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Aug 01, 2019, 08:11 PM
in pursuit of low wing loading
Gordon Johnson's Avatar
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When I molded the pieces for the tail surfaces the other night I had a length of wetted out and partially cured CF tow left. So, I grabbed a length of aluminum rod, wrapped it around it, and voila, CF spring.
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Aug 01, 2019, 08:12 PM
in pursuit of low wing loading
Gordon Johnson's Avatar
Thread OP
But, back to the plane, these are the tail pieces, cured, and baked in the oven. Next I need to design up and laser the assembly Depron jigs for gluing the internal pieces. And, then I'll have to make painting templates and paint the mylar for covering the tail pieces.
Aug 01, 2019, 11:19 PM
Registered User
Quote:
Originally Posted by Gordon Johnson
Here is the picture I promised showing how flexible the wing structure is after gluing the ribs in place. And, this is why it needs to be braced externally.
Good picture, interesting to see the level of flexibility.
Aug 04, 2019, 03:27 PM
in pursuit of low wing loading
Gordon Johnson's Avatar
Thread OP
Designed up and laser cut the foam gluing jigs. Same as my previous planes. I score where the interior straight pieces and the molded perimeter CF pieces go, and then cut circles all the way through the foam where the thick CA is applied at each joint. Now on the the tedious step of cutting and sanding to fit the length of CF rods so each joint is a snug fit.
Aug 05, 2019, 03:29 AM
Registered User
Hello Gordon,

What is the power of your laser to create the depron mold ? do you have video ?

Charles
Last edited by maulionc; Aug 05, 2019 at 08:15 AM.
Aug 05, 2019, 03:35 PM
in pursuit of low wing loading
Gordon Johnson's Avatar
Thread OP
Just to be clear, this is not a Depron mold. It's an assembly jig, to hold the CF pieces in place, and then apply glue to the joints. If you haven't already, look at the threads of my previous models, where I show more detail on this assembly process.

No I don't have a video. It is a 30 watt laser. I use a lower power setting to score the lines, rather than cut through foam all the way. It is a trial and error process to get the scored cut the right depth.

Lots of people use other methods for assembling their molded CF pieces. I use this method because I have a laser. Other people tape clear plastic down over a drawing of where the pieces go on paper, and then tape the CF pieces down, and glue the joints. Other people draw the lines for where the CF pieces go by hand on foam, and then cut out circles where the joints are with a sharpened tube. My method is just a variation of the hand drawn lines on foam method.
Last edited by Gordon Johnson; Aug 05, 2019 at 06:01 PM.
Aug 13, 2019, 07:29 PM
Registered User
What epoxy are you currently using? I've seen "West System" in threads but not which particular one. I have tried an initial test with my G-Flex, room temp cured for 24hrs and I think I could do better.
Aug 14, 2019, 02:42 PM
in pursuit of low wing loading
Gordon Johnson's Avatar
Thread OP
I'm using standard West Epoxy.
http://cstsales.com/west_system_epoxy.html

West 105 for the epoxy and either West 205 or 206 for the hardener. I prefer the 205 because it is faster. But, either works. I just have to wait longer with the 206.

The Composite Store is a good source for stuff. But they are not cheap. They carry high quality CF rod and tubes in a nice assortment of small sizes that come from the Netherlands. Their shipping charges on West epoxy are pretty high. You can do better from Amazon for the same epoxy. And, if you look around in your area you can probably find a hardware store that carries West, and then avoid shipping entirely. Marinas that carry West generally want to sell you a gallon.
Aug 14, 2019, 07:38 PM
Registered User
Thank you. These options have a quicker cure time which is nice too.

I have ordered from CST before, and have been curious about their 0.028" OD tube for a little bit, so maybe it is time to get some supplies. I think that is the Netherlands tubing and no one else seems to have it. Tubing this small looks like it may satisfy my urge for "lower density" carbon fiber which is probably never coming to market and I'm not sure anyone is even asking for it.
Aug 14, 2019, 08:21 PM
AeroDan
I sure hope to see some pics of this upon completion, and a maiden report. I LOVE Citabrias. Especially the OLD ‘72/‘73 factory starburst scheme. I saw one w/Bahama Blue base & White starburst trim on final @KTOA once from about a mile away. NEVER forgot that moment (Feb. 1986). BEAUTIFUL work, Gordon.
Last edited by Bell47G2; Aug 14, 2019 at 08:27 PM.
Aug 16, 2019, 11:50 AM
in pursuit of low wing loading
Gordon Johnson's Avatar
Thread OP
Quote:
Originally Posted by CGordon
Thank you. These options have a quicker cure time which is nice too.

