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After allowing to dry overnight, pins are taken out.
A light sanding to smooth out transition between capstrips and sheeting. Any irregularities here will show through the covering. A little filler is used where material needs to be built back up instead of sanded down. This is a good time to get to this as the structures are still firmly pinned down.
Wing panel structures are now taken off the board and put aside. Still need to apply trailing edge sheeting and capstrips to opposite side before joining.
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Also need to deal with broken sheeting mentioned earlier. It’s been a while since I have had to deal with this, so this is sort of an experiment.
Measure an even distance from the spar. Mark using pins. Tape the straightedge against the pins with masking tape. Using a new #11 blade, cut the sheeting above the break as straight as possible. Clean up all goo and globs left of the ribs and leading edge.
Graft a replacement piece of sheeting, making a hinge with masking tape. Put a bead of glue down on the tape hinge line, rib tops and leading edge. Pull the whole assembly back down using masking tape strips.
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Stick structure go together next. This goes together very quickly. Prefabrication is excellent. No angle cuts are required on any of the sticks, which saves a lot of time.
An extra part provided for the rudder assembly which I think is no longer required.
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Pin down wings upside down on building board. 1/2sq balsa sticks are used as shims below the spars to elevate above the mounting tabs. Straight 1x2 sticks are used to support the trailing edge.
Glue on the trailing edges. Above jigging ensures we don’t build in warps.
Capstrips go on while wing is pinned down, as before. Once glue is dry, blend capstrips into sheeting. Sand high spots, fill low spots.
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OK, now we break out the sanding blocks, put on the dust mask.
Chop the excess spar and sheet at the ends of the panels. Sand the trailing edge straight. Sand in the curvature in the leading edge.
This tool is a big help for this step. It’s just a piece of 4ft shelving with 100 grit sanding belt glued on with contact cement.
Once that’s complete, the trailing edge bevel and tip ribs go on. Note glue line is protected with colored tape. A little more work now, but this pays off later. No goo to sand off on adjacent wood. Provides a guide to sand flush. This tip works especially well when using foaming glues like polyurethane.
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Now we start prepping fuselage subassemblies.
The cabane assembly in this kit is balsa sandwiched in lite ply. Fiddling with gooey parts trying to get them aligned is not my idea of fun. Especially when you end up getting in a hurry, and end up with a crooked part anyway.
Here’s a good way to get it right the first time. First, preassemble using double-sided tape. Get the parts aligned perfect. If they’re off, just pry them apart and try again.
When satisfied with the alignment, drill through the assembly to fit round toothpicks. That way, once you go back with glue, the pieces just snap together. Use side cutters to remove the excess toothpicks, and clamp down on a straight surface.
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Now on to the fuselage sheeting. The instructions do a good job of taking you through this.
If you want a built-in antenna tube, this is the time to plan it. This is also the time to fine tune the throttle servo placement. If you need special hard points for mounting tanks, tuned pipes, etc. plan it now.
The skins are very easy to put together in this kit. Just a few seams to tape together.
I like to get as much stuff built up front (under the skins) as possible. That way, most of the finish work gets done when the outer skins are put on.
I like to vacuum bag these together with polyurethane glue. Weights as described in the instructions works too. By the way, this is another place where pre-fitting with toothpicks works well.
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Very nice Marty! Looks like this bipe is not going to be a headache to build. Only headache for me is waiting for South African customs to let mine come home Keep this speed up and she'll be flying in no time!
Marty, I've got to say I'm very impressed with your talent and sharing of tips! Love the toothpick idea! Maybe I could just have those holes premade with the ole laser beam!
_____________________________
Mike (Salmon) Pilkenton, Chief Slab Designer Ohio Model Planes, Team OMP Captain
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It’s like Christmas morning when you’ve had one of these cooking in the bag overnight.
Cut it open and unwrap it, pull off the tape. Sand what’s left of the toothpicks flush, sheeting even, and square with the foam all around, and this is what you get.
See this thread for a discussion about vacuum bagging these fuselages.
This is a good time to pencil mark the thrust line (nose to tail) on the sheeting. Do it on both sides, and make sure the lines are placed identically. This line will be used as reference for 1. Motor box placement 2. Horizontal stab placement/alignment/incidence 3. Horizontal seams in the covering
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Next step is getting the motor box assembled and mounted.
Motor box is fitted to the crankcase size of the motor. (Saito 100 for me) Everything is epoxyed together on the building board, per the instructions. Note second spacer on the front. This is just for alignment – It is not glued in!
Once that has set, mark the center line on the box. Then align this centerline with the thrust line drawn on the fuselage. The perimeter of the box in this location is what you need to cut out of the fuse.
Then you just epoxy in the box in the resulting cavity. Pay attention you glue it in the right direction! Spacer at the front (Guarantees rails stay parallel) is discarded after this operation.
BTW, if you have any doubts about the strength of sheeted foam construction, spend a few minutes doing some destructive testing on the chunk you just took out.
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Once the motor box has set, the fuselage perimeter can be capped all in one step. Note green tape around the perimeter (again) to guide sanding back to edges.
Wetting the wood with ammonia works well to soften the wood around contours. Slicing kerfs into the wood works well too. I did a bit of both.
This is a very straightforward job. Use polyurethane glue like for the sheeting.
Rest of the day was spent sanding all the other parts built so far. Lots and lots of sanding…
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All Forums >> RC Airplanes >> Profile and Fun Flying Planes >> RE: OMP 50in 10-300 Ultimate - Marty's Build 
RE: OMP 50in 10-300 Ultimate - Marty's Build - 
Keep this speed up and she'll be flying in no time! 
