Replies to This Discussion

Permalink Reply by martin acton on February 14, 2011 at 11:42am

Hello Joe, you have a valid point, and I was wondering the same. I am surmizing that the radius we put on the enge of the forms will correct the dimensional issue and any extra material folded over will just give a bigger footprint on the rivet line.

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Permalink Reply by Robert Crawford on February 14, 2011 at 9:05pm

Joseph,

I am scratch building the 701 and have the rudder, stabilizer, elevator and both wing skeletons done. The left wing has the top and bottom skin clecoed on and I guess the fuel tank will be next.  The material you are talking about is .016 and .025, (on the 701 anyway) about like copy paper and card stock, not a big deal. Just build the form blocks as the plans tell you and everything will work out. Don't over think it, a millimeter or two isn't going to make much difference in those areas and from 10 feet away you won't see it. I always take "hard" measurements when cutting skins and such and it pretty much comes out just like the plans says it should.

Don't make it more difficult that it is.

Bob

P.S. You may look around locally for material and save some shipping. I found a place called Metal Supermarket that carries 6061-T6 and they have locations all over.

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Permalink Reply by Chris Aysen on February 15, 2011 at 11:57am

Joseph - Robert has a point. As another plans builder I'm familiar with what you're eluding to. Just keep your total length of the individual part within that mm or 2 as Robert says and you'll be fine. Your biggest challenge on that part (horizontal) will be fitting the skin to the skeleton without twisting the whole thing...... There will be other times to sweat. I don't think your at that point right now. Best of luck!

Chris

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Permalink Reply by Joseph Begany on February 15, 2011 at 10:52pm

Thank each of you for the positive thoughts.  Since there have been so many building off of the plans I figured that the milimeters would disappear in the skeeme of things.  I did give Mark Townsend a call and talked about the numbers.  He says that he hasn't built a 750 from scratch yet but that you just tuck and squeeze and it all comes together.  It wouldn't take much to adjust the end ribs and tweak things to line things up.  May make it easier to keep things from twisting if we weren't trying to stretch the skin over the uneven skeleton so I will probably go ahead and make the adjustments.

 

I will report how it all works out.

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Permalink Reply by Chris Aysen on February 16, 2011 at 7:00am

Even with perfect measurements the possibilty of twisting is very real. But I believe you have a handle on it. Best of luck.

Chris

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Permalink Reply by Andrew Aston on February 20, 2011 at 6:22am

Hi Joseph,

I am plans building a 701, but many of the issues cross pollinate with the 750. In my experience CH does not worry too much about perfection, his idea is that form follows function. During my build I have had to 'persuade' the odd part to fit by careful use of bending pliers etc on the flange (obviously within reason and mindful of edge distances). Just to reiterate what others have said the fitting the skin without twist is the critical challenge. I built mine flat then decided to update to the thicker .063 attachments of more recent plans. I thought that grip pinning the skin into the original holes would automatically reproduce a flat part, wrong, I ended up with a twist and had to re jig it using strapping to a flat table. It just shows how important the strapping down to a flat bench is. All the best with your build.

Regards, Andrew.

See some pics on my profile:   http://www.zenith.aero/photo/albums/063-horiz-tail-brackets

 

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Permalink Reply by Martin F. Dufour on March 2, 2011 at 4:58am

Interesting observation I am just starting out and a scratch builder myself. I will be following your progress and hopefully share info with you as I progress.

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Permalink Reply by Martin F. Dufour on March 7, 2011 at 11:20am

I've been using Microstation the past two years and I'm still clumbsy with it. I really miss the ease of autocad. I have 2002 version on my laptop. What sort of prices are you getting for your watercuts? Would like to talk with you.

Sincerly Marty

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Permalink Reply by Joseph Begany on March 7, 2011 at 4:00pm

Marty

I am not doing anything with the drawings other than generating templates for my blanks.  I wish I had access to water cutting but that is not the case.  You must have me confused with another builder.  I know that there are a agroup of six guys in Canada that are building six 750's together and they are water cutting a bunch of their parts but they have quantity on their side.

Joe B

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Permalink Reply by Joe Harrington on March 7, 2011 at 9:31pm

Marty,

The machine shop that we used charges $250/hr for their water jet. It took 88 minutes to cut the parts that were 0.090" and thicker for the 6 airplanes.

Joe

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Permalink Reply by Martin F. Dufour on March 8, 2011 at 7:19pm

gee thanks a lot great info. I just spent My Mardi Gras Day drawing up the .025 parts I wanted to have watercut. I just emailed it to my local watercutter, I now know if he will be over pricing me or not.

Thank you very much

Marty

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