Lightning Build
11-19-2010, 07:57 PM
#1
Lightning Build
A few years ago, after seeing the work Mark Hunt was doing with balsa pattern planes, I decided to build my own. I enjoy the build almost as much as I enjoy flying. I drew plans on Turbocad and built a prototype back in 2007 and have been flying it ever since. The prototype is powered by a Hacker C50-14XL with TP5300 Prolite V1s and came out at 10.9 pounds. The fuselage is all wood and the wings and stab are foam.
I had no great expectations when I started the project, but it turned out to be a really good flying airplane, so I am building a second Lightning. After finishing the airplane it was evident that I had overbuilt many areas of the fuselage. It doesn't need to be much lighter, but I would like to expand my battery options by dropping a few ounces. I used the original outline and completely redesigned the internal structure to eliminate extraneous structure. I am also straying from the all balsa fuselage and will be molding a composite canopy. I think it will be a bit lighter than my planked canopy I have now, plus that was a royal pain to build.
Before I dig into the build, if you are going to build a pattern plane, read Earl Haury's PL Products Partner Build found here: http://pages.suddenlink.net/donramsey/ His methods can be applied to any pattern plane build. I have incorporated many of Earl’s building techniques even into my wood airplanes.
Here is a picture of the prototype Lightning.
Enjoy!
I had no great expectations when I started the project, but it turned out to be a really good flying airplane, so I am building a second Lightning. After finishing the airplane it was evident that I had overbuilt many areas of the fuselage. It doesn't need to be much lighter, but I would like to expand my battery options by dropping a few ounces. I used the original outline and completely redesigned the internal structure to eliminate extraneous structure. I am also straying from the all balsa fuselage and will be molding a composite canopy. I think it will be a bit lighter than my planked canopy I have now, plus that was a royal pain to build.
Before I dig into the build, if you are going to build a pattern plane, read Earl Haury's PL Products Partner Build found here: http://pages.suddenlink.net/donramsey/ His methods can be applied to any pattern plane build. I have incorporated many of Earl’s building techniques even into my wood airplanes.
Here is a picture of the prototype Lightning.
Enjoy!
11-19-2010, 09:50 PM
#4
RE: Lightning Build
Time to get to work! I "finished" the plans and printed them before I deployed for the Summer. Of course with three months in Iraq, I had plenty of time to think of more changes that had to be added. So one more new set of plans and off we go.
First off, the fuselage.
All of my parts are hand cut (well, I do use a bandsaw along with a knife, so mechanically assisted hand cut). I print an extra set of plans to use as templates. I cover the wood with strips of masking tape and then I use contact cement to glue the plans to the tape. I cut everything out and sand it to shape. Prior to removing the tape, I mark all of the centerlines by sticking a pin through the plans into the wood. After you remove the tape, you are left with bare wood in the shape of your part. The only problem with this method is the paper and tape only likes to be sanded towards the wood, otherwise the paper bunches up a bit and you lose your line. I am thinking next time I might try some iron-on sheets you can put through the printer.
The formers forward of the wing trailing edge are all 1/8" lightply while the aft formers are all 1/8" balsa.
One thing to mention, I built the prototype in my 30' by 20' shop with a build in paint booth that was in my old house. My new work space is a 10' by 6' space in the garage...and no paint booth. This may make may already slow pace come to a crawl. I really miss that shop!
First off, the fuselage.
All of my parts are hand cut (well, I do use a bandsaw along with a knife, so mechanically assisted hand cut). I print an extra set of plans to use as templates. I cover the wood with strips of masking tape and then I use contact cement to glue the plans to the tape. I cut everything out and sand it to shape. Prior to removing the tape, I mark all of the centerlines by sticking a pin through the plans into the wood. After you remove the tape, you are left with bare wood in the shape of your part. The only problem with this method is the paper and tape only likes to be sanded towards the wood, otherwise the paper bunches up a bit and you lose your line. I am thinking next time I might try some iron-on sheets you can put through the printer.
The formers forward of the wing trailing edge are all 1/8" lightply while the aft formers are all 1/8" balsa.
One thing to mention, I built the prototype in my 30' by 20' shop with a build in paint booth that was in my old house. My new work space is a 10' by 6' space in the garage...and no paint booth. This may make may already slow pace come to a crawl. I really miss that shop!
11-19-2010, 10:15 PM
#5
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RE: Lightning Build
Jeff,
A tid bit I learned years ago.
To transfer the plans to the wood, turn the plans toward the wood then go over the back of the plans with your monokote iron. It transfers the ink to the wood.
Tim
A tid bit I learned years ago.
To transfer the plans to the wood, turn the plans toward the wood then go over the back of the plans with your monokote iron. It transfers the ink to the wood.
Tim
11-20-2010, 09:35 PM
#6
RE: Lightning Build
The front of the fuselage forms a "cage" that supports the firewall and also ties into the landing gear block. This structure will carry most of the load from the motor back to the rest of the fuselage. The longerons are 1/8" lightply, laminated on one side with 0.006 unidirectional carbon fiber. The firewall is 1/8" end-grain balsa laminated with carbon fiber. This is all connected to the rest of the fuselage with 1/8" balsa fuselage sides. The fuselage sides are reinforced with 1/32 plywood doublers around both the area of the wing mount and stab mount. I put lightply hard points in the fuselage sides for the wing attachment points and adjusters.
