Got the left main ribs primed, and thanks to a streak of warm weather during my vacation, the right main ribs are a little more than half done as well. I bought some more NAPA 7220 primer, and should be able to finish the main rib priming task tomorrow.
I also want to take a moment to recognize yet another roller coaster moment for the year 2013, which just refuses to go out quietly for me. We have some good friends in California who have a little girl who had received a heart transplant when she was just a baby. Unfortunately we were informed about a year or so ago that her heart was failing, and she was in need of yet another heart transplant. Only a few days ago the wheels for this wre suddenly set into motionand she has since received a new heart, and the latest word is that all is well and she is up, walking, talking, eating, and doing all those things that the rest of us take for granted. There is still an uphill battle to fight to ensure that it will not be rejected, but so far things are looking good. My thoughts and prayers are with you and your family Jessica!
Perhaps a glimmer of sunlight on what has otherwise been a rather dark and difficult year for me. Here's to hoping that 2014 brings better times to all of us....
Monday, December 30, 2013
Saturday, December 28, 2013
Finally Priming Some Wing Ribs!
2.75 cans of NAPA 7220 primer and a small but potent amount of acetone later, I almost have all of the left wing main ribs primed. The final stage of the cleaning process was the acetone. This is where you have to be careful when you are dealing with a lot of similar looking parts. Up to this point I have been very careful to keep all the left and right wing parts together by labeling them with my blue Sharpee pen, in the proper order that they were fitted to the wing spar and drilled for riveting. There are 28 of these ribs in total, and it is important to keep the installation order in tact all the way through the priming process.
The only problem is, once you get to the acetone cleaning stage, you will remove any Sharpee markings or labels that you have written on each part to keep them properly organized. This is where I get the most worried that I will mix up the sequence of the ribs. Once the markings are erased from the metal the only way to tell which one is which is to remember the order in which you stack them. Then,when the time comes to lay them out for pirming, you REALLY need to have a method in mind to keep track of the parts. I chose to lay the ribs on my new priming table from a top to bottom, left to right fashion. The following pic is taken from the opposite direction from the reference position I use to keep track of the parts, so the number 1 most inboard wing rib is actually on the bottom right of this pic:
And here is a pic of the fully primed end ribs for both wings with the support angles reattached. I set the angles on the workbench and then set the front flanges on the bench next to each angle bracket to ensure that the support angles would be flush with the flanges of the rib to make sure that the attach bracket is as straight and true to the orientation of the rib as possible. This becomes important when checking the wing assembly for any twist or bend while it is on the wing stand. I wanted to make sure that a slight angle to the support angle bracket would not introduce any unwanted twist to wing, so the support angle and the forward flange of the rib needed to be flush with each other.
These end ribs will not be riveted to the main wing spar initially since the leading edge rib on the end must also be riveted in assembly with the main rib. All the other LE ribs are offset from the main ribs just a bit to aid in riveting. I have not attached them to the wing spars yet because I also have some minor scratches and dings in the main wing spar that need to be dressed, smoothed, cleaned and primed. After consulting with Vans about these a long time ago, they decided that these were most likely just surface scratches from shipping, and as long as I don't need to remove much material from the spar web I should be able to fix them and move on. I will admit, however, that the recent loss of our EAA Chapter 43 president in his plane has given me cause for some concern about my wing spars. It appears that this accident may have been been the result of a catostrophic wing spar failure, but we are still waiting for the NTSB reports.
I need to get some more primer tomorrow so I can continue with the right wing ribs. I also did some research to confirm something about the riveting process for the main ribs to the wing spars. It seems that the Vans instructions simply tell you to rivet the ribs to both spars when the time comes. Others have cautioned that it is easier to rivet only to the the main wing spar first, so that you can spread the ribs out to get a standard straight rivet set into position while lightly bending the rib flange out of the way of the rivet gun. If you rivet the ribs to the rear spar as you go, you no longer have the capability to spread the forward flanges out as described, making a bit harder to rivet the ribs together - especially the ones nearest the root, which are much closer together to support the added weight and loads of the pilot and passenger entering and exiting the airplane.
This has certainly been a long time coming, and it felt good to get back to working on the plane, especially when you know you are getting close to being able to rivet things together. I can't say that I enjoy putting on the chemical breathing mask every time I have to do this, or breathing acetone fumes, but in the end it is just part of the process of building an airplane so you just have to accept it and move on.
