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Old 01-21-2013, 12:42 AM   #26
Bill G
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Originally Posted by baz49exe View Post
Looking good Bill. That's a great idea to make the spats structural.
I'll keep that in mind when I eventually talk myself into a Stuka build.
Thanks Barry. Everyone needs at least 2 Stukas. One of these days I'll talk myself into flying the larger one. On the pants, I've seen some over engineered modes with actual struts inside the pants and a heavily reinforced area on the wing for the strut to mount. The shorter the strut the stronger, or in this case no strut is necessary. There's really no reason that bulky pants should add much weight, as they replace an otherwise potentially heavy strut assembly and reinforced mounting surface.


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ID:	165730 All the assemblies pretty much there now. A lot of sheeting, assembly, and covering to go.
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ID:	165731 The wing joints fit together as well as I could have hoped, after numerous checks were made while assembling the wing panels. The LEs will be joined together with a laminate glued along their rear surface.
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Old 01-21-2013, 02:18 AM   #27
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Originally Posted by Bill G View Post
Thanks Barry. Everyone needs at least 2 Stukas. One of these days I'll talk myself into flying the larger one. On the pants, I've seen some over engineered modes with actual struts inside the pants and a heavily reinforced area on the wing for the strut to mount. The shorter the strut the stronger, or in this case no strut is necessary. There's really no reason that bulky pants should add much weight, as they replace an otherwise potentially heavy strut assembly and reinforced mounting surface.
How timely! I have a 48" Northrop Gamma I built a few years ago in need of repair. I was planning to build a whole new one using the formed foam technique. The original has the landing gear done as you describe with wire LG and vacuformed spat held on with magnets to service the always troublesome struts. Since I still have the vacuform molds, I could make fiberglass spats and skip the wire gear.

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Old 01-21-2013, 05:04 AM   #28
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Originally Posted by pmullen503 View Post
How timely! I have a 48" Northrop Gamma I built a few years ago in need of repair. I was planning to build a whole new one using the formed foam technique. The original has the landing gear done as you describe with wire LG and vacuformed spat held on with magnets to service the always troublesome struts. Since I still have the vacuform molds, I could make fiberglass spats and skip the wire gear.
The magnetic pants sound like a good idea. Seems like the axle could be built into the pant setup, and then there would be no gear struts to bend or break. I used GWS gear mounts on a Stuka, and made a wire frame for the gear strut that had a "U" bend at the top. The concept is that it firmly plugs in, but will move rearward and disengage, in the event of a hard landing. I've also used the idea for seaplane outrigger floats.

Crusader:
To fit the aileron servos in the wings, the wing former perimeters were laminated with hard 1/16" stringers before making the servo cutouts. This method has worked well for numerous builds, as there is not much material left after making the cutouts. For secure screw mounting, the formers were laminated with 1/16" hard balsa. I've found the hard balsa to be ample, as the glue lamination provides a strong layer to thread the screws into, and is much easier to drill than ply. I also talked myself into adding working wingtip lights also. The 12V model railroad lights are a bit dim on 2s, but are usable for 2-3s lipo.


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ID:	165746 Crusader wing with ailerons servos fitted for fake pull-pull setup for scale looks. The bottom linkage will be pushrod wire, with the top using CL string. Couldn't resist adding working wing lights.
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Old 01-21-2013, 04:15 PM   #29
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Originally Posted by Bill G View Post
The magnetic pants sound like a good idea. Seems like the axle could be built into the pant setup, and then there would be no gear struts to bend or break.
The magnet mounted pants will release if the gear flexes too much on a hard landing, which is good but they are getting beat up and cracked. The pants on the Gamma are huge so forces would be spread out over a large surface. I could also incorporate pins with more or stronger magnets so the whole pant/wheel unit could be removed or release on hard landings.

Crusader is looking good. Really not much rib left after you mount the servo!

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Old 01-22-2013, 03:00 PM   #30
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On the servos, I actually thought of using 3gm servos in the wing. The opening would be smaller, and the aft weight would also be less. I thought about mounting the servos in the forward area of the wing, but the linkage would then be too long, since the top linkage will have a scale pull-pull attachment. With this subject, the short nose doesn't provide much distance to add a smaller amount of counter ballast.

