Fuselage

[Brock]

Build Table - check!
Mount Theo's fuselage bottom and level. - check!
Decide on firewall - whoa, stop and scratch head for a bit then ask other's opinions.

What do you think.... here are some things I've read on the firewall.
-shorten a few inches to allow W&B for the Verner 3V(LA).
-instead of mounting 13.5"W x 11.5"T (landscape) consider 11.5"W x 13.5"T (portrait).
-mount the Verner 3" high of center for prop clearance.

With all this and measuring my feet/shoes my thoughts are to just make the firewall 13.5" x 13.5".  This would help in raising the engine mount point and not cramp (horizontally) my feet.  Your thoughts?

[Chuck in Indiana]

I don't see why not if you are going to build a different station 1 anyway.

[Brock]

It's been years since I dusted off my TIG welder and struck a bead.  A few days ago I came to the conclusion that I couldn't put it off any longer and eventually I'd have to melt some filler.  So I did just that on some scrap material.  The result was appauling and discouraging.  You can see the initial results below.  Not to be beaten I sent a few txt messages to a local pro welder (recently retired) and he invited me over to run a few beads with his supervision.  WOW, I am so greatful for those 45 minutes.  By the time I left my welds were looking awsome.  I'll weld up the other side of this picture after I change out some hardware and practice some on my equipement.

[Chuck in Indiana]

Uh, yeah. That tungsten is seriously contaminated.  I like the clear cup.

[Brock]

This is an update to the picture posted above.  I've been practicing and taking advice from a welding mentor.  Today I finally stopped practicing and decided to melt metal on the airframe.  Finished up station-1 firewall frame.  Not the prettiest welds but not ugly either.  Baby steps.  This was done with a setting of 35 amps using 1/16 filler on the inside of the bend and .035 filler on the outside.

[Chuck in Indiana]

It won't come apart.  In the future, a little more filler on the outside where the base metal goes away and/or a little less heat would be just the ticket. Nice job. As you have already found out, "it ain't easy." 

[Brock]

Station 2 is finally tacked in.  Only took two tries. You know the addage "mesure twice cut once" well after welding the to sides to the the top (on the welding table) I went about to cut the sides to their proper length.  I measued each side about three times then cut them off nice and equal - uh so I thought.  I measured after and not only were they different by a 1/2" but they were both short.  Called it quits for the day and returned the next and did it correctly with little effort.

[Brock]

Progress has been slow but steady.  Spent the day puzzling over the top tube which gets suspended in outer space.  As you can see I did finally get it in place but not without some questions.

The plans call for that tube to be 29".  But it isn't clear if that 29" is from end to end or if I really should make it 29" from the center of the welded tubes comming from the instrument panel.  In that case the tubes should be cut long (I did add 1/4" on each end but that might not be enough.  Can someone fill in some lack in my understanding of this?

[pappyadkins]

I'm away from my plans & plane right now, but I believe the 29" is the center to center if I remember correctly everything on that page should be center to center (the width of your wing mounts/spars is approx 29"; therefore, NOT the length of the upper tube (It extends forward if I remember correctly or maybe that was something I added for folding the wings) - but point to point is the answer for the measurements for sure... I hope this makes sense... You'll have the square crosstube (wing mounting tube) with flat metal plates coming down to the frame members that should be the same distance as your wing mounts (i've attached a screenshot from my video)... Anyways I believe this measurement, 29 inches needs to be the same as your wing spar; so if your spars are 28.75 then these need to be the same... Hope this helps - I just realized I didn't cover that in my video (note to self, may need to add this to future video)....

[Chuck in Indiana]

I see you have changed the lower dimension to the firewall. You'll need to change the upper dimension the same amount or you will be moving the wing aft. This will negate the CG change you are aiming for. Moving the wing has considerably more effect than moving the engine on CG. Yes, from memory  the dimensions shown are from center to center. I built the wings first so knew the exact distance between the spars and made that happen. You will just have to make sure that when you build the rib jig the spar distance is the same as your fuselage fittings.

[Brock]

Edit:  Chuck, I just reread your msg.  I kept the firewall vertical and so didn't (need to) give a thought as to shortening the upper distance location.  Pay no attention to markings on the diagram above as they are not all representative scribbles.

The firewall was made taller (13.5 X 13.5 instead of 13.5 X 11.5).  Then it was moved Aft by 2" but the angle of the floor remained the same.  Thus the firewall moved down slightly as well as up.

CG:  I've been making all dimensions referencing station #2 at the floor.  Thus, no, the wing did not move.  At least I don't know how it could.

[Brock]

Today I tacked the cluster where the top seat tube and wing rear tubes meet.  Took some thinking to decide how I was going to do it but seems I should have thought about it much more.  Now I have an open tube that needs to be finished off.  Any suggestions how to finish this.  There still are two more tubes that go here (seat back and reaward brace).

[IflyHG]

In Solidworks the open ends of tubes are covered up with a thing called an end cap.  Make a disk about the same diameter as the tube, out of whatever thin stock you want to use and weld it over the end of the tube. 

[Brock]

Thanks Ifly.  Yes, end caps were how I had planned on dealing with these.  No doubt some folks here have come up with more elegant ways of dealing with these particular clusters.

[Kamcoman77]

Here is a photo of a nicely made XL fuselage.