Updated Chilli Breeze and Rival designs update

[Delks]

I have recently completed and covered the Junior Rival that I was building as a test bed for future electric projects. When I first started to read through this forum I was very surprised to read posts recommending weight saving tips regarding the Chilli Breeze airframe. By any standards a CB built as-pe-rplan

with a built-up wing is a lightweight airframe. The Junior Rival airframe is a slightly larger than the CB but used a similar amount wood for the airframe and this weighed in at 602gm ready-to-cover. Medium grade balsa was used with a 36" x 4" X 1/16" sheet weighing 18-20gm and all other sizes multiples of this weight. 3mm light ply was used for doublers in place of .8mm ply. The finished model less battery came out 1246gm and the cg was achievable using as little as a 3s 2200 lipo. I found this very interesting as the original Chilli Breeze with a built-up wing weighed 1475gm -  this was the dry weight so the flying weight would have to include an average of half a tankful of fuel so the total weight of a CB at take off was in fact approx 1600gm (about 3lb 9oz). It flew very well at this weight - the foam wing version came in about 100g more and the added weight was a bonus for windier days. At no time did I ever feel the the model was too heavy or that a reduction in the flying weight would improve the performance. It was always intended as an introduction to F3a style flying - not 3D flying  From the above, bearing in mind that the Junior Rival is a little larger than the CB, we can safely assume that the take off weight for an electric CB using modern servos etc with a 4s lipo will be appreciably lighter than the original .36 ic powered version. In fact it is going to be at least 8oz lighter than the original design weight and this will not necessarily improve the flight performance - in fact quite the contrary. Fellow forum member KC alerted me to  several posts regarding tailplane flutter and one of the forum members who had experienced flutter said he thought his problem was caused because he had used too light a grade of balsa for the tailplane and he cured the problem by substituting it for a firmer grade of balsa - a medium grade sheet of 1/4" is going to weigh between 70-80gm. 

If you want an ultra lightweight aerobat suitable for F3a style flying you are going to be limited to indoor flying or flat calm summer evenings but for average weather conditions in the UK (and a lot of other countries) I feel a Chilli Breeze needs to be somewhere near to its original design weight and it will be counter productive working out cunning ways to save weight.        

[Stuart Quinn-Harvie 1]

I loved my CB and will be building another - it's just had too many repairs now ( my flying, nothing wrong with the aeroplane. )  but it flies beautifully and is all electric.  ( I fitted a fuselage mounted undercart which was later  replaced by a carbon one. The last pic shows it after a couple of repairs and after I cowled the motor, while it was waiting for a spinner. 

The wing is built up and I used the sandwich method to make the ribs - not something I fancy doing again, I have to admit. 

She will fly happily on 3s but goes "properly" on 4. 

 

 

 

Edited April 8, 2023 by Stuart Quinn-Harvie 1

[Steven Hurd]

Stuart. 
 

lovely looking model, and a good conversion, hope it flies as good as it looks 

 

Steve.

[Stuart Quinn-Harvie 1]

Thanks! it did, though it's had so many pilot induced issues it's now retired, waiting for a replacement to take over :-)