experimentals
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Join Date: Oct 1999
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experimentals
I bought a wreck of an amphibian homebuilt because it had a nice Lycoming, for spares, but maybe I can get it flying. I do not know much though about composites, can anyone help me with the following questions?
The airplane landed last time it flew with a fault in the nosegear, which retracted and the wheel broke off. There was damage to the hull due to rubbing on the gravel strip during the rollout, and the wheel itself came up through the hull, breaking the plies right through (it is a double hull composite fuselage with foam between the plies).
The keel seems to me to have been reinforced with a wood rubbing strip, which is now mainly gone, leaving a ragged section right in the middle. The damage here is restricted to the outer plies, I can see the inner hull and frames and there is no damage showing on the inside and I doubt water would leak through as it is right now (some people have landed this airplane with gear up on bitumen and grass with no damage, although this was a gravel strip and it has abraded the bottom chine). I would have a great deal of difficulty replacing the wood, which was set in place before gluing up, and I was wondering if I could, since it is right on the bottom of the hull and I would be working on my back underneath the airplane, fill the keel with Bondo or similar. I could make it fairly stiff to stop it falling out as it cured, and I thought it would be as tough as the wood when it was finished, especially when I put a couple of layers of glass over it. I could also shape the Bondo before glassing to restore the original sharp edge.
The other damage where the wheel punched a hole looks straight forward, I plan to cut the damaged area out and put a patch on the inner and outer hulls, faired in as well as I can on the outer particularly, to retain the smoothness for running on water. But it must be strong enough to take a landing. Maybe I can fair it with filler to make it efficient on the water, and since it is on the bottom I doubt it will affect flying characteristics. Does anyone know if I can patch a composite with fibreglass? It was built this way, so I assume so, but there is always something out there to catch the unwary.
I will have a Mechanic look at it before I fly it, but want to do the work myself, as experience as well as cost saving.
Aluminium and wood don't frighten me, but plastic is a new field. Any advice would be appreciated, as always!
The airplane landed last time it flew with a fault in the nosegear, which retracted and the wheel broke off. There was damage to the hull due to rubbing on the gravel strip during the rollout, and the wheel itself came up through the hull, breaking the plies right through (it is a double hull composite fuselage with foam between the plies).
The keel seems to me to have been reinforced with a wood rubbing strip, which is now mainly gone, leaving a ragged section right in the middle. The damage here is restricted to the outer plies, I can see the inner hull and frames and there is no damage showing on the inside and I doubt water would leak through as it is right now (some people have landed this airplane with gear up on bitumen and grass with no damage, although this was a gravel strip and it has abraded the bottom chine). I would have a great deal of difficulty replacing the wood, which was set in place before gluing up, and I was wondering if I could, since it is right on the bottom of the hull and I would be working on my back underneath the airplane, fill the keel with Bondo or similar. I could make it fairly stiff to stop it falling out as it cured, and I thought it would be as tough as the wood when it was finished, especially when I put a couple of layers of glass over it. I could also shape the Bondo before glassing to restore the original sharp edge.
The other damage where the wheel punched a hole looks straight forward, I plan to cut the damaged area out and put a patch on the inner and outer hulls, faired in as well as I can on the outer particularly, to retain the smoothness for running on water. But it must be strong enough to take a landing. Maybe I can fair it with filler to make it efficient on the water, and since it is on the bottom I doubt it will affect flying characteristics. Does anyone know if I can patch a composite with fibreglass? It was built this way, so I assume so, but there is always something out there to catch the unwary.
I will have a Mechanic look at it before I fly it, but want to do the work myself, as experience as well as cost saving.
Aluminium and wood don't frighten me, but plastic is a new field. Any advice would be appreciated, as always!
Join Date: Dec 2000
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sounds like it possible to repair, but i would not use Bondo! its heavy, prone to cracking , and absobes moisture= more weight and leads to rapid corrosion/rotting etc. from what i have read, its best to fill the areas using multiple layers of fibreglass
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I'd suggest you call a local gliding club (www.gliding.co.uk will give you contact details) and ask for names of local glider repair specialists.
