Fit lower longerons

Longeron is a funny word. I’ve heard it used many times before and, until I started making them for the aircraft, I was never really sure what it actually meant. So I Googled it…

In engineering, a longeron and stringer is the load-bearing component of a framework.

https://en.wikipedia.org/wiki/Longeron

For my aircraft it basically refers to the aluminium angles that form part of the aircraft structure. There is one long one that runs from tip of the tail to the firewall, and there are a bunch of others on the fuselage itself.

In this picture you can see 4 of the longerons (silver angles running from the firewall backwards.

That was basically todays work. Finding angles, filing them to fit.

Match Drilling them to the skins and firewall brackets.

Oh and I made a Gusset too.

Overall, not bad progress this week.

Auxiliary Longerons

I managed to sneak into the workshop today for a bit of longeron fun. Last time I forgot to take so many pictures so this session I am trying harder.

First I found the main auxiliary longeron and trimmed the end as per the plans. Marked a centre line and match drilled it. Also did the same the other side.

Next it was time to make 2 attach brackets. I love making parts from basic stock metal like this. First get some standard aircraft aluminium angle.

Cut 2 pieces to off at the described lengths.

Next, carefully study the plans a million, billion times and then mark and trim the parts.

Drill holes in the right places.

Et voila! Suddenly we have aircraft parts.

Next job was to find some more aluminium angle. These ones have had a ‘joggle’ on the end done by the factory. So all I had to do was draw a centre line and match drill and cleco these to the skins.

Then I used the parts I made earlier to join the silver longeron to the yellow/green firewall angle.

Finally I just needed to back drill through the part I made to the longeron and firewall angle.

Overall, a fun day in the workshop working on the structure that strengthens the fuselage.

Drill Firewall to Skins, make attach straps and start auxiliary longerons

This week I only managed a total of 4.5 hours in the workshop.

I started by putting cleco (clamps) in every other hole of the firewall to fuselage. I did that because I wanted to pull everything together and have the most accurate match drilling.

With the fuselage being stainless steel I made sure I used a different drill bit as SS can really blunt tools quick.

Once all the holes were match drilled I then made the 4 attach straps that hold the golden F-704 bulkheads to the upper (bottom in the picture) longerons.

I also started work prepping the auxiliary longerons. These are basically aluminium angle used on the front of the fuselage section.

No pictures for those bits though cos I forgot!

Fitted firewall to fuselage

I had a change of mind regarding the longerons that I drilled last week. I had planned to leave the longerons but decided to drill them to the side skins now instead. That was because the longerons have to fit flush with the skin so there was no room for movement.

Man that was a lot of aluminium shavings!

Once the upper longerons were all drilled I then mounted the firewall and bottom skin.

I then spent a bunch of time aligning the firewall to the fuselage.

That’s all for this week except for a little arty shot of the fuselage through the firewall recess hole….

Bend fuselage skins & drill longerons

This week I focused on more fuselage work. The first task was to fit the huge skins to the center fuselage section but to do that the skins needed bending at the aft intersection to follow the contour of the fuselage.

After much research on the net I finally felt confident enough to make a start. I clamped the skin to the workbench and a piece of scrap aluminium. Then I drilled and cleco’d another scrap piece of ali.

Then carefully and methodically I coaxed the skin round to roughly the right shape.

Once it was pretty close I then offered it up to the fuselage and checked. It took several iterations before I was happy with the fit.

Once one side was done I repeated all the above with the other side and then cleco’d the lot to the rest of the fuselage.

Now that was done the next job on this weeks list was to match drill the longerons to the fuselage. Pretty boring stuff and nothing to get too excited over. I simply started at the back of the fuselage and drilled every hole… one… at… a… time!

I decided to stop drilling at the front section because I wanted to get accurate alignment of the longerons. To do that I would need to start building to forward fuselage.

That’s it for this weeks installment.

Working on seats

With the main structure now riveted together and the seats clamped in place, I fitted the baggage floors to the ribs.

Next up was to work the outer ribs into place. This involved fluting the ribs so that they curved to match the outside skin. I then drew a centre line mark for drilling.

With everything in place I carefully started drilling all the holes on the top and sides. I was working alone today so I couldn’t flip it over to drill the underside holes so I improvised!

