I just had to back and look at the wing jig.   You must be an engineer to do all this good design.

Quote from: john e. holliday on October 21, 2024, 02:27:39 PM
I just had to back and look at the wing jig.   You must be an engineer to do all this good design.

Thanks Doc, but to be clear, this definitely isn't my design.  I'm simply repurposing concepts that I've seen elsewhere. 

The first time I saw these principles in use was with the good ole A-justo-jig.  They may not have been the first but that's where i first saw a 'wing rod' type jig.  There are folks all over Stunthanger using these.  I know Dennis Nunes employed a jig like this on his 'Circulas' designs.  Great Planes had a jig like this.  Brodak sells a jig like this.  Pat Johnston designs all his airplanes for and sells a jig like this.  I'm sure there are many more.  Credit goes to all these folks....I just copied what I saw and tailored it to this Skyray project.

I spent some more time on the Skyray project this week.  Here is how that went...

Conventional wisdom is that, when scratching building, you cut out a full 'kit' of parts first....then build the airplane.  That being said, I'm still a bit undecided on how to approach making jigs/parts for the fuse.  Somewhere I saw pics of the stock Sig kit and the fuselage appears to be split down the middle, length-wise, through the wing saddle/cut out.  This appeals to me because, while I do have a nice band saw, I don't have a scroll saw.  I expected I would need to buy one at some point to complete the wing cutout on this fuse(if going the 1 piece route), but the 2 piece approach would let me use my band saw.  Since I haven't decided on how to tackle the fuse jig and parts, I decided to frame up a wing, instead...HA!

I wanted to use 1/4" square balsa for the spars.  Can we talk about how hard it is to find straight balsa sticks these days?  I tried both my local hobby shops and even a couple hobby lobby stores.  Nothing but warped wood as far as the eye can see.  So, I decided to make my own from a nice straight grained 8lb piece of 1/4 x 3 x 36 sheeting....with a Master Airscrew balsa stripper.  Of course the pieces needed to be longer than 36" so I used 20 degree scarf joints and a 48" piece of angle aluminum from the hardware store to make some nice straight, loooong spars.  Rather than center the joints, I offset them as far as I can towards the tips.  The joints end up in the 3rd rib bay from the tip, on opposite ends top vs bottom.





Next the ribs are installed on the rods.  I use 1-2-3 blocks and the lines I made on the base plate earlier, to ensure the ribs are square and spaced properly.





In this pic, I've installed a spar and the first piece of 1/8 x 1 x 48 leading edge.  The blue tape serves to protect the ribs while I shape the leading edge.





The goal is to match the rib contour when carving the leading edge.  This provides support/gluing surface for the front of the leading edge sheeting.  After the LE sheeting is installed, it is trimmed to be flush with the 1/8th leading edge.  Later, a second piece of 1/8 leading edge is laminated to the first and the final contour is carved.  For now, it ends up looking something like this.






Next comes the first piece of 1/16 x 1 1/2 trailing edge sheeting.





Once I had the back of the ribs stabilized with the first piece of TE sheeting,  I flipped the wing over and installed the 2nd spar.  Then I carved the other side of the 1/8 leading edge to match the rib contour.  I installed both LE and TE sheeting on this side of the wing....this pic is after all that has been completed.





All that was left was to flip the wing in the jig again (good thing this is simple/easy) and install leading edge sheeting on the remaining side of the wing.  I then pulled the wing off the jig to go over all the joints with thin CA.  I like using gravity to send the glue where I want it and keep it from going where I don't want it.





In person, I could see that, even without any of the shear webbing, the wing is very straight/true.  The shadows in the picture might make it tougher for you to see...so you'll have to trust me.  LOL





At this point, I'll set this one aside and frame up 2 more.  Later, I'll put the wings back in the jig to install the bellcranks, shear webs, cap strips and one side of the center section sheeting.  I also use the jig to hold the wing while I sand the final shape of the leading edge and I'll show you that too.

That's all for now.

One more thing.....

This isn't specifically a build update but it does pertain to the Skyrays...

I was about ready to order parts to build a 3rd 25LA (I only had 2) when I came across the OG of BBTU engines.  A NEW IN BOX FP20!  How could I resist? 

great looking work Steve

Quote from: John Skukalek on November 02, 2024, 07:37:09 PM
great looking work Steve

Thanks John!

Referring to earlier posts - you do not need to shorten the nose. My rebuilt model is feather light, has a 25LA with the STOCK MUFFLER, and a spinner. I have had the CG all over the place but last I measured it was 1 1/8" from the LE with no extra balance weight. Unlike flapped airplanes he it is very insensitive to the CG, it has lots of tail volume, and you can move it to change the response without it becoming unstable. Further aft, it gets more sensitive around neutral and then slows down, further forward, it is insensitive around neutral and accelerations with deflection.