I started applying some of the Monokote Brown Metallic roll that is likely as old as I am. The glue takes real force and heat to work down, and would definitely not be good for a peanut scale rubber flyer with contest weight stringer construction. The fuse will be interesting, and will likely have to be covered with smaller sections as the stretchability/shrinkability is only so good. Mixing a decent matching paint color has also been interesting, using a mixture of silver, gold, brown, and tint of orange. The weight of the covering will force the use of some ballast (as if the model didn't need some already) but then again painting a covering to get the desired color would also add weight, which the pre-colored covering avoids.

After covering the tail feathers, I'm thinking it would be a good idea to cover the rear booms before assembly, as it will be easier than covering them after attaching to the wing. I'm having the same thoughts with sheeting the top of the outer wing panels before assembling them to the main fuse assembly. This build has been interesting, in that I was about 50/50 over the concept of building the wing panels in sections, versus single panels. I figured it would be a good experiment in using a different method than the usual one piece wing panels, which would definitely be practical on a larger build.


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ID:	165792 Applied Brown Metallic AncientKote to the tail feathers. Look at the old leaflet included with the covering roll.
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Old 01-22-2013, 04:02 PM   #31
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Hey Bill i have seen this planes plan before and the first thing i thought looking at it was the rudders looked kinda small . I like the 30's/40's look and the windscreen reminds me of a seabee. joe
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Old 01-23-2013, 12:04 AM   #32
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Originally Posted by road king 97 View Post
Hey Bill i have seen this planes plan before and the first thing i thought looking at it was the rudders looked kinda small . I like the 30's/40's look and the windscreen reminds me of a seabee. joe
The Rebublic flying Volkswagon Van. Yep we have one of those. It is similar looking in the windscreen area, and reminded me of the build when forming the front window pillars. Those guys kept it simple too, as windshield can form around the contour using a flexed piece of clear plastic, versus requiring a complex molded bubble shape.

The plan for this plane showed the rudder hingeline at some bizarre angle to the stab, which it does not appear to be in photos or the other few drawings I've seen. I corrected it when locating the rudder sparring that will be used to mount the rudders, since it helps to have some solid material underneath the covering (such as balsa versus air) in the area where covering is cut away for mounting. I imagine with 2 rudders they can downsize them a bit, but the stab seemed ample. Still, the stab was enlarged a small amount for the model, as more area can be a good thing at model size. The incidence is another question, where the stab mounting flat carbon fiber spars extending from the booms are currently set to provide a 0-0 setting with the wing. The plan showed the wing in the wrong orientation, which would probably provide a bit much positive incidence if set according to plan.


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ID:	165809 The "one of these days" Seabee. I'm a bit concerned about it being undpowered, but it may go.
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Old 01-23-2013, 03:32 AM   #33
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Originally Posted by Bill G View Post
The Rebublic flying Volkswagon Van. Yep we have one of those. It is similar looking in the windscreen area, and reminded me of the build when forming the front window pillars. Those guys kept it simple too, as windshield can form around the contour using a flexed piece of clear plastic, versus requiring a complex molded bubble shape.

The plan for this plane showed the rudder hingeline at some bizarre angle to the stab, which it does not appear to be in photos or the other few drawings I've seen. I corrected it when locating the rudder sparring that will be used to mount the rudders, since it helps to have some solid material underneath the covering (such as balsa versus air) in the area where covering is cut away for mounting. I imagine with 2 rudders they can downsize them a bit, but the stab seemed ample. Still, the stab was enlarged a small amount for the model, as more area can be a good thing at model size. The incidence is another question, where the stab mounting flat carbon fiber spars extending from the booms are currently set to provide a 0-0 setting with the wing. The plan showed the wing in the wrong orientation, which would probably provide a bit much positive incidence if set according to plan.
I would think it should have a little positive on the wing and 0 on the stab . joe
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Old 01-23-2013, 05:55 AM   #34
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Originally Posted by road king 97 View Post
I would think it should have a little positive on the wing and 0 on the stab . joe
Depends on the subject, where this subject has a short nose and a tendency to tailheaviness. What I have should be very close to the full scale aircraft, when looking over all the photos that can be found. There are photos that provide a pretty clear view of the orientation of the stab to to the booms. From what I've seen, this subject does not have much positive incidence between the wing and stab.

