Another First-Time Builder Attempts the Skimmer 400

[Zymurgy]

A strange combination of factors led to this project:

1) I wanted my fourth plane to be a small sailplane.
2) I wanted to build a balsa kit (or attempt to)
3) I read about the Skimmer 400 and the extensive construction posts and tips.
4) I found that the Skimmer 400 was "only" $19 a couple of weeks ago at http://www.hobby-lobby.com.

I had been considering the E-Flite Ascent, but the Skimmer was just too tempting....

Inspired by the posts by pda4you, QuestMGD, Soholingo, and others, I thought I might be able to figure this kit out. Using tips from most of the Skimmer construction threads, I'm about halfway through with construction (after about 12 hours of work over 10 days, and I thought I'd post some image and comments, especially of things that I wish had been photographed in other threads.

Below is the box, as a starting point, but note that this picture was taken well into the process (and please forgive my messy garage).

[Zymurgy]

I've built a T-IFO recently, but I've never built a full balsa kit plane. My brother and father have built large sailplanes, but never an electric.

Following the advice in another Skimmer thread, I started by building the tail feathers first. My father loaned me an excellent cork board to build on, and the T pins with special sliders on them to hold down the balsa. At first I tried putting the pins through the some spare tail feather stock, but it just split it. The black sliders worked great.

This is pic of the stablizer and elevator. Note that the elevator isn't glued to the stabilizer (it's just there for alignment issues).

[Zymurgy]

The next part I made was the fin. At first I though cutting the angles for the sticks would be a challenge, but balsa is so easy to work with that I just put the 3/8 inch stock over the plans, marked it with the hobby knife, and then cut it on the work talbe off of the plans. Cutting a touch long was the best, because doing clean-up with the sanding block was so fast.

I'm using medium CA throughout, though not the odorless kind (I have some thin odorless, but it's so runny I have a hard time keeping it where i want it). The plain old saran wrap over the plans did a good job of "not" sticking to the glue, but there was times that I pinched the wrap between the sticks.

Here's a pic of the fin:

[Zymurgy]

After completing the tail feathers, I noticed that some recommended going onto the main wing (in fact, many seem to start there). I wasn't ready yet for all those fragile-looking ribs and stringers, so I started in on the fuselage.

Below is a pic of the two (left and right) sides of the fuselage in process (with saddle doublers and triangular stock installed). For some reason, one of my triangular stock pieces was about 3/8 inch shorter than the others. There was nothing in the plans about one being shorter... I decided not to worry about it and just move ahead (its the one on the lower left).

[Zymurgy]

The next step was to add the 3/16 inch sqare longerons to the fuselage sides. This was fun (in a good way). The most challenging was the long, curved bottom longeron (given the speed at which the CA sets with balsa). I used the pins to define the outside of the curve and to hold the fuselage side in place.

[Zymurgy]

The next step (according to other threads, but not the manua) was to sand down the tail longerons so that they could be glued together correctly later on. I temporarily clamped the middle formers in place, and then used the recommeded "sandpaper folded in half, sanding both insides of tail with both sides of sandpaper" technique on the tail.

While pinching the tail together and sanding it, however, I couldn't figure out how to get a clamp on it without making it too tight to sand. I just used my fingers, but then I found that I had sanded down the bottom longerons much faster than the top ones, so I had to adjust my technique.

[Zymurgy]

Here's a pic of where I stopped sanding, leaving the last 20% for after the fuselage was fully aligned and connected up front.

[Zymurgy]

My next step was to cement the two fuselage formers in place. I wanted them to be at right angles to the fuselage sides, so I used my trusty right angle.

Although I don't show it, I did use my Dremel to enlarge the battery hole in the forward former, just as shown in the thread by pda4you (thanks for the tip!).

[Zymurgy]

Here's a pic of the fuselage after the sides were joined with the formers.

[Zymurgy]

My next step was to finish the sanding of the tail and cement it together. I seemed to have good contact area, and I used two small clamps to hold it while the CA dried.

[Zymurgy]

One of the best recommendations I saw in the other Skimmer threads was for laser cut plywood Speed 400 motor mounts from http://www.tim.mcdonough.net. I used the square version, because I believe the round version would have been too small of diameter.

The pic below shows the mount from the kit (no holes for air intake) and the laser ply mount next to it. I used the kit mount as the pattern, and then ground the new mount to the same dimensions with my dremel.

[Zymurgy]

Here's a pic of the shaped mount. The ply is of very good quality, and the air holes line up perfectly. Like pda4you, I decided that they second wall included in the kit was redundant, and I decided not to use it either.

[pda4you]

YEA!!!

Another Skimmer in the bones. You are doing a great job Zymurgy!!!

If this is your first balsa build - I would have never known it. Your building looks very good.

Keep up the great work and keep posting your progress. I would recommend one change that I didn't do. If you have not glued on the firewall yet put in another 2 or 3 degrees of downthrust. Mine really needed that. It will slow the full throttle tendancy to zoom up so much.

Great airplane - you made the right choice!

Mike

[Zymurgy]

pda4you,

Thanks for the complients-- don't be fooled into thinking I haven't made mistakes so far.

I believe I have the exact downward thrust as spec'ed on the plans; in fact, I focused on it so much I made an error in another way (post to follow). I have an idea about how the thrust angle and downward angle could be adjusted that I'll share later.

This is a nice plane. To be honest, the E-Flite Ascent probably would have been less expensive once you figure in that the Skimmer needs the motor, the mount, the folding prop, the connectors, the pushrods, etc. OTOH, building a plane was something I wanted to do, and I think this wasn't a bad way to start.

[Zymurgy]

My next step was to use 5 minute Epoxy to attach the motor mount to the nose. I sanded down the triangular stock so that the ends were in alignment with the leading edge of the fuselage, because it had the recommended downward thrust angle. One of my triangular mounts was about a 1/16th inch behind the edge of the fuse, so I patched its end with a triangle of 1/16th inch stock and sanded it down so it was flush.

I proped up the tail so the lower part of the nose would be flat on the table. I then used pins to keep the at the correct width, and then to generally help hold the mount in place as the epoxy set.