Access Hatches
07-06-2003, 02:48 AM
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Access Hatches
Hi,
I am going to be doing my first ever fiberglass & paint job on a GP P-51. I am using a YS .63 mounted inverted. I would like to put an access panel on the top of the cowl to be able to access the regulator and the mounting bolts. The question I have is, do I do all my glass work first and then cut in the access opening, or do I build the access hatch and then do my glass work? I want the fit to be very tight so it won't look bad.
If anybody has any pics of how they did access hatches, I'd be most greatful to see them.
Thanks for any suggestions and any help you experts can give me.
Doug
I am going to be doing my first ever fiberglass & paint job on a GP P-51. I am using a YS .63 mounted inverted. I would like to put an access panel on the top of the cowl to be able to access the regulator and the mounting bolts. The question I have is, do I do all my glass work first and then cut in the access opening, or do I build the access hatch and then do my glass work? I want the fit to be very tight so it won't look bad.
If anybody has any pics of how they did access hatches, I'd be most greatful to see them.
Thanks for any suggestions and any help you experts can give me.
Doug
07-07-2003, 06:43 PM
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Access Hatches
7th Angel:
After that I don't know if I should reply at all.
Remember please, an "Ex" is a has-been, and "Spurt" is a drip under pressure! Calling me a "Has-been Drip!" Really, now! And you want me to tell secrets?
Haw.
Minn is the Real "Ex-Spurt" here, look at his excellent graphics for proof.
Sorry for the delay, I've been looking at the finally released info on the merger. I've been working on it myself so it wasn't new to me, but I wanted to see the comments of others.
And don't give up hope, this has turned into a larger post than I had anticipated, I'm writing it off-line. I'll post it when I'm finished.
Bill.
Bill is an expert...
Remember please, an "Ex" is a has-been, and "Spurt" is a drip under pressure! Calling me a "Has-been Drip!" Really, now! And you want me to tell secrets?
Haw.
Minn is the Real "Ex-Spurt" here, look at his excellent graphics for proof.
Sorry for the delay, I've been looking at the finally released info on the merger. I've been working on it myself so it wasn't new to me, but I wanted to see the comments of others.
And don't give up hope, this has turned into a larger post than I had anticipated, I'm writing it off-line. I'll post it when I'm finished.
Bill.
07-08-2003, 05:32 AM
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Fiberglass hatches.
7thAngel:
Making hatches. Let's see if I can paint a word picture good enough for Minnflier to come back with one of his great illustrations.
Goal:
1) A close fitting hatch, both for looks and aerodynamic advantage.
2) Easily opened and closed
3) Secure when closed, and well sealed.
4) Sturdy, and not prone to chipping on the edges.
These aims can be attained, all the way to waterproof if desired.
From this point the quality of the finished hatch depends entirely on how much trouble you want to take with it.
The easiest method is to cut the hatch out of the airframe, fabricate a shelf or flange on the inside to support the hatch, and the work is done. But this leaves a surrounding gap the size of your saw kerf. With a thin saw this won’t be too bad, as the paint will fill part of it. The nastiest part about this method is the corners of the hatch, they will be sharp and easily damaged.
A much better method, although a lot more work, is to make a new part to be the hatch door.
It’s not as hard as you might think. If you made the fuselage, wing, or whatever you still have the mold. Hopefully you had the panel or hatch outline in the mold, this will give you a cutting line for the hatch, and when you lay up the glass and resin for the new hatch door you will see the outline of the hatch, and know where to start cutting.
If you bought the fuselage ready made, and it has the lines molded in, it’s almost as easy, you just have to make a female mold for your new door. Use the fuselage as a “Plug,” lay up four or five layers of ‘glass and resin, pull it off, and lay up the new door. If the panel lines are not molded in, very carefully scratch them in. To do this the best tool I’ve found is a Plexiglas cutter. Not an ordinary glass cutter, a Plexi cutter is designed to scrape a groove in the material. If you keep this groove just inside the finished size of the hole you wont have any filling to do when you are finishing up. Once you have grooved it, make the mold, and then the new door. When you lay the door up, be sure the cloth is at least ¼” bigger than the finished size all around. If you can’t get to the inside of the fuselage easily where the hatch will go, make the overlap at least ½” bigger. Also, make it as close to the thickness of the fuselage as you can.
