Thursday, March 23, 2017

Polecat X – P30 Build Report

This is my second P30 rubber free flight model, the first being the NJAPF design by Al Lidberg. My first P30 sat in my basement a long time before test flights and then last year I installed the DT system and flew it in contests.  For my skill level it did well and at the last contest I thought I might never see it again because it was circling ever higher far downwind.  It did come down and Gary Oakins found it, but with a stab DT I worry if another time it might be miles away. 

Polecat X P30

NJAPF First P30

Don DeLoach was running a special if you ordered multiple plans there was a discount so I ordered the Pearl e202 E36 and Polecat X plans with short kits.  I flew the Pearl E36 a good deal last year and learned much about e36, this year I wanted to get the Polecat X flying.  There was so much different about the constructions of the Polecat X than the NJAPF so I asked a lot of questions online. First I had to order carbon strips that reinforce the wing, ¼ mil Mylar covering, and picked up Balsarite at local hobby shop to stick the Mylar down. Wing and stab construction went well but then I built my first round tube fuselage by wrapping balsa around a pipe, that went alright too. Covering with the Mylar went better than I thought it might, some Design Master spray paint gives it some color. 

Wing Before Carbon Strips

Stab With Carbon Strips

As I completed each major structure I weighed it and then again after covering to compare with the suggested weights on the plan, my weights were close but slightly higher. This is really a detailed plan which I appreciate; no other instructions are really needed.  The contest wins for this model are really impressive and it is a plane that has been refined over many years of contest flying. With the rearhook is in the very back of the fuselage and with a light airframe a really long rubber motor can be used to get a slower climbing motor run that lasts a long time.  It is my understanding it could be possible to get a 2 minute max with the rubber still turning the propeller.

DT Only might not be available
Another new item I wanted to try was the BSD Micro electronic “DT Only”. The weight without battery should only be around 1.5 grams, the battery is a single cell lipo as small as 35 mah.  After trying some ideas of mine that did not work for the DT parts on the plane, I used the method shown on the plan when using a viscous DT timer.  The tiny servo built into the electronic unit does not have a lot of force so having the proper linkage is essential. Adjustment for DT time is done with a really tiny potentiometer that is rather fragile.  When you have it set correctly the DT time should be completely consistent in all conditions. This is the first time I am using the pop off wing idea in the DT which is said to be the only sure way to bring a P30 down from a strong thermal. 

Gizmo Geezer on Test Stand

Again I am using the Gizmo Geezer propeller system, I had installed this on my NJAPF p30 the end of last season and it worked well. With the Gizmo Geezer a certain amount of tension is held in the rubber so braiding is not needed and it has a good working freewheeling system. A couple of people had a concern with all the downthrust called for on the plan if the rear of the Gizmo Geezer might touch the top of the fuselage, I still need to test this.

Now if the weather would cooperate, I could try some test flights.

Update 3/29/2017 - I tried test flights on 150 turns, flies well.

Polecat X 150 hand winds

Bill Kuhl

Related Links  Pearl Free Flight website
Gizmo Geezer Propellers  DT Only timer does not appear to be on the website any longer.  Gizmo Geezer Review Part #1  Flying With the Gizmo Geezer

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