John Payne

Hi Steve, thanks for the interest in the blog. If you are building from the kit it will be slightly different from mine as it is from the original plan. The original actually had a knock-off engine plate(!) which I have chosen not to copy.  The older models are normally the same with engine bearers and a separate plate for the engine to mount onto,either made from paxolin or plywood depending on engine capacity.  The norm was to mount the engine and "adjust" (read carve!) the cowling to suit the engine and ensure enough cooling air could get aroung the engine.  I would sugget that you mount the engine upright for ease of access, make the upper part of the cowling removable, probably secured by a couple of screws at the front and sowls at teh back, and make sure that you have access underneath to get at the lower securing nuts.  I often use another removable cover as the lower part of the cowl. I would not recommend using woodscrews to secure the engine, use nuts, bolts and washers. If the kit uses a modern mount with a ply firewall, just carve the cowling to suit the engine you use, again with enough cooling air around the engine, and glue/screw the cowling into place so that you have access for maintenance and removal if necessary. Either way, do not glue the cowling in position so that you have to cut it away for access to the engine once it is installed. You only need one bolt to come loose and it would ruin your day! Hope that helps. If not, let me know.

OK Timbo, thanks for the quick response.  That clears it up.  Now I can go ahead with Spektrum kit.   Cheers, John.

Timbo, I am considering getting some Spektrum gear, the DX7 plus a couple of other receivers to help move over completely to 2.4, and a comment in one of the earler posts made by you made me think.   You said that you often have to wait a long time for the transmitter and receiver to lock together.  Why is that? Not wishing to start a Futaba/Spektrum war, I have a Futabe 2.4 set and it is a matter of switch on and go. What am I missing? Is it to do with the different technologies used, and what is a long time?   My apologies if I have misunderstood what you wrote.   Thanks for the help.   Cheers, John.

Hi Sheldon, thanks for the post and the compliments.   The engine is being made from scratch from plans published by the Model Engine News. the engineering work is being done in Frank's home workshop and some more details should be coming out soon via this build log.   I am glad to hear that you have used this type of servo on bigger models as this is the first time that I have used them this small.

That is true Simon, one or two little things did show up on the quick assembly. Easier to fix now than once it is covered, that is for sure!   Thanks for the post.

Progress on the airframe has been slow but steady over the last couple of weeks. As I said earlier in the build log I have to wait for the engine to be finished so that I can finally complete the front of the model.  We don't know how the exhaust system or fuel tank are going to be put into the frame and rather than finish the tail end and potentially damage it when I move it around to fix the front I will leave it unattached.   So the progress to date is to complete the tail components to a position where they can be fixed when ready, fix in the tail wheel mounting plate, fix in the servos and fit the wing seating strips in.   The first photo shows the tailplane and elevators, from 1/4 sheet, with the joining wire, from piano wire, for the elevators. In the photo below you can see the slot I had to cut to get the rudder control down to the servo.   The secured tail wheel mounting, with wire bound on with thread and epoxied in.   The next photo shows the tail fin and rudder with the control wire, again from piano wire.  The rudder was locally reinforced to take the control wire.  The connection to the control rod can just be seen. It is a simple aileron connector secured by a collet.   The wing seating strip it there to allow the wing to sit nicely on top of the cabin area and is made up of 3/16 square strip.  The wood for the cabin header is made up of two pieces of 1/4 balsa and will be finally shaped once the front end is complete.   The final photos show the final assembly to this stage and is one thing that I like to do regularly as I go through a model build, just to enjoy the way it progresses to a final model.     The next bit will be to cover the wing, which I can finish, and finalise the connections to the servos and the servo cover, but I can't secure it yet.

