Jemima Again

[Fredrum]

I'm hoping a Mod might be able to help me with a tech issue. I have just tried to update my blog but when I click on the Insert Image button to upload a photo, the last 9 pictures I uploaded to my album ('Jemima' don't appear in the list of available photos. I opened another window and checked the album and the photos are there. Am I missing something?

Edited By Fredrum on 11/11/2014 11:37:59

[Fredrum]

OK, I worked it out. Once the image count got to No. 99, the album reordered numbers 100 and up to come after image 09.

Anyway, I spent a bit of time doing some design work on the cowl. I have decided to incorporate some air vents on the sides. I don’t know yet if this will be in character with the original design, but if I don’t like it, I can redesign it later. I only got as far as making up the blank for the cowl ply facing plate for now. The cutouts for the motor mount and battery opening were made and the plate was put in place. The outline of the fuselage was traced onto the mating face of the ply and the final shape drawn on. I also drilled for the locating dowels. Eventually I will make another ply plate for the front of the cowl then plank it (I’ve always wanted to have a go at that).

 

Edited By Fredrum on 16/11/2014 05:23:44

[Fredrum]

I managed to get a full day’s modeling in today (well it is my birthday!). I have been putting off the tail attachment and cowl for a while because I need an extended session to get them going. Perfect opportunity Starting with the tail attachment: I have been giving this a bit of thought and the limiting factor is sourcing a screw long enough to go from the bottom of the fuselage and through the tailplane and fin while still being thin enough to be contained within the structure. I have been unable to find anything suitable, so it will have to be made. I bought some hardware from the LMS yesterday (more birthday perks) including some 4-40 allthread and some T nuts. I cut the head off an allen bolt, drilled and threaded it to take the rod and held it in with super thread-lock ending up with a bolt that is around 2.5mm diameter and as long as I want.

A hole was drilled in the bottom member of the rudder to give a clearance fit for the bolt. Putting the rudder back in position, A hole was marked and drilled through the tailplane. Both these holes were hardened with some thin CA as the bolt will be used quite a bit.

The sides were ground off a T nut which was glued into a hole drilled in a piece of scrap balsa. The allthread was inserted into the hole in the assembled tailplane rudder and the T nut/ balsa block glued in place and the edges sanded flush.

I intend having the 4-40 bolt contained within an aluminium tube for location. A cross brace was drilled to support the top of the tube and was glued in under the tailplane seat. A matching brace will be added to the bottom of the tube later.

Unfortunately, the ply I used for the cowl facing plate was bit warped and doesn’t sit flat against the firewall, so the first job on the cowl was to make a new one along with a ply nose plate. I also decided at this stage to reinforce the firewall as I had used 3mm ply and it was a little flexible.

Locating dowels were glued in and the facing plate positioned against the firewall. I made up a jig to hold the nose plate in position on the motor while I built the cowl frame in-situ. This consisted of a spacer turned up on the lathe to locate the nose plate centrally on the prop adaptor and a block of MDF counterbored to position the nose plate the correct distance from the firewall. The nose plate was held onto this block with double sided tape and the whole assembly held on the motor shaft using the prop adaptor.

The basic outline of the cowl was sketched in using scrap 6mm balsa at the top & sides taking care to get each side fairly similar. The lower ones were a bit trickier as they curve in two planes, so I used 20mm balsa to make some chunky blanks to give me plenty to play with.

Here it is so far with the jig removed.

[Fredrum]

Started on the top of the nose. A piece of scrap 6mm was placed behind the top of the cowl, and cut slightly over-size. A piece of 20mm balsa was made a bit wider than the windscreen support in the same fashion and shaped to size before gluing it in place it in place to form the lower windscreen support. The 6mm piece was glued in behind the top of the cowl (but not to the cowl itself). Two lengths of 6mm sq. were glued in either side. These four pieces will form the opening for the nose hatch.