   I do not say that 1 1/8" is some magic setting that is optimal. But almost everyone's airplane will be heavier than my rebuilt model, heavier moves the CG back, so I don't think there is any reason at all to try to shorten the nose. And they are generally light enough that adding weight won't hurt anything.

      Brett

That being said, I'm still a bit undecided on how to approach making jigs/parts for the fuse.  Somewhere I saw pics of the stock Sig kit and the fuselage appears to be split down the middle, length-wise, through the wing saddle/cut out.  This appeals to me because, while I do have a nice band saw, I don't have a scroll saw.  I expected I would need to buy one at some point to complete the wing cutout on this fuse(if going the 1 piece route), but the 2 piece approach would let me use my band saw.  Since I haven't decided on how to tackle the fuse jig and parts, I decided to frame up a wing, instead...HA!









In this pic, I've installed a spar and the first piece of 1/8 x 1 x 48 leading edge.  The blue tape serves to protect the ribs while I shape the leading edge.





The goal is to match the rib contour when carving the leading edge.  This provides support/gluing surface for the front of the leading edge sheeting.  After the LE sheeting is installed, it is trimmed to be flush with the 1/8th leading edge.  Later, a second piece of 1/8 leading edge is laminated to the first and the final contour is carved.  For now, it ends up looking something like this.






Next comes the first piece of 1/16 x 1 1/2 trailing edge sheeting.





Once I had the back of the ribs stabilized with the first piece of TE sheeting,  I flipped the wing over and installed the 2nd spar.  Then I carved the other side of the 1/8 leading edge to match the rib contour.  I installed both LE and TE sheeting on this side of the wing....this pic is after all that has been completed.





All that was left was to flip the wing in the jig again (good thing this is simple/easy) and install leading edge sheeting on the remaining side of the wing.  I then pulled the wing off the jig to go over all the joints with thin CA.  I like using gravity to send the glue where I want it and keep it from going where I don't want it.





In person, I could see that, even without any of the shear webbing, the wing is very straight/true.  The shadows in the picture might make it tougher for you to see...so you'll have to trust me.  LOL





At this point, I'll set this one aside and frame up 2 more.  Later, I'll put the wings back in the jig to install the bellcranks, shear webs, cap strips and one side of the center section sheeting.  I also use the jig to hold the wing while I sand the final shape of the leading edge and I'll show you that too.

That's all for now.
[/quote]

One way to cut the wing hole with a band saw or jig saw is to enter from the front between the engine mounts.  The excess slot is then plugged with balsa of the necessary thickness.  The cut will be buried under the plywood doublers and it won't weaken the plane of be noticed.

Quote from: Brett Buck on November 02, 2024, 08:46:14 PM...Referring to earlier posts - you do not need to shorten the nose...

Duly noted. 

Quote from: Paul Smith on November 03, 2024, 06:15:39 AM..One way to cut the wing hole with a band saw or jig saw is to enter from the front between the engine mounts.  The excess slot is then plugged with balsa of the necessary thickness.  The cut will be buried under the plywood doublers and it won't weaken the plane of be noticed.

Thanks Paul.  This is so simple and obvious (like all good ideas), it's no wonder I didn't think of it.  LOL

I mentioned in my opening post that I didn't expect to teach anything there.  What I didn't mention, is that I DID expect to learn a few things.   Looks like I was right.  -rSS

This build is getting my desire to build again going.  But I need to finish the flooring in the shop.

Not being one to rush things, I wanted to ensure the glue had ample time to dry before I continued. 

The following was completed since the last post:

-Framed up 2 more wings
-Laminated 3 fuse blanks (I use 1/4" X 2)
-Made the fuse template.
-Made 2 more trips around the Sun. 

That leaves me with a build kit that looks like this...





I plan to finish the wing builds before any fuselage work.  This includes:

- Bellcrank Install (Rabe Style Mounting)
- Shear Webs
- Tip Weight Boxes
- Adj Leadout Guides
- Center Sheeting & Cap Strips

Stay tuned for the next installment due in the Fall of 2029 (or later this week if I can stay on track).

If and when I get bak in the shop may have to put a Skyray together for grand daughter.   She used to like flying when John B was in town.  Time will when I get past all these health issues.

Yup.  Been there.  Done that.  Don't have a T-shirt, though...

Quote from: Mark Mc on July 31, 2026, 10:03:35 PMYup.  Been there.  Done that.  Don't have a T-shirt, though...

