The Shoestring is another of Ivan Pettigrew’s plans, based very loosely on the American pylon racer of the late ‘50s. See how tiny it is? Ivan’s plan is only 58” span, and yet it is about1/4 scale. There’s lots missing - the cheek cowls, the spats, the carb intake, the long spinner, and there’s lots that’s isn’t right, such as the depth of the fuselage, the sub-fin, and yet, and yet...
Ivan sent me a copy of the Shoestring 58” plan about 18 months ago. It’s an almost ¼ scale (very semi-scale) model of a famous pylon racer from the ‘50s and is built in the now familiar Ivan minimalist style.
Ever since I started modelling, my flying skills have taken a back seat: I much prefer research, design and building. At least, this has been my story up until this year. At Chilliwack, Ivan was good enough to let me fly his much-repaired Shoestring (and I added to the scars, I’m ashamed to say), but he also took the time to give me some coaching in the more basic manoeuvres and by the end of the afternoon I was looping and rolling and landing on the middle of the patch, at least some of the time.
For some months Trevor had been telling me that I needed a model to fly with, rather than admire in the air at a distance, and that it needed to be one without too much investment: one that could be repaired after the inevitable accidents without worrying that it was no longer perfect. The Shoestring fitted the bill.
I built it pretty well off the plan, making only a few changes to simplify construction. I gave the ribs a flat aft underside profile so the wing could be built flat on the board (a half at a time, propping up the built half while the other one was built, thus making the top of the wing level) and made the main spar straight (it has a slight sweepback on the plan) but that’s about it. The covering is Solarfilm. It’s the first time I’ve used this material since the ‘80s and it seems lighter and easier to use than I remembered, but it looks fine. The excellent graphics are by Tim (35mHz), one of our Club-members. When flying his, I found Ivan’s Shoestring needed some downthrust, so mine has 2 degrees down and side, which has proved to be about right, and I strongly recommend building some in.
I still have not sourced a decent canopy, but the search goes on!
Roly at Sarik Vacforms produced a couple of excellent canopies from my balsa mould and although I should have popped a pilot in before using the RC Modellers’ Glue, she does look a lot better. The Sarik service was excellent.
It’s powered by 3 cells and a 3530-1100 motor from 4-Max http://www.4-max.co.uk/ppo-3530.htm with a 11x5.5 prop. This is more than enough power for me at the moment, and gives a couple of vertical rolls before running out of puff. The next motor up is a 3536-1000, which gives 400 watts, 50 more than the 3530, and could take 4 cells. It has the same fittings, so might be a sensible upgrade for a flier needing more power.
Flying weight is typically Ivan: just 1024 grams (2 lb 4 oz) with a 2200 mAh 3-cell battery and 1160 grams (2 lb 9 oz) with a 3700 mAh 3-cell.
How does she fly? Once trimmed and with some time on the sticks, she is by far the most responsive model I’ve built and easily the most rewarding to fly (notice she’s a “she”, not an “it” now!) and makes me feel confident in trying our the various scale-like manoeuvres that I’ve admired in others’ models. They are not very smooth yet, but it's early days.
She also is one lucky plane! While taxiing back along the strip the other day, I gave her too much throttle and she leaped into the air. The subsequent bump merely dislodged the motor mount bulkhead, which epoxied back in a few minutes. But last Monday, on a misty day, she flew into a low cloud and completely disappeared! I put the controls at neutral and left the throttle where it was, and tried to track her by sound, but was really having no luck. After what seemed like 15 minutes, and can’t have been less than 15 seconds, she appeared serenely out of the cloud, straight and level, as if it was all part of the fun. Wow!
Anyone who would like a quick-build, low cost, lots of fun flying machine need look no further. Thanks Ivan!