Chilli Breeze & Chilli Wind plans (was RCME June 1994)

[Jonathan M]

Fun thinking this through together...

A single 'dihedral-brace' piece of ply is doable, but would need to be tapered in thickness towards each end (as well as faired slightly across the width to match the wing camber). It'd be simpler to assume the wing-bandage will give enough binding strength and just make separate ply pieces - although these could then be doweled together at the root for extra security. The aft-running feet can remain separate with their own saddle-clamps (avoids lengthening the main run of torque-spring any further). My sketch wasn't to proper scale, but the feet don't need to be quite that long as shown, and of course the clamps would position right by the bends.

The only reason I left the outboard ends longer (as per the built-up wing plan) was to spread out any shock-force up the main UC leg, but the ply could now of course be wider rather than longer to achieve the same outcome.

I'd radius the corners (say 5mm rad) and scribe these in to avoid the weakness of hard stress points in the veneered foam.

[kc]

A flat ply plate could go right across the dihedral by just recessing the middle ribs or foam  a little and building up a balsa filler bit on the outside - with cutouts for the clamps. Much easier than tapering ply in thickness!

Edited By kc on 26/06/2019 12:11:09

[Nigel R]

I think you're in danger of reinventing the wheel here...

I wouldn't put the clamps or wire in the area of the bandage. I think it will be too awkward to get the wire clamped correctly withe the glass getting in the way.

I also wouldn't do a single piece underneath, whether L shaped or not. All the torsion loads will then serve only to try and rip it out. This approach will load the glue joint in its weakest direction, and rely mainly on the foam substrate holding together in tension (which it is absolutely terrible at).

If you go with the pieces set into the top surface (or the full depth broom handle), it only has to resist fore (mostly) motion only, the magnitude of which is reduced because it is some distance (i.e. thickness of wing) away from the lower surface. The top wing skin will provides ample strength to resist this movement. If you're at all worried, you could make sure the very inboard end of the leg is just within the glass area, then the top plate is held in place by both wing skin and glass. It's also a quick way to do it, as there is no shaping required for the ply parts, just rout out the 1/4" depth cavities and stick in the ply plates.

[Jonathan M]

The wheels are actually lower down - we'll get 'round' to re-inventing those shortly...!

Talking of lower down (and given that this is all hypothetical at present as I'll only be starting the CB later), how would one deal with retract units in a foam-veneer wing? Same problem?

[Piers Bowlan]

If I were considering retracts I would definitely do a built up wing as it can be properly engineered and more likely to survive a hard landing than retracts screwed to wood, bonded to foam. That's just me.

[Nigel R]

On a foam wing? Fly from a concrete runway!

I've seen several methods used.

1/2" square hardwood beams, as long as practical, two beams per retract unit.

1/4" ply plate, which can be reinforced using 1/4" dowel at right angles (i.e. poking up into the foam)

I've done the first, which was ok, providing every landing was greasy smooth. The cons with the second, if things do get torn out, it causes a lot of damage.

A light model helps - less stress on the gear. And the smoother the strip the better. As per Piers comment, with a built up you can engineer in some reinforcements to take the loads back to the spar structure.

[Bob Cotsford]

With all due respect to Nigel's comment above, I've had a few models with retracts mounted in veneered foam wings, my favourite method being to embed a U-shaped 1/4" ply plate into the foam then fill in above the ply with soft balsa shaped to blend in with the wing profile. I fly from grass and haven't ripped a leg out - yet!.  The ply plate method gives a lot more gluing area than does the wooden beam way of doing it.  As for keeping the model light, yes it's always a good idea but my 63" span Crescent Tornado was nearly 8lb and was always flown from grass.  The ply plates are glued in with Gorilla Glue (the foaming type) these days.

