Originally Posted by
WeeTed
Thanks for this explanation. I am building a "Tomboy Senior" 48" and the plans call for a 1.3 Mills. From what I read it might be a bit under-powered using an early Mills (I have just picked up a Mark 1 series 2 )and whilst a good series II would be better, I thought a 1.5 might be the answer.
There is an Irvine Mills 1.3 on eBay and that might be an answer (but its very expensive). I could just use a PAW 1.5 but was trying to keep it as "vintage" as I could.
Any advice?
Build the back end light-as light as you dare....the Tomboy has a very short nose-and even more so when enlarged from the original size since the tail moment works to your detriment with any enlargement....ie a gram heavy on the tail might take 10g in the nose to compensate. Anecdotal evidence on other fora indicates a tendency to tail heaviness in the Senior variant unless very careful weight control is used during building. Result a lot of lead in the nose and a sluggish model.... This is one case (the other being the very popular 'Simplex) where a heavy engine is a godsend....though the Mills 1.3 and the TB Snr seem like a perfect combination for relaxed flying. My experience of 1.3s (and I have quite a few of them) is the MkIIs run very well on a Topflite 10x3-1/2 nylon-though for max power you want a 9x4... On the 10x3-1/2 they're well below the BHP peak-but sound very happy and run very sweetly-and of course you move quite a bit more air with the 10" diameter compared to the 9" one....for identical reasons I prefer an 8x4 on the 75 rather than a 7x4
ChrisM
'ffkiwi'
PS Give some thought to what you're going to use for control linkages....since weight is an issue down the back, you can't get any lighter than a push-pull cable setup....though its a bit more work installing and tensioning.