Hollow moulded wing D Box repair

[Jef Ott]

Hi Guys.

Shortly after repairing the wing as detailed here...

Pete sold me the same Xplorer. It flew well but looked sad, so I gave the model some serious abuse with P38 lightweight filler, and car body spray paints.

It looked nearly as good as it flew, and having already had a heap of success with it in low lift conditions at Little Bentley, I ventured south of the Thames with the model and flew at a Tonbridge Multi Launch comp.

Going into the last round of the comp, I was told that I needed to do well to get into the fly-off. No pressure then!

As the hooter sounded announcing the start of the slot, I still had no idea where the best air was, a flat sky and no birds (we had been seeing buzzards all through the afternoon), but needed to pull something good out of the bag. So, for no reason other than I had to do something, I headed as far to the left of the launch area as I felt I could safely control the 3.5m cross tail model. I was coming down all the way over to that point and was about to fly back to where the others were, when I noticed a slight twitch as I turned back.

I put in a couple of turns and felt that the rate of descent was a lot better there than where the others were, although I had given height away when I had ranged so far.

I stuck with it for a few turns, then the very light lift fizzled out and I had to make my way back. As I did so, Eddy started to make height in the middle ground between the launch area and where I was flying the Xplorer. I eased my way back, first losing height as I did so, then I hit a bubble and started working it. Eddy came to join me. We were a long way out. As we turned it suddenly became apparent that we were closer than I thought! Yes, they collided. A wingtip left a model and fluttered down alone. The rest of that model had made a much quicker descent which ended in a horrible clatter. 

One model remained in the obviously good air. It flew OK considering there was a big chunk missing from the leading edge. In fact it was going up. Both pilots (Eddy and myself) were convinced that they were doing OK, but one of the planes was eating dirt.

I was the lucky one.

The Xplorer flew out the slot and landed in the landing area for 1000 points and I had the option of a place in the Fly Off. Luckily I had another model with me (FVK Mistral vee-tail).

Anyhow, the Xplorer's centre panel needed repairing.

To assist with the repair, I enlisted the best engineer I know. My Dad.

We worked together to make a lightweight epoxy glass replica of the D Box profile just outboard of the damaged area, on some polythene sheet.

Once this was cured, we removed it from the wing, and stuck it in place over the damaged area with Selotape Diamond.

That was good enough to see me through to the end of the summer of 2015.

So, now to the permanent repair.

I cut from the leading edge back to the spar, square to the leading edge, and just encompassing the extremities of the damage.

The glass repair section was then cut down to fit the resulting hole.

Then I made some ribs and strip and spar uprights (to space the middle rib), all made individually to fit the damaged wing.

Once this balsa frame was cyanoed in place, and a leading edge added, I needed to pack the profiles a bit (the repair section was thinner than the original skin and I added thin strips of balsa sawn from 1/4" sheet (of about 15 thou thickness). That was a shame, because the neat frame looked untidy with bits stuck all over it. I gradually sanded back the excess until the glass was very slightly thinner than the surrounding section, to allow for some paint and glue. I used Araldite to glue the painted glass section, and kept it in place, during the curing stage, using masking tape. 

Some P38 lightweight "Easy-Sand" filler and sanding was necessary, before priming and spraying.

The result is a strong and light repair (it is still the lightest side of the panel) which has approximately the correct shape and colour.

Please feel free to ask questions.

 

 

 

 

[martynk]

Thats very neat Jef

[Jef Ott]

Thanks Martyn.

I hope that people frightened of repairing 'non-structural damage' will be happier about doing such repairs, when they see how easy it can be.

Jef 

[Eddy Small]

Neat repair Jef. Any weight gain after spraying.

 

Eddy.

[Jef Ott]

Bit personal Eddy.    
Yeah, I've put on a couple of pounds this last week, but will be riding my bike a lot over the next couple of weeks.

I don't worry about glider weights. The heavier they are, the quicker they leave bad air. 

The Xplorer is still the lightest loaded of all my electric models.

I put three light top coats on the bottom and one coat on the top. 

< @Austin why does the font / formatting get mucked up if I use an emoticon in my text while using the tablet? >

[Jef Ott]

@ Eddy,

The centre panel now balances on it's centre, where the repair weight moments are now similar on both sides!

This was pure luck.