On the tail weight, I have the nose cap and firewall efficiently fitted for lead ballast, which is the most effective area to place it. The nose should be able to punch through brick walls. It's a bit of a guess without the motors and ESCs mounted, which will provide some ballast, but the amount appears to be in the ball park. You can't mount the gear forward enough in this subject. After covering the booms (yet adding more aft weight) I can start assembling the booms/tail/wings.


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ID:	165814 Sheeted the wing tops before attaching to the main fuse assembly. The nose cap and firewall behind it are efficiently fitted for ballast.
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Old 01-24-2013, 09:10 PM   #35
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After tacking the booms in place, I now have a better measurement of the wing-stab incidence which is 2 degrees, shown in the photo below. The plan created taller than scale booms, which required them to be repositioned a bit on the wing for proper alignment with the TE. This causes the booms to protrude a bit higher across the wings than scale, but I can live with it.

The rudder linkage is worked out, where bellcranks in the booms will transfer motion to the rudders, from pushrods routing to the rudder/tailwheel servo in the fuse. Checking numerous times, the rudder and tailwheel directions and rates should be properly synchronized. Rudder adjustment is provided by overlapping two pushrods in a single E-Z link on the rudder/tailwheel servo. The slightly more complex linkage setup is well worth using, to avoid the need for individual rudder servos mounted in the booms


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ID:	165853 The rudder pusrods which route to the booms are overlapped in the E-Z link, in the servo on the right. This will provide adjustment for both rudders. The tailwheel is also ran from this servo.
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ID:	165854 Bellcranks will be mounted in the booms to transfer motion to the rudder pushrods running inside the tail booms.
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Old 01-24-2013, 11:04 PM   #36
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My head is starting to hurt just thinking about having to work out the rudder linkage, and in such a small space to boot! Nice work.

Have you ever used the tiny Sullivan S507 cable and sheath pushrods? You can bend them as tight as a 1" radius and they are very light. I've used them for the twin rudders on my D-18 and on a HE-219 I'm building now. If you tin the end of the cable with solder you can put a Z bend in the cable and avoid the weight of the clevis. The cable is 1/32" and the sheath just over 1/16" diameter.

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Old 01-25-2013, 12:31 PM   #37
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Originally Posted by pmullen503 View Post
My head is starting to hurt just thinking about having to work out the rudder linkage, and in such a small space to boot! Nice work.

Have you ever used the tiny Sullivan S507 cable and sheath pushrods? You can bend them as tight as a 1" radius and they are very light. I've used them for the twin rudders on my D-18 and on a HE-219 I'm building now. If you tin the end of the cable with solder you can put a Z bend in the cable and avoid the weight of the clevis. The cable is 1/32" and the sheath just over 1/16" diameter.
I've been watching the 219 build. Nice build and subject.
I'm a big promoter of the Sullivan gold cable, with about 10 planes using it for ailerons. I like the benefit of using only one servo for weight reduction, when possible. A guy built a nice version of this plane on RCG a while back and made use of cables. Tinning the stranded cable is a good idea for making a z-bend. The ability to create z-bends with solid wire is one reason for using solid wire. The cable systems can even work well with .015"-.020" solid wire, although there's the issue with having slop in the small horn holes that need to be created for the wire, and tend to enlarge. One of the few issues I've had with the cables, is that the clearance between the cable and the sheath can create a considerable difference in the overall arc length, when they are transitioned 90 degrees. The cable then will buck back and forth inside the turn, causing freeplay in the cable. If the overall travel and control horn moments used for the setup are reasonably large then it is less of an issue, but if the throws and horn moments are short, then it can be considerable. The rudders on this plane will have fairly short horns. With cable or sheath, the adjustment would be done using the same wire/cable overlapping method at the servo E-Z link, as avoids adding adjusters in other locations. Tinning again sounds like it could help a cable when overlapped in an E-Z link, as they otherwise kink when the set screw is tightened, causing issues when readjusting.

