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Joined: 11/30/2003 From: Cadillac,
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Thanks, Stryk
Got both of the wing retention blocks glued in, and drilled the holes for the bracket screws.
If anyone's interested, I used the strut brackets off of TopFlite's Staggerwing Beech ARF, and #4x3/4 button head sheet metal screws. I located the hardwood blocks inside the wing panels and the fuse as close to the plan as I could, and everything lined up nicely.
Tower item numbers LXD987 and TOPA1691
Going to finish glassing the wing tube boxes, now.
Did you see that note on the old thread about the guy building 3 deg downthrust into his, and how well it flew?
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Seems like everything's happening at once lately, and not much time left over for airplane building.
I did get started on the pod today- the last sub assembly. Here's my version of the 3 degree downthrust shim. I cut a firewall shaped piece out of 1/8 lite ply, and glued it to the main firewall, then used a disc and belt sander to taper it from the top to the bottom. It's mostly gone at the bottom, and untouched at the top. By clamping the motor mount to the completed firewall, I was able to use the motor mount holes as drill guides, so the holes went in at the proper angle.
Worked with an individual who did CL for years. Never bought a kit, always scratch built from plans. We were discussing building and he mentioned cutting the spar slots with the same size of wood with a piece of sand paper on one side. Just sand the slot into the ribs. Works fast to make accurate tight joints at any angle.
I've built a couple of swept wings that had swept spars, and learned that it's better not to cut the spar notches in the ribs until they are pinned in place and ready for the spar to be installed. I lay the spar on top of the ribs over its location on the plans, and use a felt tip to mark both sides of it on top of the ribs. It's then fairly easy to use a razor saw and a hobby knife to cut out the notches. This results in a very tightly fitting spar with good glue joints.
< Message edited by Jim_Purcha -- 5/18/2008 3:57:51 AM >
Seems like everything's happening at once lately, and not much time left over for airplane building.
I did get started on the pod today- the last sub assembly. Here's my version of the 3 degree downthrust shim. I cut a firewall shaped piece out of 1/8 lite ply, and glued it to the main firewall, then used a disc and belt sander to taper it from the top to the bottom. It's mostly gone at the bottom, and untouched at the top. By clamping the motor mount to the completed firewall, I was able to use the motor mount holes as drill guides, so the holes went in at the proper angle.
Heh yeah, I thought the project was stopped .
Regarding the firewall, nice work in so far as it's not easy to achieve proper sanding... However, wouldn't have firewall tilting been an easier route ? Sanding bottom and top edges to taper them is required but it seems easier to me. That's how I've always done it...
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That's what I thought at first, and then I realized that in order to tilt the firewall in relation to the vertical mounting stick, the entire design of the fins and rudder would have to change. The upper rib on the lower fin would have to tilt, the bottom of the upper fin would need to be re-angled, and the rudder would have to be lengthened and reshaped on the top.
There's so much material in the cowl area, due to the internal 1/2" triangle in the corners, that I think the sanding should go OK. Might look a touch strange, tho.
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Got on a roll, today, and finished the pod/engine installation.
I think the second pic shows the downthrust, and you can see the difference in the slope of the cowl between top and bottom. Also, the top decking is not on yet, as I need a way to clamp the firewall to the spruce upright during gluing.
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Hello again,
Your build looks great. I am right in the middle of building a Northstar from a Balsa Usa kit. I must say I am having a great amount of fun with it. It is so far knock on wood going really well and easy. I am at the point of shaping and adding weight to the nose cone. I was planing on trying to cram 10oz in there. Do any of you have experience with this or recomendations on how much weight to put in the nose. The engine weights about 17oz so I figured with the 10oz in the nose plus the radio gear I should just about come out where I need to be. Any thoughts would be most welcomed.
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Chris:
The only time I successfully "preselected" the amount of ballast in an airplane was with a Pavel Bosak F-4. What I did was measure from the C.G. on the plans, to the various points where the heaviest masses were to be located, in inches. (servos, battery, engine, landing gear) I weighed each of the masses (or took the manufacturer's stated weight, such as for the engine) in ounces.
By multiplying each mass (oz) by it's distance from the C.G. (inches) the inch-oz of torque generated is realized. If the stuff in the rear yields, for example, a total of 100 in-oz of tail down torque, and the stuff in the front yields 50 in-oz of nose down torque, then you need 50 in-oz more for the nose.
Then you have to take the empty airframe (with pushrods installed) and see how much nose or tail weight it takes to balance it. Add 50 in-oz to that and you should be pretty close.
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The view in pic 1 is topside through the radio hatch. Yup. The bottom of the servos, which I installed through the bottom of the fuse.
I pre-drilled all the pushrod tube holes in the formers before I assembled the fuse, and I used the pattterns shown in the plans, which lines everything up perfectly with the control horns on the elevons and rudder. This also puts the servos, if installed right side up, way down in the bottom of the fuse. (Also shown on the plans.) Not a good idea in seaplanes, I think.
By flipping the servos, they are now up above the bilges instead of in them. Moreover, the servo horns line up perfectly with the pushrods. This happened because I used a couple pieces of 1" x 3/16" basswood, and glued them across the lower 1/4 square balsa longerons that form the hatch opening. 3/16 ply would have worked, also. A little 1/2" triangle stock glued in the corners strengthens everything nicely. Another plus to inverted servos in seaplanes is that water which collects on the exposed pushrods in the rear, which are submerged before TO, cannot drip onto the servo arms after it wicks up the tube and then run past the servo shaft and into the works like it can if the servos are upright. Three of my early seaplane attempts crashed because of this phenomenon.
The flight control pushrods are Sullivan Composite Flex Rod 4-40. (Tower #LXFV44) Kinda pricey at $24.00 for three of them, but I was looking for the least amount of give in the rods, no temperature related trim changes, and no slop. A 1/16" drill run through the HS-325BB servo horn holes opens them up the precise amount to fit the clevis' with no slop.
At the other end, I'm using Dubro Safety Lock Kwik Link 4-40 (Tower #LXWH34) connected to Dubro Heavy Duty Control Horn .40-.91 (Tower LXEMF9) There is almost no slop in this arrangement, as well. I like these horns because one can adjust their length infinitely so as to get everything lined up very nicely. They are also nice when using very thick balsa flight control surfaces as on the Arrow. They are also very easy to disconnect when removing the wing panels for transport- the tiny brass lock is slid away from the pin, a tiny screwdriver is used to prise the pin up, and they're disconnected. No fighting with the snap type clevis'.
< Message edited by Mustang Fever -- 5/20/2008 12:38:22 AM >
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Got sidetracked by a NexstarTrainer and a Big Stik 60. First time in a long time I've had three projects going at once and the whole basement full of half built airplanes.
Here's the fuse, top sheeting on but not rounded yet, and the fin/pod just sitting in place.
Can't decide whether to completely finish the fuse and then cover it, or cover the fuse, fins and pod separately before assembly. I'm leaning towards the latter, even tho it will mean leaving the top off the pod and part of the bottom off the fuse so I can get at both ends of the 1/2" square post with clamps.
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RE: Laddie M's Arrow - 2nd Attempt - 
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