The flying monkeys got me...

Helis and fixed wing

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Monday, July 18, 2016

Great Planes Big Stik Build Days 2-3 or so...

I've made some progress on my Big Stik 10 cc gasser build. It's required a few modifications, and trial and error solutions to problems, adding hours of work and re-work. It was at times frustrating so I didn't take as many pics as I could have...

The 260cc gas tank. It stops at the front bulkhead, not the firewall, which is as I would like it. The nitro tank is designed to fit into the middle hole of the firewall, but this would crowd the air intake for the gas engine's carb which faces rearward. I need the space between the foremost bulkhead and the firewall for the ignition, and I want some of the increased weight being a gasser back towards the CG. This means that the tank was sitting on the middle bulkhead like a teeter-totter, so I build a small base to support it anteriorly. This went in just behind the foremost bulkhead.

I put darts on half of the underside of the horizontal stab.

The horizontal stab only used three CA hinges, which I thought a bit weak. I am using Dubro nylon hinges on all of them, and added two CA slots.

I am making mine a tail dragger. I wanted a steerable tail wheel and MacGyver'd this. It clears max deflection of the elevator. Took a couple of attempts with fresh wire to get this right.

This is how the tail steering rod comes out on top of the horizontal stab and attaches to the rudder.

A full view of the tail mod. Let's hope it lasts. Worst case it casters.

I put down a piece of plywood to give the underside where the tail wheel attaches some oomph it lacked for this application. I used it to further secure the horizontal stab, which was simply epoxied into place.  I secured it with RTL Fastners servo screws (long ones). Love those screws.

On Day 1 I installed some plywood to establish a sound platform for the landing gear so they would lay anterior to the CG. The holes at the bottom of the pic are the original blind nuts for the tricycle configuration, which I did not use. In this pic you can also see how I shouldered the bulkhead to help the longer tank pass.

I covered the screws with a little foam. You can see where I had to cut the middle bulkhead to get the tank in.

Tank lined in and the servos installed. There were several steps and mis-steps to get here. The issues were that I didn't want (nor needed to) drill any holes for the throttle control arm. I needed to change the connection to the card a couple of times before I found a nice combination that did not bind and was secure. I completely invented the upside down station for the throttle servo. The stock design has all three servos in that bay. This would require  significant geometry issues getting the rudder and elevator control rods to the servos. This eliminated most of that angle issue, but there is still a little angulation as you can see. I toyed with using the servos externally on the back of the fuse, but decided on the cleaner internal location.  As part of the throttle servo box I reconstructed the cross bar of the original middle bulkhead I had to remove to fit the tank.

The landing gear installed for the tail dragger config. Note the opening underneath just behind the firewall. This allowed me to access the fuel tank fittings and to pass the Hall sensor wire to the ignition (the only new hole I put in the firewall. I didn't want to use the center hole as I don't want to obstruct airflow to the carb. This is also where I put the ignition box. I Dual-Lock Velcro'd it to the side of the fuse inside there. The fuel line nib is on the opposite wall.

The access hatch is in place with the spark wire, fuel line in and out of the QuikFire fuel filter and balancer (the blue thingy) emerge from it. When I was having trouble with the first 10cc I took it off, but am using it again.  Its very light, effective in all it advertises. This is the RCGF-USA 10cc gas engine and ignition from the ill-fated Spitfire. The ignition worked after the soaking, but I don't know if its damaged. I have a replacement from Hobby King coming in case, but that's gonna be a while as its coming from Hong Kong. The ignition and receiver packs are likely toast. I pulled them out and they looked ok, but I squished one and foamy water came out... I opened them and they are corroded, so tossed them and have new ones coming. I thought about using LiFe, but only my base charger can charge them, so went with NiMH. And yes, I finished installing all of the engine mount screws.

I am getting to the end of the build. I want to add some more support to the front of the wing, Right now it only has the single post that is built in, and that's likely enough, but I want a little insurance. I will also be testing the receiver, which seemed dry from the crash: it looked like it was just above the waterline that ended with the packs partially submerged. The switches and the receiver seemed to be dry, but time will tell. I am using the Spektrum AR7000 from the Spitfire. So wing mod, electrical to include receiver, remote cut out, and switches. Then she will be ready to start and tune. I hope that goes well. I ran the motor after the soaking and it ran. I wanted to see if it would, it did, but rough. I learned during the demolition recovery that the clunk had wedged anteriorly and attribute the odd running to that, but I still don't know about the state of the ignition.

More to follow. Couple of days of work-work ahead, then play.

ADDENDUM: By the way, I learned a couple of things. Dubro wheels HATE alcohol, and bubbled up like poison ivy on skin where ever it touches. I cleaned a hub and watched a wheel blister... And when grinding off an axle, those sparks will leave hundreds of tiny little holes in them where they melt in.

1 comment :

  1. The style of that aircraft reminds me of one I used to fly many years ago called the Avicraft Moronic (Avicraft is a UK company), it was designed for a .40 -.46 so of course I stuck an OS 61 pumper on it with a tuned pipe.

    Very simple construction with a flat wing, very lightweight construction for its time (this was back in the very late 1990's)

    It did have quite a long life until I folded the wing at the top of a touch and go loop, but amazingly I managed to land it safely with majorly crossed up controls. Everyone at the field was amazed I landed it in one piece. I retired her after that lol.

    I predict that you will have massive amounts of fun with this one!