The only problem is, once you get to the acetone cleaning stage, you will remove any Sharpee markings or labels that you have written on each part to keep them properly organized. This is where I get the most worried that I will mix up the sequence of the ribs. Once the markings are erased from the metal the only way to tell which one is which is to remember the order in which you stack them. Then,when the time comes to lay them out for pirming, you REALLY need to have a method in mind to keep track of the parts. I chose to lay the ribs on my new priming table from a top to bottom, left to right fashion. The following pic is taken from the opposite direction from the reference position I use to keep track of the parts, so the number 1 most inboard wing rib is actually on the bottom right of this pic:
It became apparent rather quickly that my new table will only hold 12 of the 13 additional ribs I needed to prime. I already primed the two end ribs. Regardless, the new table did what I expected it to do, and it was nice to be able to setup a lot of parts for priming all at once. I have found that the key to doing something like this is to be prepared to do the entire job in one session. That means allowing enough time to prime one side, drying, then flipping them over and priming the other side - all in one single work session. That way you do not forget the order that the parts are set on the table. I have also found that in cases where you are dealing with lots of parts for both left and right side assemblies, it is best to do one side and finish the entire process for those parts, before trying to work on any of the parts for the other side. This prevents me from mixing up the left and right side parts. Everyone has their own method to handle this, but it is always the last step in the process prior to actually being able to rivet things together. As such it is a very important part of the entire preparation process that you must figure out ahead of time to avoid confusion, or worse yet, the possibility of riveting the wrong part in the wrong place later on.
Here is a shot of the smaller table I have used in the past with the 13th rib:
I need to get some more primer tomorrow so I can continue with the right wing ribs. I also did some research to confirm something about the riveting process for the main ribs to the wing spars. It seems that the Vans instructions simply tell you to rivet the ribs to both spars when the time comes. Others have cautioned that it is easier to rivet only to the the main wing spar first, so that you can spread the ribs out to get a standard straight rivet set into position while lightly bending the rib flange out of the way of the rivet gun. If you rivet the ribs to the rear spar as you go, you no longer have the capability to spread the forward flanges out as described, making a bit harder to rivet the ribs together - especially the ones nearest the root, which are much closer together to support the added weight and loads of the pilot and passenger entering and exiting the airplane.
This has certainly been a long time coming, and it felt good to get back to working on the plane, especially when you know you are getting close to being able to rivet things together. I can't say that I enjoy putting on the chemical breathing mask every time I have to do this, or breathing acetone fumes, but in the end it is just part of the process of building an airplane so you just have to accept it and move on.
Friday, December 27, 2013
(Think Musically from your Childhood) - This is the Way We Wash Our Parts, Wash Our Parts, Wash Our Parts..........
Due to the unseasonably warm weather over the holiday week here in Denver, and the fact that I managed to take some much needed time off from work, it was time to get back to business in the airplane factory once again. Those of you who have followed my blog in the past have undoubtedly read the following phrase many times: "Wash, Rinse, Repeat.."
Well this time I mean it quite literally. Today was washing day - not for my clothes, and not for my car (although both are sorely needed) - but for my wing ribs that have been sitting patiently in their scuffed up state, just waiting for final preparation steps to be taken to get them all cleaned and primed. The mission for today was to wash all of the main wing ribs for both wings (28 in all) with my usual mix of warm water and regular Dawn dishwashing liquid. I also wanted to clean the two end ribs and prime them so that I could re-attach them to the main wing spars and remount them back on the wing stands.
I am happy to report that I managed to accomplish both goals today in our lovely 60 degree weather.
Here are some pics:
First are the two HD buckets - one with the detergent water,and the other with the rinse water:
Now also for those that are aware of my trials and tribulations this year - you know that I had to deal with two bathroom remodels this year. The upstairs bathroom now has a much larger new bathtub. As I began to plan for this washing and rinsing task for my wing ribs, I briefly thought about using that new spacious bathtub for this task. It would certainly make easy work of the entire process for washing and rinsing all my wing ribs.I stopped short of following through with this thought when I realized that the new tub is not cast iron, but is fiberglass, and it would not take much fora piece of sharp metal to cut right into the tub and cause all sorts of additional pain and suffering that frankly I just don't need right now. So I quickly got that idea out of my system and filled up the HD buckets instead.
The idea was to wash them, rinse them, and set them somewhere to dry. Here is my jury-rigged drying table made up up spare wood and two saw horses - very high tech indeed!
