made the weight so high - was it just something at hand and was just too large? Can you post a picture of that project?

Sorry if that was all explained before and I just missed it for some reason!

So, I guess we'll just give Vaulter the honors of the first FWE R/C vehicle application, EVER! Unless that, too, can be successfully challenged, of course.

L Cottrill

[Eric]

The boat was made for a much larger engine, about 10 lbs thrust, and I also put some ballast on it to keep it nice and slow.

I will try to get ahold of Robert K. and see if he powered anything with his fwe's yet. He was going to put one on a glider for takeoff's. I havent heard from him in a while.

I'll try to find the pics later tonight, right now I gotta run and do some welding before we get another storm and a power outage.

Eric

[Vaulter]

I did play around with the water injection for a while. I found one good spot right inside of the inlet, but also it pumped well way down by the bend in the inlet. I found it a little difficult to tell the spot with the most water flow and least flow out the inlet, but I am just going to try what looks best. When I tried running liquid fuel the engine picked up well, but would not sustain with the propane backed all the way down.
For now I am putting together a fuel bladder system. I will try a radial stinger similar to my Lockwood setup.

As far as the present setup, I am confident the tank connections are free flowing. My first attempt was to drill out a propane torch regulator, but then found a fitting with no restrictions right out of the box. The tanks do get frosted during the run. I need to adjust the position of the needle valve relative to the servo, though. I set the valve while running on a big tank, and I have seen better results from the small tanks when I was manually controlling the valve.

Thanks for the R/C reconition.

[Mark]

Vaulter,
Nice little run there with you twin tank car. What kind of ignition did you use for it?
Mark

[Eric]

You might be giving it too much liquid fuel. It needs suprisingly little liquid, and even a 1/16" id tube will provide more than you need if it is unregulated.

If you try the liquid setup again try using a needle valve, or a pair of vice grips on the flexible fuel line, and use the screw adjustment as a needle valve.

Certian spots will run really rough, and you can hear that it is partially blowing fuel out just by the way it runs, when you get it in the right spot the sound will become nice and smooth.

The setup is probably just a bit off, with a bladder it should help the engine get fuel enough to sustain it.

For the radial injector use very small holes. Try 3 holes of 1/32" diameter, even that would be a little big. If you have some drills smaller than 1/32" then try 3 or 4 holes in that size.

Liquid fuel should be lots of fun for you, especially since you will be able to lower the engine, and carry more fuel in a smaller package.

Every time I try to play the video it stops downloading about 60% of the way through, I just see you starting to turn the throttle on the remote, and then it stops, did you get to drive it around in that video?

Eric