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Simon's Ballerina


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Hi Simon,

... a bit overwhelming for me such an amount of precision... surprise

Question if allowed, please:

As you are giving 2° of right thrust to your ply mount, shouldn't you adapt the offset of the mount as well to ensure that the back of your propeller is situated spot on the vertical trustline - ie viewed from the back having a small offset to the left for the crossmount?

Keep on the great work, please

Cheers

Chris

BRU -BE / CTR Offset Control

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Chris - you're absolutely spot on, if the prop shaft ends up very far off the centre line then strange things may well happen, but (possibly worse) - it'll look very odd! Strange behaviours can sometimes be trimmed out, a wonky front end will just annoy perpetually (well, it'd annoy me). With a smallish motor such as I'm using, things may not end up far off. But with this design of box, it's fairly straightforward to shift the whole thing portwards if necessary, simply by slotting the mounting holes in the firewall, and make it horizontally adjustable. I'll know more when I get to doing a trial fit ready for cowl construction...

Edited By Simon Feather on 24/01/2016 22:24:24

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For reference, I worked out that 1.5 degrees sidethrust needed a 2.5mm/0,1" offset on F1 for an IC installation (4 1/4" length iirc) so I'd guess your offset for electric would be in the order of 1.5mm on your motor box for 2 degrees. As Peter has set the incidence as 0-0 I'm not adding any downthrust.

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Apologies for the infrequent updates and slow progress compared to you others - who look like you've nearly finished in some cases! I've been struggling with various problems - not all aeromodelling related - and with other calls on my time, so building time has been very limited. Still, as the old adage goes - slow progress is still progress!

Some photos showing where I've got to.

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F1 - F6 glued in and fuz sides coming together. The weights are granite place mats - very flat and heavy, just the job for this. The clamps are because I discovered my F4 had a slight warp on it - but only discovered after being glued to one fuz side, hence being clamped to a bit of ply to straighten it whilst fixing to the other side. It's perfect now. This picture also shows very nicely how distorted mobile phone lenses can make things look - My F6 *is* dead straight and square even though it doesn't look it in this picture!!! The lens also makes the top fuz side look a bit bent. It's not!

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out from under the weights...

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a bit more detail showing my modified F2 and the vestigial battery box and esc comparment. F2A will form part of the removable hatch for battery and radio access.

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into the jig for a dry fit of everything - which is the point I discovered, as others have, that the rearwards formers are too wide as per the plan. So, I shall clamp the tail join then trim everything to fit the resulting nice smooth natural curve. Hey ho, we just love solving problems in this hobby, don't we!

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and finally a quick shot of my tail fillet piece - This is an offcut of aileron balsa which looks like it's got just about the perfect angle on it. Needs trimming, and reducing in size a bit, but seems like a spot on fit.

At this rate I may have the fuz complete for Greenacres!! just joking, hopefully things will speed up a bit from now on.

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  • 2 weeks later...

so... a little more of an update. Time is still ... difficult. Some days I've done nothing, one day the only progress made was to to cut and glue in 4 small pieces of triangle section...

Here's where I've got to.

I've got some ribs now and other wing parts; I decided that since I was struggling to find much workshop time, I'd give myself a little leg up and bought the ribset. Some parts missing on arrival, very quickly rectified by Beth (thanks Beth!!).

Since I'm doing wing mounted servos, the pushrod holes of the original design weren't big enough so I had to enlarge them. My solution to this was a piece of 15mm copper pipe, sharpened on the inside and with a couple of small nicks to act as saw teeth. Then, for alignment, I found one of my eversharp pencils was a perfect fit in the existing holes, so fitted this as a guide with small balsa plug to keep it centred. Tools looks like this:

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and the end result was this - all nicely aligned, very pleased with the neatness of the cuts (only had to resharpen the tool about 3 times, and that was down to using it to cut the liteply too..)

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I've made the u/c mounts for the wings too (no pics yet, they're back under the weights after having 3mm captive nuts fitted on the back), but then back to the fuz.

