Clean up, Glassing & Paint Prep

2/20/05

It's time to look everything over and fix anything I find now and hope I didn't forget something. The bomb bays needed some filling where the fuselage meets the door and the wing needed to be fit into the fuselage.

The finishing stuff.

The fuselage needed some filling at the tracks and I cut some strips of balsa and glued them to the outside of ply tracks on the fuselage bottom so they are flush with the doors when closed. I still haven't actually finished the bomb bay doors but I'm pretty sure it will work so I went ahead and finished up the tracks.

2/25/05 - 4 hours -

Mated the wing to the fuselage. First thing to do is to set the wing incidence. There was already a 1/4" hole for the alignment pin in the fuselage wing rib so I needed to get it aligned and drill a hole in the wing root rib. The problem I had was I was over zealous when drilling lightning holes in the root rib and put a 3/8" hole right where the alignment pin needed to go. Luckily I have a plug cutting bit that fit the hole perfect so I was able to fill the hole without too much trouble.

With the wings aligned I went on to putting in the wing holding bolt. I put in under the wing tube because that's where there were no other holes. Now the wings are aligned and bolted to the fuselage.

The gap around the wing where it meets the fuselage needed to be worked on to get it as small as it can and still get the wing in & out. Way back when I built the fuselage I cut out the wing hole but it wasn't even close in some places so I added some balsa where needed and then slid the wing on, traced around the wing, slid it out, sanded, slid it in and repeated until the wing could be slid all the way in with a minimal gap.

The fuselage is now ready for glassing.

2/28/05 - 5 hours - Worked on getting the wings finished up and ready for glassing.

The nacelles curve inward at the cowl flaps but not on the sides so I needed to duplicate that. I had already glued on extra sheeting at the sides and did some preshaping so all that needed to be done was to add some filler and finish it up. It required a few cycles of filling and sanding but I got it looking fairly good.

The wing tips got their final shaping.

The pieces cut from the inner nacelles for the gear was tack glued back in and filled/sanded. I'll cut it out again after glassing. I also put the flap and aileron hatches in so I can glaas them at the same time. I'm hoping they don't get glued in. 3/10/05 Update- They got glued in a bit. I would glass them separate next time.

I did a final filling/sanding of the wing and leading edge and that does it. Now I can send it to the finishing shop.

Fiber-Glassing

3/2/05 6 hours total -

Started the fiber-glassing today. I'm looking forward to getting a hard shell on the balsa. I settled on ZAP Z-POXY finishing resin because I have read good things about it and my LHS has it in stock. I am using 12 oz. of the epoxy and 6 sq. yards of 3/4 oz. glass from Gator R/C. I will use the "lay down cloth, pour on epoxy mix, spead it out with scraper and acid brush, scrape off as much epoxy as you can, go over it with toilet paper" glassing technique.

Started first on the bottom of the left wing and it was almost a disaster. I thought I could glass the entire bottom, nacelles and all with one piece of cloth and finally did get it all laid down before the epoxy set up but it was close. On the right wing I glassed the flats then the nacelles and it went much better. The glass cloth lays down very well on flat or curves and the Z-Poxy works great. The Z-Poxy instructions say to use at 69f and above for best results but I used it at temps ranging from 60f to 72f with the only difference that I could tell was it set faster with the warmer weather.

Continuing on with the rest of the aircraft was uneventful. Glassing in 30 min chunks, It took a total of 6 hours over 5 days to glass everything. I did the Fuselage in four sections but I think I could have done it in two.

Paint/Flite Metal Prep

3/7/05 - 3 hours

Sanded down the epoxy. Now on to filling the weave. I am using two meathods to fill the weave. What i've used before and liked, Dupli-Color Filler Primer . It works great for filling since it sprays on thick, dries quick and sands easy and I can get it at the auto parts store. The other is Bondo spot filler. I saw it used by someone on RCUniverse.com and thought i'd try it.

Dupli-Color High build Filler/ Primer. Expensive at $ 4.50 per can. Easy to apply (spray can) sands off quick but you must wet sand.

 

Bondo spot putty filler. Cheap, I did both wings with one tube. Sands easily and does not need wet sanding. I didn't like that now everything is orange, including my back yard. Dries so fast you have to apply it quick and in small chunks.

The orange spot putty doesn't show defects very well so I had to spray on some primer to highlight the defects then fixed them with more spot putty. A coat or two of the gray filler/primer over everything, sand it off, and it should be ready to aluminize.

 

Weight in grams
 
Wing before glassing
After glassing
After filling the weave
Total weight gain from glassing and filling
Left
738
808
802
64
Right
727
791
802
75

Glassing and filling only added 2.3 and 2.6 oz. It's interesting that the weight decreased after filling the weave but the wing was weighed before sanding off the excess epoxy and then after sanding off the excess epoxy and filler. I only weighed the wings but this shows a typical weight gain from glassing for this aircraft. it comes out to around .025 oz. per sq. in. of area

It's getting close. I'm estimating only about 200 hours to go before flight testing.

I'm done with the finishing for now. I will install the flaps and then work on the plastic parts before doing the final filling and sanding.

Next up - Building and installing the flaps

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Updated July 14, 2009