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RE: Blue Angel - Build
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The ¼” balsa strips had been rough cut to fit so they required a little work with the razor plane and then final sanding. While I was sanding I gave both sides of the core surfaces a light sanding.
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RE: Blue Angel - Build
ORIGINAL: jquid What brand of retract is that? I am having trouble locating a good tri gear pneumatic system. robarts new one uses a pull pull for the nose requiring another servo fro steering. Then there is their older style, but is costly. Any recommendations? They are Spring Air retracts. See page 2 and 3 of this thread for more detailed pictures and info. They are very well made and top quality. I like the steering setup that Spring Air uses rather than the tiller type used on other brands. |
RE: Blue Angel - Build
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To determine the wing wheel well positions I set aircraft on a flat surface with the gear down. I then adjusted the length of the main gear struts by moving the adjustable axels and measured water line at the tail and nose of the aircraft. I like to have about 1/8” of nose down rake between the tail and nose. After this adjustment I checked to make sure the right and left gear struts were the same length.
I used a piece of balsa as a template to rough cut the wheel wells out using my usual hot wire method. I made the first cut smaller than the final size so I can adjust the size later after the wing skins are glued on. Notice that I have not cut the struts off yet so I can make fine adjustments on the final fit. To be continued… |
RE: Blue Angel - Build
My Tower order arrived with my third Futaba S9252 digital servo along with a Sullivan cable for my nose gear steering and throttle connection. I’ll be using S9252s on the ailerons and elevator and a S3151 for the rudder.
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RE: Blue Angel - Build
The gear wells look great. I have a couple questions about your servo choices. Why the 3151 for rudder? It puts out less than half the torque of the 9252s. I was of the understanding that rudders usually demand greater torque; but maybe that's only the case with contemporary 3-D models, and not with vintage pattern designs. Are you choices based more on the precision of the servos than their muscle? I can see that the 9252s would definitely give you more precision for aileraons and elevator.
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RE: Blue Angel - Build
ORIGINAL: rainedav The gear wells look great. I have a couple questions about your servo choices. Why the 3151 for rudder? It puts out less than half the torque of the 9252s. I was of the understanding that rudders usually demand greater torque; but maybe that's only the case with contemporary 3-D models, and not with vintage pattern designs. Are you choices based more on the precision of the servos than their muscle? I can see that the 9252s would definitely give you more precision for aileraons and elevator. |
RE: Blue Angel - Build
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Before gluing the gear mounts into the wing with epoxy I drilled 3/16” holes for dowels that project into the foam to help lock in the mount. The dowels project so that they stop just under the top surface of the foam. They are glued into the wing and mount with epoxy. I decided that two would be enough for each mount.
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RE: Blue Angel - Build
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Because of the swept wing and the way the mount is installed at an angle to the airfoil, the mount had to be countersinked into the foam. This left a space that was filled in with scrap foam. I then sanded the foam to the shape of the airfoil.
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RE: Blue Angel - Build
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I cut the slot in the wing for the retract gear air line using my usual hot wire. I normally fill in the top edge of the slot with 1/16” balsa.
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RE: Blue Angel - Build
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Before hacking holes in the wing for individual aileron servos I recheck how a single servo would work in the center of the wing. Not much room so I’m going to use two servos in the wing outboard from the retract units.
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RE: Blue Angel - Build
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I cut out the servo openings and servo lead pathways to the servos using the usual hot wire method. A 1/32” countersink in the foam around the servo opening provides space to glue in a 1/32” plywood frame. The plywood servo mount has been cut and drilled but not installed yet. Because I’ve made the large cutout for the servos so close to the retract mount I’m going to add some more dowels to the retract mounts for strength.
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RE: Blue Angel - Build
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View of the 3/16” dowels added to the gear mount.
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RE: Blue Angel - Build
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I completed the gluing of the 1/16” X 4 “ X 36” balsa sheets together for the wing skins. I use Titebond glue. I weighed and sorted the sheets before gluing so could use the lightest sheets on the right wing to help compensate for the right mounted engine. There was not much difference in weight between the sheets but every bit helps the weight management.
The Dynamic Balsa sheets are cut clean enough that no trim work is needed on the edges before gluing. I usually just sort through the sheets and find sheets that will fit together without gaps. The sheet seams are pulled together very tightly using masking tape and then I add a full piece of masking along the seam. I always stretch the masking tape slightly as I tape so it pulls the seams together tightly. After all three sheets are taped together on one side I turn the sheet over and open the seam slightly and run a small bead of glue in the seam then close the seam by laying the sheet on a flat surface. I then wipe away the excess glue and tape the seam very tightly in about 5 or 6 places along the seam. The idea is to have very little glue at the seam edges. The side that has the full length tape will be the outside surface because the other side always ends up with a little glue residue from wiping away the excess. To be continued… |
RE: Blue Angel - Build
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The wing sheets cut to size and ready to be glued to cores.