One reason I had thought about using cables, is that the bellcranks are close to where harnessing is routed, and could have potentially been and obstruction. I almost went to a slightly smaller ESC. The nacelles were sized for them, with a plan for routing the harnessing, but just barely. I like the Dynam ESC with on-board switching BEC, but I really don't need it here with 4-sub micro servos planned for 2s lipo. I managed to fit the motors and ESCs in the nacelles as planned, with the harnessing routing under the bellcranks. I had planned to possibly cut through the LE behind the nacelles for added harness room, but didn't care to and now do not need to. One issue with motors like these, is that they do not solder flexible leads onto the motor windings at the motor. You pay extra for that type of motor. I learned in the past that the motor leads can be broken if flexed too hard, especially at the motor or the connectors. These motor leads were flexed as much as I care to, and fortunately they are still working, now packaged with the ESCs in the nacelles.

The tail booms are now mounted, which was good to get past. Measure, mark, check, re-measure, re-check....You can't put enough effort into mounting straight and level booms. The effort of building a framed setup with close to tab-slot type alignment had paid off, as it made the process much easier than locating and attaching the booms to something like a foam wing, with no indexing points. The framing locked in the front-rear position, and also located the booms on the main spar, reducing the amount of final positioning work.


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ID:	165858 Tail booms now permanently mounted. The booms will need to be faired into the wing, strengthening the attachment of the booms to the wing TEs.
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ID:	165859 These are the two boom locating points where the boom formers butt against the wing formers, and the booms rest on the main spar. Thr front boom former was later glued to the LE after fitting shims to fill small gaps.
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ID:	165860 Motors and ESCs just fit in the nacelles per plan and are servicable. A plate is needed to separate the ESCs and wiring from the motor, which may be done by placing a drilled bar across the lower motor mount holes, versus gluing in a separator plate.
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Old 01-25-2013, 02:43 PM   #38
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That first photo looks so cool! Lots of stuff crammed into not much space!

It's true what you say about foam building: sometimes you have to get clever about keeping things aligned during assembly. With the style of building I do, you are "off the plan" almost immediately and have to cut wing saddles, stabilizer cut outs, and the like in situ.

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Old 01-26-2013, 03:03 AM   #39
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The nacelles with motors/ESCs are now mounted, wired, and working. Sanding and installing custom motor shims from 1/32" ply was and interesting task, as well as installing the motor mount screws in the tight space. It's almost impossible to have perfect prop shaft alignment on a subject like this, without some final adjustment. The CG looked good with the 22gm lead coin in the nose, 2s-800 lipo, and the tail feathers tacked in place. The additional 18gms of lead (hopefully using even less) fitted in the nose cap should counter the aft weight to be added by the rear fuse covering and wing panels with slightly aft mounted aileron servos, yet to be attached to the plane. Given the subject and full weight covering being used, 40gms of ballast or less is acceptable, which could also be reduced with a slightly larger battery.


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Old 01-26-2013, 06:59 AM   #40
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Originally Posted by pmullen503 View Post
That first photo looks so cool! Lots of stuff crammed into not much space!

It's true what you say about foam building: sometimes you have to get clever about keeping things aligned during assembly. With the style of building I do, you are "off the plan" almost immediately and have to cut wing saddles, stabilizer cut outs, and the like in situ.
You said it Pat. Just where I am with my latest foam build now. It's been a joy to watch Bill set up this model so accurately during the design and build process. A real contrast to cutting free hand at block foam!
I still can't afford balsa though

Barry
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Old 01-27-2013, 02:08 PM   #41
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Originally Posted by baz49exe View Post
You said it Pat. Just where I am with my latest foam build now. It's been a joy to watch Bill set up this model so accurately during the design and build process. A real contrast to cutting free hand at block foam!
I still can't afford balsa though

Barry
One thing that's nice about the 36" span is that there really isn't much balsa used. When you go much larger, that changes really quickly. Efficient us of the sheet really matters also, as I try to plan out how the parts will be cut out from the sheets. It's nice to cut a keel from one single, long piece but that gets really expensive, so I'll go to the extra effort to section them together from shorter lengths. I also glue scrap together, throwing out only pieces smaller than a dime. After years of balsa builds, I only have a small box of scrap.

