Originally Posted by
WeeTed
Thank you for this insight Chris. I understand the concern regarding the Tomboy being tail heavy. I watched the Mark Robinson videos and he used carbon fibre control rods on his version to keep the tail weight down. Please can you shed some light on the engine choice? I could try to find an Irvine Mills 1.3 and use a big prop like the 10 x 3-1/2 or a 9 x 4. or for a bit less buy a new PAW double ball race R/C and have throttle control. The Mills would keep it vintage which is what i wanted to do, but if it is not able to power it then a more powerful engine is needed. That was why I was considering the Aurora Indian Mills 1.5. I tend to agree with you that a 15% increase of "not a lot" will be pointless, especially if a decent Irvine 1.3 might be as good.
There is no right or wrong answer here-the TB Snr is a reasonably popular and proven design and it is known to fly more than adequately on a Mills 1.3...in fact Boddo specifically scaled the original to a size he considered appropriate to the power of the 1.3. ...that being said the original designer has no control over how other builders build it and their choice of wood, covering and fittings....bad choices or inexperience there...lead to poor outcomes-ie tail heavy as built-requiring a lot of lead to get the CG correct. A Mills will give relaxed flying, a PAW 149 far more power...on much smaller props-but the advantage of throttling-though with a bit of effort you can find throttles for Mills 1.3s....either original or aftermarket units-I have both types on some of mine. If you plan on other models -especially non vintage sport types-then the PAW 149 might be a little more useful than the 1.3. A lot would depend on the quality of the Indian 1.5-the 75s and 1.3s are known to be quite variable in fits and machining-though I would expect the 1.5 and 1cc versions-which came along towards the end of production-to be a bit more consistent between examples. But I would certainly take an Irvine over an Indian any day. The PAW of course you have the advantage of being UK produced and well supported by the manufacturer, whereas the Indian offerings are out of production now.
CF pushrods as used by Mark Robinson are fine-and less fiddly than pull pull cables-though the latter probably have a slight edge when it comes to the weight of the control system...I know Boddo liked them and used the setup quite a lot on some of his later designs-especially for rudder control.
....I've just pulled out an 'Old School Model Aeroplane Factory' short kit of the Tomboy 48.....which
AFAIK is the same ass the Tomboy Senior....looking at the plan in detail with a critical eye I can only reiterate my earlier advice to build the back end light-that means the fin and rudder, tailplane and elevator and any sheet parts like the subfin and sheet infill areas-choose good light wood.....and go for a light covering as well...depending on preference...tissue, silk or a lightweight iron on like Oracover light. At the end of the day I'd still go for a Mills up front...purely because it looks right, if nothing else.
ChrisM
'ffkiwi'