Rays Rant #8 – The challenges

Ray’s Rant #8                                                                        October 2015

I am going to pause on the subject of building wooden airplanes, and take you the steps you would need to go through if you decided to build a certain model.94 resized

The present state of the ARF model world gives quite a wide choice of aircraft, but doesn’t always include an airplane you really like and would like to model.  Down through the years, the model magazines always had a project or two of models, with the appropriate plans to build that airplane.  These plans seem to have disappeared from the usual places you would have found them, but I am sure they are around someplace, and will show up again when modelers once again turn to building.  Right now, the market is very limited for plans, but if you were like me, you bought the plans of models you might like to build down the road.

Sometimes we even bought the kits, and stored them in our basements and workshops until the right time came to build them.  The following story is of one such project.

In the summer of 2011, Ron Pettigrew and Peter Schaffer approached me, and asked if I would join them in a project they had in mind.  Ron had the plans for a Curtiss C-46 Commando, which was a twin engine transport plane used in the second world war.  This was not only quite a project in itself, but it was a larger model than I had ever built up to this time.  It had a wingspan of 8’, and was a model of the largest twin engine airplane used on the allied side during the conflict.  Ron also had the laser cut kit for it, and that would make the project a bit easier, as all the formers, and wing ribs, and other parts were already cut and ready to use.  Before I could decide to join in the project, I would need to look at the plans, and see what I was getting myself in to.  The project seemed doable, so I said I would join in on one condition, and that was that the finished model was their’s, and that my part would be to help teach them how to construct the model.  One of the necessary decisions in deciding to build a certain model, is that you liked the plane, and wanted to model it.  The amount of work needed to get the model up to flying status is huge, and only the desire to see the model fly will keep you going.

The plans for the C-46 are quite large, and are made up for four large sheets.  They are quite complete for those of us who are accustomed to building from plans, and required a bit of time just to digest them.  We needed to find out many things that would make up the project.  What engines to use; how to mount them.  The fuel tanks and system used; how scale were we going to do it; retract wheels or not; real windows, or paint them on.

The first decision we made had to do with the engines.  Ron had an OS90FS he was not using, and I had one as well.  So we decide to use them, instead of two 60 size two cycle like the plan showed.  We felt the 4 cycle engines have a more reliable idle, and on twin you need both engines to run reliably.  In this regard  we then decided to install them sidewinder and not inverted.  Next, we looked at the way the designer installed the fuel tanks.  They were side by side on top of the centre section, and that gave us a possible problem with the fuel siphoning down to the carbs and flooding the engines while not running.  So we moved the gas tanks into the space behind the firewalls, where they would just fit.  That gave us the problem of repositioning the throttle servo’s, which the designer had put in the space behind the firewall’s.  We relocated them to the space where the flap servo’s were, and used a cable to run the throttle.  The only other thing we looked at was the outer wings themselves.  They looked rather thin both in width, and thickness.  So the question we asked was, “had anyone built the model and tried to fly it?”  If we knew that answer, it would have helped in our decision.  However we went with the plan, and the log book showed we had put in 279.5 Hours to complete the model.  We know there were things we did that were not recorded, esp. when we got to putting the finish on, so figure 300 hours closer to what it took to construct the model, and do the engine runs, and taxi tests.IMG_0754-w

We had taken the model to Gimili that year(2012), even though it was not ready for flight.  A group from the US had brought up to the flyin a DC-3 dome up in Buffalo colours as well.  My memory is fuzzy, but I don’t think they tried flying their plane either.  It may not have been ready to go, the same as ours.

We had done the taxi tests and engine run ups in the fall, so the plane was taken to the 2013 flying, and test flown by Mark Sharpe.  Someone used their phone to video the flight.  The take off was great, and the plane flew around and was a good flyer.  During the landing as the plane slowed down, and rounded out for the landing, it dropped its right wing, in a tip stall.  We were glad that we had the video to see what happened, as it happened so quickly.  The damage was slight, and a bit of five minute epoxy would have had it repaired and ready to go, but the tip stall was not a flying error, but a wing problem, and needed to be looked at.

Flaps were not used on the landing, which might have helped, but I really doubt they would have helped.  We brought the plane home, and knew that we had to redesign the outer wing panels to eliminate the tip stall problem.  We did that by widening the tip almost two inches, and thickening the tip as well.

old and new wing

95 resized

We did this by using rib #9 as the tip rib, and having 94 resizeda new set of ribs made on a computer programme.  The new outer wings were constructed during the winter, and in Aug of 2014 at Gimili, we tried again.  When we redesigned the outer wing, we also put in separate servo’s for each flap section, as the joiner the designer had didn’t allow the flaps coming down equally.  This time the plane flew and landed o.k.

During this first flight, the port engine quit, and the plane flew on as if nothing had happened.  In fact the pilot was not aware of the engine out, as the plane flew around just as well, and landed without incident.  On the second flight, everything ran as it should, and the plane landed using the flaps for the first time.

It handled just like it should, but another problem showed up, and that had to do with the tail wheel.  It kept coming loose, so we couldn’t taxi the plane in.  So during this next winter we installed a Robart tail wheel, which handles well in taxi tests, but high winds in Aug. 2015 kept our bird grounded.  We look forward to next year, and hope to get a lot more flying on the model.

Some modelers have said that flying is everything, but that is not our experience.  Seeing your project fly and perform in the air, is a much more rewarding experience, and you won’t agree with this until you have built and flown a successful project, like we did with the C-46.

At this point, I want to say that feedback, and different opinions are welcome.  It is only as we share our experiences with each other as modelers, that we can have greater success in our flying of our projects.

I am adding pictures to this blog, to show the differences in the outer wings, and how only an expert measuring the model to the real airplane would know we had made any changes.

Ray