The wings are finally attached, which was a good step to get beyond. They were close to self aligning, but still required conservative tack gluing during the initial process, so that a joint could be cut apart if the alignment wasn't correct. Setting the dihedral required most of the attention. I'm pleased with the incidence match and straightness across the panels. A slight amount of washout will be set in the outer panels before applying the bottom sheeting. In the past I've done this by inserting braces that are fitted to slightly flex the framing. The concept is that they are installed under compression, which creates a small flex in the panel to create the desired washout angle.

When testing the aileron servos before sheeting the wing bottom panels, I came across a bad y-connector. After narrowing it down to a single wire in the lead, I took the outer connector apart to check continuity across the wire and pin. This is done by pricking the wire with a pin, and then checking continuity across the pin and the connector. I never had to go that far, as the connector pin fell off of the wire. Apparently it was never stripped, and the sheathing was also poorly crimped in the strain relief. The point of all that is that I often build my own leads, and am seeing the value in it. While I don't have all the "proper" crimp tools, at least I know exactly how each crimp has been done. There's enough things that can go wrong already, without having bad extension leads.


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ID:	165909 Wing panels attached. The panels were sheeted with additional sheet past the inner former, which was shaped to fit to the nacelle contour. This eliminated the need for a small filler strip of sheeting between the outer panels and nacelles.
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ID:	165910 CF tube sliced lengthwise, used to join the dowel rod wing leading edge across the inner and outer wing panels.
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Old 01-28-2013, 03:26 PM   #42
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Originally Posted by Bill G View Post
While I don't have all the "proper" crimp tools, at least I know exactly how each crimp has been done. There's enough things that can go wrong already, without having bad extension leads.
This D-sub crimper from Radio Shack works pretty well. There are much nicer ones out there but this one is cheap and was available locally.

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Old 01-29-2013, 07:22 AM   #43
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Originally Posted by pmullen503 View Post
This D-sub crimper from Radio Shack works pretty well. There are much nicer ones out there but this one is cheap and was available locally.
I'm making up my servo lead sockets as well having bought a bag of bits from HK. I must admit I hadn't thought of just crimping the wire to pin connection.
I've been tinning the last few mm of wire with solder, placing it into the crimp wings on the pin and then soldering it into place after bending the wings over. I haven't got a crimp tool, just small needle point pliers.
I guess I just don't trust the connection without the solder joint.
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Old 01-29-2013, 01:57 PM   #44
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Originally Posted by baz49exe View Post
I'm making up my servo lead sockets as well having bought a bag of bits from HK. I must admit I hadn't thought of just crimping the wire to pin connection.
I've been tinning the last few mm of wire with solder, placing it into the crimp wings on the pin and then soldering it into place after bending the wings over. I haven't got a crimp tool, just small needle point pliers.
I guess I just don't trust the connection without the solder joint.

I did the same before I got the crimper. Its hard to make a mechanically sound joint crimping but hand. Soldering makes sure you don't pull the wire out in use. The properly crimped joints do fit better in the connector shells.


The Crusader is coming along nicely. Got a projected weight yet?

