Back to the beginning: Project Tiger Cub Story part 6

Dreaming up some improvements

Next came a bit of a rethink, I’m looking at so many mods that this job could take forever. Maybe it would be better to take it a bit at a time instead of trying to bury Tec office in paper I’ll do it in stages and sneak up on them. The first thing to consider seems to be which of the mods is best built in when the aircraft is reassembled and which can be readily altered or added later? OK

(1) Engine cooling, as built the Cub had a large hole though the firewall, This allowed access to the recoil starter which filled the hole. An early mandatory required the removal of the recoil starter as the engine mounts were fixed to this and the starter casing proved unequal to the task. After cracking was found the engine mounting was modified which involved the discarding of the starter and it’s housing. This of course moved the engine much closer to the firewall. Engine cooling at this stage was still fine until another mandatory mod to restore the integrity of the firewall insisted the  hole was covered by a plate. Whoops, nowhere for the hot air to go. Right what was needed was another mandatory mod to turn the cylinder heads to an angle to improve the flow. Most Cub owners also fitted a duct from the firewall plate and out though the floor and that mostly does work. I wanted to experiment with fitting a scoop to act as a sort of venturi to improve the airflow from the rear cylinder. That I think can go on the to be done later list.

(2) Seat Belt mod. As the present layout for the shoulder straps makes me shudder when I think about the effect of an accident on my spine. The reason for this is also in the chequered past of Cub mods. The tank was first mounted clear of the fuselage to the rear cockpit sub frame at about pilots head level. Although this had advantages, it was removable for filling and was clear of the blue foam that forms the structure between the longerons (petrol has the nasty habit of dissolving blue foam) it was possible for it to blank the tail surfaces .So It had to be moved. The U section channel that the tank was supported on also act as the anchor point for the shoulder harness so, of course this moved also. The mod involves lowering the tank so that it is within the fuselage taking with it the harness anchor point. This made the harness ideal for compressing the spine in the event of even a minor prang. I was not happy with that as I have no ambition to learn how to drive a wheelchair. The mod that I want in place  involves running a cable from the aft bulkhead though the rear fuselage and adding a raised section to accommodate the strap attachment at the correct level. I hope that I can make that resemble the elegant hump that the SE5 sported. I guess thats one for the initial build list

(3) Tank Mod. As I said before I have two Cubs and only one Cub Tank the other one having ended up fitted to a Rans at North Coates. I do however have a 25ltr Thruster tank and this is a superior item in every way and that is the one I prefer to fit in the first build. This will mean making a mounting system that will withstand 6G when full and as it is aft of the C of G the weight will need to be carefully monitored. Alternatively I can redesign the fuel pipe system to fit a drain valve at the lowest point. That’ll do the job, even if it isn’t such a neat solution. No mod required for that, so my first build will go that way.

(4) Undercarriage. As I mentioned before I intend to revert to a tailwheel undercarriage because it’s lighter, tougher and creates less drag and besides it looks a hell of a lot better.

I also intend to have the main wheels strut braced like the main wheels of the nose wheel undercarriage. As this is effectively a new layout it will require rigorous testing. I do have a set of the standard wire braced main gear from SU.

So I think that I’ll fit this initially thus just reverting to standard Cub undercarriage, no mod needed. I can develop the strut braced version later.

(5)  Streamlining. All those round struts. They are everywhere, wing struts, cockpit struts, undercarriage struts and they are all round factually and figuratively. the drag must be horrendous. Weight of course could be an issue but I’d have to dismantle most of the aircraft to fit them later. So, one more for the initial build list

(6) Clear vision panel…

Whilst the view from a Cub is pretty good for a Bi Plane you just can’t have too good a view so I’d like to make a centre section with a large clear panel though it. That will give me a better chance of spotting those Class A pilots that spend too much time playing with the toys on their instrument  panels and not enough time looking out.

There does appear to be increasing numbers of these. As I have two centre sections I can work on this and add it later. One more for the deferred list.

So, lets see, that’s two mods to be incorporated in the initial build and three to be developed later. That should make life bit easier.

So from these first two a logical order appears. Number one assemble the cockpit sub frame and fit seat. Next make the tank mounting and fit to sub frame. Fit tank and straps check clearance from seat. Offer up to rear fuselage and check clearance from control runs. Load test tank and mountings. Photograph, prepare drawings and write out mod submission.

Number Two, while front and rear fuselage sections are together determine height needed for shoulder strap attachment. Ensure wire from rear bulkhead can reach this without interfering with any of the control runs. When sure that it will work buy the new harness. Then when work to the tank is completed run the wire make the.” hump” from ply and lath ( shades of a Hurricane) or to make something from blue foam which may be lighter. Then as before with photos, drawings and writing.

Number Three, The streamlining. First look into the weights of the materials available, alloy, glassfibre or maybe even carbon fibre. submit mod as before. Fit to tubes on final assembly. Simple innit (OH Yeah)

Just in case there is any problem with runs of the harness rudder cables I’ll fit the tank mount for testing purposes to the cockpit framing from kit 208  from the Cub that was never completed. So taking them out of store I put them together, now with parts to be included in the build and parts that won’t be both in the workshop I must continue to be meticulous in my labelling and stowage. It is both satisfying and exciting to watch the first bits really taking shape .To satisfy my curiosity I try fitting parts from SP, SU and KM to the structure of kit 208 and they all fit. Obviously jig made, but as SP and SU were quite early in the production of the kits and KM and 208 were quite late it does wonders for the confidence.

Then before offering up I need to place the elevator control rod in place in the rear fuselage section . Then I need to run two strings to follow the course of rudder cables to ensure that there no danger of anything chafing or obstructing.

Having got this far life got in the way. The runway at Sheepcoates Farm was now operational so there was grass to cut and roll, huts to build and decking and slabs to lay.
Also the need to fly, preferably DF. Hell that is so close to addiction, almost like being a druggie.

So poor SP once again in her life was neglected. This time it was only for 4 months but on my visits to the workshop once or twice a week to turn over the engines I felt very guilty until the great day I could go back to restart work.

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