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RE: Blue Angel - Build
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I used Dave Brown Southern’s Sorghum contact cement to glue the balsa wing skins to the cores. I brush it on the balas sheet and core as thin as possible and let it dry for about ½ hour. Needless to say I do one side of the wing core at a time. I find it helpful to mark the inside of the balsa sheets so I don’t get them mixed up and brush the glue on the wrong side. The balsa tends to curl from the glue so I lay it on a flat surface next to a wall and put one end my steel three foot straight edge in the middle of the sheet and lean it against the wall to hold the sheet flat.
After the glue is dry, I lay the balsa sheet on my flat building board, line up the front edge of the core with the front of the sheet and press it down and then roll the core onto the sheet. I then turn the core over and rub down the sheeting tightly. At this point, I always sight down the leading and trailing edge of the wing to make sure it is true. If not the wing can be carefully bent a little to make sure it is true before the balsa skin is glued to the other side. Once both sides are glued on the core it is pretty hard to make any adjustments but it can be done before the contact glue is fully cured. I use Sorghum on wings that will be MonoKoted and epoxy for wings that will be painted. The Sorghum works well with MonoKote and holds up excellent in our hot and cold southeastern weather. To be continued… |
RE: Blue Angel - Build
DBP Sorghum works remarkably well when used right as 8178 has specified. A couple of years ago I had occassion to cut into a oft flown flying boat built in the early 70's that used Sorghum to attach 1/16" balsa sheeting to its foam core. The blasa would not separate from the foam anywhere, instead tearing out chunks of foam wherever the sheeting had to be removed. As near as I could tell, the bond was still perfect after all those years.
That said, Sorghum does not like continued exposure to heavy moisture and will eventually separate if so exposed. Film covering and long term storage in a relatively dry environment will prevent any problems. (The flying boat was glassed over the balsa and so the bond wasn't exposed.) Sorghum remains my contact cement of choice for foam and balsa wings. Back to building the Blue Angel ... Tony |
RE: Blue Angel - Build
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After the wing sheeting was completed I cut out the retract gear area and installed the ¼” leading edges on the wing.
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RE: Blue Angel - Build
8178, I have really enjoyed watching this project take shape. Your gear installation looks perfect. I'm sure you wouldn't be taking the time to photograph and describe your building techniques if you didn't hope that other RCUers could learn a thing or two. Thanks. Having said that, I hope you document the glassing and priming stages of the fuselage in detail.
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RE: Blue Angel - Build
ORIGINAL: tony-howard A couple of years ago I had occassion to cut into a often flown flying boat built in the early 70's that used Sorghum to attach 1/16" balsa sheeting to its foam core. The blasa would not separate from the foam anywhere, instead tearing out chunks of foam wherever the sheeting had to be removed. As near as I could tell, the bond was still perfect after all those years. |
RE: Blue Angel - Build
ORIGINAL: rainedav 8178, I have really enjoyed watching this project take shape. Your gear installation looks perfect. I'm sure you wouldn't be taking the time to photograph and describe your building techniques if you didn't hope that other RCUers could learn a thing or two. Thanks. Having said that, I hope you document the glassing and priming stages of the fuselage in detail. |
RE: Blue Angel - Build
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After the glue setup I razor planed and sanded down the leading edge. The final rounded shape will be done soon but I find it works best to do the shaping one step at a time. The very leading edge is flat at this step.
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RE: Blue Angel - Build
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I started work on the ailerons. I cut the hinge slots first and then inserted 1/32” thick plywood tabs in the slots and glued the aileron stock to the trailing edge of the wing with rubber glue. After the glue set, I glued the 3/32 basswood trailing edge on the aileron stock making sure the trailing edge was straight. The tip of the Blue Angel aileron extends past the end of the wing and into the wing tip block. The basswood can also be used on trailing edge of sheet stock and used as a guide to plane the balsa to a tapered aileron.
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RE: Blue Angel - Build
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Using my Little Giant razor plane I made fast work of rough cutting the ailerons to shape. I think I bought my Little Giant razor plane in 65 but I’m not sure they still make them. They are a very awesome tool. This one has a lot of old Ambroid glue on it.
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RE: Blue Angel - Build
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The rough cut aileron is on the left and the aileron on the right has been sanded to the final finish. The second image shows the completed aileron still rubber glued to the wing.
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RE: Blue Angel - Build
Flawless work and some ingenious methods, too. I really like your idea of using 1/32 ply tabs and rubber cement to hold the ailerons in place. The ailerons appear to be part of the airfoil itself. One thing I didn't like about the Kaos I built was that the ailerons were just balsa strips attached onto the trailing edge of the wing and not really part of the airfoil contour. Have you weighed your wing at it's current state with the retracts and servos in place? I'd be really curious to know where it's at before covering.
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