More match drilling again, this time skins to the ribs.
Another session today drilling the J Stiffeners to the skins and ribs. The process was pretty much the same as the other stiffeners. Draw a centre line, fit the stiffeners and then back drill through the skins and ribs.
The first job of this session was to finish off the tailwheel skin trimming. On checking I wasn’t 100% happy with the clearance of the skin to the tail spring mount so I filed a bit more. I also opened up the forward hole to allow access to the nut that holds the spring in the mount.
Once I was happy with the tailwheel skin and mount it was time to start on the ‘fun part’ (actual words from the instructions!). First I laid out two saw horses.
Next I located the aft fuselage bottom skin and clecod on the F-708 & F-709 bulkheads and bottom J-Stiffeners.
Next I loosely placed the upper J-Stiffeners and clecod on the right side skin.
Then the left side skin.
Now I clecod the F-706, F-710, F-711 & F-712 bulkheads in place.
I tell you what the instructions weren’t wrong, that really was fun and it looks so awesome!
Motivated by my earlier session I spent the rest of the afternoon building the Aft fuselage. Instructions insist on removing any twist from the fuselage before drilling the stiffeners. I tried to do this with the fuselage the right way up but I soon realised it was much easier to make sure it was square by turning it over. I then put a plumb bob line at each end of the fuselage and used the tooling holes on the aft bulkheads to ensure that the string was centered over both holes. On the front bulkhead it was not so easy so I centered a ruler over the pushrod hole and aligned the plumb string with the tooling holes.
And the rear bulkhead…
Once I was sure that the fuselage was square I aligned the centre line I drew previously on the stiffeners with the pre-punched holes and then drilled the upper stiffeners to the structure on both left and right sides.
That’s all for today.
This is it! Making this cut will make this aircraft a tailwheel, a decision I agonised over for many hours. The plans gives a template for the cut but, like many other builders, I didn’t want to cut the original plans so I made a photocopy of the template from the plans and used that to mark the skin instead.
Once I marked the template I then used a 1/4″ drill bit to drill the end of the curve and broke out the dremel to rough cut the lines.
Next I used the dremel with the drum sander bit to tidy up the cut followed by hand filing for even more accuracy. The cut out is so that the tail spring mount can fit between the F-711 and F-712 bulkheads but when looked at the part it didn’t look quite square. I decided to check how far out of square it was…
Thankfully it looked worse than it was, it was actually only 1/32″ out of square. I can live with that. On first attempt I noticed the mount didn’t fit so I had to trim the cut I made earlier. Unfortunately it still didn’t fit but after referring to the instructions again I realised that F-712 also needs trimming to allow room for the welding fillets.
It took several iterations to remove just enough of F-712 bulkhead. I really didn’t want to take too much off so it was a case of trim a bit, check and repeat. Next I needed to drill the tail mount to the forward F-711 bulkhead through the vertical bars as well. The trouble is that is a deep hole and it was difficult to see in there. The instructions simply say to drill it square to the bulkhead, talk about understatement! Eventually I read Mike Bullocks blog which gave a fantastic tip of marking a line 12/32 from the top and from the edges. It worked a treat though it was an absolute bear lining it up and clamping it all. In the end I got it done and the bolt holes are drilled #30. I’ll final size them later on.
This session was a lot of work for not much reward. I’m pleased it’s done though.
That’s all for today.
Just one task today and that was to trim the aft end of the J-Stiffeners as per the plans. I pretty much followed what other builders logs did here and drilled a 1/4″ hole and then cut with the dremel. Then I filed it all to final shape.
The next task on the longerons is drilling the aft canopy deck to the longerons. This involved placing the deck on the 28 1/4 mark and making sure the longeron bend matched the curve of the deck. It did so I clamped it in place with lots of clamps then drilled it in place.
Once both longerons were drilled to their decks I then had to find a place to store them for a while. I chose to rest them above the wings where they are out of the way and safe.
Lastly for today, I found the J Stiffeners and cut them to the 3 different lengths on the plans.
That’s all for today.
Helpfully, Vans provide a full scale template of the curve/bend required and suggest making a cardboard template for accuracy. To be honest, I’ve never had much joy with the accuracy of cardboard templates but luckily I had a bit of 4mm plywood lying around so I decided to use that instead. I cut out the paper template and stuck it to the plywood. Then, using a stanley knife with new blade, I carefully followed the curve of the paper template. I repeated the cut numerous times until I cut through the plywood and had a nice template.
Earlier in the week a very kind RV builder offered to lend me their bending dies which involved a quick trip over to Wycombe airfield to collect them and swoon at their flying RV. With that in hand I felt quietly confident about getting these bends done.
The first problem I encountered however is that the longerons wouldn’t fit in the vise because various items on the workbench were in the way. I decided to relocate the vise to the portable workbench instead. Once there I then sat the dies in the vise but found that they would sink to the bottom of the vise and be tricky to keep in place. I popped a piece of wood below the dies and it was problem solved.
I then put the longerons in the dies in the vise and set about squeezing the vise until I could feel the dies touch the longerong and the felt it bend slightly. On first attempt it was clear I didn’t bend it enough. So on the second round I added another 1/4 turn of the vise handle. Unfortunately that was too much and I over bent the longeron. Not a problem as it is easily unbent by gripping it in the vise and unbending by hand. Eventually the bend matched the template perfectly.
Once the curve was bent it was time to do the sharp downward bend. This was a lot more draconian and involved clamping the longeron in the vise and whacking it with the mallet several times. Nothing too difficult though but it did make everything on the workbench ‘dance’! The last task was to twist the sharp bend so the end of the longeron was at 17 degrees. I used a large wrench to make the twist without any difficulty.
After lunch my wife joined me to help bend the right longeron. It is amazing how much easier (and more fun) it was with an extra pair of hands.
That’s two longerons bent! I’m not 100% confident that all the angles are perfect but it was pushing 30 degrees in the workshop and I was losing motivation fast. Time to stop for the day before I make a silly mistake. I popped them on the floor before I left to avoid any silly accidents overnight.
Not bad for a days work, but I think it does need another check.
I couldn’t put it off any longer, those longerons needed to by cut. I brought home another tape measure from work to make sure sure sure there was no mistake. I also recruited my son to come and double check the plans and the measurement marks.
While reading one of the builders blogs earlier in the week I noticed they had a small chop saw so I couldn’t resist and treated myself to one too. I am delighted I did, it arrived perfectly set up and cut through the longeron like butter. I’m very pleased with it.
Once cut I checked the measurement again…
I’m pleased with the cut, a bit of filing will trim that to perfection but I’ll wait until much later in the project to do that. Next I marked the longerons for left and right and forward too. Then I trimmed the aft ends of the longerons as per the plans.
Finally I marked the bend location along with marks at every inch to help with the bending process.
That’s all for today. I’ll do the bend another time.
Now the parts are starting to get bigger, not many rivets to put these together but they are pretty darn large!