Spar-es (oz3551)

About this Plan

Spar-es. Rubber sport duration model.

Quote: "Back in the late 1940s there used to be an annual publication by the Swedish magazine Hobbyboken which included aircraft, boats and cars; many of the aircraft were from the Scandinavian countries but there were also Russian, Dutch, Swiss and other countries' models sketched as simplified three views. Looking through the 1945 issue one simple looking model caught our eye, but it was soon seen to be a small one and the page was turned. However, the image wouldn't go away and we looked it out three or four times before it was realised that it could prove an excellent subject for a vintage one-design event.

Its advantages seemed to be that it was unquestionably vintage and it was simple, cheap and small - under 24 in span - which could appeal to those who build half-size Wakefields and small scale type rubber models, but it also had a two blade folding prop (8 in. dia!) and the very brief comments were that it had a rapid climb and a good glide, so it might also prove an amusing diversion for those of competition inclination. Remembering the little Club series of models, 'Whitewings', 'Bluebird' etc, and how well they flew in 1938/9, we succumbed!

The original model was constructed (and, presumably, designed) by Aage Peterson of Denmark and the drawing published suggested the position of structural members but with no guidance on material sizes. It also shows a slightly sectioned lifting tail, but the accompanying notes definitely say tailplane section neutral and wing section 'Clark Y style'. There is too, slight discrepancy between fuselage length as drawn and as stated, so the drawing has been followed in this respect, although the model photographed has been built with a flat plate tailplane, ie neutral as in the notes, after examination of another larger model by the same builder.

As far as material sizes are concerned, we have drawn what seem reasonable, although there is no reason why the fuselage should not be from 3/32 sq (2mm nominal) instead of 1/16 sq (1-1/2mm) if preferred. The wing ribs are 1/16 sheet sanded to about 1mm, which seems more likely than 1/32 sheet, and the nose has been panelled with the same.

One other queriable area is the wing attachment, but the system shown was not unusual at the time and is better than trying to fumble the wing through a band stretched round the fuselage. In view of the very narrow tail end, the last side bays were left uncovered far access to the rear hook; tissue would soon split from contact with the rubber.

By this time the model had been mentioned to SAM 35 enthusiasts (we understand, having provided a copy of the plan, that an example was flying in the USA before ours was covered!) and since there was a lot of interest shown, SAM 35 have offered to run a competition at either Halton or Old Warden in August for all corners. Publishing the full size plan in the magazine gives everyone the opportunity of tackling a simple vintage model and bringing it along to fly; more details of the competition will follow, but there will certainly be a prize for the highest scoring junior in addition to senior prizes.

Construction: There is nothing unusual about the basic structure, though one or two details may be slightly non-standard, for example the tail end of the fuselage and rear hook. The sub-fin and wing end-plates are best attached after covering and the tailplane and fin can be lightly cemented in place after covering, or if a D/T is felt desirable, the fin can be cemented to the tailplane of the unit held on with rubber bands to tip in the normal way.

Opinions seem to vary on 'build one fuselage side over the other'. Until recently this has always meant pinning down the longerons in pairs and cutting and fitting pairs of spacers. However, some present day builders appear to build a single side, then build a second over the top of the first. No doubt the end result is similar but the older way makes it easier to produce matched sides, since the longerons may be matched for curve and both pinned down at once; the spacers are usually cut consecutively off a strip and are likely to match closely for hardness and weight..."

Supplementary file notes

Planfile includes article.

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