Making the shelf/flange can be a pain, or it can be easy. If you have access to the inside where the hatch will go, it’s easy. Skip the next step.
If you don’t have easy access to the inside where the hatch will go, we need to make the flange before the new door is taken out of its mold. Lay up the flange directly on the back of the door, when cured mark the door and the flange so you will know which way it fits. Pop it off and trim the edges. Set it aside for the moment.
Now make the hole in the fuselage, trim and finish the edges. Lay two or three layers of glass around the edges of the door, Position the added ‘glass so that you will have a reinforcement about ¼” wide after fitting the door. Cut the door to size, using your mold marks from the grooves you made in the fuselage as a guide. Trim it to fit, be careful, ideally you’ll make it fit well enough that friction will hold it in place. This should give you as close to zero gap as you can get.
Now we get to the big difference between internal access and no internal access.
If you have internal access put the door in place, using tape to hold it in place. On the inside lay up glass and resin to form the flange. Use at least two layers, I’m happier with three or four unless I have worries about total weight. On this lay up you want the mold release only on the door, of course. When it has cures pop the door out, trim the inside of the flange, and you have a nicely fitted door all done.
Without internal access. Get the flange you molded against the door, recheck the fit against the door. It’s almost certain you’ll have to do some trimming since we put the reinforcement on the door. When you have it fitting nicely, lay some more cloth on the face, outside of the area where the door seats, to add the thickness of the reinforcement. When it looks about right work it inside the fuselage, through the hatch, and trim or sand the part that will fit against the inside of the fuselage to get as good a match as you can.
Glue it in temporarily with a couple drops of CA. Wont hold well, but that’s good,
Then check the door fit again. If it wont fit down flush you are ready for the final step. If the door drops below the surface you need to thin the cloth you just added. Ideally the door will be just slightly out from the fuselage surface all around.
Take the door out and pop the flange free. Clean the inside of the fuselage where the flange will fit, and the mating surface of the flange. Steal a long balloon from your kid, mix some filled epoxy. Put a narrow bead of the epoxy around the mating surface of the flange, put it back inside the fuselage. You did mark it to know which way it goes, didn’t you? Put the door in place, and tape it firmly. Stick the balloon inside the fuselage, blow it up, and tie it shut. The balloon’s your clamp. Except for the mounting screws, or hinges and latch, you are finished as soon as this last epoxy cures.
Hope this helps, if you want anything about screwing it down or hinging an latches, come back for more.
Bill.
Attached picture is the right nacelle of my TiggerKitty, showing the hatch for tank and gear access. And yes, the blue pipe to the left of center is the engine exhaust. Plane is about ten years old.
Making hatches. Let's see if I can paint a word picture good enough for Minnflier to come back with one of his great illustrations.
Goal:
1) A close fitting hatch, both for looks and aerodynamic advantage.
2) Easily opened and closed
3) Secure when closed, and well sealed.
4) Sturdy, and not prone to chipping on the edges.
These aims can be attained, all the way to waterproof if desired.
From this point the quality of the finished hatch depends entirely on how much trouble you want to take with it.
The easiest method is to cut the hatch out of the airframe, fabricate a shelf or flange on the inside to support the hatch, and the work is done. But this leaves a surrounding gap the size of your saw kerf. With a thin saw this won’t be too bad, as the paint will fill part of it. The nastiest part about this method is the corners of the hatch, they will be sharp and easily damaged.
A much better method, although a lot more work, is to make a new part to be the hatch door.
It’s not as hard as you might think. If you made the fuselage, wing, or whatever you still have the mold. Hopefully you had the panel or hatch outline in the mold, this will give you a cutting line for the hatch, and when you lay up the glass and resin for the new hatch door you will see the outline of the hatch, and know where to start cutting.
