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Andre

Fuel Tank Leak - What to do?

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Tip, sorry forgot to answer your question.  No I don't have a "Shim" part #.  Here is the CTLS Parts manual... please see pages 30 and 45... it will give you an idea how the wing marries the fuselage.  I don't have an SW, but I am sure there is a similar manual out there for that too.

http://documents.flightdesignusa.com/Parts & Assembly Manual CTLS USA.pdf

Here is a video revealing the installation of SW wings being attached to the CTSW.  A reasonably skilled carpenter/epoxy guy could custom "shim" the spar to fit its wing mate.

This I do know... none of our planes are perfectly level.  If you put the same amount of air in the tires and place the plane on a level surface... and place a measuring tape at a common point at the end of each wing, one will be higher than the other.  Mine is out by about an inch.  The FD guy told me that the shimming for level perfection is in two places... the wings and the shimming in the main landing gear.  It is an inexact science and the root cause is the human being element of manufacturing the laid up Parts.

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2 hours ago, AGLyme said:

Tom, sorry should have stated — “similar”... Naturally, the “boxes” are different, they do different things but the engineering principals and the way the pre-made Parts (wings or CTLS struts )fit into the boxes, and shimmed, are “similar”.  
 

The wings are not fitted in a box like the gear leg. The gear leg goes in a socket with 2 bolts and a clamp. The tolerances are not very tight allowing it to be shimmed, and replacement gear legs to be installed without any special matching process.

The spar box is intregal to the structure of the fuselage, but has nothing to do with the attachment of the wings. It provides rigidity to the cabin structure, but neither the wing spars or the pins touch the box. There is an inboard and outboard bushing in each spar. The pins pass through the inboard bushing of one spar and the outboard bushing of the other spar. The position of these bushings in each spar must match the other perfectly, and are very close tolerance. After the pins are installed the cap goes inplace and pulls each pair of bushings together. The load of the fuselage is transferred to the wings by 2 pins bonded to the inboard rib of each wing that engage in receptacles in the fuselage. The rear is fixed, and the front is a Heim fitting to aid in alignment. The front is where the tube crosses by the windshield. The fitting of these pins are mathced to the fuselage. 

The wings can actually be put together seperate from the fuselage, but I wouldn't suggest doing that.

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So... a box is a box Tom...  In aerospace "box" is a real term, please Google it.  I don't think you are saying that we cannot buy replacement wings anymore...   all I wanted to get across to the FD owner population is that one can buy a replacement wing and with a little sanding and epoxy one can buy one in the secondary market.  I think we are in agreement then.

 

 

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No I am still saying that one wing is not interchangeable in the way you are indicating, at least from the used market. The two wings are a matched pair because of the spacing of the bushings in the spar. My guess is that the bushings are reamed in place to get the perfect match. 

I know what a spar box is. A piper Cherokee has a spar box. The wings slide into the box and are attached to the box, and it provides a structural path for the load imposed on the wings to be transmitted to the fuselage. What is often called a spar box on the CT really has nothing to do with the spar, other that keeping it hidden. The spars do not attach to the box in any way. They do not touch the box in any way. They do not directly transfer any of the load from the wings to the fuselage. They do not provide any structural strength to the spars. They have nothing to do with the fit of the wings to the airplane.

 

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Tom, good explanation of the wing attachment. I didn’t realize that the pins in the wing root are what actually transfer the load.  

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I have been made aware that Flight Design does have a process to deal with the issue of misaligned spar pin bushings when replacing a wing, and I am not surprised. This means that a wing can be replaced when damaged. The process involves boring the existing bushing out, plugging the hole and drilling to match the existing wing. This process would take care of the misalignment I mentioned in one of my earlier post. I suspect a similar process is used during production minus the boring and plugging of the bushing.

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My bet is 

2 hours ago, Tom Baker said:

I have been made aware that Flight Design does have a process to deal with the issue of misaligned spar pin bushings when replacing a wing, and I am not surprised. This means that a wing can be replaced when damaged. The process involves boring the existing bushing out, plugging the hole and drilling to match the existing wing. This process would take care of the misalignment I mentioned in one of my earlier post. I suspect a similar process is used during production minus the boring and plugging of the bushing.