Slow but positive progress on the airframe this week.   One thing that has given me something to think about has been the way that the radio guidance would be completed and I didn't want to have any more evidence of it than necessary. I finally came up with a method of mounting micro servos in the lower part of the tail fin.  This would do a few things.  I am sure that tail weight will be needed to counter the weight of the engine. I wanted to keep the installation simple. It his the controls under the tail plane. It gave me an opportunity to make the tail plane more secure as I am not convinced about the narrow fixing on top of the lower part of the fin.  The original had a banded on tail which was on top of a diamond shaped ply plate on the lower fin portion.  If it got knocked on landing it was simple to refit. The following photos show the servos positioned in the lower fin, not yet screwed into place.     The servos are 2Kg units.  As the intention is for radio guidance rather than anything aerobatic I think these will be fine. I have used "full size" square servo mounting grommets and will use a single screw to secure them. They will get a cover over them to keep the diesel residue off them and it is this cover that will help secure the tail plane to the lower fin. I haven't worked out the final details yet but it should help brace the joint.  I cannot complete this yet as I haven't finished the engine installation, which cannot be completed until the engine is finished, hence the slow progess at the moment (my excuse anyway!).   I have also bent up the tailwheel mounting wire from piano wire.  this will be fixed to the former shown earlier in the build log.  It just needs the holes in the former to enable the wire to be bound into place.  I will fill in around the exit point for the wire so that I can cover the fuselage properly. The photo does not show the shape of the mounting very well as it is a straight on view.  

Hi Malcolm.  You didn't miss much.   I used quick set epoxy for a couple of reasons.  The main one was that as I was physicaly holding them in alignment while it set, teh whole thing took a lot less time and I deidn't get too much cramp in the fingers!  I do it this way as I have had wings move in the past when I thought I had got them secured well during gluing, only to find they have moved out of alignment. Not easy to correct!   The second reason was I figured that as a butt joint the glue would be strong enough to hold the wings together while I secured the braces in place.  After that , I'm not sure that the joint itself comes under that much stress so a stronger epoxy wouldn't add that much. I am also going to add a narrow strip of nylon around the centre joint to provide bonding between thesheeting on the wings and this should add a lot more strength for a very small weight addition and provide support at the rear of the joint. At the moment the wing stands at 5 1/2 ounces.   As you suggested I did lightly sand the plywood to get rid of any release agent on the wood and make for a better bond.   Thanks for the note. 

For those people interested in the engine, I have included below a couple of photos of the crankshaft, which is now virtually finished and can report that the liners are now done with the exception of the transfer and exhaust ports.   From memory, only the prop driver taper has to be finished on the crankshaft and this will be done at the same time as the prop driver itself.  The sharp eyed will notice the rougher apperance of the diameter where the taper will be.  The extension on the front of the crankshaft was to lead in the die used to cut the thread on the crankshaft and will be removed later.   I have also persuaded Frank to join in with the forum to explain, better than I can(!), the progress of the engine manufacture and pick up any queries anyone may have about how he is machining the components.

On with the assembly of the wings.   The first job was to roughly plane and sand the wings to shape and make sure that they are the same profile.  This was done using a razor plane and a Permagrit sanding block.  I stopped at getting the wings to roughly near shape as I still had to handle them and the possibility of minor damage meant that the final sanding to shape could be left until the complete wing was ready for the covering stage.  To get them together I glued them up and held them in place using 5 minute epoxy and held it until it had achieved a good enough set to hold them in place without my help.  I then left the assembly to completely cure. The final result is shown below after the wings were joined.   Next I had to fit the dihedral braces to the front and rear of the main spar.  The original plan shows a two piece wing with tubes and dowels holding them together for flight.  I had to modify this for RC use and putting a 1/16 ply dihedral brace at the front and rear of the main spar looks as though it will be strong enough. I took the braces out to the third rib. To get them into place I cut out the lower sheeting to give me enough room to clamp the glued in brace to the spars.  I did it this way round to make sure the braces were a good fit to the final dihedral, rather than juggle with the central rib angle to suit the braces (don't forget these braces are my addition and not detailed on the plan). To cut the slots I used two hacksaw blades together which gave me a slot equal to the width of the plywood used.  Once the slot was cut into the relevant ribs, it was a quick clean up to ensure a good glue joint and the rear brace was glued in and left to fully dry.  The photo below shows these operations, with the blades cutting the front slot after the fitting of the rear brace.   The wing was now solid enough for the fitting of the front dihedral brace, using a similar cut and fit exercise.  Doing it this way round I believe that no undue stresses are introduced into the wing in this area and the braces were slid into place and secured, rather than trying to get the wing together around the dihedral braces in one assemble operation.  Just a personal choice really.  The photo below shows the securing of the front brace.   To finish the wing I simply glued back in pieces of sheeting to replace those removed to allow access and a final sanding will make the cut and shut exercise look OK.