And another showing the operation in full swing, including my new priming table with the two end ribs on top:
And another shot of the two end ribs after applying the NAPA 7220 self etching primer:
And then finally, if you have any doubts about the need to thoroughly clean all of you parts before you apply primer, just take a look at this next pic of what used to be clean, clear water!
The amount of residue and grime just from the washing process is amazing. Even more amazing is the final part of the process which is cleaning each dried rib with a microfiber cloth and acetone (or your favorite carcinoginic cleaning chemical). Even more grime get lifted from this process, if done thoroughly and correctly. It is not inherently difficult - just time consuming. I still need perform the acetone cleaning step forthe remaining ribs, but to have them all initially cleaned is a major accomplishment for me, so I will take it. One other side note about all this. Once you get to the rinse and acetone stages of this process, you need to wear protective rubber gloves to prevent depositing oils and grime from your own hands back onto the parts. There is nothing I hate worse than having to re-clean something over again, so I always keep a large supply of rubber gloves handy. I think I may have gone through about 8 pair for this little session today. I changed them to a dry pair to perform final drying of each rib with a clean, dry cloth, and then again just prior to applying the acetone. Seems to work pretty well for me.
It felt good to work on the plane again - even if I am still not quite ready to rivet some parts together...
Well this time I mean it quite literally. Today was washing day - not for my clothes, and not for my car (although both are sorely needed) - but for my wing ribs that have been sitting patiently in their scuffed up state, just waiting for final preparation steps to be taken to get them all cleaned and primed. The mission for today was to wash all of the main wing ribs for both wings (28 in all) with my usual mix of warm water and regular Dawn dishwashing liquid. I also wanted to clean the two end ribs and prime them so that I could re-attach them to the main wing spars and remount them back on the wing stands.
I am happy to report that I managed to accomplish both goals today in our lovely 60 degree weather.
Here are some pics:
First are the two HD buckets - one with the detergent water,and the other with the rinse water:
Now also for those that are aware of my trials and tribulations this year - you know that I had to deal with two bathroom remodels this year. The upstairs bathroom now has a much larger new bathtub. As I began to plan for this washing and rinsing task for my wing ribs, I briefly thought about using that new spacious bathtub for this task. It would certainly make easy work of the entire process for washing and rinsing all my wing ribs.I stopped short of following through with this thought when I realized that the new tub is not cast iron, but is fiberglass, and it would not take much fora piece of sharp metal to cut right into the tub and cause all sorts of additional pain and suffering that frankly I just don't need right now. So I quickly got that idea out of my system and filled up the HD buckets instead.
The idea was to wash them, rinse them, and set them somewhere to dry. Here is my jury-rigged drying table made up up spare wood and two saw horses - very high tech indeed!
And another shot of the two end ribs after applying the NAPA 7220 self etching primer:
The amount of residue and grime just from the washing process is amazing. Even more amazing is the final part of the process which is cleaning each dried rib with a microfiber cloth and acetone (or your favorite carcinoginic cleaning chemical). Even more grime get lifted from this process, if done thoroughly and correctly. It is not inherently difficult - just time consuming. I still need perform the acetone cleaning step forthe remaining ribs, but to have them all initially cleaned is a major accomplishment for me, so I will take it. One other side note about all this. Once you get to the rinse and acetone stages of this process, you need to wear protective rubber gloves to prevent depositing oils and grime from your own hands back onto the parts. There is nothing I hate worse than having to re-clean something over again, so I always keep a large supply of rubber gloves handy. I think I may have gone through about 8 pair for this little session today. I changed them to a dry pair to perform final drying of each rib with a clean, dry cloth, and then again just prior to applying the acetone. Seems to work pretty well for me.
It felt good to work on the plane again - even if I am still not quite ready to rivet some parts together...
Monday, December 16, 2013
It's a funny thing about this airplane building business.........
Sometimes you will rack your brain for days trying to come up with the ultimate solution to a problem. Sometimes it will lead you down a path where you end up thinking that thereis just no way to accomplish what you are trying to do. And then sometimes, when you least expect it, a light bulb goes off in your mind, and you finally realize the solution to your problem.
I have had many such moments while working on my plane, and I expect that I will end up having many more. For months I have been mulling over the best and safest way to make a modification to my leading edge to make a small portion of it modular and removeable so that I can interchange them with the "fun"one and the "normal" one. I have struggled with many safety-related issues, including introducing weakness in the structure at a critical location along the wing, and disruption of normal airflow at a critical point over the wing, and so on.