My bet is that is process can only be done by someone factory trained.

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FD Woodstock has a guy who did work on a crack in my door... he's a genius and he has performed tons of like repairs on CT's, including hard structural ones.  You may be right Tip about the wing spar.  There are probably tons of folks from the boat building industry, or super experienced Diamond people, or our hero in Woodstock who could do the repair and eventual fitting, but, I think it would be hard to get someone to get "Certified" to do it without taking a bunch of risk from a factory perspective.  

Let's just say that this wing replacement idea, at least in the secondary market, is (for now until the aerospace epoxy skills-market scales) "Busted"...; )

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Can i ask for some clarification regarding this "access port" or hatch/patch that has been mentioned on this topic.     Is this 'access port' on the bottom of the fuel tank?  If so, why is there a access port?     Is this access port visible (borescope) on the inner part of the tank (closest to fuselage) or closer to the fuel refill cap?    

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11 hours ago, cdarza said:

Can i ask for some clarification regarding this "access port" or hatch/patch that has been mentioned on this topic.     Is this 'access port' on the bottom of the fuel tank?  If so, why is there a access port?     Is this access port visible (borescope) on the inner part of the tank (closest to fuselage) or closer to the fuel refill cap?    

Yes as dumb as it sounds this patch is on the bottom of the tank.  It's about mid span between the root and filler cap.  I found it easy to see via the fill hole, but it'll take a while to "find" it with a boroscope.  I suggest you shine a bright flash light at the bottom in a dark hanger, that will help you locate the patch from the outside (the body work is not amazing) you will see the bulge.

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OK thanks for reply.  Yeah i had read about the few fuel leak problems and mine being CTSW 2006 is of concern.  I recently noticed a couple of tiny paint blisters under the fuel tank and started inspecting the area in alot of detail.   I noticed an area no bigger than 5-7inches that looked a little different and when pressing on the skin it was a little softer than the surrounding area and entire wing.  Note it was hard but just ever so slightly softer.   Same on both wings Left and right.    The mind went into overdrive thinking that this might be the beginning stage of a fuel leak problem.  (note: no fuel leak, no staining as of now).     After reading and re reading this thread, im thinking its just the "access hatch"  thats been discussed here.  Hope my concern was just a pointless freakout. :)   Getting ready to do the overdue wing inspection so i will take a look inside too.    

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Re-sealing the tank is fairly easy. When I had my small wing leak on the bottom I just sloshed some Kreem Wiess in the tank and all was well. It was fairly painless.

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We reached out to Arian and he suggested Caswell tank sealer.  Note that regardless of the product you use, pay special attention to the temperature requirements.  Caswell had a required application and cure temp of 70*, we did this in the winter so we had to tent off an area of the hanger and bring in some heaters to get the wings and sealer warmed up.  Also for application we used large syringes we purchased from Amazon and clear tubing.  using the borescope and flash lights we watched the sealer pour over the patch.  You can seal the entire tank, but I was worried about the patch as it's not flat (as seen in pics above). We wanted to insure a complete coating up and over the previous sealer (seen in pics as the orange mountains around the patch).  While you are at it, take a look at the leading edge as there is a seam that has leaked on many planes and caused a bubbling of the exterior composite on the leading edge.

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When I did my wing seal I took a small space heater and got some 4" OD clothes dryer aluminum flex tube. Safety wired it onto the front of the small heater and then brought it up to the open fuel bulkhead port and It was a perfect fit. Then I  removed the gas cap. The air flowed from the bulkhead through the tank and out the fuel filler opening.  Then I turned the heater on low and let it cure for 3 days. Worked out well.

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On 2/17/2021 at 5:57 AM, Roger Lee said:

When I did my wing seal I took a small space heater and got some 4" OD clothes dryer aluminum flex tube. Safety wired it onto the front of the small heater and then brought it up to the open fuel bulkhead port and It was a perfect fit. Then I  removed the gas cap. The air flowed from the bulkhead through the tank and out the fuel filler opening.  Then I turned the heater on low and let it cure for 3 days. Worked out well.

Ingenious.

Good job, Roger.

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