# Here's a challenge

Discussion in 'Sheet Metal' started by PTAirco, Dec 30, 2009.

### Help Support HomeBuiltAirplanes Forum by donating:

1. Dec 30, 2009

### PTAirco

#### Well-Known Member

Joined:
Sep 21, 2003
Messages:
3,501
1,013
Location:
Corona CA
My local flight school just bent their Cessna 172RG, which was a really nice airplane to fly. Someone was doing touch&gos when they lifted the gear too soon, settled back down and the nosewheel collapsed. The mains stayed locked. Almost new engine and prop totalled, cowling bent, but the gear doors took the brunt of it. The plane was an insurance write-off, they bought it back and are hoping to fix it.
Here's the joke - Cessna wants $4300 for the gear doors. EACH!! None can be found at salvage places, anywhere. Knowing I mess with homebuilts, they gave them to me to see what could be done. They are a mess and only the hinges can be salvaged. Now, I think there is nothing that can't be done in metal, but this looks pretty tough. Compound curve outer skin. Matching inner skin with a stiffening bulge running down the center. Spot welded edges. 0.025" 2024. One could use an English wheel and a wooden buck to do the outer skin, but it won't work for the inner. One way to produce these from scratch would be to: Produce pattern/plug from wood to match the contour of the skin and the hole the doors cover. Modify the pattern to allow for springback. Make a concrete, female mold from the pattern, line with felt and beat the outer skins into it. Remove and planish. Make the stiffener bulges out of hardwood and lay into the mold in the correct position and beat the inner skin into it. Remove and planish that. Joining them by spot welding is a little tough for the home workshop. I guess you could dimple them and use flush rivets, since they don't interfere with anything. I am thinking I'd be nuts to attempt it, but considering their only alternative is$8,600, maybe I ought to give it a try, since anything less than that would be a bargain for them??

#### Attached Files:

File size:
72.8 KB
Views:
209
• ###### RGdoors2.jpg
File size:
86.8 KB
Views:
219
2. Dec 30, 2009

### Tom Nalevanko

#### Well-Known Member

Joined:
Oct 10, 2007
Messages:
1,316
132
Location:
Alpine, WY
I don't believe that it is legal for you to undertake this part replacement project. That said, you could fairly easily craft a set of composite doors from what you have...

3. Dec 30, 2009

### orion

#### Well-Known Member

Joined:
Mar 3, 2003
Messages:
5,800
135
Location:
Western Washington
Although this is not necessarily conclusive, i have been informed in the past that non-critical airframe items can be replaced, often times with non-certified components, as long as the new items are deemed satisfactory. Officially there is somewhat different wording involved but in general, non-critical items do not necessarily have to have certification. As an example, there is at least one company that is marketing and selling (legally) non-STC replacement gear doors for the Bonanza.

But here's the practical side of it - given the time and materials that will be needed to make a new set of doors, I'd hazard a guess that the $8400 price tag for the Cessna parts may not be as bad as you think. 4. Dec 30, 2009 ### Tom Nalevanko ### Tom Nalevanko #### Well-Known Member Joined: Oct 10, 2007 Messages: 1,316 Likes Received: 132 Location: Alpine, WY If you can find another RG, (always ask permission), put packing tape over the outside doors and lay up 4 or 5 BID of fiberglass, let it set, mark the contours and any other significant points, trim and use this model to make a composite or metal door using the hinges that you have. Not a big project; really. You have relatively LOTS to work from... Where are you located? I have several friends at KSZP who might give this a try... For a lot less than$8,400.

5. Dec 30, 2009

### PTAirco

#### Well-Known Member

Joined:
Sep 21, 2003
Messages:
3,501
1,013
Location:
Corona CA
It's not a replacement part - it's a repair! The hinges and brackets will be re-used. This is perfectly acceptable to the FAA. It is certainly a long way from the "jack up the data plate and slide a new airplane underneath" which people do all the time.

You can produce a lot more than people generally think. Owner produced parts are perfectly acceptable as long as they match the original drawings in every respect, but like I said, this would be basically a re-skinning job and would be signed off by the A&P working on it.

And yes, it would be a breeze to produce some composite doors for it! They actually look exactly like a composite piece, with an outer flush skin and a 1/2" foam core bonded to the inside . (I'm in Corona, CA by the way.)

As for $8000 plus that Cessna wants - sure that is reasonable if they employed some artisan with nothing more than a mallet and some tin snips, and he is taking three weeks to produce them. But Cessna simply pulls these from the press and stick them together -(actually they pull them form a shelf where they have been sitting since the last RG was made). Material cost? Maybe$40. Labor? 3 or 4 hours, or let's be generous and call it 6 hours - it's still daylight robbery.

6. Dec 30, 2009

### eric_marsh

#### Member

Joined:
Dec 28, 2009
Messages:
14
0
Location:
Lockhart, TX
How about taking them by a good auto body man?