One example is illustrated in this thread

Edited By Bob Cotsford on 27/06/2019 09:11:46

[Nigel R]

I probably wasn't very clear about the ply plate damage statement, I meant if the plate with dowels is torn out it will take a fair chunk of foam with it. Although with the dowels, there is even more glue area, and better leverage for the structure to resist the torsional loads from the gear.

Bob you are right, the ply plates can be plenty strong, ensuring lots of gluing area is the thing with foam I believe.

Is the foamed PU glue a little flexible? I used epoxy in the past, I suspect it neither reached into the foam that well, nor flexed much. Both would tend to make a poorer bond with beaded foam. The foaming glues would seem to reach into the foam much better.

[Bob Cotsford]

Over the years I've tried various glues such as PVA and epoxy to bond bearer plates for fixed and retractable gear and while they work, they are relatively heavy unless you have a very accurately cut cavity to take the mounting plate or beams. Gorilla Glue does expand into the surrounding foam filling any cracks and cavities giving a 100% bond. Once dry it is absolutely rigid, and heavy arrivals seem to bend the leg before the the plate comes out.

I often use GG as a filler around snake exits and the like, once set for 24 hours it can be cut, sawn and sanded quite easily.

[Jonathan M]

I can see the issues more clearly now.

Retracts would be slick to factor in, but I'd foresee the wheels and wells getting right covered in fuel residue in my IC version, which a fixed U/C would avoid.

Either type though leads to a possible third solution for securing bearers in a foam wing - which occurred to me having seen Bob's/Piers' half-buried plate for retracts.

This would have slots for ply plates (either two narrow ones as 'cross-beam' foundations for fixed U/C surface-bearers or single wider ones with cutouts for retract casings) first cut into the wing from the L/E of the foam, i.e. before the balsa L/E is later glued on. These slots would be long enough to penetrate down the chord of the wing (the direction in which torsional forces need to be contained) and the ply then buried in with expanding glue. Excavations would then be made through the underside of the wings - either for fixed U/C bearers to contact with and be secured to the buried ply cross-pieces, or for retracts directly down to the cutouts etc.

The main technical challenge would be in accurately boring down the middle of the wing section to 'mill-out' the foam, but if the ply plates were left long enough initially (to be flushed off later before the L/E is glued on) then the milling out could be a bit oversize, the sacrificial overhangs would provide a reference and adjustment-point for accurate alignment down the centreline of the chord (or angled as desired), and the expanding glue would do the rest.

Just an idea.

[will -0]

Hi, thie other consideration with retracts is weight. You already have a foam wing and this is quite a slippy model.

[Nigel R]

The 40 size would carry retracts quite happily, although I don't think Jonathan is planning on retracts for this one though.

[will -0]

Fair enough

I would be a nice nippy model mind and has been done:

**LINK**

[Delks]

The photo of the Chilli Wind in the Aug '93 RCM&E was the 57" span version as published  but was slightly stretched - 3" on the tail and 1/1/2" on the nose and also had a basic flat sheet tail. The OS .46 was replaced with a YS .45 rear exhaust  which had an integral pump and worked well the Bolly pipe . The "60" size Chilli Wind had a wing span of 67" and was about 67" long. The film covered prototype had a foam wing, fixed u/c, powered by a piped OS .61 and weighed in at 7 1/2lbs. Plans for this were not published but were available from myself. It is pleasing to see that there is still interest in the designs - it all seems so long ago now.  

[Delks]

It has been interesting looking through the posts re the Chilli Breeze and the subject of power requirements seems to come up regularly. I designed the prototype with the OS .32 in mind this proved to be a good little engine but the more powerful Irvine .39 was even better - the all up weight should be around around 55-60 oz so it would also perform well with a good .25 up front. Many people have also had success using electric power for the Chilli designs and it should be very easy to find a powerful set up without having to worry too much about the weight problem. 

[Jonathan M]

Hi Delks

Good to have your input here!

My own Chilli Breeze is yet to be built (stack of balsa, foam wing and other components all sitting ready on the shelf) but I decided on a SC32 as just right for mine.

