Posted 11 Nov 2016 Together, with my brother in-law, we are building a Ridge Runner 3. This kit does not use the spar stiffener like the avid and kitfox. We both feel the stiffener is the way to go. We contemplated using the extruded aluminum ones but we can't find them. So, we felt the original AC Plywood design would be our best option. However, we would like to pick the brains of those here regarding our choice to reinforce the stiffeners with fiberglass and a carbon fiber lattice.I know carbon fiber can cause galvanic corrosion if it contacts the aluminum spar, so i plan to only use the carbon fiber lattice within a 75% area of the stiffener side. I have included a "rough" sketch of my idea below. My question to all of you is; would this be worthwhile or a waste of time? I do not like the fact that the wings are not reinforced. And after seeing some of the ways this kit was put together to save on manufacturing costs, I am determined to ensure our safety in anyway possible. I am not worried about weight. it is safety that concerns me.Any suggestion, thoughts etc ...? Share this post Link to post Share on other sites
Posted 11 Nov 2016 You can buy the aluminum stiffeners from Just Aircraft. I think they were $35 each when I talked to them a year ago. 4' long if my memory is correct. JImChuk Share this post Link to post Share on other sites
Posted 11 Nov 2016 (edited) You can buy the aluminum stiffeners from Just Aircraft. I think they were $35 each when I talked to them a year ago. 4' long if my memory is correct. JImChukThat price may have gone up some since Harry died. Suberavid paid more than I paid. Still cheaper than Kitfox. Jim, I was thinking 60" long Guess I could go measure them - You may be right at 4 foot? EDMO Edited 12 Nov 2016 by EDMO Share this post Link to post Share on other sites
Posted 12 Nov 2016 Hi, that's an interesting idea. If you simply lengthen the ply spar it's good to 1400lb gross, lengthened plus hardwood quarter round, even more. I should think way plenty for a RR3. Did you find this information? Share this post Link to post Share on other sites
Posted 12 Nov 2016 (edited) Unless you have all the scrap materials, Epoxy, laying around, and you have nothing else to do, I don't think you can design or build something better, easier, or cheaper than the (4' or 5'?) Just Aircraft aluminum inserts. EDMO Edited 12 Nov 2016 by EDMO Share this post Link to post Share on other sites
Posted 12 Nov 2016 I have emailed Just Aircraft but have not heard back. It's been a week. Hope they reply quicker than Rocky Mountain Wings. Share this post Link to post Share on other sites
Posted 12 Nov 2016 (edited) I have emailed Just Aircraft but have not heard back. It's been a week. Hope they reply quicker than Rocky Mountain Wings.I got them right away on the old-fashioned cel-phone. Gave them my CC number and got the inserts in 3 days. EdMO Edited 12 Nov 2016 by EDMO Share this post Link to post Share on other sites
Posted 12 Nov 2016 (edited) You could maybe buy just two of the inserts from Just and cut them in half. If the speedwing only used 18" ones, you would be way longer than that. They would probably chop them in half for you and you would save some on the shipping. JImChuk Edited 12 Nov 2016 by 1avidflyer 1 person likes this Share this post Link to post Share on other sites
Posted 12 Nov 2016 Just curious but are the stiffeners in both front and rear spars? Personally I think I'd just build them out of wood to the plans. Way cheaper than worrying about getting the aluminum ones. Plus you could have them finished in just a couple hours of workshop time. 1 person likes this Share this post Link to post Share on other sites
Posted 12 Nov 2016 (edited) Just curious but are the stiffeners in both front and rear spars? Personally I think I'd just build them out of wood to the plans. Way cheaper than worrying about getting the aluminum ones. Plus you could have them finished in just a couple hours of workshop time. The inserts are in both the front and rear spars. I don't see how wood can compare to the quality and longevity of aluminum I-beams that are made to fit the inside radius of the round spars. Kitfox never used wood. EDMO Edited 12 Nov 2016 by EDMO Share this post Link to post Share on other sites
Posted 12 Nov 2016 Just curious but are the stiffeners in both front and rear spars? Personally I think I'd just build them out of wood to the plans. Way cheaper than worrying about getting the aluminum ones. Plus you could have them finished in just a couple hours of workshop time. The inserts are in both the front and rear spars. I don't see how wood can compare to the quality and longevity of aluminum I-beams that are made to fit the inside radius of the round spars. Kitfox never used wood. EDMOI can appreciate the quality of aluminum but lets get real about this. How much difference does either one really make? Wood in a controlled area (away from always getting wet) will last a VERY long time. Besides that fact, how much extra stiffness do the spars really NEED? I realize the plane may be flown at gross occasionally but for the most part people aren't going to fly it that way every single flight. If they are then maybe it's not the right plane for the job. I'm not knocking anyone that flies the plane at or above gross, just stating that the stiffeners may be more of a mental boost on how you feel the plane will hold up when loaded heavily. Share this post Link to post Share on other sites
