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Mark's Ballerina MK1

A pretty standard build, Saito FA40a powered

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Mark Elen31/12/2015 12:39:05
328 forum posts
577 photos

Hi All,

Just thought I'd start my build log, but its going to be a week or two before I get started properly, as I'm still finishing off the RM Trainer that I have on the go at the moment.

I've got all of the materials in stock and have had the plans copied ready to start.

I know Peter has used balsa for the spars, and I appreciate that he has done some testing with another model, but I'm going to be using something a little harder, as my first ever build met its demise due to poor balsa selection for the spars - all my own fault, but I still prefer to err on the safe side.

Anyway, a build log isn't a build log without photos, here are a couple of mine to get started:

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I'm really looking forward to this, as I've never had a model with a pilot in it..... Also, its my first go with a four stroke, something else I'm looking forward to.

Cheers

Mark

john stones 131/12/2015 13:18:57
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9370 forum posts
1428 photos

Spruce spars for me Mark, I usually have a lady pilot in mine, they're better flyers as long as your fields not near a shoe shop wink

John

Mark Elen31/12/2015 13:23:36
328 forum posts
577 photos

Nice one John, made me chuckle... smiley

Regards

Mark

Biggles' Elder Brother - Moderator31/12/2015 15:33:13
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Moderator
15233 forum posts
1407 photos

Yes, if you are going to use balsa for the spars it does need to be hard. A lot of sucessful models with balsa spars and of course Peter knows what he's doing.

Spruce is good for spars - and much stronger, but of course you do have a weight penalty. And it may not be necessary for a model like this - unless of course you like the added security.

There are other ways of adding strength to the spar assembly than upgrading the material and, given the power levels I'm planning for mine and the way I like to "throw them around" a bit, I will be at least considering some of them in my build - when I get to the wings!

BEB

Mark Elen31/12/2015 17:33:42
328 forum posts
577 photos

Thanks BEB,

It's just a bit of peace of mind, I've not decided what I'm using yet, I've got Spruce, Cyparis and Bass in stock, so I may have a weighing session before I make the decision.

Thanks for your comments and Happy New Year

Cheers

Mark

Gazza5806/01/2016 12:40:46
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125 forum posts
1 photos

Hi Chaps,

I have made a start with the fuselage and am turning my attention planning wise to the wings.

I have both 1/4 balsa and spruce on my stock shelf and am considering what to use as spars. My question is should all three spars be spruce... or just one or two. Its been a looong time since I used spruce and this model will address that on wings and fuselage. The 1/4 balsa is not particularly hard and obviously there are three of them with webbing between both.

I ask this only in the light of building a Tomboy Senior with the single spar as shown on the plan. It lasted about 3 minutes before clapping hands and plummeting to Earth in a spectacular way. I have now built a new wing for it which is much stronger. I would like to avoid this with Ballerina

Best Regards

Gazza

AVC06/01/2016 12:50:25
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486 forum posts
123 photos

Hi Gazza

Probably the designer is the best person to answer, but I don't think you'll have problems with three spars, even if the three of them are balsa.

You may use spruce, but in my opinion this would only add unnecessary weight to the wing. As long as the whole structure (sheet, spars and ribs) is built accurately, the resulted wing will be strong enough.

Biggles' Elder Brother - Moderator06/01/2016 12:52:49
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Moderator
15233 forum posts
1407 photos

As I suggested above Gazza, I feel that hard balsa, allied to the shear webbing and the leading edge sheeting forming a D-box, should be strong enough for this model - unless you're planning on flying it 3D!

Yes spruce is stronger, but its also heavier! If you go for a combination then you need to make the upper and lower front spars connected by the shear web out of the same material really (whatever it is) so that the whole assembly flexes together as one unit. If you just make one of them spruce and the other balsa then, as spruce is much stiffer, it will end up taking most of the load - and that could be weaker than two hard balsa spars working together!

BEB

Gazza5806/01/2016 13:10:33
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125 forum posts
1 photos

Thanks Chaps,

BEB... That is precisely the reason I asked about mixing Spruce with balsa. (Cross ply & radial on the same axle).

In all honesty I am not sure if we worry a little too much about weight in an instance like this where the difference is but a few grammes. A large wing like this will easily support such minor weight differences. Indeed I believe that Ballerina will fly with a considerable weight strapped to it. Nevertheless, I am trying to build the model as light as I can whilst still ensuring structural integrity.