11-24-2010, 03:31 PM
#9
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RE: Lightning Build
Cool....
I hope you take plenty of photos of the cowl buildup... it's not something seen every day yet if done correctly can be very effective.
I hope you take plenty of photos of the cowl buildup... it's not something seen every day yet if done correctly can be very effective.
11-24-2010, 06:10 PM
#10
RE: Lightning Build
Will do Mark. The cowl and the canopy on the prototype are both removable and fully built up. Those seem to be the parts everyone enjoys taking a peak inside to see how they were done. The front end of the airplane was relativly easy to form, but the canopy was a different story. I removed the skin from it at least once because I wasn't happy with it.
11-24-2010, 06:34 PM
#12
RE: Lightning Build
Now that the parts are all made, it is time to make something that looks like an airplane, or at least part of one. For the fuselage, I use a very simple jig. I use a base of 3/4" fiberboard that is mounted to my workbench. The stand-offs are each made from two pieces of cheap Lowe's 1/4" plywood, both glued and screwed to a small 45-45-90 triangle cut from pine on my chop saw. The stand-offs are mounted to the base directly over the top view from the plans using hex head machine screws. The fact that they are hex head IS important as later on, you will not have room to get a screwdriver in to remove them from the base. The formers are clamped to the stand-offs, along with a little rubber cement to keep them from slipping. I mount the firewall to its stand-off using 4-40s and several nuts so I can adjust the thrust. I measure the thrust offset and back it up with the digital level. Not very complex, but it results in a fuselage as straight as you line it up, so I spend quite a bit of time double and triple checking each former's placement.
One note, one a previous post, I showed the "cage" put together. It was not glued together, that will be done in the jig.
One note, one a previous post, I showed the "cage" put together. It was not glued together, that will be done in the jig.
11-30-2010, 05:58 PM
#15
RE: Lightning Build
To stiffen the tail, I use a piece of 1/8" balsa laminated on one side with carbon fiber. This web with run from the former aft of the stab tube to the former forward of the stab incidence pin. It runs length wise slightly above the stab tube. The piece came in at 5 grams.
11-30-2010, 06:09 PM
#16
RE: Lightning Build
Now it is time to finish up the fuselage sides and get some skin on those bones. The 1/8" balsa sides are reinforced with 1/32 ply doubler around the wing mounting area and around the stab mounting area. There is a 1/8" by 5/16" balsa stick that runs the length of the side, both top and bottom. Why a crazy size like 5/16" you ask? That is so I get a full 1/4" bond to the fuselage side, and also a 1/16" lip sticking up to act as a guide for the top and bottom sheeting when it is applied.
11-30-2010, 06:24 PM
#17
RE: Lightning Build
Putting the sides on is a bit of a chore as they extend all the way up to the nose ring which gets into some serious compound curves. One note is that sub 6 pound per cubic foot balsa forms very nice, almost to nice. If you wet it, and then throw it on the formers, it with ripple between the formers (lesson learned on the first build!). The sides bend enough while dry, but it is a pain to glue and tack everything down at the same time with the sides attempting to spring back flat. My solution was to dry fit everything, running tape around the nose to hold it in place. I then misted the front section with water, taking care not to soak the wood. Once it was dry, I removed the sides leaving a near perfect curve in the wood, and no rippling. Now all that is left is to put glue on everthing and clamp it all in place.
Starting to look like an airplane!
Starting to look like an airplane!
12-12-2010, 05:39 AM
#22
RE: Lightning Build
Back from a semi-warm tropical vacation with my wife, great time!
Now it is time to put 3/32" balsa gussets between the formers and the fuselage sides. Once that is complete, 1/8" by 1/4" balsa stringers are run down the turtle deck. One word on stringers; pre-cut balsa sticks are 10 pound plus balsa. You can save some weight by cutting your own from 6 to 8 pound balsa. I finally bought a Master Airscrew stripper and it worked like a champ, I would recommend it for a project like this.
Now it is time to put 3/32" balsa gussets between the formers and the fuselage sides. Once that is complete, 1/8" by 1/4" balsa stringers are run down the turtle deck. One word on stringers; pre-cut balsa sticks are 10 pound plus balsa. You can save some weight by cutting your own from 6 to 8 pound balsa. I finally bought a Master Airscrew stripper and it worked like a champ, I would recommend it for a project like this.
12-12-2010, 05:59 AM
#23
RE: Lightning Build
Once the stringers are in place, the turtle deck is sheeted with 3/32" balsa. The sheeting is first glued together into one sheet, large enough to cover the deck. Next, I pre-mold the sheeting so I can start fitting it. To mold it, I wet the center of the sheet with water and pulled it around a wrapping paper tube ('tis the season) to form a shape that is close to the shape of the turtle deck. Once it is dry, it is taped to the turtle deck and pulled to the final shape. As with the nose section, I lightly misted the wood and left it to dry. Once dry, I removed the tape and the sheeting maintains nearly the exact shape of the turtle deck. This is a bit more difficult than it sounds as the turtle deck is a compound curve shape and the sheeting requires some finessing to conform.
