Another New Build
My Sbach 342 build hit a snag due to the provided hardware for the control linkage not creating the best slop free setup and my inability to find substitutes at the local hardware store. On Saturday I did some materials gathering and basic setup. After getting in some DLG flying on Sunday I decided to spend the hot afternoon trying to get as much done between dealing with my two girls.
The weekend ended up being one of those rare weekends when I could get a bunch of time to myself. It was so stinking hot outside that I decided I’d wait to do yard work during the week after work and my two girls just cooperated with what everyone wanted to do (it also helped that my wife and both girls took a nice long 2 hour nap). In the end I got a bunch done.
Building the Formers
Traian, the kit designer, has created one sweet building kit. He’s also done a ton of work making sure there is video documentation on how to do all the non-trivial building parts. The first thing he covers is how to get setup building the formers.
Traian HowTo: Gluing the Formers
The formers are used to hold the wing skins in place and to form so that the wing skin will have the correct outside shape. Using 3M 77 contact cement on a piece of MDF shelving with a laminate covering you apply a thin coat of the contact cement followed by the plans for the formers. Some kit builders will be concerned that you’re basically ruining the plans, but this kit isn’t designed in such a way that you can avoid this. Some of the “plans” are actually laser etched on the wing skins.
After the plans are neatly laid out and the formers are removed each former needs to be checked so that none of them have a tab from the cutout on the bottom. If they do smooth this out so that all formers are completely flat on the bottom. Each former will be glued directly to the plans with thin CA. In Traian’s videos he mentions to “tack” the formers up using only a couple of drops of CA. I highly recommend just adding a drop of CA on the front and back of the former and getting them all into place before going back through and running a bead down the length. If you notice you get one off you can easily break off that small bit of CA than having to worry busting the whole former.
Also in Traian’s videos he does the formers for the ribs before doing the former for the trailing edge. I think it is important to also follow this method. When I was playing with all the pieces in my hands I thought it would be easier to do this in reverse, but I saw that it would be easier to make sure that the trailing edge was straight for its entire length by having the rib formers glued in to make alignment easier.
Once the formers are all glued down you can test fit the skins. Notice that the correct “up” side has the laser etchings for rib and shear web placements.
Preparing the Wing Skins
An important part of the build is using the formers to hold the shape for the wing skin. To do this each wing skin is prepped with tape to hold it onto the formers. Using double sided cellophane tape (you can look for the Scotch brand which has a yellow label) applied on the underside at the trailing edge, the root rib, and where each rib will be applied. When this is done the double sided stick tape will be applied to the top of each former and hold the wing skin down to the former. The trailing edge should be flush. It seemed like the root side and tip wouldn’t line up perfectly. If I had the root on the last former the tip wouldn’t hit the outermost former and the opposite would happen if I lined up on the tip end. I just made sure that the skin had a little bit on each former so that if I applied pressure it would be directed into the former.
If you notice there is masking tape that is put on the d-box section in the leading area also along the bottom of the wing skins. This will be used later when joining the top wing skin.
Another tip when placing your skin on the formers. Run your fingers up and down where each rib will go. Underneath this area should be a former. This will make sure that the double stick tape seats correctly against the former and the skin takes the shape of the formers.
Traian HowTo: Taping Part 1
Traian HowTo: Taping Part 2
That Wing Skin Ply is Thin!
The kit is designed to be light but strong. That really thin ply while strong can be ripped. USPS did a nice job of doing this for me. On one wing skin there was rip that went through almost to the root. I was able to get it aligned and set straight when taping. The root ribs will go over this section. Gluing them will fix any issues here.
If you’re really unlucky, like I tend to be, then you’ll have a skin where the root area is completely busted off. Double check around in the box. You may end up finding it stuck in the corner of the box. Again, you can use the double sided tape to realign the piece if found. If your luck is really that bad and you can find it but you still have that triangle bit of stock like in the previous picture you can cut a bit out here to make up the missing piece. Make sure to shake your fist at the mail person next time they come around. They really love that!
Ribs and Shear Webs
Before attempting this section make sure you watch the video on ribs and shear webs by Traian. It will help you out if you need a slight confidence boost. Also, he explains how to align the ribs to the etched marks on the skin.
One thing to note, and you can see this in both pictures below and you can reference the picture above, the root 1 rib goes along the root of the skin. The trailing section of this rib has a doubler. For some reason I didn’t see this in the skin until someone pointed it out later, but there should be an approximate 1/4″ gap between these two such that the root 1 rib is along the root of the skin and the “doubler” TE rib goes along the other side of the skin so that it is along the side of the skin where the flap would be. You can see this in the etchings on the skin. The outer two sections are wider which will align to the ribs where the inner section is actually thinner than the rib. If you butt the ribs together like I did don’t fret. Go back to the stock and use the cutout as a template to make another “doubler”. You’ll need to think it, but you can make the rib and sand it to shape.
Another note that wasn’t called out in the videos. The wing TE piece should go to the root. I made mine go flush to the tip and then brought it in to the root. While you can do this and fill the root end in with some scrap you’ll just have more sanding to do when you shape the TE to the ribs (the taper will be off).
Make sure you have this TE piece glued into place and ready to go before doing the ribs. You’ll want to glue in the ribs so that they’re being pushed into the TE.
Traian HowTo: Gluing the Ribs
Traian’s videos cover doing the shear webs. If you’ve built a kit before the shear web installation shouldn’t be anything difficult. His videos do cover how to create the pocket for the wing joiner. As a note all the webs did have to be trimmed to fit.
Traian HowTo: Shear Webs
Shear web #15
When doing the shear webs you’ll trim a little off each one until you get to the last one. The #15 web is much longer than what you would think is necessary.
Each of these pictures show that the #15 web goes well beyond the tip. I had to reach out to the RC Groups thread to figure out what to do.
One Wing Half With Ribs and Shear Webs
The wing half on the lower section of the board has been completed (with the exception of web #15). The webs have been laid out for the other half.
This build is going incredibly well. Other than the two goofs, the separation on the root ribs at the TE and the wing TE not going all the way to the root, I think I’m doing quite well. I’m pretty sure that if my wife and girls would have slept for another hour I could have been able to finish gluing up the leading edges! Oh well. I guess I need to save something for next week!
All videos in this post were created by Traian and can be found in his thread for building the Evolution W. Traian’s email is gatorprops [At] yahoo dawt com.