Thursday, May 24, 2007
The canopy is attached to the frame
Lots or work still to do on the canopy, but at least it is securely attached to the frame at this stage.
Wednesday, May 23, 2007
What have I learned so far about Sikaflex?
The canopy - see the previous blog entry - is now glued and the clamps removed. Pictures to follow.
What have I learned so far:
1. The -4 canopy is a very difficult shape to work with in order to get a good cosmetic finish. Perhaps my gun is to big! Having said this my confidence has already risen to the point that there is no way I would consider riveting it. I will sort the cosmetics of the bead line later.
2. The cleaner, -226, is a very efficacious liquid. It can find 'dirt' on surfaces I considered clean. Etch primer disappears with the utmost ease.
3. The primer, -209N, is slightly unusual to work with in that you can feel it grip the metal as you brush it on. Beware of one thing, it can spatter and I got one tiny blob onto a small area of Plexiglas that had escaped masking. It cleaned up easily with the cleaner but I would not want to have left it without attention.
4. The -295UV squirts out of the gun quite easily and it is NOT a material that is prone to sag. It largely goes where you put it. Where I found it quite difficult was getting a clean looking line when I finished it with a spatula. My difficulties were compounded by the fact that I perhaps removed the masking tape to get a sharp line, a little early. Removal sometimes had the effect of rippling the otherwise good surface. I can attend to all these issues once the material has cured, plus fill in the areas between the clamps and spacers.
5. Have more rubber gloves than you think you will need standing by. I have no idea but would guess I used 30 or 40 pairs in the space of two hours. They are cheap!
What I would like to know:
My outstanding question is what is the best way to fill in the voids where the clamps were, and how to add more Sikaflex on top of yesterday's Sikaflex? Should I remove old primer and put on new where the old is showing, or should I put primer on top of old primer after cleaning again? Should I put a layer of primer on old Sikaflex after cleaning, when I want to add more Sikaflex. I have not read anything about this yet, nor had a reply to my email to Sikaflex. Anyone know these answers?
What have I learned so far:
1. The -4 canopy is a very difficult shape to work with in order to get a good cosmetic finish. Perhaps my gun is to big! Having said this my confidence has already risen to the point that there is no way I would consider riveting it. I will sort the cosmetics of the bead line later.
2. The cleaner, -226, is a very efficacious liquid. It can find 'dirt' on surfaces I considered clean. Etch primer disappears with the utmost ease.
3. The primer, -209N, is slightly unusual to work with in that you can feel it grip the metal as you brush it on. Beware of one thing, it can spatter and I got one tiny blob onto a small area of Plexiglas that had escaped masking. It cleaned up easily with the cleaner but I would not want to have left it without attention.
4. The -295UV squirts out of the gun quite easily and it is NOT a material that is prone to sag. It largely goes where you put it. Where I found it quite difficult was getting a clean looking line when I finished it with a spatula. My difficulties were compounded by the fact that I perhaps removed the masking tape to get a sharp line, a little early. Removal sometimes had the effect of rippling the otherwise good surface. I can attend to all these issues once the material has cured, plus fill in the areas between the clamps and spacers.
5. Have more rubber gloves than you think you will need standing by. I have no idea but would guess I used 30 or 40 pairs in the space of two hours. They are cheap!
What I would like to know:
My outstanding question is what is the best way to fill in the voids where the clamps were, and how to add more Sikaflex on top of yesterday's Sikaflex? Should I remove old primer and put on new where the old is showing, or should I put primer on top of old primer after cleaning again? Should I put a layer of primer on old Sikaflex after cleaning, when I want to add more Sikaflex. I have not read anything about this yet, nor had a reply to my email to Sikaflex. Anyone know these answers?
Added 20 June '07. I am nearly finished with the Sikaflex now. To answer my own question, experience tells me this. For cosmetic additions, to bond Sikaflex to itself use the primer. If it is a structural bond onto metal or Plexi, remove old primer and add new.
Finally, in case you have not already found the main link to previous offenders experience start here. http://www.matronics.com/wiki/index.php?title=Gluing_Your_Canopy&redirect=no
Sunday, May 20, 2007
Setting up to glue the canopy
The canopy has been trimmed with 1/8th inch spacers installed, to allow for Sikaflex in the joints. Compared with the -9A I built, there is very little excess material on the RV4 canopy. It would not be a problem if I planned to rivet it on, but since it is to be glued, I had to be very cautious in the area to the left/right of the pilots shoulders.
A final test fit on top of the fuselage seemed appropriate. In fact I have still not trimmed quite enough off at the rear of the canopy, but that is intentional. I intend to do that when the structure is glued together, in order (hopefully) to get a very tight fit between the plexi and the fuse skin.
I have made a 'gallows' to hang it on while I work. All the other RV canopies allow you to walk in at the end for gluing, but the -4, being one piece requires you to have it held quite high if you want to work on it the right way up. At this stage I am unfamiliar with the properties of the Sikaflex so in case it sags feel I will have much better control with it this way up.NB AS you can see in this picture its a gallows with a heater! Got to keep the victim warm!
Thursday, May 10, 2007
Canopy frame and latch mechanism.
(As always, you can get larger pictures by double clicking on them.)
With a lot of encouragement to keep tweaking the front bow, and not split it, (from VANSAIRFORCE members), I have finally made the frame fit reasonably well. The latch mechanism is mostly complete, though I still have to install the UHM blocks. It becomes a lot easier once you realise there is no reason why the push rods should not be slightly bent.
The canopy frame needed a little grinding to allow it to fit over the roll bar in several places. You can see an example here.
I recently had the role bar powder coated. Needless to say I also had to cut a part of that away as you see in this picture in order to allow the canopy bulkhead to come fully down.
I have used the spring from the RV9A release mechanism, rather than the one VANS provided for the -4. It is a similar stiffness, but the slightly greater length seemed preferable. There is so much friction in the system at the moment that it is quite incapable of closing the mechanism, though I guess its purpose is to stop it from wandering open.
Now I need to think about VANS safety latch, and how to fit a gas strut.
With a lot of encouragement to keep tweaking the front bow, and not split it, (from VANSAIRFORCE members), I have finally made the frame fit reasonably well. The latch mechanism is mostly complete, though I still have to install the UHM blocks. It becomes a lot easier once you realise there is no reason why the push rods should not be slightly bent.
The canopy frame needed a little grinding to allow it to fit over the roll bar in several places. You can see an example here.
I recently had the role bar powder coated. Needless to say I also had to cut a part of that away as you see in this picture in order to allow the canopy bulkhead to come fully down.
I have used the spring from the RV9A release mechanism, rather than the one VANS provided for the -4. It is a similar stiffness, but the slightly greater length seemed preferable. There is so much friction in the system at the moment that it is quite incapable of closing the mechanism, though I guess its purpose is to stop it from wandering open.
Now I need to think about VANS safety latch, and how to fit a gas strut.