I have ordered from CST before, and have been curious about their 0.028" OD tube for a little bit, so maybe it is time to get some supplies. I think that is the Netherlands tubing and no one else seems to have it. Tubing this small looks like it may satisfy my urge for "lower density" carbon fiber which is probably never coming to market and I'm not sure anyone is even asking for it.
The DPP rods/tubes are from this company in the Netherlands
https://www.dpp-pultrusion.com/en/the-company/
I like their rods. I have gotten rods from other sources and sometimes have found them to be soft and not as high of quality.

CST recently added a new section on their website with High Modulus CF rod, which also seems to be from DPP. It is available in fewer sizes, and not in the 0.5mm (0.020 in) diameter that I use for these projects to be the same diameter as my molded CF rod. So, I haven't tried any of their High Modulus rod yet. And, from what I can calculate, it's not any lighter.

I did get some elusive super-super-high modulus CF tow that some of the free-flight rubber guys are using to make molded CF prop outlines. And, I made some CF rod from it for tests. First, it was not any lighter. Second, it was much more brittle. I can take a length of 0.5mm super high modulus self-made straight rod and just snap it off in short lengths with my fingers without much pressure. That's not the case with DPP 0.5mm commercial rod or my own straight self made 0.5mm rod. So, for now I'm sticking with what I make from ordinary CF tow from CST Sales (which is pretty much the same modulus CF filaments as what you get in ordinary run of the mill CF woven cloth).
Last edited by Gordon Johnson; Aug 16, 2019 at 12:29 PM.
Aug 16, 2019, 02:23 PM
Indoor FF is pretty neat
funwithplanes's Avatar
Quote:
Originally Posted by Gordon Johnson
I did get some elusive super-super-high modulus CF tow that some of the free-flight rubber guys are using to make molded CF prop outlines. And, I made some CF rod from it for tests. First, it was not any lighter. Second, it was much more brittle. I can take a length of 0.5mm super high modulus self-made straight rod and just snap it off in short lengths with my fingers without much pressure. That's not the case with DPP 0.5mm commercial rod or my own straight self made 0.5mm rod. So, for now I'm sticking with what I make from ordinary CF tow from CST Sales (which is pretty much the same modulus CF filaments as what you get in ordinary run of the mill CF woven cloth).
Was the high modulus tow any stiffer once cured than the CST tow? I recently got my hands on a prop outline jig for F1D, and am trying to figure out what tow to use. The high modulus stuff is pretty expensive now, so I'm wondering if I can get away with standard tow.

Ross
Last edited by funwithplanes; Aug 16, 2019 at 02:32 PM.
Aug 17, 2019, 08:13 AM
in pursuit of low wing loading
Gordon Johnson's Avatar
Thread OP
Ross,
I think you would be just fine with regular tow. I'll try and remember to bring you some of the high modulus tow to NEAT. Then, you can try both.

Gordon
Aug 17, 2019, 11:31 AM
in pursuit of low wing loading
Gordon Johnson's Avatar
Thread OP
Finally got around today to gluing in the interior pieces for the rudder and elevator. Elevator CF complete weighs 0.31g and the rudder is 0.11g. Now on to painting up the mylar and then covering.
Aug 17, 2019, 06:39 PM
in pursuit of low wing loading
Gordon Johnson's Avatar
Thread OP
Quote:
Originally Posted by Bell47G2
I sure hope to see some pics of this upon completion, and a maiden report. I LOVE Citabrias. Especially the OLD 72/73 factory starburst scheme. I saw one w/Bahama Blue base & White starburst trim on final @KTOA once from about a mile away. NEVER forgot that moment (Feb. 1986). BEAUTIFUL work, Gordon.
Glad you like it. I've done a few Citabria's through the years. So, it was a logical for a stick plane.


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