[Fredrum]

I wanted to make up some framework to support the planking on the nose area. I started by installing the retention magnets in the cowl facing and some cut off screws in the mating face on the firewall. The cowl snaps into place tightly, but not so tight as to require squeezing too much to get it off.

The cowl frame was sanded a bit more to get the geometry right. The location of the transverse frame pieces was marked on each of the existing frame members. With the cowl off, the outline of the ply facing plate was traced onto some 5mm balsa sheet, making up four pieces. The shapes were cut out and the mating joints were adjusted for a reasonable fit, pinned on and glued.

The battery hatch frame was constructed in situ with some paper inserted all round the edges to create some clearance. The hatch area and new cowl framing was sanded down flush. It’s starting to look a bit like the nose of an aeroplane

While I was at it, I finished off the tail fixing assembly by gluing in the aluminium guide tube, the lower tube fixing and cutting the bolt to length.

[Fredrum]

Time to attack the metalwork. I bought myself a new 60W iron just for this job and I must say that after hearing many modellers say that they dislike this part of the build, I didn’t mind it at all.

I wanted to make the undercarriage screws captive so that they don’t get lost when the model is packed away. The T nuts were attached to some ply packers then were glued inside the undercarriage plates. I made up some P clips for the undercarriage by bending some brass around some undercarriage wire in the vice. This took all of a few seconds after figuring out the first one. The clips were drilled a tapping size for the screws and the screws themselves were used to tap a thread. The thread on the screw was filed away just under the head so that when they are tightened, the screw is free to turn in the hole.

The clips were slipped onto some wire and the two pieces bent to shape. The two wire components were screwed to a ply board using the P clips and the joints bound with copper wire. Out with the new soldering toy, which made short work of the joints. I realized later that I could have done a neater job and made the job easier at the same time by using strands from electrical cable rather than the heavy stuff I found at the hardware store some time ago.

While trial fitting the assembly on the plane, I discovered that there was a lot of flex as I had used a thinner gauge wire than that recommended because it was what I had to hand, so I made up a pair of cross braces & soldered them in.

Next job was the tailwheel assembly. I made up a ply plate to go into the underside of the tail with two T nuts on the inside. It was a bit thinner than the space it was going into, so I faced the outside with balsa for sanding flush. The bracket itself was made from thickish brass with some thin brass soldered over the holes, again for screw retention. A short piece of brass tube was soldered into a hole at the back end to act as a bearing. The tail undercarriage was bent up and brass washers soldered either side of the wheel. I will insert it into the bearing and do the final bend later.

Both assemblies were painted with metal paint. I realized after fitting that I should have soldered the P clips to the wire as the undercarriage is free to slide a bit sideways with a little effort. I might take some paint off and solder them later.

[Fredrum]

While I was in a metalworking frenzy, I made up a pair of clevis adaptors for the pull-pull rudder system. These were made by inserting a threaded rod into a brass tube, lightly crimping to hold them in place then soldering. The other end of the tube was flattened and drilled.

I had a go at making up the windscreen. I wasn’t sure it would work, but I remember reading about this method some years ago. I started by making up a cardboard template, adjusting it until it was a good close fit over the nose. Another template of the windscreen profile was traced onto a piece of 1/16^th scrap and used to make up a wooden plug. The cardboard template was wrapped around this and the nose curve drawn on the plug with a felt tip pen.
The bottom and top were cut off a soft drink bottle. This one had a smooth section just the right size in the middle. The plug was placed inside and the bottle shrunk with a heat gun. It worked much better than I expected and the plastic is quite thick and solid but completely clear. I did discover however that this method doesn’t like sharp corners. Luckily, I made the plug higher than I need, but next time I will round off the top edge to help shrinkage.

The plastic was cut around the edge of the plug, including the line I had drawn for the nose curve and it was done. I can trim the top and sides to exact size and glue on later. All I have to do now is work out how to make the long side panels.