7. Dec 30, 2009

### JimCovington

#### Well-Known Member

Joined:
Mar 30, 2009
Messages:
217
0
Location:
Burlington, VT
Your "always ask permission" phrase got me laughing - thinking about midnight mold making by flashlight at the local airport with Butch Cassidy bandannas over your nose...

8. Dec 30, 2009

### Tom Nalevanko

#### Well-Known Member

Joined:
Oct 10, 2007
Messages:
1,316
132
Location:
Alpine, WY
Actually the greater concern of 'permission' is whether you ask the FAA for permission or forgiveness. They are not real big on the former and don't believe in the latter. After all, they are not happy until you are unhappy... LOL

9. Dec 30, 2009

### BBerson

#### Well-Known MemberHBA Supporter

Joined:
Dec 16, 2007
Messages:
12,642
2,581
Location:
Port Townsend WA
Can you buy the formed skins only, from Cessna? Might be more reasonable than a complete door.

Last edited: Jan 2, 2010
10. Dec 30, 2009

### JimCovington

#### Well-Known Member

Joined:
Mar 30, 2009
Messages:
217
0
Location:
Burlington, VT
Ah, ok - that makes more sense. I got "ask permission from the airplane owner" in my head. Much more amusing.

11. Dec 30, 2009

### plncraze

#### Well-Known MemberHBA Supporter

Joined:
May 12, 2006
Messages:
1,684
376
Sometimes the aircraft manufacturers price things to discourage folks from ordering them. The market for Cardinal nose wheel well doors is probably pretty slim. A salvage yard might be able to get parts for you.

12. Jan 1, 2010

### MrHorsepower

#### Active Member

Joined:
Mar 23, 2006
Messages:
31
0
Try Wentworth salvage in Minneapolis. They always have lots and lots of used Cesna parts.

13. Jan 1, 2010

### Joe Kidd

#### Well-Known Member

Joined:
Apr 9, 2008
Messages:
192
1
Location:
Tennessee
Well, I’ve seen aluminum boats with worse damage repaired with great results and no parts replacement. I’m still learning welding and metal fabrication so my .02 cents worth of senseless advice are to try to do the repair as a learning experience. The mold ideal is excellent as a dimensional check but I’d fabricate a jig to straighten the doors in and weld tears. You’ll need a stick welder that spot welds tabs onto the metal for dent pulling (same tool body shops us) as well as one of the hydraulic pull sets. Harbor Freight carries these.
Once you’ve straightened everything and repaired the tears you can either pull the dimples or simply re-skin the panels with either a synthetic or metal cosmetic skin over the blemished piece. A lot of people can piece together aluminum with nearly invisible welds; I’m not one of them though. Hope this is a feasible suggestion for you.
Joe

14. Jan 2, 2010

### bmcj

#### Well-Known MemberHBA Supporter

Joined:
Apr 10, 2007
Messages:
13,166
5,080
Location:
Fresno, California
A diligent search of the internet will turn up a large number of aircraft salvage yards around the country. There used to be one at El Mirage dry lake (not too far from you), but I don't know if it is still there.

Bruce

15. Jan 2, 2010

### PTAirco

#### Well-Known Member

Joined:
Sep 21, 2003
Messages:
3,501
1,013
Location:
Corona CA
Apparently they tried just about every salvage yard in the country and they can't be had!

16. Jan 3, 2010

### Autodidact

#### Well-Known Member

Joined:
Oct 21, 2009
Messages:
4,513
799
Location:
Oklahoma
A 172 RG getting totaled W/O messing up the gear doors would have to be one of those "unusual" accidents :

#### Attached Files:

• ###### 6520g-runs-again0002.jpg
File size:
68.7 KB
Views:
166
17. Jan 3, 2010

### Othman

#### Well-Known Member

Joined:
Aug 23, 2004
Messages:
355
4
Location:
I would still question the legality of the job...

Even for a repaired part, the work needs to be done by a licensed A&P (which you might be, I don't know). Since the aircraft belongs to the flying club I assume it is commercially registered. If this were in Canada, the work would have to performed/signed out by an Approved Maintenance Organization (AMO)... I'm 99% sure the US system works the same way, but I don't remember the accornyms used. Basically the part has to have a "Serviceable" tag on it before it can legaly go on the aircraft (and not one you print yourself ).

Anyway, I recommend that you look into it a bit more before you waste your time making beautiful door stops.

18. Jan 3, 2010

### BBerson

#### Well-Known MemberHBA Supporter

Joined:
Dec 16, 2007
Messages:
12,642
2,581
Location:
Port Townsend WA
That's a cool photo. I guess the pilot is clutching his chest because the control yoke is largely nonfuntional.:grin:

19. Jan 3, 2010

### vortilon

#### Well-Known Member

Joined:
Jul 7, 2009
Messages:
453
5
Location:
Marana AZ USA
Too far gone for repair.

20. Jan 3, 2010

Joined:
Jul 7, 2009
Messages:
453