Posted 12 Nov 2016 My quad City Challenger never had them, I think those spars were 2 inches and maybe .049 could have even been .035 I flew it at 1000lbs all the time ha, but for some reason I needed 60" long Ibeam inside my 2.5 .083 spars, Weird how that works, Share this post Link to post Share on other sites
Posted 12 Nov 2016 (edited) I think the original Kitfox spars with the integral full-length I-beam may be the strongest made, but no comparison tests were ever published that I know of. However, their .065 wall spars with the long aluminum insert and 18" rib spacings have been rated up to 1550 lbs GW, so I cant argue with success. EDMO Edited 12 Nov 2016 by EDMO Share this post Link to post Share on other sites
Posted 13 Nov 2016 I have been trying to contact Just Aircraft but, all emails keep getting returned undeliverable. Are they still in business? I guess I can call them on Monday. Share this post Link to post Share on other sites
Posted 13 Nov 2016 (edited) I have been trying to contact Just Aircraft but, all emails keep getting returned undeliverable. Are they still in business? I guess I can call them on Monday.They moved at one time - maybe you got old email address - phone calls work. I think in N. or S. Carolina now? If anyone gets desperate, I can look on my package for the address. Worst case, I might sell you mine. EDMO Edited 13 Nov 2016 by EDMO Share this post Link to post Share on other sites
Posted 14 Nov 2016 They were exhibiting at the Deland aviation showcase last week, so they are still around.Mark Share this post Link to post Share on other sites
Posted 19 Nov 2016 (edited) Warpedwing told me that he got a price of $75 each, plus shipping, for the Just insterts - Still cheaper than Kitfox. I might sell my 4 for that if someone wants them. Their prices will go up. EDMO Edited 23 Nov 2016 by EDMO Share this post Link to post Share on other sites
Posted 29 Nov 2016 Well, just as an FYI. I finally got in touch with Just Aircraft. They have changed there e-mail address and had not corrected it on the website. The new address is justaircraft@netzero.net . They also charged me a lot more for the inserts than others have posted. They charged me $75.00 each per 60 inch section. Since I will be using 30 inch inserts on my Ridge Runner, I only needed 2 of them. The funny thing is that they came in a package with UPS labels on them where they were shipped to them by Aircraft Spruce. I actually checked AS but could not find these listed on there website. Guess I will have to check again. Lol... Anyway, I have another question regarding the inserts. They relief cut on each end, is there any formula or rule of thumb on how deep the cut should be or the angle it should be cut? I don't seem to be able find ant reference to this on the site here. Share this post Link to post Share on other sites
Posted 29 Nov 2016 Well, just as an FYI. I finally got in touch with Just Aircraft. They have changed there e-mail address and had not corrected it on the website. The new address is justaircraft@netzero.net . They also charged me a lot more for the inserts than others have posted. They charged me $75.00 each per 60 inch section. Since I will be using 30 inch inserts on my Ridge Runner, I only needed 2 of them. The funny thing is that they came in a package with UPS labels on them where they were shipped to them by Aircraft Spruce. I actually checked AS but could not find these listed on there website. Guess I will have to check again. Lol... Anyway, I have another question regarding the inserts. They relief cut on each end, is there any formula or rule of thumb on how deep the cut should be or the angle it should be cut? I don't seem to be able find ant reference to this on the site here.Is there still a part number associated with them from Aircraft Spruce? Maybe you could look it up that way. I'm curious now too. I'd like to know where to get them as well. I'm seriously considering rebuilding Pursang but need to build on new wing from scratch since the spars bent. If I remember correctly somewhere on this forum there is a file or picture with dimensions for the stiffener. Might want to try a search. I don't remember where it was exactly either. Share this post Link to post Share on other sites
Posted 29 Nov 2016 (edited) Here is page from Kitfox 4 manual - I don't think it is critical, except that you want to round everything and make it smooth to prevent any stress points. I like using a PVC pipe with a slot in it better than wood, but either works. Mark it both for depth and on top to keep stiffener vertical. EDMO Edited 29 Nov 2016 by EDMO 1 person likes this Share this post Link to post Share on other sites
Posted 29 Nov 2016 Is it possible the ACS labeled package was just a box that was reused? Share this post Link to post Share on other sites
Posted 13 Jul 2018 Really, with the huge differences in strength and stiffness between plywood and aluminum, these inserts are really spar crimp preventers, not stiffeners. Their real role is to prevent compression buckling on the top of the spar tube under high G conditions. If the spar tubing thickness is 0.049", one could use the next tubing size down (1/8" smaller O.D.) or an internal doubler to accomplish the same thing. But really, all you need is something to immobilize the top of the thinwall spar at this max-stress span location. -Turbo 1 person likes this Share this post Link to post Share on other sites