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Old 01-29-2013, 10:22 PM   #45
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Originally Posted by pmullen503 View Post
This D-sub crimper from Radio Shack works pretty well. There are much nicer ones out there but this one is cheap and was available locally.
I have one similar to that, but they seem to work better for slightly larger pins. The problem with S-connector and JST connector pins, is that if they aren't perfectly folded over then they won't fit in the connector. I've been carefully folding the tabs over with tweezers, which enables them to fit in the connector. A good pressure crimp can be applied afterwards. The JSTs are a real pain with 18GA wire. For soft silicone battery lead insulation, the tweezer "wrap around" method works well for the strain relief, as a hard crimp cuts through the soft silicone. Soldering like Barry suggested makes a really good connection, but it's difficult to not flood the connector with solder unless you're careful and use a pin tip iron. The darn expensive MPI sets that I buy at the LHS give you no extra pins. I'll have to buy a more cost effective quantity like Barry did, as I hate to ruin even a single pin. Given the several bad servo and extension lead connectors I've encountered over the years including one here, I'll still trust a crimp that we make with tweezers over one that we haven't looked at and are trusting blindly.

With everything on the scale, the AUW should be 16-17oz, accounting for the additional covering required, receiver, clear window plastic, and a few other items. The roughly 40gms of ballast that it should need is really not that bad, as I could reduce or eliminate it with a heavier battery. I often use small lipos in the 800-900mah range for planes this size, as they allow for smaller battery compartments and access doors. Using ballast at the furthest point in the nose is also more efficient than using a heavier battery, as it is not located as far forward as the ballast.

Lots of faring work to be done now, and then that exciting covering stage. I'm thinking it will be wise to install the tail feathers much later, as it may be difficult to not abuse them with all the handling still to be done.


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ID:	165968 The window line is parallel with the root incidence, and has apporximately 2 degrees positive incidence to the stabilizer mounting CF spars. Washout is approximately 1.5 degrees.
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Old 01-30-2013, 03:26 AM   #46
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Looks cool from the back!

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Old 02-01-2013, 11:31 AM   #47
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Originally Posted by pmullen503 View Post
Looks cool from the back!
I think it looks kinda like the back of the cars from that era, as if you stuck a 36 Chevy body on a P38.

Not much done lately, but I've finally added the wing and boom farings. I'm notorious for omitting wing farings on warbirds and other planes, but this plane calls for them even more than a Spitfire, with the large farings that flare far onto the fuselage and wing. Wouldn't look right without them, although covering them with the old, heavy Monokote will be interesting. I may apply Balsarite to the fuse and farings, to increase adhesion.


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ID:	166015 Rouded gussets formed to create the wing farings, which will be sheeted with 1/32" balsa.
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ID:	166016 The farings are coated with a layer of CA after shaping, to add strength to the already thin, and now sanded even thinnner balsa sheet.
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ID:	166017 Filler added to farings for final sculpting. Most of this liberal application of filler will be sanded away.
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Old 02-01-2013, 01:46 PM   #48
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Someday I'll figure out a good way to do fillets....

Covering that with Monocoat should be interesting!

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Old 02-01-2013, 10:49 PM   #49
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Originally Posted by pmullen503 View Post
Someday I'll figure out a good way to do fillets....

Covering that with Monocoat should be interesting!
There is no good way.
Seriously this method worked out pretty well, once I realized that it was better to just get started cutting out the fillets and fitting the individual sheet sections, rather than debating how to do them with fewer individual pieces. It was less work than expected once started. Sculpted foam would be a good route, although with this old, heavy covering, the foam would also have to be coated with something that would resist damage from the iron force required to work the covering down. Even with the CA coated thin balsa sheet I'll have to be careful. The Balsarite should really help however, as the covering is now sticking down with much less working force.

Coating with Balsarite seems to really help adhesion with an ancient roll of Monokote covering. I started covering some of the rear fuse, and the bond was much better than with the booms. For the booms, I basically just wrapped the covering around, ironed the overlap seam, and then used a heat gun to shrink the covering. Without the Balsarite the adhesion was terrible, which certainly wouldn't have worked for the complex fuse shape. Other than having to work with relatively smaller sections, the covering will be fine. At least I'm now past the worst part, which is getting started. I can spend forever debating how to partition a covering job like this.


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ID:	166023 Started covering the rear fuse using Balsarite, which really increased the adhesion. I have a feeling this may take a while, as I can only take covering in short sessions.
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Old 02-01-2013, 11:04 PM   #50
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Foam fillets may not have taken the heat either.

I like the color; looks like a something from the 30's.

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