 

[Nigel R]

8 hours ago, Delks said:

Plans for this were not published but were available from myself. It is pleasing to see that there is still interest in the designs - it all seems so long ago now.  

Fits my definition of classic; one of the best or one of the first. In this case, one of the best, one of the best combining high performance with minimal build complexity.

At the time there seemed to be a lot of needlessly complex designs, maybe done with misdirection in mind (variable pitch props, dive breaks and snap flaps and all that), maybe not deliberately, but the Chilli was one of the designs that demonstrated contest aerobatic performance without all the unnecessary stuff.

[Jonathan M]

Nice.  Breeze or Wind?

 

[Nigel R]

Wind. Goes up on ~750W of electric.

[Delks]

I have never been a big fan of retracts in simple sports models and saw no need to consider them on the Chilli series - even the 67" span 60 size version featured a fixed u/c. Wing sections were also becoming slimmer around that time and this was another good reason to "keep it simple". The Chilli Karma shown in the photos featured a carbon fibre undercarriage mounted on the fuselage and this was a very practical, lightweight alterative to the piano wire version mounted in the wing and, for my taste, much preferred to retracts - further refinement included a separate servo for each aileron. The OS .46 is using a C-Vec device in place of the standard silencer and this worked quite well in terms of boosting power but the Bolly pipe was wonderful and quiet too!. I have included a pic of the "stretched" Chilli Wind showing the YS .45 RE/Bolly pipe installation and also the arrangement that was featured in the magazine article for those who are interested in the oily side of life.

[kc]

Delks - I gather that you are the designer of the Chilli series.   Great to have you on the forum.   Could you explain how the Karma fits into the series?

I  think the various designs are

Chilli Breeze 48 inch for .32    RCME free plan

Chilli Wind   57 inch for .40  RCME plan now also on Outerzone.

Stretched  Chilli Wind 3.5 extra length& 1.5 extra nose   ( not actually published?)

67 inch span for .60  never published? but plan from designer at one time

 

Karma   was this a published design?

 

[Delks]

 

5 hours ago, kc said:

Delks - I gather that you are the designer of the Chilli series.   Great to have you on the forum.   Could you explain how the Karma fits into the series?

I  think the various designs are

Chilli Breeze 48 inch for .32    RCME free plan

Chilli Wind   57 inch for .40  RCME plan now also on Outerzone.

Stretched  Chilli Wind 3.5 extra length& 1.5 extra nose   ( not actually published?)

67 inch span for .60  never published? but plan from designer at one time

 

Karma   was this a published design?

 

Hi Kc - I did the Chilli Karma design back in about 2004 and planned to do an article but a house move came up and the project got shelved. Although the photos show a .40 size model of about 57" span the magazine article was going to be for a Chilli Breeze size model of around 48" span and I had even got as far as sourcing a purpose made carbon fibre u/c for the project. 

[Delks]

On 15/02/2021 at 07:11, Jonathan M said:

Hi Delks

Good to have your input here!

My own Chilli Breeze is yet to be built (stack of balsa, foam wing and other components all sitting ready on the shelf) but I decided on a SC32 as just right for mine.

 

Hi Jonathan - have a look at the photos I posted this morning before deciding on your choice of u/c I think they may interest you.

Cheers, Mike

[Jonathan M]

15 hours ago, Delks said:

Hi Jonathan - have a look at the photos I posted this morning before deciding on your choice of u/c I think they may interest you.

Cheers, Mike

Hi Mike

Really appreciate these extra photos and input.

There are clear advantages in mounting the U/C on the fuselage:  would make my Breeze less 'tippy' on our sometimes bumpy patch, and would save having to beef up the foam wing.  There's certainly enough room in the fuselage for two modern micro servos for the ailerons, but modern wing-mounting would also be an option.

Cheers

Jon

[Nigel R]

Penny has dropped on your identity Mike, good to have you onboard the forum ?