[Fredrum]

My first intention for the control system was to use a snake for elevator and a pull-pull system directly to the servo for the rudder. I found it difficult to find a direct path to the tail end for the pull-pull cables without cutting into the fuselage frame so it seemed that an intermediate control arm would be needed. Even then, it would have been necessary to have it back in the covered part of the fuselage, which raises a maintenance issue. It would be annoying to have to cut away the covering just because a nut came loose or a cable needed replacing.

I decided to go back to the pioneering days of aviation and have the cable run entirely outside the fuselage. The idea is to have a pushrod from the servo operating the control arm, which projects outside the fuse and cables going back to the rudder horn, which is the same length as the control arm.

I set up my control system geometry checker to make sure that the throws are in the ballpark with this set up. After drawing it up full size in relation to the airframe and a bit of fiddling here and there, I have all the measurements and servo placements.

A control arm and rudder horn were knocked up from 2mm ply, taping the blanks together and drilling to ensure the hole spacing is identical. The outer holes in the control arm were bushed with 1/16^th” OD brass tube where the fishing trace will go though. I have to get some larger tube for the clevis pins and centre bearing in the control arm. The rudder was notched where the horn will be glued in after covering.

[Fredrum]

Some brass tube with a bore to take a 4mm bolt was used as a stand-off for the rudder control arm and another piece used as a bearing inside the central hole which was bushed with the next size up tube.

The whole thing was assembled on a platform and glued in place in the fuselage. A servo tray was made up and the servos screwed in. The control rod from the servo to the control arm was installed, the servo tray positioned and glued in. As I intend on glazing the windows, I coloured the inside of what will be the visible part of the interior of the model as well as the outside of the frame under the glazing.

Finishing off the fiddly bits at the back end. The elevator control horn was made up in brass. The keyhole in one end is for a short 1/16^th wire key to take some of the torsional load. The horn was threaded onto the elevator joiner wire, which was then bent to shape. The key was inserted into the keyway, wrapped with a strand from electrical cable and soldered by hanging the horn down over the edge of a scrap block.

The holes for the joiner were drilled in the LE of the elevator halves and various grooves and notches cut to make the whole thing work. The tail wheel assembly was finished at this point by threading the undercarriage through the bearing and making the final bend. The LE of the rudder was drilled and undercarriage inserted.

The whole thing was assembled and attached to the fuselage. On full right rudder, and up elevator, the elevator horn and the rudder are quite close, but I think I will just get away with it. Fingers crossed!

You can see here that I misjudged the location of the slot for the rudder control horns, which had to be made lower. I wasn’t too upset about this, as I had made the slot a bit too wide anyway. I’ll plug it up later.

Fit the elevator snake and a surround for where the rudder control horn protrudes from the fuselage to give some support to the covering.

Finished off the cowl framing and finally on to the planking of the cowl. This is something I have been keen to have a go at for some time. Much more time consuming than I expected.

[Fredrum]

The planking was finished I one piece from the windscreen area to the nose after which the cowl and nose hatch were separated with a scalpel. I didn’t really have enough support framing in the hatch and the planking was flexing a bit, probably because there are a few gaps. This was fixed by a method I use to repair tambours on furniture. I cut a couple of pieces of cotton sheeting and glued them into the underside with thinned glue; sort of like antique fibre glassing. Once dry, the planking was quite solid. The outside was looking a bit rubbish at this point, but with a bit of sanding and a touch of filler, it doesn’t look too bad.

Some flat head nails were ground down smooth on the head, cut down to about 6mm and inserted into the hatch opening using some scrap at the rear and drilling into the firewall corner brace at the front. Some corner braces were glued into the underside of the hatch and four 5mm magnets epoxied into corresponding holes. I had originally thought of gluing an antenna into the top of the hatch to use as a handle, but I find I can easily reach in through the wing opening and pop it up from the inside. Still some sanding to do.

