Bending elevator trailing edge...

miyu1975 · #1 01-28-2009, 05:51 PM

Didn't think bending the trailing edge was so difficult. I have bent and bent but it won't bend enuf to pass the straight test. Could it be that my garage is 20 degrees, thus the metal being cold doesn't want to reform. Should I heat it with a blow dryer???..thx

schristo@mac.com · #2 01-28-2009, 06:11 PM

make sure that you are not bending it with such a tight radius that it binds up... you need to maintain 3/32 to 1/8" at the trailing edge... if you try to force the part to form a tighter radius it will resist. also you might try flipping it over. in the end it may take a bit more force than you expected, just apply it evenly and smoothly.

Auburntsts · #3 01-28-2009, 06:14 PM

Could be your brake as well. What are you using?

miyu1975 · #4 01-28-2009, 07:48 PM

I made a 2x6in x 5ft brake as per other sites I have seen. I am using a 1/8 dow in the center of the bend as to not over bend and crack it..

miyu1975 · #5 01-28-2009, 07:56 PM

right now I have it cleco'd to the spar so I could final drill it..(had to move on to something else while waiting)...wondering if it is ok to put the trailing edge in the brake I have made and squeeze it while cleco'd together...?

schristo@mac.com · #6 01-28-2009, 08:12 PM

try removing the dowel; it sounds like the brake is pinching the dowel before it can bend the skins...

miyu1975 · #7 01-28-2009, 08:24 PM

pic..
http://picasaweb.google.com/lh/photo...eat=directlink

try again tomrw.

UnPossible · #8 01-28-2009, 08:42 PM

I just bent mine last weekend. I had to remove the 1/8" dowel for the final bend...... one last squeeze without the dowel and now it looks great.

Jason

miyu1975 · #9 01-29-2009, 09:17 AM

thx all..think it would help to heat skin a little with a blow dryer or something.

RBR · #10 01-29-2009, 02:43 PM

I bent mine 2 days ago with great success, mind you the shop temperature is 82F. Can't help on the blow dryer theory though, but some of my process might help, if not you, others following the 'journey'.

Before contemplating the bend, I spent hours researching using the Search facility here.

My brake is constructed using an MDF sandwich, using 5 hinges with no lateral slop when exercised. I went without using the dowel, but had the trailing edge of the skin tight against the hinges. In place of the dowel, my brake boards are set 1/8 apart at the hinge line. I squeezed very gently, rotated the skin, squeezed again, rotated etc., until the brake could do no more. The stiffeners were gently touching the opposite skin.

For the final squeeze or series of them, I used my Avery Hand Seamer. I specify Avery because it is the vise grip style, meaning you can set an exact jaw size, and produce a consistent radius along the skin's length. (My Isham seamer relies on me to set the jaw size, by the pressure I can exert on the handles.) Go very gently though, with a 1/8 turn increasing increment on the grip adjuster each pass. (I had to use some plumbers tape on the screw adjuster of the grip, as the screw would work it's way free and slacken the angle. I also marked the end of the adjuster with an arrow to show the incremental step increases). I might have made 5 passes each direction, squeezing slightly tighter each time. Take great care though, a little goes a long way. Also, don't put the skin fully into the throat of the seamer. For consistency, I took MEL's advice and used some electrical tape to protect the skins, but this also allowed me to place the skins at a consistent point within the mouth of the seamer's jaws.

Bending the first skin was one of those 'big gulp' moments, but I am now very happy to do so, all thanks to the search facility above. You are very close a radius that will please you, but more importantly, you have a beautifully straight line leading to the radius!