Latest Work Completed Mantua, New Jersey
Original Site:
September 2004
E-mail: usav8or@yahoo.com
The Radical Radial Fuselage.
January 3, 2008
Bungee Truss: The saga continues... three hours, four holes and
a few tacks
Tack welded the one side on January 2... as was expected,
a lot of heat tends to twist and bend metal. The truss raised
up on it's ends about 1/8". Wasn't sure if I could take it
out of it's jig to tack weld the other side before drilling
the holes, or just drill the holes in it with a slight bow.
Threw the question out to the guys on the biplane forum.
Got an answer from Nick, up in Maine. Said he wasn't making
the bungee truss, but he found that the fuselage warped when
he tacked the one side in the jig but straightened right out
when he tacked the other side. Neil, on the fourm, said that
it's best to tack weld on the sides, not the tops of the tubes
to minimize this tendancy.
I took these answers as a yes, since nobody else threw out
a response.
Here goes nothing. I took the truss out of the jig (it wasn't
really wedged into it - good sign) and tacked the other side.
I then slid it back into the jig. Piece of cake.
Time to drill the 1 1/8" holes for the bungee hangers and
the 1" holes for the longerons (yes.. 1" for the Radial version
of the Skybolt.)
I laid
a piece of 2x8 on the drill press table then placed the bungee
truss jig upside down on top of the 2x8 to sandwich the bungee
truss. Made sure that it was leveled in all direction after
I clamped it to the drill press table and drilled first the
1 1/8" then the 1" holes. Remember, make sure to use cutting
fluid when doing this.
You
may notice when drilling the first hole that the racheting
sound of the hole saw going through the tube stops. Ya ain't
done yet... that's just the teeth of the saw now cutting through
the bottom of the tubing where there is a lot more surface
to cut and makes it appear that you are finished with your
cut when in actuality you still have another .063 to cut.
Moral of this sentence... don't un-clamp the jig from the
table 'cause it's a pain in the ass to get it back to where
it was before you thought you were done. And yeah.. I know that's a run on sentence.
OK...
where was I ? Oh yeah. Got all four holes cut and now we're
ready to tack on the "hangers." I took the truss and set it
upright in the jig (see picture.) Made sure that they were
centered and made my marks. I've read where some builders
put it in the jig, make sure that it's square, then tack weld
it onto the truss. I decided to place a small tack weld with
the truss out of the jig, with it still sitting in the jig
upright. After tacking them in place I placed them back in the
jig (now I don't have to worry about supporting the hangers
at the right height in the jig, or messing with getting it
centered) and with a few taps of my hammer, squared them up
and put four good tacks to hold them in place.
Yes, you too can spend three hours drilling holes and tack
welding a bungee truss. Hope I just made it a little easier
for yas.
Tack the caps on the bungee hangars then weld this bad boy up and it'll be finished.
Next... I get to finally start cutting the tubing for the fuselage sides.
When it arrives, I'll finish welding up the bungee truss and make those other solid welds look nice and purty.
Lesson Learned: Don't let those welding goggles turn into blinders. An excessive amount of anything ain't good. Whether you're eating donuts or adjusting the amount of gas to the tip of your welding torch, moderation is the word.
August 23, 2008
Bungee Truss: The saga still continues... A month and a half of waiting
and I'm the one that needs to come up with the solution.
A little over a month ago I started to fit in, for shits and giggles, the intercoastals that go from the center of the tube at lower station 0.o to the upper longerons at station 24.o. It was more shits than giggles.
Me being the novice builder, I didn't realize that the hydraulic truss that was to be welded at location 5.o is pointing downward. No fear of the intercoastals hitting them when they're pointed down. Not so for a mass of 1 1/8" tubing sticking up at that same location. Threw the question up to the guys on the biplane forum. Question: Which way to point the truss ? And... Where to locate it ?
I walked away from that threaded discussion with basically two thoughts.
One, Randy wrote, "Upright truss is loaded in compression. Inverted truss is loaded in tension. I'm not an engineer but I would guess the difference is like night to day."
And two, Scottly wrote "I was under the impression that Steen halted use of the hydraulics....you may want to call them and see if they have an answer for you. They may have already figgured this out."
It was obvious, from Randy's statement, that the truss needed to point skyward. And, although Steen hasn't halted the hydraulic gear, I called them as Scottly had suggested.
When I called Steen, they told me that they hadn't stopped the use of the hydraulic gear (didn't I just say that ?). David Stone actually thinks that the hydraulic gear is being used on the Radial Skybolt being built in the Land Down Under. When I told David that I want to use a bungee truss instead of the hydraulic gear that the plans showed he didn't see why it couldn't be done but he would have the guys in the shop look at it and figure it out.
(insert Jeopardy music here) A month and a half rolls by and I hear back from Steen. They said they had spoken to (someone who had built a radial engined biplane very similar to the Radial Skybolt) and that I need to give him a call so that he can answer any questions that may arrise during our conversation.
The next day I give this builder a call. He was cordial but really didn't want to play "consultant." Hmmmm... I thought Steen had this worked out with him where I would be calling. Anywho... the one very tiny smidge of information I gleened from the call was that I need to keep the bungee truss over the front pivot point of the landing gear. I'm glad that I heard that one sentence, or the conversation would have been a waste of my time.
"Keep the bungee truss over the front pivot point." OK...
I had the bungee truss now un-tacked from the fuselage
so I began to play around with it. Moved it from station 5.o
to 10.o and then 13.o. OK... so the intercoastals miss it
when it's moved off of station 5.o but are the intercoastals
my issue ? When I moved the truss off of it's original station
(5.o) I was able to visualize how the bungee would be pulling on the
truss. They wouldn't be pulling with a downward motion on
that 1 1/8" x .o65 walled tubing, they would be pulling at
the small .o40 plate that was ment to keep them from slipping
off the tube. When I saw it from that perspective I made the
decision that the truss must stay at it's original
location.
Now... what to do with the intercoastals. After thinking about it, and moving a piece of 7/8" tubing around (the size of the intercoastals), I saw that if I displace the intercoastals 2 1/2" on either side of center, on station 0.o, they would clear the bungee truss with room to wrap the cords over them. To concentrate the forces of the intercoastals to the center of the cross tube, at station 0.o, I will weld in gussets, both on the top and the bottom of the tubes. I'll post of photo of it after I have it completed.
Thinking back on this whole ordeal... I had a feeling that I wouldn't get an answer, and that it would be left up to me to make a decision on it. I can see why they wouldn't want to "waste" time on something that they could end up being sued for. And, from a financial stand point, what do they have to gain from it ? I waited on their response in hopes of having the problem solved.
Using a jack hammer to plow through this wall that was in front of me... I've gotten this truss figured out I can move forward with the fuselage.
September 23, 2008
Bungee Truss: The saga continues... ...for someone else
Just an after thought...
I was on the biplane forum site the other day and read a post by one of the guys building a radial engined Skybolt. Apparently... moving the truss to station 13.o is causing all kinds of problems with his landing gear. The landing gear, from the front pivot point to the back pivot point is suppose to be 21". By moving the pivot point back to station 13.o the two pivot points are only 13" apart. He's not sure of the ramifications of having it like this.