Minch

Can anyone offer any advice

Just been fitting a P70 into an avonds Rafale and according to the Jetcat manual it shows a 20mm gap between the rear of the exhaust (the wide part) and the start of the bell mouth, although the drawing shows a P80. I just wanted to know whether this distance is critical and what effects are likely to be if I shorten or lengthen the gap, the install is not a full bypass and there is plenty of airflow around the turbine.

Thanks In advance

Nick

Dave Wilshere

Nick

It needs the 20mm, tail pipe is like the P80 (P70 is a P80 with small case)
if you reduce it the temp could go up as it won't draw cool air into the pipe.
My Inspiration I have 25mm. Distance can depend on tail pipe dia too

Dave

Minch

Dave,

Cheers for the info, 20mm it is then, don't think I can go any further forward as I have a 1.5litre dubro tank to fit between the front of the turbine and canard joining bar (In an Avonds Rafale).

Many Thanks

Nick

Mark 5

Nick, according to the Jet Cat manual, the duct inlet should be 1/2 to 3/4 of an inch after the end of the exaust nozzle of the P70. I have my P70 set at 3/4 of an inch in my Skymaster F16 and it has great power and runs cool. I am also building a Rafale( aviation Design) and trying to deside which turbine and retracts to use, I will be flying off of very thick New Jersey grass,so I need the strongest retracts and the lighest most powerfull turbin I can fit in my Rafale. Nick,please keep me updated on your progress, by the way,what does your Rafale weigh,and what retracts are you using.Talk to you soon Mark.

Minch

Mark 5,

My Rafale is a converted D/F and I am now using Airpower retracts, if you do know airpower they are based in Taiwan, carry alot of stock and shipping etc to UK usually about 7 to 10 days. Airpower website is http://www.airpowernet.com, although I believe that dreamworks in the US does very similar retracts etc. Reason for airpower retracts and especially oleos is the Avonds retrats are mounted at an angle so the oleo axle needs to be set to 105-110 degrees with respect to the oleo and airpower do legs at various angles.

As the the weight of the aircraft I weighed it a few weeks ago and it was 10.75 lbs but I still have to add turbine etc about 3.6lbs (2.6lbs turbine +1 lb ancills) and a UAT with 4 oz fuel. I am aim for a dry weight of 14.5 - 15 lbs. Fuel wise I have managed to get a total of 2.1 litres on board, so anticipating 18 lbs take off weight.

One thing to consider is that with an Avonds thrust tube (bifucated one) you can loose about a 1lb of thrust (according to Avonds), don't know if the AD raf is the same. I have flown it with a 13lbs Wren 54 and found it a bit gutless, flew alright but performance not exactly sparkling.

I did consider a Merlin 90 but with the current exchange rate it is £350 ($550 ish) more then the P70, in the currrent economic climate a bit too much for me at the minute. and all my other turbines are Jetcat and have so far proved nearly 100% reliable, I have had a few minor issues with a P60 but this was sorted under warranty within a week.

I will try and post some pics over the next week or so when I get the turbine mounted.

Nick