Spar Stiffener reinforcement


21 posts in this topic

Posted

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 ...?

 

Spar Stiffener.jpg

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Posted

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

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Posted (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.  JImChuk

That 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 by EDMO

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Posted

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? 

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Posted (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 by EDMO

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Posted

I have emailed Just Aircraft  but have not heard back. It's been a week.  Hope they reply quicker than Rocky Mountain Wings.

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Posted (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 by EDMO

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Posted (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 by 1avidflyer
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Posted

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. 

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Posted (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 by EDMO

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Posted

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

I 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. 

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Posted

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,

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Posted (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 by EDMO

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Posted

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.

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Posted (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 by EDMO

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Posted

They were exhibiting at the Deland aviation showcase last week, so they are still around.

Mark

 

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Posted (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 by EDMO

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Posted

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.

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Posted

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.

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Posted (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

Scan0349.jpg

Edited by EDMO
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Posted

Is it possible the ACS labeled package was just a box that was reused?

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