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Used Firestar Checklist

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mikemac

Joined: 22 Apr 2016
Posts: 18

Posted: Sun Aug 07, 2016 9:22 am Post subject: Used Firestar Checklist

When buying a used Firestar 1 or 2, would you please list what you would want to find out. I have never owned a Kolb. Any suggestions appreciated.

I was told by some local high time kolb jockies to make sure it is a seven rib as opposed to five. Thank you in advance for any help.

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victorbravo(at)sbcglobal.
Guest

Posted: Sun Aug 07, 2016 11:46 pm Post subject: Used Firestar Checklist

I just bought a used Firestar, and I found a potentially dangerous problem with one of the bolt holes in the wing spar attach lug (the piece of thick steel sheet coming out of the wing root).



The hole had been drilled far far too close to the edge of the metal, and under certain loads, gusts, or other flight conditions could easily have caused a crash. 



Although these are of mcourse non-certified airplanes, the FAA and the engineering community have researched this and come up with a very clear explanation of "edge distance" for structural fastener holes for certified aircraft. Because this is primary life or death safety, this is one area where ultralights, experimentals, and commercial airplanes all need to adhere to the same principle. 



Measuring from the CENTER of the hole, you need to have at least two times the diameter of the bolt before you reach the edge of the piece of metal.This is a rule for "sheet metal", which in general is anything under 1/8 inch thick. Plates (above 1/8 inch), tubes and billet have different limitations for fastener attachments.

Bill Berle

www.ezflaphandle.com  - safety & performance upgrade for light aircraft

www.grantstar.net           - winning proposals for non-profit and for-profit entities



--------------------------------------------

On Sun, 8/7/16, mikemac <mmacpherson(at)homesale.com> wrote:



 Subject: Used Firestar Checklist

 To: kolb-list(at)matronics.com

 Date: Sunday, August 7, 2016, 10:22 AM

 

 

 "mikemac" <mmacpherson(at)homesale.com>

 

 When buying a used Firestar 1 or 2, would you please list

 what you would want to find out. I have never owned a Kolb.

 Any suggestions appreciated.

 I was told by some local high time kolb jockies to make sure

 it is a seven rib as opposed to five. Thank you in advance

 for any help.

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=459295#459295

 

 

 

 

 

 

 

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    - MATRONICS WEB FORUMS -

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 Dralle, List Admin.

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stuart(at)harnerfarm.net
Guest

Posted: Mon Aug 08, 2016 5:39 am Post subject: Used Firestar Checklist

Bill,



Good thing you caught that, you certainly don't want a bolt hole pulling out during flight.



Since that hole is drilled during the alignment of the wing to fuselage you can't just drill a new hole somewhere else without messing with the alignment of the wing. In some cases the recommended procedure to fix an out of alignment wing is to weld the hole shut and re-drill it in the proper place.



So this leaves the question, is the wing currently aligned properly?



If not, perhaps moving the hole will fix two problems at once. 



If the wing is aligned properly, then there may (stress only may) be a problem with the wing elsewhere. A couple of things come to mind like covering might have pulled the wing out of "square" or something was not built properly internally.



I would start by getting it into a flight attitude, level in all directions and start checking things like wing angle and square. Also look for any "twist" that should not be there.



Curious about a couple of things. Has this plane flown? Did you buy it from the builder? If you look down the leading edge, do the wings align?



Give Bryan at the factory a call, I bet he has seen this before and will know the best way to proceed.



Good luck and let us know what you come up with. Post pictures too. Might help someone else.



Stuart



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racerjerry

Joined: 15 Dec 2009
Posts: 202
Location: Deer Park, NY

Posted: Mon Aug 08, 2016 7:56 am Post subject: Re: Used Firestar Checklist

Just exactly how much "meat" is left at the narrowest point between the hole and edge?  I am betting you don't need ANY mod as 4130 is plenty strong.  Caliper measurerment?



For a reinforcement, maybe you could weld a washer to each side and not disturb alignment?  Or sandwich  a 4130 plate of similar thickness to one side (better). See if there is enough room.



I remember when setting my own Firestar up, that I wanted a bit more edge distance myself, so I set the tiniest degree of forward sweep into the wings.