Edited By Fredrum on 21/04/2015 01:30:49

[onetenor]

Hi Can I jog in here > I have a couple of ideas which may be of interest. A) glazing flat or just curved in one plane is best done with with a strip of Acetate or whatever applied from the inside.. Clear glues like UHU work well with most of these plastics. Test out first. A contact type glue will stick those that won't secure with the others. And now ( B )Why not make the tip panels removable / knockoffable. Handy for transport and crash protection. Box and tongue with hard balsa pegs would do it. Eezee Peezee as they used to say and fits in with the vintage feel of this lovely model. Saved me a repair many times landing a lightly loaded plane in a crosswind. and fits nicely into a travel box. . Give it a try next time you do polyhedral wings. An old trick but a good 'un. VERY nice build BTW . .I'm Watching with interest.

P.S. Bare balsa colours nicely with sprayed on water coloured paint water with no weight penalty to speak of..

[Fredrum]

Thanks Onetenor. Acetate is probably the best way to go for for the side panels. I was going to get some sheets for overhead projectors, but out our way, I would have had to buy a whole packet, its not cheap and I only need a small amount, but now that you have mentioned it, I will be on the look out for some packaging material. I have some canopy glue, so there's no problem there and as long as it has a reasonable shelf-life, I imagine it will do me for many models

The wingtip idea is a really good one and I wish I had thought of it. It certainly would have made transportation/ storage a lot easier as well. If I do another polyhedral wing I will certainly consider it. I understand the principle of sliding them on and off, but what would be the best way of retaining them to allow them to come off in a hard landing?

[Fredrum]

Have spent some time adding in a few bits here and there to support the covering scheme I have in mind and have sanded the entire airframe.

I haven’t been able to source 1/64” ply anywhere so have decided to just sheet the centre section of the wing in 1.5mm balsa. I may even finish this off with fibreglass to avoid crushing when fitting the wing bands. I brushed some ammonia onto the front of the sheet to aid bending. It easily went round the leading edge without splitting and I have glued it back to the first stringer underneath.

[Fredrum]

Unfortunately work has been getting in the way of my modeling activities lately (I know, I need to sort my priorities), but I have managed a few bits and pieces over the last couple of months. The planking on the cowl has been filled and sanded and I have fibreglassed the centre sheeting on the wing.

I have added a small amount of extra sheeting on the wing and tailplane to support my intended colour scheme and the airframe has been sanded ready for covering. The only thing now is to sand and fill the fiberglass and get covering. I have already covered the underside of the horizontal stab. It was my first attempt at iron-on covering and although it’s not perfect, I’m reasonably pleased with it. I should have the techniques down by the time I get to the upper surfaces & fuselage.

I have also worked out how I’m going to approach the glazing and framing, but more on that later.

[Fredrum]

Finally, after just over a year of piecemeal construction (apologies to anyone who may still be following this), I finally get to add a bit of colour. Not having used shrink film before, I started on the underside of the tailplane and elevators for a bit of practice. Having gained some (over)confidence, I had a go at producing a basic colour scheme on the top surface. In the right lighting conditions and at the right angle, and with a bit of squinting, it doesn’t look too bad.

Just a little bit of filling and sanding on the firbreglass, and I can get going on the wing.

[Foxfan]

I used to get 1/64th ply from John Flack, but when he died, Eileen's Emporium took it all over. Model boat suppliers are your most likely source otherwise.

Cheers,

MrTin

[Fredrum]

Thanks Mr T. When I start my next build, I'll certainly be looking into model boat suppliers. Sorry for the lateness of the reply. Work has been keeping me out of the workshop for a couple of months and for some reason I didn't get a notification on your comment.

I have been doing some boring odds & ends like filling and sanding the fibregalass on the centre section sheeting on the wing and sorting out the radio installation. I've finally bought a couple of LiPos and the AUW and the CG are looking promising.

Managed to get a few hours in this evening so I covered the underside of the wing. I think I’m starting to get used to this Monokote lark. There are a couple of slightly dodgy bits such as the step in the leading edge at the centre sheeting. It can’t really be seen in the photo, so maybe I shouldn’t have mentioned it

In its bare frame state, this is a very large wing but with the covering on, it looks absolutely massive. The sharp-eyed among you may spot the very clever and well executed vent hole near the centre (got a bit overzealous with the heat gun). I may patch it up after covering the top, or I might not bother seeing as how it will be inside the fuselage when the wing is mounted. I’ll have to wait and see how much it bothers me knowing it’s there.