If you bought the fuselage ready made, and it has the lines molded in, it’s almost as easy, you just have to make a female mold for your new door. Use the fuselage as a “Plug,” lay up four or five layers of ‘glass and resin, pull it off, and lay up the new door. If the panel lines are not molded in, very carefully scratch them in. To do this the best tool I’ve found is a Plexiglas cutter. Not an ordinary glass cutter, a Plexi cutter is designed to scrape a groove in the material. If you keep this groove just inside the finished size of the hole you wont have any filling to do when you are finishing up. Once you have grooved it, make the mold, and then the new door. When you lay the door up, be sure the cloth is at least ¼” bigger than the finished size all around. If you can’t get to the inside of the fuselage easily where the hatch will go, make the overlap at least ½” bigger. Also, make it as close to the thickness of the fuselage as you can.
Making the shelf/flange can be a pain, or it can be easy. If you have access to the inside where the hatch will go, it’s easy. Skip the next step.
If you don’t have easy access to the inside where the hatch will go, we need to make the flange before the new door is taken out of its mold. Lay up the flange directly on the back of the door, when cured mark the door and the flange so you will know which way it fits. Pop it off and trim the edges. Set it aside for the moment.
Now make the hole in the fuselage, trim and finish the edges. Lay two or three layers of glass around the edges of the door, Position the added ‘glass so that you will have a reinforcement about ¼” wide after fitting the door. Cut the door to size, using your mold marks from the grooves you made in the fuselage as a guide. Trim it to fit, be careful, ideally you’ll make it fit well enough that friction will hold it in place. This should give you as close to zero gap as you can get.
Now we get to the big difference between internal access and no internal access.
If you have internal access put the door in place, using tape to hold it in place. On the inside lay up glass and resin to form the flange. Use at least two layers, I’m happier with three or four unless I have worries about total weight. On this lay up you want the mold release only on the door, of course. When it has cures pop the door out, trim the inside of the flange, and you have a nicely fitted door all done.
Without internal access. Get the flange you molded against the door, recheck the fit against the door. It’s almost certain you’ll have to do some trimming since we put the reinforcement on the door. When you have it fitting nicely, lay some more cloth on the face, outside of the area where the door seats, to add the thickness of the reinforcement. When it looks about right work it inside the fuselage, through the hatch, and trim or sand the part that will fit against the inside of the fuselage to get as good a match as you can.
Glue it in temporarily with a couple drops of CA. Wont hold well, but that’s good,
Then check the door fit again. If it wont fit down flush you are ready for the final step. If the door drops below the surface you need to thin the cloth you just added. Ideally the door will be just slightly out from the fuselage surface all around.
Take the door out and pop the flange free. Clean the inside of the fuselage where the flange will fit, and the mating surface of the flange. Steal a long balloon from your kid, mix some filled epoxy. Put a narrow bead of the epoxy around the mating surface of the flange, put it back inside the fuselage. You did mark it to know which way it goes, didn’t you? Put the door in place, and tape it firmly. Stick the balloon inside the fuselage, blow it up, and tie it shut. The balloon’s your clamp. Except for the mounting screws, or hinges and latch, you are finished as soon as this last epoxy cures.
Hope this helps, if you want anything about screwing it down or hinging an latches, come back for more.
Bill.
Attached picture is the right nacelle of my TiggerKitty, showing the hatch for tank and gear access. And yes, the blue pipe to the left of center is the engine exhaust. Plane is about ten years old.
07-08-2003, 08:33 PM
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Access Hatches
Hi Bill,
Thank you for taking the time to post a very informative response to my question! I think I've got the idea now and I'll be able to make it work.
Thanks Bill and MinnFlyer for your help! I really appreciate it!
Doug
Thank you for taking the time to post a very informative response to my question! I think I've got the idea now and I'll be able to make it work.
Thanks Bill and MinnFlyer for your help! I really appreciate it!
Doug
07-08-2003, 08:39 PM
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Access Hatches
For the application you mentioned, it seems like a whole lot of trouble for little if any gain. I have NEVER had any reason to access the regulator on my YS .63. It is properly set when it comes in the box, i.e. flush with the engine case. Messing around with the regulator settings is sure to cause problems.
