BMJR Sniffer Build Report

Purchasing the BMJR Sniffer kit was a bit of an afterthought, I was purchasing a Witch Hawk 500 free flight and thought I remembered there was a discount for a second kit. The Sniffer caught my eye because of the classic old timer look and I had a couple of Cox PeeWee .020 engines. Turns out the discount ended the month before but I still think the Sniffer was a good purchase.  I thought I could enter it in PeeWee 30 event at the Nats but people told me there were much more competitive designs so I am building a Basic Yeller for Cox PeeWee .020 power and using electric power for my Sniffer for sport flying.  It will have radio control equipment for motor control and DT, my hope is to be able to fly it from a rather small field if I want to and bring it down at will before flying into a tree.

Midwest kitted the Sniffer and Super Sniffer a larger version back in the 1950’s. The Sniffer would often use a milder .049 engine of the time but the Cox PeeWee .020 is said to be a good match, stronger .049 engines are too much power but would work in the 48” wingspan Super Sniffer. I was thinking of the option that I could add a rudder to fly mine RC but from reading experiences of people who have converted the Sniffer to RC it appears it has too much polyhedral to control properly.  Rather defeats the charm of free flight too.

Doubler Added Inside of Fuselage at Splice

Building the BMJR Sniffer kit was really straightforward; I did make a couple of modifications in areas I thought might be a little weak. First I had read a couple of people had the fuselage break at the splice point so I used a thin balsa doubler over the splice. For the landing gear I used plywood doubling instead of balsa and added a couple of gussets.  Not sure if it is needed but I would rather not have to fix broken landing gear mounting later if possible.

Landing Gear Mount - Plywood and Gussets Added

Electronics I will be using was purchased for a RC conversion I did of a Guillow’s Cessna 150. The small brushless motor was really too much power for the Cessna 150. This same motor I have in a couple of RTF RC planes, Sbach and Pitts, 2 cell 180 mah lipo battery. I think for the somewhat larger free flight Sniffer it should be about right and I can always use less throttle.  My hope is to learn from observing the power pattern from launching at varying power levels.  I feel also with complete control of motor I can climb to the altitude that I think the field size will justify. When I took motor off the RC flying wing I had it mounted on I noticed the plastic motor mount was broken. 

Electronics

No doubt I could have ordered a new motor mount but I decided I could make one out of thin brass stock and brass tubing. Materials were found at local hardware store and cutting and drilling was easy, soldering the tubing to the thin flat brass sheet, not so easy. Using my soldering station at the highest setting of 680 degrees wasn’t enough heat to get the solder to flow well. After trying long enough I did get the job done but it looked like heck.  

Sloppy Solder Job

To open myself up to criticism I posted a picture of my soldering job on the Internet. Actually people were kind and gave me a couple of good suggestions.  One was to use a small butane torch and the other is to use Stay Bright brand solder. These are things I want to try in the future but my solder job seems adequately strong. Actually I would like it to break loose in a really hard crash.

I just finished up covering and just have the final details before test flights. Then I can see if the plane lives up to its’ name and sniffs out thermals.

Bill Kuhl
http://www.ideas-inspire.com

Related Links

http://www.bmjrmodels.com/free-flight/sport-free-flight/sniffer   BMJR Sniffer
http://www.bmjrmodels.com/super-sniffer  BMJR Super Sniffer
http://scienceguyorg.blogspot.com/2014/10/guillows-cessna-150-flies.html Guillows