Fitted the servo bearers: you'll see I'm doing this work without either the cockpit floor, F5, or the wing retaining plate. I thought working space would be just a bit too restricted with all those in place, so they'll come later.

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Fitted the snakes - as a result of the formers not being quite right on the plan and having to be reduced in width to get the natural curve back on the fuz, the snake holes weren't quite right as I originally made them, so a bit of mucking about needed... and as you'll see from the second pic, a patch to the fuz to correct an exit...

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and then the wing retaining plate:

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Drilling holes in balsa like this can be troublesome - if you use a normal drill bit it just tears the wood. But I've found that if you run the drill BACKWARDS, because balsa is so soft it still penetrates and doesn't tear... works rather well so long as you're careful. Experiment with the speed of the drill and the pressure required and some quite good results can be had. These are ok, I think. Because the wing bolts will be going in and out of these holes, I've hardened them up with cyano to try to reduce wear and tear.

Hopefully tomorrow night I might get onto F5 and the stringers. Quite looking forward to that!! then to the battery hatch and cockpit area.

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All these carefully refined bits, fitting and drilling with such care and precision etc. Make me feel rather inferior. I do tend to go bang, bang, straight through. OH! that looks about right!!

Well, I do make sure that holes that matter are in the right place and even roughly the right size.

Mind you they do look OK at 50 in the air so that is OK.

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Hi Simon,

I noticed that you asked a question about 'Pierre, the driver' on Martyn's blog.

No, Pierre is not 3D printed. He's made of molded Polyurethane (PU) out of a latex mold. Please have a look at my Bella blog for more details.

Only problem so far is the weight as the rotation method still gives too thick 'walls' to the figurine. I will try a 'new' method when I have a bit of time. If you're not in a big hurry & if my other approach is satisfying, I can send you a Pierre pilot if you want.

Hakuna matata

Chris

CTR - BE / CTR PU Control

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I'd better not try any rolls or loops then....

seriously, it's built as per plan with 1/8 ply as the mounting plate to which I've fitted M6 T-nuts; the balsa you see is just infill as per plan, though I've got some triangle section on the back of the plate too just in case.

None of this will be accessible for repairs once the model is finished so need to make sure!

btw, my method for fitting T-nuts, particularly ones in vital places like this, so as to minimise the chances of them coming loose (I've had that happen on an artf... luckily spotted before it got ugly) is to fit them in place, draw them in slightly, then a dab of epoxy between the nut and the wood and squeeze them in tight in an engineer's vice (if the part is loose and can be put in a vice - remembering to line the vice first!), or draw them in with a sacrificial bolt/washer/bit of wood/elbow power if not; then a little more epoxy round the edge/over the top if necessary. Not too much, not slathering it on, but enough to be fairly confident they can't work loose.

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+1 on the epoxy

Posted by Simon Feather on 09/02/2016 14:27:15:
.........then a dab of epoxy between the nut and the wood and squeeze them in tight in an engineer's vice (if the part is loose and can be put in a vice - remembering to line the vice first!),

and that how I discovered that a lot of captive nuts are more than 6mm long on the tube part! I bought some 5 and 6mm penny washers from Wickes and keep a couple handy for just this sort of use.

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A little more progress: stringers on now. You can see in this picture the aerial tube: I'll be using an AR610 and this is a simple way of getting the long aerial behind the servos. Brown paper tube, rolled around a bit of dowel then glued and varnished and stuck in place with canopy glue. I did one with dope too to see which worked best (remember dope?) which worked just as well, but I bent it which was a shame 'cos I think it worked better (was stiffer).

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Infill in place but not trimmed:

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and finally trimmed and the scallops cut. Anyone spot the vital building aid in the background?

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The end result.

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... and that is probably it now for a few days. Children stuff tomorrow and the weekend.

ps - I did find the stringers a bit fiddly to do, and apologies to Peter for not getting them all totally evenly spaced.  Hopefully won't show too much once it's covered!

 

Edited By Simon Feather on 11/02/2016 23:40:38

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