Jim.Thompson's blog View Details
Archive for January, 2012
Posted by Jim.Thompson | Jan 24, 2012 @ 02:42 AM | 7,741 Views
I have cut the foam cores for the wing plugs. The cores are in 5 panels with one panel parrallel for the centre section. The plan is to glue ply or fibreglass laminate ribs to each end of this centre section and to the mating ends of the wings prior to joining. A piece of wing joiner tube will be in place also, embedded in the foam cores so that joiner rods can be inserted in the finished plugs to set up the mould accurately. I will glue them together with a thin cardboard spacer so that they can be easily and accurately cut apart with a thin kerf hacksaw after the complete wing is fibreglassed and vac bagged.
The joiner rods then become the alignment jig for the final wing and fuselage tubes.

I am about to layup a fuselage out of the old mould to build on to make the final plug. The centre section (above) has to be incorporated with their tubes etc. The "V" tail joiners have to be included in the plug. Then a "final" mould will be made from that.

The challenge as I see it, is the "V" tail joiners........

More soon.

Jim.
Posted by Jim.Thompson | Jan 24, 2012 @ 02:31 AM | 7,712 Views
I have posted a report of some RF problems I've had here:
https://www.rcgroups.com/forums/show....php?t=1572618
and also on the FlyDream thread here:
https://www.rcgroups.com/forums/show....php?t=1207547

The short story is that I have resorted to 36 mhz equipment for my Wompoo. I tried two brands of 2.4 ghz in it unsuccessfully.

Jim.
Posted by Jim.Thompson | Jan 07, 2012 @ 03:08 PM | 7,350 Views
Some of the bubbles that occured in more than one of my vac bagged wings has developed into a significant delamination. This one is on my 1.8mtr. homebrew "Endorphin". The bubble had spread to an actual compression ripple due to inflight stress's. There is no spar in this wing.
I repaired it very successfully using vacuum applied under the skin on one end of the ripple. I used a sports inflation needle (used to inflate footballs I think), inserted through a drilled hole. Then in another hole at the other end, I applied low viscosity epoxy using a syringe untill I could visually see the epoxy bubbling out the needle through the clear vinyl tubing.
I have previously tried repairing these by just syringing the epoxy under the skin with very limited success: the epoxy simply will not spread enough to cover the affected area.
This worked very well and emboldened by this success, I went and repaired several other bubbles.
I have since identified what is the cause of this phenomenon. I used to mix "Q" cells with the spackle that I filled slight dings on the foam cores before vac bagging. The "Q" cells caused slight dust which repelled the epoxy slightly, sufficiently so to reduce adhesion. Any offgassing of the foam with heat (during hot box post curing or simply in the hot sun), would then cause a bubble or more.

Jim.
Posted by Jim.Thompson | Jan 05, 2012 @ 05:25 PM | 7,473 Views
I have completed the fit out and ballance. It took 300 grams of nose weight. And the AUW is 2 kg.! Much heavier than I anticipated, but it will be ok in "big air" conditions. The sort of conditions we get out at Mt. Borah NSW where our annual slope festival is held.

That work out at close to 70 g./sq.Dm wing loading, the highest loaded plane that I have. My Cobra flies very nicely at 65 g./sq.Dm, so this should be fine. I still have the provision for ballast, two cast lead slugs totalling 650 grams, but.......................

Jim.
Posted by Jim.Thompson | Jan 03, 2012 @ 02:27 AM | 6,579 Views
I have got the paint job done. No clear coat yet, I will wait untill I give it the maiden flight and any necessary trimming before I do that.
I'm quite pleased with the job, the fuse came out with an almost "gloss off the gun" while the wings are a bit flat. No problem though, a wet sand with 600 - 800 grit to level off the masking ridges etc. and then a clear coat will make it look ok.
It seems the trick with acrylic lacquer is to use a high dilution rate, almost 2:1, and apply several coats, preferrably many. But of course, the danger of runs is high, so care must be taken. Any pro's reading this? I would appreciate any tips.
I just need to fit the cast nose lead (200grams), the batteries and final fitting etc. The servos and pushrods are already in, and the tx. program sorted out to suit.
Then ready for that maiden flight out at one of the beach headlands.

Jim.

p.s. The model now has a name. "Circa" latin for, well, you know what!