The other evening I thought I had come up with a sound solution that involved a small, built up leading edge section with some span-wise support baffles or spars. Ithought I had it all worked out - - right up to the point where I suddenly realized that my grand solution was going to result in a very small sliver of wing skin on the inboard side of the leading edge of the wing, right where it attaches to the fuel tank skin by using a .032 inch thick joiner plate. I realized this as I was staring at one of my many drawings of this modification. Sadly, I also realized that this probably was not going to work very well, and I headed off to bed with my head hung low, with a thought that maybe I was not going to be able to do this safely after all.
Then, right as my head hit the pillow, I had an epiphany. I know how to spell that fancy word because I have had several of them during the build, and you just have to get to a point where you at least have to know how to spell it - even if you don't fully understand how or why or when they occur. I suddenly realized that all I needed to do was take a formed sheet of .032 2024-T3 sheet, and replace one of the W709 wing ribs with one more W408-1 wing rib, and use this as a kind of undergarment support skin in between both ribs. I can then apply the top skin section directly over the supporting skin underneath,and screw it down with as many nut plates as are necessary to secure the entire thing to the leading edge of the wing.
There I was, all but ready to either face defeat, or succomb to fabricating a rather complex rib-supported small LE wing structure, when all I really needed to do is to replace the W-423 Joiner plate strip with one contiguous piece of .032 sheet aluminum between the two W-408-1 ribs. The hardest part will be forming the leading skin,but I think I have plan for doing that as well. The full "under sheet" of aluminum will slide underneath the leading edge skin where it can be riveted in place to the two ribs and the top and bottom wing skins. Then I just simply need to detach one leading edge section, and replace it with the other one whenever the need arises - completely and easily interchangeable.
Of course I will still need to build a mockup, and perfect my fabrication technique for bending the LE contour, but the important thing is that I now know that this is do-able, that I will not sacrifice strength (in fact I will probaby enhance it), and that I will not negatively affect the airflow over that section of the wing. It will basically fit like a glove over your hand and just slide right into place - easy-peazy. All it will take is a properly sized piece of .032 aluminum sheet, two W408-1 wing ribs, and a healthy supply of nut plates.
I will eventually have pictures that will show the process I am describing in the weeks to come. At least I now have a solid plan to make this happen, and that makes me very happy. You just never know how or when some of these things will come together. Sometimes it happens when you least expect it. All I can tell those of you that may be facing the same challeges with your build is that you need to adopt an attitude and a way of thinking that can be best-conveyed from a line from the movie Galaxy Quest: "Never give up, never surrender!!!" Just keep pluggin along and eventually you will figure it all out, even when you think that there is no chance that you ever will.
I have had many such moments while working on my plane, and I expect that I will end up having many more. For months I have been mulling over the best and safest way to make a modification to my leading edge to make a small portion of it modular and removeable so that I can interchange them with the "fun"one and the "normal" one. I have struggled with many safety-related issues, including introducing weakness in the structure at a critical location along the wing, and disruption of normal airflow at a critical point over the wing, and so on.
The other evening I thought I had come up with a sound solution that involved a small, built up leading edge section with some span-wise support baffles or spars. Ithought I had it all worked out - - right up to the point where I suddenly realized that my grand solution was going to result in a very small sliver of wing skin on the inboard side of the leading edge of the wing, right where it attaches to the fuel tank skin by using a .032 inch thick joiner plate. I realized this as I was staring at one of my many drawings of this modification. Sadly, I also realized that this probably was not going to work very well, and I headed off to bed with my head hung low, with a thought that maybe I was not going to be able to do this safely after all.
Then, right as my head hit the pillow, I had an epiphany. I know how to spell that fancy word because I have had several of them during the build, and you just have to get to a point where you at least have to know how to spell it - even if you don't fully understand how or why or when they occur. I suddenly realized that all I needed to do was take a formed sheet of .032 2024-T3 sheet, and replace one of the W709 wing ribs with one more W408-1 wing rib, and use this as a kind of undergarment support skin in between both ribs. I can then apply the top skin section directly over the supporting skin underneath,and screw it down with as many nut plates as are necessary to secure the entire thing to the leading edge of the wing.
There I was, all but ready to either face defeat, or succomb to fabricating a rather complex rib-supported small LE wing structure, when all I really needed to do is to replace the W-423 Joiner plate strip with one contiguous piece of .032 sheet aluminum between the two W-408-1 ribs. The hardest part will be forming the leading skin,but I think I have plan for doing that as well. The full "under sheet" of aluminum will slide underneath the leading edge skin where it can be riveted in place to the two ribs and the top and bottom wing skins. Then I just simply need to detach one leading edge section, and replace it with the other one whenever the need arises - completely and easily interchangeable.
