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A Rebuilder's Journal

The Mini-Nimbus Project
Part I - Inspection and Purchase

by David Cahoon

This is the first of a series of articles which will chronicle my purchase and restoration of a damaged sailplane.  Articles of this nature are quite common among the experiential and homebuilt aircraft groups, but seemed lacking in our sport.  Maybe we just like to fly ‘em.  I have been involved in both worlds as a member of the Experiential Aircraft Assoc. and the SSA.  Over the years I have had the opportunity to become involved in several restorations of classic aircraft and last year completed my first homebuilt, a Van’s RV-4.  The RV-4 is an all metal 160 hp. two place package of fun.  Along the way I earned my A&P Mechanics license.

Following completion of the RV-4 I decided to look for a sailplane project to rebuild or restore.  I would like to share with you my approach and experiences in this project.  One of the things learned from the RV-4 is that you can never ask too many questions nor can you read too much material in preparing for and caring out your project.  There is a world of material and people willing to help you achieve whatever you may set out to do.  Hopefully, this log will help someone.

The project that I chose is a Schempp-Hirth Mini-Nimbus.  The Mini is serial number 84 and was built in 1978.  It is a standard class  15M racer with carbon fiber wing with a listed L/D of 42:1.  I found mine listed in the classifieds of Soaring, it was located in Florida and had been damaged during an off field landing.  One wing had hit a fence post and the other had a deep cut from the barbed wire, the canopy was broken, but the fuselage was untouched.  The aircraft was licensed as experiential. 

The first step in deciding whether to purchase was to determine the extent of damage and whether it was in fact a rebuildable aircraft.  This was going to require a trip to Florida.  Before going, however, I decided to call upon my previous experience and begin asking questions.  I needed some advise on what to look for in inspecting a damaged sailplane.  The obvious is of course there.  What is unknown is what can get you.  Older mechanics will tell you that anything on an airplane can be fixed, it is just a matter of how much time and how much money you want to invest.  Somebody built it the first time and somebody can rebuild it.  For advise I called George Applebay and also talked with Mr. Gehrlein, both experienced rebuilders.  Initial photos of the damage was mailed to both, followed up by phone advise.

After looking at the photos, both advised that the spar was their major concern.  The spar  in this sailplane is build like an I beam, consisting of a vertical spar, a cap strip on top and bottom, and webbing to transition to the foam wing skins.  Both advised that if the breakage and/or cuts had not reached the webbing, that likely there was no spar damage.

Here are some of the things to look for in an inspection:

1. Find out how the accident happen, and draw a mental picture of the forces causing the damage.
   

2. Determine if there was any difficulty in the disassembly of the wings or tail surfaces.
   

3. Put the wings back on for yourself to make sure that the damage was not transferred to the connection points, frame, pin and control linkage.  If it all goes back on without problems then you know it was not bent.
   

4. Inspect the connections for cracks, misaligned bearings, support structure, cracks in the fibreglass surrounding the contact points, discoloration of the main spar beams, indication of damage.
   

5. Does the landing gear work, inspect for damage gear supports, freedom of movement, bent control rods.
   

6. Inspect for any cracks in the metal frame which provides the main support for the wing connection.  Any broken welds.  Carry a mirror and use it to see the back side of everything you inspect.
   

7. Mount the tailplane, inspect the connection pins.  Is anything cracked or stressed, whether fibreglass or metal.

8. Take a close look at the logbooks.  Are all AD’s complied with, has there been any damage repaired in the past.  Are all of the required documents available?  Registration, Airworthiness Certificate, Weight and Balance, Operating Manual.  You will need them to get the aircraft registered  and re-licensed. 
   

9. Will the canopy open and close.  Does the release work.  Radios, Varios.  You can do some condition determination just by installing a battery and trying them out.
   

10. Finally, if you are in doubt, call in some help.  It is not likely that the ship will be sold out from under you.  Get an answer or at least know the down side if your suspicions are correct.  Get on the phone and price some parts, make a list and see if you can get the parts for what you think.  Some items like the canopy, will knock your socks off.  Fibreglass, resin, gel coat and paint are not cheap, but at least they are reasonable.  It you make the deal, be sure you leave with all the pieces, even the broken ones.  You never know what you may can fix or rebuild if only you had a pattern.

The next step was to travel to Florida and make the inspection.  In additional to the above checks I was very concerned about the spars.  However, after laying the wings out, taking flashlight and mirror, I found no problems.   Before leaving home I had a title search completed.  This is very important in any aircraft purchase to determine first, who is the owner and second, whether there are any liens against the project.  I made my deal, assembled all the parts and headed for home.

During the process of making the inspection and learning what was going to be involved, I had gotten an estimate on the wing repair.  It turned out to be quite reasonable and so I decided to deliver the wings to Applebay’s in New Mexico.  This would speed up my project and give me some real assurance that all was fine with the wings.  This is another lesson on rebuilding.  You may find a project that looks over your head, but realize that some of the more difficult items can be farmed out to more experienced repairmen.  It just takes some shopping and research.

Here are some of the initial photos of the sailplane:

The canopy is clearly gone, but no major damage was shown.  Other photos showed no damage to the remainder of the fuselage or tail section.  Canopies can be replaced!  If I had found a broken tail boom I would have moved on.

This photos show the damage to the left wing caused by the barbed wire.  The question to determine was whether the spar was involved.  Repairing the cut to the skins is a can do.

However one big hole was more than I wanted to tackle without some expert assistance.  Again, the question was spar damage

After deciding to let Applebay Aviation make the wing repairs, I turned my attention to the fuselage.  While there was little damage, only some scrapes and the damaged canopy, the gel coat was crazed all over.  The gel coat needed to be taken off and redone.