doxilia

My Feedback: (3)

Lamar,

Yes, the 55AX would be an excellent choice. Of the three engines, that's what I would use. As for the side mount, that's something I wouldn't worry about much since you're going to have to give your FW and cowl some TLC to get them back in shape. If you prefer the side mount, stick with it. The advantage is that it positions the muffler with the exhaust pointing downwards so if you are going the run the 55 with a muffler, go side mounted. If you plan to pipe it, I would rotate to vertical (or 20 deg CCW) for an easier and faster model to assemble and disassemble at the field. The pipe would put the exhaust past and over the wing which can also be directed downwards with a silicone deflector. That said, I would strip all paint and covering from the model and take a good look at the integrity of the FW and engine mount before proceeding with engine mounting. One more advantage of the side mount is that it puts the carb line closer to the tank center line on Bridi designs such as the DB.

In that case, just strip it, reattach and do some fresh epoxy/microballoons (MB) fillets around it in prep for reglassing the fuse. Or you can glass and then reattach (my preference). You could use Koverall on the fuse as well but I think a 3/4 oz glass cloth and laminating epoxy (or polycrylic resin) finish would produce a more durable and harder surface for the primer and paint.

Yes, this was the common approach with mechanicals back when servos were expensive 30-40 years ago. Most classic builders dispense with that approach today as using dual servos (one for the mains and one for the NG) makes life much easier. Having to connect the NG pushrod to the wing servo each time the wing is mounted/unmounted (much like the pipe but more tedious IMO), is inconvenient at best. If you decide to stay with a mechanical setup all around (assuming you can either get the mains working properly again or buy a set of new mains), I would use a standard retract servo in the wing for the mains and add a mini servo (it doesn't need to be a retract servo nor does the one for the main for that matter) to the NG bay for the nose. This will allow you to close up the unsightly gash in the wing bottom (why the servo is mounted inverted I don't understand but the builder probably figured it was easier to install the wing, attach the pushrod from the underside and then cover up the gash with a hatch plate. Not too elegant but an easier solution nonetheless).


I would agree with Ken in that if you can clean up the gear and get them to work, it will be one less task to do on the wing and nose. If the mains are more trouble than they're worth, then installing some Hobbico, Dave Brown or other mecahnicals is not rocket science. You will have to unsheet the wing probably about the width of the wheel well (it looks like its coming unsheeted in any case) and install a pair of 1/2" wide by 3/8" deep hardwood (or plywood) rails much like is shown on my wing build in the previous post.


And yes, you can and should use the same wheel wells as the LG axis is set on the plans and is CG dependent, or, otherwise put, the axis is typically just aft of the CG allowing the model to rotate easily upon takeoff and landing on to the mains. Often the LE of the wheels is aligned with the CG.

As mentioned above, you can use either a standard analog mini servo for the mains or a retract servo. The latter are high torque but more importantly they are 180 degree servos meaning they don't "run" (i.e., draw current from the battery) after their cycle is complete. On the negative side, they don't have end point adjustment like regular servos so you have to adjust the retract throw with the pushrod location on the output wheel of the servo. This is usually not an issue as these servos have output wheels designed for this purpose. Modern retract servos such as the Spektrum A7040 are end point adjustable and their rotation speed can be adjusted (if your radio has such capabilities), although 2 sec "slow" by default on 6V, for more realistic operation. The draw back is that they are not auto shut off (at least not to my knowledge) like the older analog versions (e.g., Spektrum A7000). Here's the web page for the A7040 FYI:

http://www.spektrumrc.com/Products/D...odID=SPMSA7040

Another option for the mechanical mains is to use dual mini servos essentially converting the mechanicals into e-tracts of sorts. The photo below shows how this is often done on scale models. The dual mini's and shorter linkages are equivalent in weight to the longer linkages and single retract servo in the middle. Each system has its pros and cons but I won't get into that.

The refurbishing process will give you plenty of latitude to decide what you want to do. Some like the torque system but instead of using a single servo as you show in the photo, they install dual mini servos side by side with the linkage of each torque arm going to the outside of each servo. This allows for trim adjustments of each aileron independently and even allow flaperon type functionality which although not of much effect on strip ailerons, is something one can play with. In short, if you are going to remove the controls (wise decision) and re-hinge with new hinges, putting the servos outboard of the LG about 1/3 of the way along the control is more effective and keeps your wing center section "clean" avoiding any potential interference of the aileron linkage with the rest of the gear in the radio bay. For these reasons, dual outboard aileron servos is the standard approach today but essentially it is an extension of the dual servos on torque rods concept. Of course, if you remove the ailerons for finishing you can get rid of the torque rods from the wing OR..., if you wanted to experiment with flaps, you could simply use a centrally mounted flap servo with a single Y-forked pushrod to the torque rods. You would then replace the inner portions of the ailerons with a 5-6" length per side of wider flaps (e.g., 2" wide). The ailerons would be shortened correspondingly which is not a bad thing anyway as it would keep them out of the prop wash. You can have the aileron/flap junction flush or put a small piece (1" or less) of fixed TE in between - whatever you like best. These of course are just ideas on mods you can make to the design given the refurbishing opportunity. Also, they serve to illustrate the type of setups we have on some classic pattern designs such as the Aurora shown by Ken or, the probably better known Prettner Curare.

David