Of course I will still need to build a mockup, and perfect my fabrication technique for bending the LE contour, but the important thing is that I now know that this is do-able, that I will not sacrifice strength (in fact I will probaby enhance it), and that I will not negatively affect the airflow over that section of the wing. It will basically fit like a glove over your hand and just slide right into place - easy-peazy. All it will take is a properly sized piece of .032 aluminum sheet, two W408-1 wing ribs, and a healthy supply of nut plates.
I will eventually have pictures that will show the process I am describing in the weeks to come. At least I now have a solid plan to make this happen, and that makes me very happy. You just never know how or when some of these things will come together. Sometimes it happens when you least expect it. All I can tell those of you that may be facing the same challeges with your build is that you need to adopt an attitude and a way of thinking that can be best-conveyed from a line from the movie Galaxy Quest: "Never give up, never surrender!!!" Just keep pluggin along and eventually you will figure it all out, even when you think that there is no chance that you ever will.
Friday, December 13, 2013
Capturing some Measurements of the Leading Edge ribs, and dealing with yet another trategy a little too close to home
Today I got to experience the shock and terror that a parent goes through when you hear that there is a school shooting in progress, and that your child is currently on lockdown. Thankfully my son was not at the same high school where this trategy unfolded, and we got him home safe and sound, but we all know several families with kids that do attend that school, and my heart goes out to each and every one of them.
This year just really needs to end soon - I don't know how else to put it - there has just been too much shit this year. I have never been very superstitious, but I am coming to believe more and more that the number 13 is nothing but pure bad luck, and perhaps it even holds a bit of an evil stigma with it as well.
Please pray for the 15 year old girl that is still clinging to life in critical condition tonight in a local hospital. That's about all I am going to say about this.
Since building the plane definitely serves as therapy for me in a number of different ways, I decided to try to focus my attention on getting some measurements for the leading edge ribs for the mod. So I took a W408-1 L rib and a flexible sewing ruler and recorded the followingmeasurements:
The reference point at the front of the rib for all flange length measurements is the separation point between the upward and downward facing flanges. That is the starting point for all of the flange-length measurements that I took:
Upper flange length (front to back full length): 18.5 inches
Lower full length flange: 17.75 inches
Reference line for nose rib separation: just aft of the vertical portion of the "T" web stiffener in front of the first lightening hole
Upper Flange length from nose to reference line: 4 1/8 inches
Lower flange length from nose to reference line: 3 5/8 inches
Straight line measurement from the nose reference point to the edge of the vertical stiffener:
2 13/16 inches
Distance between the vertical stiffener and the stiffener forthe first lightening hole (at closest point): 3/4 of an inch
Straight line measurement from nose reference point to the rear of the stiffener for the first lightening hole: 7 3/4 inches
Straight line measurement from nose reference point to forward line of the rear vertical stiffener: 8 22/32 inches
Upper flange measurement to the forward line of the rear vertical stiffener: 10.25 inches
Lower flange measurement to the forward line of the rear vertical stiffener: 9.5 inches
Minimum distance between the rear edge of the first lightening hole stiffener to the forward edge of therear vertical stiffener: 3/4 of an inch
These are the measurements I need to deal with when figuring out where to cut the separation line for the modular leading edge section.
More later...
This year just really needs to end soon - I don't know how else to put it - there has just been too much shit this year. I have never been very superstitious, but I am coming to believe more and more that the number 13 is nothing but pure bad luck, and perhaps it even holds a bit of an evil stigma with it as well.
Please pray for the 15 year old girl that is still clinging to life in critical condition tonight in a local hospital. That's about all I am going to say about this.
