Hi all , what are most of ducted fan flyers With BVM engines using for tank pressure .
Puffer or Pipe pressure
From my experience I have nothing but problems with pipe pressure.
If Pipe works for you I"d like to hear from you
Thanks Rcpete

I am not using BVM engine--OS exclusively, but I use pipe pressure all the time. I also use header tanks and the BVM inflight needle valves in conjunction. Using this combo, I have had no problems with pipe pressure.

One last thing, I always wrap my tanks in fiberglass cloth in case the pipe pressure is excessive enough to possibly damage a tank seam..

Rod

rcpete347

First of what jet do you intend to use the Bvm engine in ?

My experience with the BVM .91viojet/.96viofan, BVM inflight needle has been excellent both using the same BVM pipe. Both where pipe pressure. I had it in a BVM F-86

Never a dead stick with eithier engines and the transition from Idle to full power very smooth.

From my use there are 4 things i was told by Bob V himself (which are on his website ) that he recommended i do.

Wildcat 10% D/F fuel
Use McCoy 9 D/F plugs
Ducted Fan glow plug coil adjustment
Hopper tank location. (Use the 2 oz. hopper tank located on the right side of the fuselage just below and forward of the Viojett shroud)

You try do all of the above you should not have a problem using pipe pressure


Now as for Fan Pressure.

This was new to me, i had not heard of it before until i bought my 2nd ducted fan jet, of a ducted fan using fan pressure. My experience up to this point was only with Bvm engines. Still lots to learn.

The setup is OS.91/ramtec fan/Bvm pipe/BVM inflight needle/ Fan pressured. From what i have been told Fan pressured as the advantage of you can place the hopper tank futher away from the carb. In my case i use an 8oz hopper located way forward from the fan (near the nose), i believe its 15inches away from the carb on the OS 91, Vs with the 2oz hopper on BV's engines was 3".

On this jet the OS 91/ramtec are inverted.

With this i use
5% WC D/F
McCoy 9 D/F plugs
Ducted Fan glow plug coil adjustment.

Again not one complaint 10 flights so far so good, engine runs smooth, transition is great. Starting it takes a little longer than the BVM engines, but i believe thats just due to the location of the hopper.

If the above setup is good for Bob V and he has had 100s of flights using pipe pressure for his engines then its good enough for me. I do not have one complaint using PP. I believe if the above setup is used and you have a good running Ducted fan engine you should not eithier.

Robert

Robert,
Could you please explain what you mean by "ducted fan glow plug coil adjustment"?
I've never done anything to the glow plug for ducted fan use. Is there something which makes them work better?
Johnny

Sometime ago in the BVM Tips and hints section this was published....



Ducted Fan glow plug coil adjustment


If your D/F engine is a bit fussy in the idle and throttle-up mode - here's an easy fix. Use a fine tool such as a dental pick to pull the coil out of its chamber about 1/16".
This brings the ignition source closer to the center of the combustion chamber and allows the engine to throttle-up more reliably even with a mixture that is slightly rich.
Check the coil position after one flight to be sure you haven't over done it. We have had success with this technique with both the McCoy 9 and K&B H.P. glow plugs.


http://www.bvmjets.com/

I read somewhere else that this adjustment should be preformed ater you heat the plug first as it will soften the plug coil and make it eaiser to strectch the coil without possible damage....

Rod

D/F coil adjustment,

As mentioned above i try and do as little of the adjustment as needed, i fear breaking the coil, because i'd pull it out to much coil. It needs to be done very carefully.

I believe the turbine guys do the same thing, and to my surprise it actually does improve transition from idle to full power.

Thanks...Great to know.

I knew about the modification to the glow plug for turbine use...I've even done it for my RAM 1000. It didn't seem that the element was too fragile, but I can see why you'd want to heat it first. I guess that anneals the wire.

Thanks again, Rod & Robert.
Johnny

Pete,
Never had a problem with pipe pressure on BVM and OS91 engines. I bought a used jet last year that had fan pressure. What I didn't like about it is its limited range of authority. Each time I went out I would have to set the transmitter knob to full lean, peak out the engine by manually adjusting the needle, then once in the air I'd have to rotate the transmitter knob to full rich in order to get a decent contrail. Yes it had the extra large fuel tubing.

After 10 or so flights I felt I had enough and converted it to pipe pressure. I initially adjusted the needle after conversion and have never touched it since. Now with the extra pressure, the same knob on the transmitter can take it from too lean to too rich regardless of the weather conditions. Now I start it up, peak it out using the transmitter knob, and take off. Once in the air I can richen it up as much as I want.

Joe