They work day in/day out with composite aircraft, and understand what's cosmetic and what's structural. Also, I'm pretty certain (glider pilot but not repairer) that fixing double-skinned composite hulls with a foam core is not a job for the amateur. Many gliders use this form of construction, so you'd likely be speaking to an expert.
My experience with glider repairers is that they are happy to give initial estimates and are usually concerned to keep your costs down.
I forgot to add that I think that double skinning with a foam core means that section is structural. However, I would ask an expert.
They work day in/day out with composite aircraft, and understand what's cosmetic and what's structural. Also, I'm pretty certain (glider pilot but not repairer) that fixing double-skinned composite hulls with a foam core is not a job for the amateur. Many gliders use this form of construction, so you'd likely be speaking to an expert.
My experience with glider repairers is that they are happy to give initial estimates and are usually concerned to keep your costs down.
I forgot to add that I think that double skinning with a foam core means that section is structural. However, I would ask an expert.
You might want to see if the manufacturer/designer has any approved structural repairs for the thing before you get too far into it. There is a good chance the keel is the primary structure for the hull. You also may be able to get the drawings for the machine and figure out if you can ndeed splice in repair pieces for this.
As far as doing real repairs on composites, they are not that hard, you just need the materials and tooling. A great resource for this is Aircraft Spruce, in addition to the supplies you will need, they also have some good reference materials regarding composite build/repair.
As far as doing real repairs on composites, they are not that hard, you just need the materials and tooling. A great resource for this is Aircraft Spruce, in addition to the supplies you will need, they also have some good reference materials regarding composite build/repair.
Join Date: Jan 2003
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I fly an amphibian with fibreglass hull over an Al tube frame.
Firstly you don't tell us exactly how the plane is constructed so it is difficult to know what to tell you, but in general terms:
Even in my plane the "non structural" fibre glass hull has structural application, a) stiffness, b) Keeping the water out, c) keeping the passengers in. It is not safe to believe that areas are non structural if you do not thoroughly understand the design and construction.
Repairing cored fibreglass requires specific technique. The areas to be repaired needs to be cut out and repaired in particular way for proper integrity. Again it is not specially difficult but it needs to be right. You can do it easily but if you have not done it before then you should visit a local specailist and let them tell you how.
The keel area needs to be structurally sound and watertight, rebuild it before you add another keel guard.
Micro baloons are used in boatbuilding for fairing (making smooth) rather than bondo, It is too heavy and does not act as an efficient seal. If you are proficient with other media, wood, metal etc, you should enjoy fibre glass however if you have not used it before i find out how first, either get a book and make a couple of practice pieces or go and ask a local fabricator if you can hang around and watch them do it, even help out a day or two.
Obviously working on a plane is a little different to working on a car or boat because weight is so important. You can't just build stuff up with loads of material, so again, it has to be done right.
Finally, if you have not flown off water it is absolutely vital you get training. It is not the same as land flying, much scarier and a good deal riskier to the uninitiated.
Firstly you don't tell us exactly how the plane is constructed so it is difficult to know what to tell you, but in general terms:
Even in my plane the "non structural" fibre glass hull has structural application, a) stiffness, b) Keeping the water out, c) keeping the passengers in. It is not safe to believe that areas are non structural if you do not thoroughly understand the design and construction.
Repairing cored fibreglass requires specific technique. The areas to be repaired needs to be cut out and repaired in particular way for proper integrity. Again it is not specially difficult but it needs to be right. You can do it easily but if you have not done it before then you should visit a local specailist and let them tell you how.
The keel area needs to be structurally sound and watertight, rebuild it before you add another keel guard.
Micro baloons are used in boatbuilding for fairing (making smooth) rather than bondo, It is too heavy and does not act as an efficient seal. If you are proficient with other media, wood, metal etc, you should enjoy fibre glass however if you have not used it before i find out how first, either get a book and make a couple of practice pieces or go and ask a local fabricator if you can hang around and watch them do it, even help out a day or two.
Obviously working on a plane is a little different to working on a car or boat because weight is so important. You can't just build stuff up with loads of material, so again, it has to be done right.
Finally, if you have not flown off water it is absolutely vital you get training. It is not the same as land flying, much scarier and a good deal riskier to the uninitiated.