Since building the plane definitely serves as therapy for me in a number of different ways, I decided to try to focus my attention on getting some measurements for the leading edge ribs for the mod. So I took a W408-1 L rib and a flexible sewing ruler and recorded the followingmeasurements:
The reference point at the front of the rib for all flange length measurements is the separation point between the upward and downward facing flanges. That is the starting point for all of the flange-length measurements that I took:
Upper flange length (front to back full length): 18.5 inches
Lower full length flange: 17.75 inches
Reference line for nose rib separation: just aft of the vertical portion of the "T" web stiffener in front of the first lightening hole
Upper Flange length from nose to reference line: 4 1/8 inches
Lower flange length from nose to reference line: 3 5/8 inches
Straight line measurement from the nose reference point to the edge of the vertical stiffener:
2 13/16 inches
Distance between the vertical stiffener and the stiffener forthe first lightening hole (at closest point): 3/4 of an inch
Straight line measurement from nose reference point to the rear of the stiffener for the first lightening hole: 7 3/4 inches
Straight line measurement from nose reference point to forward line of the rear vertical stiffener: 8 22/32 inches
Upper flange measurement to the forward line of the rear vertical stiffener: 10.25 inches
Lower flange measurement to the forward line of the rear vertical stiffener: 9.5 inches
Minimum distance between the rear edge of the first lightening hole stiffener to the forward edge of therear vertical stiffener: 3/4 of an inch
These are the measurements I need to deal with when figuring out where to cut the separation line for the modular leading edge section.
More later...
Tuesday, December 10, 2013
More research for the Wing Leading Edge Mod
As I previously posted, I think I have made a decision to construct a removeable short nose section of the leading edge of each wing to make a completely modular, removeable section of the wing leading edge. Last night I decided to do some research on some P-51 web sites to try to find a drawing or somthing that would show the internal wing structure, especially around the machine gun ports. I was pretty certain that there was an additional short spar in between one or two of the LE ribs to serve as a support for the gun barrels and provide some extra strength to the bay in which all the guns reside. I did this to tryto determine if I would need a similar short spar in between the two ribs that form the edges of the bay that I will use for my mod. Then it turns into an analysis to determine if I need a spar for the removeable section,or if I only need a spar in the location where the removeable section will detach from the ribs on either side and the wing skins on the top and bottom.
If I do decide to use a spar for the removeable section, then there is the question of what thickness of aluminum to use. This then led me down apath of taking a look at some builders that have modified their aircraft to incorporate some integral auxiliary fuel tanks into the leading edge of the wings. Ron Duren and Mike Rettig immediately came to mind. I had not visited Ron's site for long time, but I knew that he was still chipping away at finishing his RV-7. I was pleasantly surprised to find a recent post wherehe talked about finishing up his wiring and then being ready for a first engine start soon.
I was also able to dive into his blog to find all of the detail around the Tuckey-Duren Leading edge aux fuel tanks that he built. Hopefully my mod will be bit simpler, but I will most likely need to fabricate my own spars, and that means precise bending of the flanges on all 4 sides - yuck! This becomes even more complicated bythe fact that there are lightening holes on the ribs on both sides, and stiffener indentations that firther restrict where the flangesof the spars can attach to the ribs. I could replace the LE ribs with end ribs for the fuel tanks, which have no lightening holes. THis would make it easier to place the spars where I want to put them,but the problem with the tank ribs is that they are shorter than the LE ribs since a baffle plate is used to seal the back of each tank, and this baffle plate sits forward of the main wing spar by a couple of inches. I could probably modify those ribs by extending the length with another piece of aluminum, but that leads to more structural strength questions.No matter what I decide to do, I will always have to takeinto account the effect of this mod on the forces of shear, tension, and torsion that may be applied to the wing under a variety of different flight conditions.
I must continue to resist the urge, no matter how great, to experiement to the same great degree of trial and error engineering that the Wright brothers must have had to use. IOW,I don't want to just slapthis together and then go try it out, even though the Experimental Aircraft Certification category basically allows me to do just that. I value my life and the lives of others just a little to much to be that brave. (read stupid, bold, etc.-reminds meof the old saying:
"There are bold pilots, and there are old pilots, but there are no old, bold pilots" - I think you get the point.
Anyway, I am taking fine measurements of everything right now so that I at least I will know the dimensions of all the parts I am going to need for this little project. Even though I am not slamming rivets just yet, it feels good to get back into the businessof designing and building an airplane.
If I do decide to use a spar for the removeable section, then there is the question of what thickness of aluminum to use. This then led me down apath of taking a look at some builders that have modified their aircraft to incorporate some integral auxiliary fuel tanks into the leading edge of the wings. Ron Duren and Mike Rettig immediately came to mind. I had not visited Ron's site for long time, but I knew that he was still chipping away at finishing his RV-7. I was pleasantly surprised to find a recent post wherehe talked about finishing up his wiring and then being ready for a first engine start soon.