I saw Peter mention that rock hard balsa spars are needed if not spruce. I can see that it makes sense to use all spars from one material. I looked for 'rock hard' balsa and found nothing even close. I am thus leaning toward spruce at the moment, unless I can be persuaded otherwise.

Thanks again for your thoughts

Gazza

Gazza5806/01/2016 13:11:42
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125 forum posts
1 photos

What's 3D...? I can just about keep it airborne

Percy Verance06/01/2016 15:46:43
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6495 forum posts
110 photos

Gazza

I'll see if I can persuade you to use an alternative to spruce. A good few years back I got to know a joiner/cabinet maker, whom was also a very accomplished model flyer. He was also heavily into wood turning, and was familiar with the characteristics of the different woods he worked with.

He advised avoiding spruce for wing spars, as spruce has natural oils within it which can, over time, de-bond joints made with several types of modern adhesives. He cited one of the worst (for spruce) as epoxy. Most epoxies dry slightly rubbery, which (he said) didn't help the bond one bit. He reckoned the best alternative to spruce was cyparis. For any given section it's lighter, stronger, and takes adhesives much better than does spruce. It's also a nice wood with which to work, and has a nice close grain....... Most balsawood suppliers will stock cyparis in various sizes.

He was also the bloke who advised me to lightly sand the face of plywood prior to applying glue, as most modern plywood will have traces of release agent on the faces from being pressed in the manufacturing process......

Oh, and in answer to your question regarding what 3D is. It's when someone has a model plane Gazza, when they really ought to have bought a helicopter...... wink

Happy Landings.........

 

 

 

 

Edited By Percy Verance on 06/01/2016 16:04:26

AVC06/01/2016 16:15:36
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486 forum posts
123 photos
Posted by Percy Verance on 06/01/2016 15:46:43:

Oh, and in answer to your question regarding what 3D is. It's when someone has a model plane Gazza, when they really ought to have bought a helicopter...... wink

Happy Landings.........

This is one of the best definitions of 3D I've read! laugh

Gazza5806/01/2016 19:32:22
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125 forum posts
1 photos

Hi Perce,

Thanks for your input. I'll go lookout some cyparis at the lms.

I'm only relieved that I didnt turn up at the patch with a pair of 3D glasses.......

Gazza

Mark Elen02/10/2016 19:57:44
328 forum posts
577 photos

It's about time I got my finger out and started this build. So today, I have cleared my bench and got the plans out...

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Got this little beaut to go in too.

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Mark Elen02/10/2016 21:40:45
328 forum posts
577 photos

Well, I've finally got started.

Got the ply cut to size + 1mm to allow for sanding to final size and the 1/8 formers cut and glued ready for shaping.

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It feels good to finally make a start. 😁

AndyD02/10/2016 22:08:15
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681 forum posts
497 photos

nice to see the ballerinas are still being made,is the rm trainer ready for flight,im building a electric version which is ready for covering,nice engine for the ballerina,mine might be converted from electric to glow soon as ive lost a lot batterys lately.

Mark Elen02/10/2016 22:19:48
328 forum posts
577 photos

Hi Andy,

Yes, the RM Trainer is finished and flies beautifully. One of the guys at my club bravely offered to maiden it for me back in March - I've not flown fixed wing for about 8 years. A few clicks of trim and it flies great. Unfortunately, due to work and other commitments, yesterday was the first time I got to get out with it since. Managed about 10 flights and I'm getting back into the swing of things.

It's spurred me on to get started with this build.

I'm an IC kind of guy, but I really don't like the messy cleaning up after. The other guys at the club yesterday were all leccky, and I was kind of jealous of the pack it away clean that went with it....

Cheers

Mark

john stones 102/10/2016 22:30:59
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9370 forum posts
1428 photos

Not a lot of mess with the Saito Mark yes

Chris Barlow02/10/2016 22:46:01
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1727 forum posts
1172 photos

They still have to clean the dead flies off the leading edges and wind shield though! The cleaning process with I.C is also a good and essential time to check for damage and any maintenance needed before the next flight. Something often missed with electric!

I was out flying my Ballerina this afternoon in another session of balance adjusting to move the CoG further back to make it more agile like John Stones model. I was also messing with the flying speed and was very impressed with just how slow she could fly without loosing height. Lots of low and slow and touch and go's. laugh

john stones 102/10/2016 22:59:35
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9370 forum posts
1428 photos

It's a Ballerina it's supposed to be light on it feet female

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