[Fredrum]

A bit of mucking around with the glazing this evening. I’ll be doing each window as a separate panel so a bit of plastic coke bottle was shrunk over a piece of thin ply which will provide a panel each side. I’ve been pondering how to firmly attach the windscreen and have decided to bury the bottom of the panel in a slot just behind the battery hatch. To make the slot, the profile of the windscreen was traced onto the fuse with a fine marker. A sharp scalpel was used to make two parallel cuts using the line as a guide. The waste was picked out with an old scalpel blade ground to a shape similar to a very fine hinge-slotting picker.

The windscreen was inserted and trimmed to size.

[Fredrum]

Wings all finished, but not without its dramas. I had to pull the covering off one wing tip when I burned through it with the heat gun. It’s not perfect, but I’ll just keep telling myself that I’m at the beginning of my RC journey and the next one will be better

[Fredrum]

Bought myself a cover for the sealing iron and a Coverite thermometer. Wow, what a difference. The iron is no longer marking the film and it turns out I was using the iron way too hot. Wish I had done this at the beginning.

Fin & rudder covered.

[Peter Miller]

SLEC sells 1/64" ply

[Fredrum]

Hi Peter. Fancy sending a widget addict like me to the SLEC website. I almost had to call for an intervention. Will be worth looking into for my next project (under strict supervision). Thanks.

Underside of the fuse is covered. Also covered the cowl. I had two goes at it; the first attempt with the heat gun (rubbish) and the second (more or less successful) with the iron. Very time consuming and a bit dodgy in the end.

I also partially covered one side of the fuse, but I stupidly gave the framing under the wing a coat of enamel thinking I would get an extra bit of colour on it before covering. Of course, the heat from the iron just turned it back to liquid and there was very little adhesion, the result being that when I shrunk it with the gun, the join gave way (not to mention blistering the enamel). So I pulled the covering off and cleaned off the adhesive and enamel with acetone ready for another go tomorrow. The frame is still red, but it doesn’t have a build up of paint on it, so fingers crossed. Ah, so much to learn!

[Fredrum]

I have been doing some bits for the last few weeks such as covering the fuselage and sorting out the glazing, radio installation and control set up.

I’m having an issue with a faulty antennae warning on my Taranis so unfortunately I couldn’t use it to set up the controls. I have a JR 36mHz PCM9 that I bought many years ago when I wanted to get into the hobby, but never used. I had it serviced recently and it works great so I installed the receiver temporarily which explains why I have a 9 channel receiver in a 3 channel model. Might have to upgrade to ailerons, flaps, retracts, slats, airbrakes, bomb drop, ejecting pilot etc just to fill up the channels

Glazing installed. The framing was done with Monokote stuck onto double-sided tape then cut into strips.

[Fredrum]

The control runs have been finalized. Closed-loop for the rudder and golden rod for the elevator. The throw on the elevator worked out fine, but the maximum on the rudder is only 35mm as opposed to 45mm specified. I’m only going to be puttering around with it, so we’ll see how it goes on the maiden. If I need any more, I’ll move the attachments at the rudder end further in towards the hinge line.

[onetenor]

Looking good. Does your wife buy cakes etc in acetate type packaging .A good source of windows .Ref the wing tip retention a friction fit should ensure that the tips come off in a tumble but stay in place for flight. If you must have a retention system that will knock off a couple of round headed pins pushed into the L.E. and a small rubber band looped round them not too tight ly will keep things secure Also as I mentioned earlier spraying bare wood with water colour paints sprayed on without weight penalty and no loss of adhesion once dry. Old tricks but useful. Colour tissue AS YOU WATER SHRINK IT using the coloured water idea