I was also able to dive into his blog to find all of the detail around the Tuckey-Duren Leading edge aux fuel tanks that he built. Hopefully my mod will be bit simpler, but I will most likely need to fabricate my own spars, and that means precise bending of the flanges on all 4 sides - yuck! This becomes even more complicated bythe fact that there are lightening holes on the ribs on both sides, and stiffener indentations that firther restrict where the flangesof the spars can attach to the ribs. I could replace the LE ribs with end ribs for the fuel tanks, which have no lightening holes. THis would make it easier to place the spars where I want to put them,but the problem with the tank ribs is that they are shorter than the LE ribs since a baffle plate is used to seal the back of each tank, and this baffle plate sits forward of the main wing spar by a couple of inches. I could probably modify those ribs by extending the length with another piece of aluminum, but that leads to more structural strength questions.No matter what I decide to do, I will always have to takeinto account the effect of this mod on the forces of shear, tension, and torsion that may be applied to the wing under a variety of different flight conditions.
I must continue to resist the urge, no matter how great, to experiement to the same great degree of trial and error engineering that the Wright brothers must have had to use. IOW,I don't want to just slapthis together and then go try it out, even though the Experimental Aircraft Certification category basically allows me to do just that. I value my life and the lives of others just a little to much to be that brave. (read stupid, bold, etc.-reminds meof the old saying:
"There are bold pilots, and there are old pilots, but there are no old, bold pilots" - I think you get the point.
Anyway, I am taking fine measurements of everything right now so that I at least I will know the dimensions of all the parts I am going to need for this little project. Even though I am not slamming rivets just yet, it feels good to get back into the businessof designing and building an airplane.
Monday, December 9, 2013
How to work on the plane when it is too cold to work on the plane...
Well the weather decided to show up right on schedule. Just when I need some fair weather to finish cleaning and priming my wing ribs, a large arctic blast shows leaving several inches of snow and below zero freezing temps - about normal for me.
Since I have no desire to get my hands wet in a bucket of luke-warm water to wash freezing cold aluminum wing ribs, I decided to find some research work to do to kill some time while this ridiculous air mass slowly moves out of town. So my thoughts turned back to my LED light machine gun project, and how to design the removable section of the leading edge so I can interchange it with the gun assembly and a "normal" clean leading edge.
I was planning on doing the whole thing in fiberglass to avoid removing any metal from critical sections of the wing, but themore I have thought about it the more I do not like that idea because it modifies the airflow at a critical location on the wing to the point where it may affect the function of the inboard section of the aileron, which is not good. My technical counselor got me thinking more about that when he started asking me how I was going to address any fairing that I may need to make to blend the part into the top and bottom skins of the wing.
So I started thinking about a different solution that does involve cutting off the rounded section of the leading edge in between the first two nose ribs of the leading edge where the fuel tank ends and the leading edge begins. To avoid getting into too much detail it will involve ordering 2 more 408-1 ribs for the left and right wings, new .032 inch thick strips of aluminum to make a slightly wider joiner plate than normally called for, some additional sheet aluminum for making the LE skin sections and short spar sections, and some additional stall warning mounting bracket nose rib sections. I am also going to order some Duckworks blank template landing light kits, hoping that the cross spars in those kits have top and bottom flanges that actually touch or support the wing skins. I cannot find any pics from other builder logs that clearly show the top and bottom flanges and how or if they support or touch the top and bottom wing skins, so I will just haveto order some and find out for myself I guess.
This first pic shows what a new scotch brite pad looks like after using it to scuff all of the main wing ribs. The new one ison the left and the 2spent ones are on the right. It took 2 pads to scuff all main ribs for both wings.It will probably take at least one more to do all of the nose ribs:
Next is a pic of my lovely drawings for the leading edge mod that I am about to undertake:
I have ironed out most of the details of this mod, but there are a few critical elements where certain parts have to be sized to exact measurements, and the more I have to measure and apply the math to properly bend a flange to a precise dimension, the less likely it will happen. So if I can use some prefabricated parts to do at least part of the job, then that would be a good thing. Hopefully this will come together well, but I need to order some parts first, and then wait for warmer weather. Ho ho ho.... :(
Since I have no desire to get my hands wet in a bucket of luke-warm water to wash freezing cold aluminum wing ribs, I decided to find some research work to do to kill some time while this ridiculous air mass slowly moves out of town. So my thoughts turned back to my LED light machine gun project, and how to design the removable section of the leading edge so I can interchange it with the gun assembly and a "normal" clean leading edge.
