Latest Work Completed Mantua, New Jersey
Original Site:
September 2004
E-mail: usav8or@yahoo.com
The Radical Radial Fuselage.
January 2, 2008
Making the Bungee Truss ??? Hydraulics ? What am I looking at ?
Reading over the biplane forum's Skybolt Manual, the chapter on building the fuselage, I read where I should build the bungee truss first, since it will be
attached to the fuselage. OK... no problem. wait... there is a problem. Looking at my supplemental plans for the R version of the Skybolt I see what appears to be called a Shock Absorber Fitting, for a WHAT ?, a hydraulic system ? WHAAAT?
What's a Shock Absorber Fitting and a Hydraulic system ? And what is it doing in place of my bungee truss ? These shock absorber fittings are made out of .125 4130 steel and they look purty mean. Time to call in the troops.
I throw the question out to the group on the biplane forum. There are only a few guys on there building the R version, a very few. Dennis, aka Pelican, is one of them. He replied to my email saying that
he spoke to Steve Culp about the bungee truss "area" and that Steve suggested that he use the old set-up that was used on the standard. I believe that it's close to what he
uses on the Culp Special. Don't quote me on quoting him 'cause this is all second/third hand.
Hearing this from Pelican, who is an engineer at Boeing, who heard this from Mr Culp, was reason enough to go that way. But the weight of the radial on the front of this biplane has me thinking it needs to be
beefed up a little. Soes... I throw a question out to Randy, a man who has built three Skybolts already, asking him his opinion. He suggested that I go with 1 1/8" x .065 tubing for the entire structure (the Standard has 1 1/8" x .049.)
He also suggested that I slide reinforcing tubing in the longerons from the firewall back to station 34.5 and rosset weld them in. This would give a helluva lot of extra reinforcement to that area of the fuselage and damn near makes it
indistructable.
My final plans... I'll be following the Skybolt Standard plans for the bungee truss, using 1 1/8" x .065 4130 tubing for the entire structure. In addition, I'll be sliding tubing inside of the 1" x .049 lower longerons from the firewall back to
station 34.5.
My only question is... how close does that tubing need to be to the ID of the 1" x .049 tubing ? A 1" x .049 tube has an ID of .902. I'm thinking 7/8" x .035. I'll let you know when I hear back from a few of the
experts.
January 31, 2008 we ain't jumpin' off no bridge....
with these bungees
Been working on this bungee truss on and off all month. Should I do this... should I do that ?
Tried cutting the EXTREME angled tubes with the old pattern and grind it method. You can read about that here.
It wasn't working for me at all. Tried using snips on .063 wall tubing... wasn't cutting it for me or the tube.
Dale, one of the guys I know on the biplane forum, wrote an instructional sheet on how to use the Joint Jigger. Thought I'd give that another read and see if it was something that I could tackle
without too much problem, seeing that using the grind-it method was giving me all kinds of canipsions. Finished reading the article and decided to put my money down on Dale's suggestion. Getting that
Joint Jigger ranks up there with me learning to weld. Read all about it here.
Oh... I found out that the tube you slide inside another tube, for additional support, needs to be as close to the tubes ID as you can get.
In my case... the outside tube tube is 1" x .049 needs to have a tube that is 7/8" OD. I chose .035 for it's wall thickness. Guess I'll be leraning to weld
rossettes before long.
january 31... cont. sheeeeeet...
gotta tell ya a little about
makin' my bungee truss
don't I ?
First thing on your list to do. Get that Joint Jigger. As I've said on other pages in my blog... beg, borrow or steal one.
You'll also need to get yourself a 1 1/8" and a 1" bi-metal holesaws. Better yet, get at least two of each, you're going to go through them. Even using cutting fluid and a good Lenox holesaw, I burned the 1 1/8" out just cutting the tubes for the truss. I still need to cut the 1 1/8" holes for the
two 6 1/4" bungee tubes. Looks like I'll be going out and buying another holesaw.
Make the jig, per the Standard Skybolt plans. I used 1 1/8" x .063 tubing for ALL my tubing on the truss. (the difference between using .049
and .063 on this piece amount to ounces but a helluva lot additonal support for that Gorilla of an engine you're going to hang on the front of your radial engine biplane. It's the same thickness tubing
that Steen calls out for use on the "hydraulic gear" of which I won't be making for my biplane.
I cut the large cross tube first, then cut the exteme angle cuts of the two outter tubes. The Joint Jigger wouldn't allow me to fully center the tube on the holesaw so I got it as close as I could
and cut the "shape" of what the cut was suppose to be. I then took the file and grinder to it and inched my way to cutting the notch in both tubes. Take a little off then check, take a little off then check... on and on and on until it was a good fit. Took about 2 hours for each tube but well worth the end results.
The reason why I cut the extreme notched angles before the top angle is because the top angle is an easy cut. Cut the top one first and there is a good chance of you cutting the bottom a little off kilter from the top and
then the entire piece would need to be thrown out. Cut the harder cut first then the second one is a piece of cake.
After cutting the two extreme angled tubes I cut the top tube that connected to these two tubes. I then notched in the two smaller angled tubes, following the instructions as set forth by Dale in his article. Take your time and
think it through. Think fo the holesaw as the tube that you are notching the tube into. It's easy to get turned upside down with these two pieces. I almost made a wrong cut on my last cut. Instead of plowing ahead, like I almost did, because I took so much time making sure that it
was level and I just didn't want to believe that I had to take it out to double check that the right side was right side up. Something was just eating at me so I unleashed it from the Joint Jigger took it over to the jig and sure enough...
I was right. It was wrong.
Don't forget to put those "oil holes" in your tubing. That is, if you're going to oil the inside of the frame. Just a reminder. (I'll probably forget.)
Cut the "caps" for the bungee tubes out of .063 4130 flatstock. The same thickness that Steen calls out for the Standard's caps. I made mine oblong to give it a little extra lip. Right now I'm just not sure of the size bungees I'll need. Can always grind them down later
if I need to.
Here's the finished piece. Still need to tack, drill and weld together, but you get the idea.
I'll post the completed piece once it's finished.
Note: Before tacking bungee truss to fuselage, drill oil access holes into it (if you're going to do that with your fuselage.) If you don't do it now,it's impossible to do it when it's tacked onto the frame. I even tried blowing a hole through it with the torch. I finally gave that up.
Guess it's a little more than a little. Here's another entire page on the bungee truss. Click here.