Longeron mishap

[Jkkinz]

I woke up this morning feeling much better in knowing that I am not dyslexic or a complete idiot.
I have spent the past few days trying to perfect the bend in my longerons and get them to match the canopy deck. As the instructions indicated, I cut the full size template for the longeron bend off of sheet 17 and taped it to a flat board. Again following the instructions I made the measurments on the angle for the start of the bend and the end of the bend. I placed the angle in the vice and used the rubber mallet to create the gradual curve. Everything went as planned and I felt good to have the curve within the 1/16" of the line as required. So next it was time to fit and drill the canoppy deck...no joy. The flat portion of the forward deck followed the longeron perfectly but as I continued further aft the two edges did not come close. The aft end of the deck was extending laterally over the longeron by more than 1/4".
So what did I do wrong? Well after hours of checking and rechecking my measurments, reading and rereading the instructions as well as reading all that I could find on the forum and in other websites; I was at a loss to understand what I was doing wrong. So finally I called Vans for an answer. I was able to talk to Ken about my problem assuming that I had just missed something. But after describing to him my problem, he informed me that he had been noticing that the printing process for the template has not been all that accurate. He further said that they needed to look into why the printing was distorted and was planning to send out a notice to builders to explain the discrepencies in the template. Finally he said that it is most important that the longeron match the canopy deck and to just bend the longeron so that it will match the deck edge. He also said to use the template as a guide and not worry so much about matching the template perfectly. Wow that was a load off my shoulders, at least I know am not loosing it.
So last night I went back out to my trusty rubber mallet and vice and after several whacks in both directions I now have a perfect fit to the canopy deck. Next to the drilling and and beyond!
So the moral of this story is, if there are any others out there that think they are loosing it, have heart and know that you will persevere.

Happy building
Jim Kinsey
7A Fuselage

 

[JonathanCook]

Great storry Jim.


What day are you planning to go to Sun-n-Fun.

I am over in Celebration, maybe we can finally meet up in Lakeland.

I can be reached at jonathan.cook (AT) symech (dot) com

 

[cwreeves]

Longeron

Jim,
If you haven't already installed the longeron to the fuselage I'd recommend clecoing the canopy deck to longeron from the underside. This will keep the longeron from springing or deforming as you manipulate during the build up process. I've heard several builders have had problems with longerons loosing the proper curve and when it's time to rivet the canopy deck on they don't match. This miss/match can be as much as 3/4". I suppose you could force it to alignment,but I personnally don't want the longeron and deck preloaded. I cleco'd the canopy deck in place as mentioned during and it worked great. Just my opinion.
Charlie, Tucson

 

[Jkkinz]

Charlie,

Thanks for the advice. I haven't got to installing the longerons yet as I am now working on the center section. I had already planned to have the canopy deck in place when I back drill the longeron. I figure that if I have the deck on, it will allow for a close fit of the side skin to the overhang of the deck. I did not think about the longeron springing back so I will definitely have it in place.

Thanks again

Jim Kinsey
7A Fuselage

 

[aerolite]

Any advice!

Hi Jim,

As your post was back in March I was thinking you probably have your longerons
installed and can answer a couple of questions I have. There isn't much info on the forums regarding this. I'm glad to hear Ken's response to you as I have had the same concern and went with the 721 as a guide plus the template. I have spent the better part of seven hours "perservering" and have the curves pretty darn close with one 721 clecoed in place. (in my 25 years of machining this is the first time I've ever had to bend angle!) When I put the angle on the floor the top of the curve angles upward slightly but it takes very little downward pressure to make it sit flat. I'm hoping when I put the forward downward bend and twist in (my next step) it will cure this. I'm pretty anal about things and quite often put too much time and effort into things that didn't require as much. I would like to know how much tweaking can be done when installing the longerons after the bending process. Van's says within 1/16 is fine and I'm thinking I should be able to make small adjustments when fitting everything together.
Van's supplies so many parts that would be very easy to make yet they have us bend the longerons which are so important to get right. I am suprised that Van's doesn't supply these already formed as a bending jig at the factory would be more accurate. I'm sure the quickbuild factory in the Phillipines has one!
Thanks in advance for any advice forthcoming.

Steve
RV7

 

[Jkkinz]

Steve,

To give you an update on the fit of the longeron, I have the fuselage all clecoed together and will begin riveting this weekend. The fit of the longeron is great. Using the canopy deck as a guide worked well.

I also got a slight twist in the angle as I was bending it. The twist can be removed by placing the longeron in the vice and using a little pressure to get it straight. I used a 4 foot level to insure the twist was out and the top surface of the angle was straight and level.


Jim Kinsey
7A fuselage