I was planning on doing the whole thing in fiberglass to avoid removing any metal from critical sections of the wing, but themore I have thought about it the more I do not like that idea because it modifies the airflow at a critical location on the wing to the point where it may affect the function of the inboard section of the aileron, which is not good. My technical counselor got me thinking more about that when he started asking me how I was going to address any fairing that I may need to make to blend the part into the top and bottom skins of the wing.
So I started thinking about a different solution that does involve cutting off the rounded section of the leading edge in between the first two nose ribs of the leading edge where the fuel tank ends and the leading edge begins. To avoid getting into too much detail it will involve ordering 2 more 408-1 ribs for the left and right wings, new .032 inch thick strips of aluminum to make a slightly wider joiner plate than normally called for, some additional sheet aluminum for making the LE skin sections and short spar sections, and some additional stall warning mounting bracket nose rib sections. I am also going to order some Duckworks blank template landing light kits, hoping that the cross spars in those kits have top and bottom flanges that actually touch or support the wing skins. I cannot find any pics from other builder logs that clearly show the top and bottom flanges and how or if they support or touch the top and bottom wing skins, so I will just haveto order some and find out for myself I guess.
This first pic shows what a new scotch brite pad looks like after using it to scuff all of the main wing ribs. The new one ison the left and the 2spent ones are on the right. It took 2 pads to scuff all main ribs for both wings.It will probably take at least one more to do all of the nose ribs:
Next is a pic of my lovely drawings for the leading edge mod that I am about to undertake:
I have ironed out most of the details of this mod, but there are a few critical elements where certain parts have to be sized to exact measurements, and the more I have to measure and apply the math to properly bend a flange to a precise dimension, the less likely it will happen. So if I can use some prefabricated parts to do at least part of the job, then that would be a good thing. Hopefully this will come together well, but I need to order some parts first, and then wait for warmer weather. Ho ho ho.... :(
Sunday, December 1, 2013
Wing Rib Prep Cont'd, and the loss of another good friend.....
I managed to finish scuffing the main wing ribs for both wings. In total I think this took me about 8-10 hours or so just to scuff and deburr the 28 main ribs (14 per wing). The last two ribs are the end ribs that are used to support the wing spar on the wing stands, so this meant that I had to remove both wing spars from the stands, remove the end ribs, and detach the angle mounting bracket from each rib. The leading edge ribs still need to be scuffed (14 more of those to do).
The next steps are to clean and prime the two end ribs so that these can be remounted to the wing spar so I can put the apars back on the wing stands. In fact, once these are primed I think I can go ahead and rivet them to the wing spar. The cleaning process is a bath in warm water and original formula dawn dishwashing detergent, followed by a deep cleaning with acetone and a micro fiber cloth.
For the primer I am currently thinking about using the NAPA 7220 from the spray can instead of the two part epoxy primer - mostly for time saving reasons, and because my two part primer has been sitting around outside in the garage for a long time and may now be unusable, and because the weather is expected to get colder next week.
And as if there isn't enough sad news in the world today, I just got word that another very good friend and Civil Air Patrol acquaintance John Butler has passed away. I spent a lot of time in my last several years of CAP service working with John by conducting a variety of different training courses for the Jeffco Senior Squadron. John was a great guy and he will be sorely missed. John had some medical issues but I don't have any details yet. All I know for sure is that at least he did not parish in an airplane crash. Rest in Peace John - Lord knows you have sure earned it.
This year just can't end soon enough for me.....
The next steps are to clean and prime the two end ribs so that these can be remounted to the wing spar so I can put the apars back on the wing stands. In fact, once these are primed I think I can go ahead and rivet them to the wing spar. The cleaning process is a bath in warm water and original formula dawn dishwashing detergent, followed by a deep cleaning with acetone and a micro fiber cloth.
For the primer I am currently thinking about using the NAPA 7220 from the spray can instead of the two part epoxy primer - mostly for time saving reasons, and because my two part primer has been sitting around outside in the garage for a long time and may now be unusable, and because the weather is expected to get colder next week.
And as if there isn't enough sad news in the world today, I just got word that another very good friend and Civil Air Patrol acquaintance John Butler has passed away. I spent a lot of time in my last several years of CAP service working with John by conducting a variety of different training courses for the Jeffco Senior Squadron. John was a great guy and he will be sorely missed. John had some medical issues but I don't have any details yet. All I know for sure is that at least he did not parish in an airplane crash. Rest in Peace John - Lord knows you have sure earned it.
This year just can't end soon enough for me.....
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