Using my full face mask I laid on my back and drilled the belly skin to the rib using the centre line I drew earlier as a guide. Worked out pretty well in the end. Lastly I drilled the end holes up to final sizes for rivets and the bolt.

Next on the list was to drill all the seat and baggage floors to the ribs. That was one of the easier jobs on the list. Once the seat and baggage floors were drilled I enlisted the help of my two kids to help me join this section to the rear fuselage. I’ve finally found a use for teenagers!

After what felt like an eternity for the kids (7 minutes for us humans) the two sections were now one and I admired the structure over a well earned coffee. Finally, I fitted the side skins to help keep everything square and to give the whole structure a bit of strength while I’m away from the workshop.

It’s really rewarding to see this structure take shape.

Continued riveting fuselage centre section

This weeks work was split into lots of different sessions working on the same section, riveting the fuselage centre section.

I decided to work in small sections and set small goals, like riveting the ribs to the main (gold) spar first, then working on the centre baggage ribs outward with the seat back spar in place.

Once that was done I cleco’d on all the skin, marked what should NOT be riveted at this stage. That was the centre section skin ready to rivet but there is no way I can rivet this alone.

So I asked my Dad to help. He was on the gun and I was on a wheely mechanics trolley with the bucking bar from the other side. Once again, good communication is key here. He would say ‘On It’ when the gun was in place and then I would say ‘ready’ when the bucking bar was in place. He would then give it a short burst with the gun. That method was taught to me by another builder and works really well when two people are working together.

After a couple of sessions we managed to get the entire skin riveted in place and on the bench upright ready for the next phase. I couldn’t resist popping the seat trays on though to check that everything was square. It was.

Overall, quite a productive and rewarding week.

Crotch Brackets & Seat Ribs

So now the centre fuselage parts are all primed and cured it is time to fit start final assembly of those parts. I started by riveting the nutplates and doublers onto the cutout for the control sticks. This cut out makes it possible to fit and service the control sticks once this area is all fully assembled.

I also decided to top coat the crotch strap brackets with white Plastikoat. This stuff is really hard wearing and given that I expect the straps to rub over time due to vibration I thought it was best to give these parts the best possible coating. I only top coated the visible and wearing parts though to save weight.

Once the top coat was dried I started final assembly of the seat ribs and crotch strap brackets by riveting the brackets to the ribs and then the ribs to the main spar.

That was a good start to the seat ribs. Like various other builders I started with these ribs to make it easier to solid rivet the brackets and to make access to the other ribs easier.

That’s it for this weeks work sessions.

8.15.1 – 4 – Notch longerons and fit to aft fuselage

While I wait for the centre fuselage parts to dry I decided to skip ahead a little today and get the longerons down. To fit them to the fuselage first they need to be notched to fit around the vertical bars at the back of the fuselage.

Given the amount of work that’s already gone into the longerons this is one scary task so I decided to really slow down and take my time. Preperation started last night by reading the manual, studying the drawings and research others’ builder logs.

This morning I felt confident enough to give it a go.

Having read the other build logs I knew that the longerons may not fit in the bulkhead cut outs so first task of the day was to check with a scrap piece of angle. As expected it didn’t fit so I filed the notches a little to make room.

After all 6 notches were done I set up the longerons on the benches and clamped the aft deck in place as per the drawings and triple checked the measurements and orientation.

Once I was satisfied that it was correct I marked the notch.

Then I removed the deck and drilled two 3/32 holes and cut the notch with a hacksaw.

After several iterations of trial and error I finally had a nice fit around the vertical bar. I double checked it was correct by fitting it to the fuselage and popped on the aft deck too.

I’m pleased with that! So I fitted both longerons and flipped the fuselage over ready for the centre fuselage when that’s done.

Next was a little bit of workshop re-organising. While searching for the aft deck earlier I realised that the huge fuselage crate was taking up a lot of room in the workshop unnecessarily so I relocated the few parts that were left in there and removed it from the workshop. I also took some time to finish packing away some of the hardware. After an hour or so of sorting out nuts and bolts I still had a bench load of stuff left to pack away!

That’s for another day though.

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