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_________________
Jerry King

Last edited by racerjerry on Wed Aug 10, 2016 4:46 am; edited 1 time in total

victorbravo(at)sbcglobal.
Guest

Posted: Mon Aug 08, 2016 8:53 am Post subject: Used Firestar Checklist

The edge distance problem in this case is that sweepback would make the problem worse rather than better.The hole is too close to the inboard edge of the mounting lug.



Sweep forward would resolve this particular issue, but then it would create a lot of other problems. It's not the right way to do it.



I consulted with a VERY highly experienced aerospace engineer with 50 years of experience. This is not a matter for a "garage" fix or a "that's about right" approach. His recommendation was also to verify the wing alignment, and make up a patch plate doubler that was bolted to the existing lug. The problem is that welding up the hole often creates a hard spot where it becomes difficult to drill back out accurately. 



The airplane had apparently been flown, the tachometer shows 147 hours. I bought it from the second owner, who had not flown it. The story I got was that the builder flew it, did a little damage to it one day, repaired PART of the damage, fixed the fabric at the wingtip, and repainted the airplane. So the damaged wingtip was repaired, but the slightly longeron tubes in the forward fuselage were not bent back into place. I am betting he replaced the nose cone, because in order to bend those tubes the way he did the nose cone would have shown a fiberglass repair.



Last Saturday, after consulting with my engineer on the wing mounting lug, I carefully bent the longeron tubes back into place using bar clamps and a scissor jack, and got everything almost straight as new. A little more work will get it perfect, but I need to figure out the right tool for that. 



Bill Berle

www.ezflaphandle.com  - safety & performance upgrade for light aircraft

www.grantstar.net           - winning proposals for non-profit and for-profit entities



--------------------------------------------

On Mon, 8/8/16, racerjerry <gnking2(at)verizon.net> wrote:



 Subject: Re: Used Firestar Checklist

 To: kolb-list(at)matronics.com

 Date: Monday, August 8, 2016, 8:56 AM

 

 

 "racerjerry" <gnking2(at)verizon.net>

 

 Just exactly how much "meat" is left at the narrowest point

 between the hole and edge?  I am betting you don't need

 ANY mod as 4130 is plenty strong.  Caliper

 measurerment?

 

 For a reinforcement, maybe you could weld a washer to each

 side and not disturb alignment?  Or sandwich  a

 4130 plate of similar thickness to one side (better). See if

 there is enough room.

 

 I remember when setting my own Firestar up, that I wanted a

 bit more edge distance myself, so I set the tiniest degree

 of sweepback into the wings.

 

 --------

 Jerry King

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=459326#459326

 

 

 

 

 

 

 

 Forum -

    - MATRONICS WEB FORUMS -

 MATRONICS LIST WIKI -

 List Contribution Web Site -

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 Dralle, List Admin.

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stuart(at)harnerfarm.net
Guest

Posted: Mon Aug 08, 2016 9:19 am Post subject: Used Firestar Checklist

Bill,



Sounds like you are on the right track about this.



I do like the idea of adding "more tab". Welding would be ideal. Welding a hole shut does pose hardening problems, usually solved with "normalizing" heating. Neither are things I would like to do after the wing is covered, but it can be done with careful planning.



If after checking alignment you determine that a new hole has to be drilled, perhaps you could over size the existing hole and weld in a short steel tube of the proper ID. That way you don't have to drill through a weld bead but you can relocate the hole by moving the tube around in the oversized hole. Alignment could be tricky.



The idea of sandwiching some flat steel on one or both sides of the existing tab is a good one provided you have the space to put some bolts. I would think at least two would be preferred so that the extension cannot pivot around the clamping bolt(s).



If the plane was damaged enough to bend fuselage parts, keep looking and checking everything. Sounds like you have quite a project on your hands, hopefully it is all just cosmetic stuff.



Stuart



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rmurrill(at)cox.net
Guest

Posted: Mon Aug 08, 2016 9:25 am Post subject: Used Firestar Checklist

Before "fixing" it I would suggest your very experienced aerospace engineer 

do some basic calculations of the loads on the fitting.  He will be well 

aware of how to calculate the "lug efficiency factor" for the steel part. 

