bandit arf by-pass????
 

hey guys...just finished my bandit arf and the second start i had with it the bypass seams to be getting hot. the heat sheald that you paint on inside the bypass is starting to bubble. the turbine is sitting where the plans show it to be and is centeard in the bypass.
the gsu reads 620 to 670 so its not getting real hot i wouldnt think. and its always started in the wind. what could be the pronlem?

thanks...mike

RE: bandit arf by-pass????
 

Gap from turbine to the pipe looks awfully long to me.

RE: bandit arf by-pass????
 

The pipe needs to come in the bypass to about .5-.75 inches max from the nozzle of the turbine.

RE: bandit arf by-pass????
 

hi guys thanks for the reply, the pipe fits over the by-pass not in it. thats what the bvm plans show. should i just slide the engine back in the mounts?

thanks...mike

RE: bandit arf by-pass????
 

Try that, but it looks like you do not have enough to do it. A P120 has a longer nozzle. are you using a BVM bypass?

RE: bandit arf by-pass????
 

Mike,
As I interpret your photos, the drawing shows 5.25 inches from the bypass tube/inlet extension to the engine can forward edge....your ruler shows 5". Therefore, it looks to be 1/4" too far forward.

Slide the engine aft .25 inches (1/4") to attain the 5.25" dimension.

Also, did you apply three coats of Heat Shield, as the plans indicate? If not, I would recommend the addition of Heat Shield to reach the three coat thickness.

Harley Condra
BVM REP
JetCat REP

RE: bandit arf by-pass????
 

Sounds like good advice.

Raf

RE: bandit arf by-pass????
 

Having built 2 for myself and a flying buddy ,i had the same problem with my first , i cannot find any paint that will stand the heat [&o],the P80 outer is just too close regardless of any gap and coats of BVM HP paint ! ,I stripped my b/pass back to edge of the turbine body
and used matt black exhaust paint ,leaving the gloss on the rest.
I know how you feel i watched mine bubble up after the first run[:'(]

RE: bandit arf by-pass????
 

hey guys...the by-pass does have the 4 brushed coats of heat shield. the turbine is set at 5 1/4 as per plans the photo just sucks. and yes it is all bvm...the by-pass the pipe.

thanks again...mike

RE: bandit arf by-pass????
 

Here's something else to do.
Please realize that this help I am offering is coming from about 2500 miles away, and by just looking at your photos, makes it very difficult.

Try raising the back end of the engine exhaust nozzle about 3/16". Your "up the pipe photo" makes it look like the nozzle is pointing slightly down. Is that from parallax also, or am I going blind?
With the lens centered in the pipe, the engine should look centered...it doesn't. The nozzle looks like it is pointing down.

Just checking one more time might be just what you need to solve the problem.

"Measure twice, cut once".

Harley Condra
BVM REP
JetCat REP

RE: bandit arf by-pass????
 

hey again...i thought the same thing with the photo but the heat is bubbleing to top of the bypass. i tried to adjust down and i still get the same issue. 2500 miles away is still good healp.

thanks...mike

RE: bandit arf by-pass????
 

Let us know what you think after the first flight!

Harley Condra
BVM REP
JetCat REP

RE: bandit arf by-pass????
 

harley...i really dont want to fly it the way it is. im really scared of a fire and a total loss to my jet or our field. maybe it would be ok in flight...i dont know. im going to take another picture of the pipe and the turbine.

thanks...mike

RE: bandit arf by-pass????
 

I would venture to guess that the problem is most likely that the turbine is too far forward in the bypass.
This is allowing the column of exhaust gas to expand before it reaches the tailpipe.
I would suggest moving the turbine back in the mounts about 1/4" and see if it improves.

RE: bandit arf by-pass????
 

harley....any better? and the bandit.

RE: bandit arf by-pass????
 

Looks closer in that photo.
Nice looking Bandit. You will love how it flies!

Here's a photo of my Super Balsa Bandit .......It now has composite wings.

Harley Condra
BVM REP
JetCat REP

RE: bandit arf by-pass????
 

thanks thats a nice bandit...ive been wanting to put the wing tanks on mine...can i? and if i wanted could i also use composit wings? well i guess i will just try to fly it the way it is.

thanks...mike

RE: bandit arf by-pass????
 

You could install the underslung wing tanks if you wish.
I am not sure if the internal structure of the ARF wings have the hardwood blocks installed, but there is more than one way to add the mounts.

The tanks are available from BVM for $155.00 per pair, and include the pylon kits.The pylons are made from plywood and balsa, and are very easy to fabricate.
The part number is 6705.
All of the necessary instructions are on the Super Bandit drawings.

You can contact Dustin Buescher at BVM to find out where the internal structure is located in order to install the tank mounting blocks. 407-327-6333
Dustin is the Bandit ARF daddy. He heads up the airframe design group.
My pylons contain the pnuematically operated BVM EZ Drops so I can drop the tanks or drop bombs in flight.
I have an extra air tank with a micro servo operated air switch operating the EZ Drops.


Harley Condra
BVM REP
JetCAt REP

RE: bandit arf by-pass????
 

cool...thanks, when you balanced your bandit did you do it upside down or riteside up? because it does differant things both ways.

thanks...mike

RE: bandit arf by-pass????
 

Lateral Balance:
Balance the wings individually first. Add weight to the light wing as follows..example..if the right wing is 1oz heavier than the left wing, add 1/2 oz of lead in the aileron servo pocket of the left (lighter) wing. Glue the lead in securely.

Install the wings, and balance the aircraft right side up, gear down, zero fuel and full UAT.
It should be the same upside down....CG is CG.

Harley Condra
BVM REP
JetCat REP

RE: bandit arf by-pass????
 

ok... sounds good. thanks for all the help harley and all that have posted about my problem.

thanks...mike

RE: bandit arf by-pass????
 

hey harley....i think i found the problem, the straps that mount the engine even after tightening the crapout of them the engine with a littel force does move up and down buy with force. maybe the engine tilts up or down when i get on the throttel maybe????

thanks...mike

RE: bandit arf by-pass????
 

Are the clamps completely closed ? If so, did you use the black metal 'spacer' that BV includes in the mounting kit ?

Sometimes you will find that the clamps are long enough that they close completely without being tight enough. By using the black spacer material you effectively increase the distance that the clamps have to cover, thereby allowing for a bit more tightening.

RE: bandit arf by-pass????
 

If you have a loose engine, it can and will move around. Each landing would reposition the engine.

Gordon has broken the code.....On certain mount straps, the shim is required under them to make them tighten sufficiently.
If no shim material is included with your engine mount straps, just slip a thin metal shim between the strap and the engine can to make the straps effectively longer. The local hobby shop that carries K&S metal will have some thin brass or stainless steel shim that will do the job.
Don't overtighten them....it is possible to deform the engine case.

RE: bandit arf by-pass????
 

hey guys,
i think the black strap you speak of is actually supposed to be formed into a small "tophat" shape that the "brim" gets placed under the 2 straps and the "hat" portion between the straps and projects downward to touch the bypass bottom. this keeps the engine centered especially when there is a hard landing.
picture engine held on the sides by the 2 tabs, and being held up by the tophat which is between the lower turbine body and the bottom of the bypass.

Kirk