Nice.  Are all of yours still in one piece, Mark? 

The Skyray is a super simple airplane. - easy to build.  However, 3 at once starts to become an actual project.

Steve:

For a reference point, my Skyray with the OS 20FP tips the scale at 32.5 ounces dry. FYI, you scored a nice 20FP in that it's the newer one with the ABC setup. By the way, I successfully used a 90cc RC clunk tank on my model with the steel version of the FP. The only hassle was after a hard crash, the tank's clunk wanted to lodge in the front of the tank, so I needed to tap it loose to reposition.

Now for a proposal. Pictured below are three, 90cc clunk tanks plus a bronze filter. The tanks aren't high end specimens, but they worked for me. If you want, they are all yours gratis. Just PM me here with your address and then reimburse me for postage.

Dave Mo...

I didn't make as much progress as I had hoped for this week.  But there was some progress none the less.  As mentioned, I wanted to try 'Al Rabe style' bellcrank mounting on these airplanes.  It seems such an elegant solution and I struggle to see a downside.  Surely, someone will be along shortly to tell me all the problems that I hadn't considered. 

At any rate, I had this hardware pack from Brodak that I repurposed for my situation:




I ended up shaving down the brass eyelets, enlarging the hole in the plastic bushing that came with the bellcrank and pressing an eyelet into either end of said bushing.




I planned on using 2 of the washers from the hardware pack, one on either side of the bellcrank. 




Next I made the mounts, which span the center 2 rib bays and will pull double duty as shear webs as well.  These are laminated from 1/8" balsa with 1/32" ply caps.  The grain on the balsa runs span-wise and I wicked a bit of thin CA into the end grain that the pivot pin will bear against, prior to laminating.  You can see the gap between the balsa pieces, where the pivot pin will ultimately live.




The real head-scratching happened as I determined where to cut the bellcrank relief.  I had to make sure there was clearance for the bellcrank, ball link and ultimately the pushrod throughout, what I guessed to be, the full range of motion.  There's also a lower spar that I didn't want to compromise as I made clearance for the under slung ball link.




That's all for now...

Quote from: realSteveSmith on August 01, 2026, 05:29:33 AMNice.  Are all of yours still in one piece, Mark? 

I left them with my son when I moved from Portland to Tulsa five years ago.  Still on his wall.  I did take the 1/2A with me.  It's still in one piece.

There's still lots of work left to do on the 'framed up' wings...time to get after it...


First I installed cap strips and center section sheeting on one side of wing (this becomes the top)....





Then I flipped the wing over and installed more cap strips, the bellcrank mount and shear webs (2 bays left empty until I'm done using the jig).





I installed some sub-spars behind the bellcrank mount to further key it into the center section sheeting.  It ended up looking like this:




The bottom center section sheeting will get installed once I've had a chance to see exactly where the push rod will exit, and I prefer to have the fuse and tail mocked up to figure this out. 


Till next time....

Next up I'll work on the tip weight box....

I use these handy laser cut ply boxes from Pat Johnston.  They are sized to work with the Brodak 1/4 oz weights.  I briefly considered leaving off the wing tips (like a Twister) so I could sink the tip weight box right in the end plate.  Luckily I came to my senses and decided to use stock shaped wing tips and sink the weight box into the leading edge sheeting.  As such, after assembling the box, I add a filler block to the lid to help match the leading edge shape later.




Next, I glued some 1/8" balsa around the ply box.  Here's the sharpened brass tube I used to make a clean hole in the filler block so the bolt can still bear down on the ply lid.  All the old pros know how this method works...and they they probably also spotted my obvious mistake in this photo.  I, on the other hand, was still blissfully ignorant of it at this point.




Time to hack into that wing. *gulp*

I would describe myself as 'light on skill, but heavy on tricks'.  Maybe my skill is coming up with tricks?  Who knows.  At any rate, when tasked with drawing 2 straight, parallel lines on that leading edge sheeting, I'd likely come up with lines that were neither straight nor parallel.  But, that piece of blue tape gave me both at once.  I cut the opening to within 1/16" of final size with a #11 and then finished it up with a 150 grit standing stick. 



...and then with the tape removed...




That mistake I mentioned above still hadn't dawned on me.  Right after I took this pic, I put the first drops of CA on, gluing the back of the box to the spars.  Only then did I notice the grain running the wrong direction in the box.  Of course, there was no turning back at this point. 




Here's another trick...I use lots of that blue tape but I rarely sand something I didn't mean to.
 




And then finally we end up here.  And there's no mistaking that end grain where it shouldn't be, either.  LOL




Till next time...