The largest load is in the transverse direction for this part not the 

usually worrisome lug tension direction, so he will need both the lift and 

drag forces carried by the fitting.  The lift strut actually puts a fair 

amount of compression into the fitting.  Should be pretty easy to estimate. 

Also compare the strength to the adjacent load carrying parts.  Best of 

luck..



Bob

--

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victorbravo(at)sbcglobal.
Guest

Posted: Mon Aug 08, 2016 10:04 am Post subject: Used Firestar Checklist

You guys are certainly on the right track with your thinking too  



My engineer (who I am SO lucky to have available!!!) looked at the fitting and estimated that the loads are.. about... in THAT direction. The combination of lifting loads, drag loads, and the inward force from the wing struts were all taken into account. 



This particular engineer is more than capable of setting up a classic engineering "Free Body" diagram and calculating the loads and directional vectors on the fasteners exactly. But in this case his experience indicated that the calculations would very likely indicate that a good "factor of safety" and conservative thinking would both point to adding material around the hole.



I believe that he suggested a bolted doubler instead of a welded doubler only for the sake of heat management, since there are rivets and fabric near the fitting that would be affected. Welding large washers tot he fitting would certainly also be an option.



But I believe that the actual repair will be guided by how well the wings are aligned, as one or two of you have mentioned. If the alignment is poor, then the hole should be moved, which leads me more toward the extra effort of welding. If the hole alignment is accurate, then a doubler system (with two additional bolts to prevent rotation) maty be the easier way to achieve the same strength.



While I'm on this subject, I would like to ask a question about this wing mounting lug system.



The mounting lug on the spar fitting looks like it is .090 steel material. The space between the "Ears" or  lugs on the square fuselage tube looks like there is 3/8 or 1/2 inch between them. So even though the wing cannot slide fore and aft (because of the trailing edge U-joint), there are still unsupported gaps between the spar fitting and the fuselage lugs. In this case, that means the bolt or pin is not really in proper "double shear" load, the open space on both sides of the spar fitting allows a bending load at the unsupported parts of the bolt/pin shank.



Can anyone tell me if there is any good reason for this gap to be there? It would seem to me that a short section of tube welded in to the spar fitting would put that wing bolt/pin in proper "double shear" load. I'm NOT saying that the Kolb design is defective, I'm asking why this critical bolt is not supported in the gap between the fuselage lugs.

Bill Berle

www.ezflaphandle.com  - safety & performance upgrade for light aircraft

www.grantstar.net           - winning proposals for non-profit and for-profit entities



--------------------------------------------

On Mon, 8/8/16, Bob <rmurrill(at)cox.net> wrote:



 Subject: Re: Re: Used Firestar Checklist

 To: kolb-list(at)matronics.com

 Date: Monday, August 8, 2016, 10:25 AM

 

 

 "Bob" <rmurrill(at)cox.net>

 

 Before "fixing" it I would suggest your very experienced

 aerospace engineer 

 do some basic calculations of the loads on the

 fitting.  He will be well 

 aware of how to calculate the "lug efficiency factor" for

 the steel part. 

 The largest load is in the transverse direction for this

 part not the 

 usually worrisome lug tension direction, so he will need

 both the lift and 

 drag forces carried by the fitting.  The lift strut

 actually puts a fair 

 amount of compression into the fitting.  Should be

 pretty easy to estimate. 

 Also compare the strength to the adjacent load carrying

 parts.  Best of 

 luck..

 

 Bob

 

 

 --

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byoungplumbing(at)gmail.c
Guest

Posted: Mon Aug 08, 2016 11:34 am Post subject: Used Firestar Checklist

I'm not a structural engineer,,, so think on this,,,   when the wing I's creating lift the lift strut (because of the triangular geometry)  pulls the wing to the center.   with almost equal sizes of wing panels inboard and outboard from the liftstrut,  the in board attach fitting should have very little up or down pressure.    

 

with that said the edge distance should be most affected by the drag pulling the wing back. 

  but without wind tunnel testing I don't know which force is greater. 

Boyd Young

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