Martyn K Posted December 7, 2015 Share Posted December 7, 2015 Place holder posting and official notification that I am taking part. I haven't missed a MB yet and I don't intend to start now.. My MB plan for 2016 is to scale Peter's Ballerina plan to 115% and fit an OS70FS. Why? Well 2 reasons 1. I like the look of the Ballerina, it's reminiscent of an Astro-Hog and if I wasn't building this then I may build another Astro-Hog. My other two are now flying in that great flying field in the sky. 2. I have a spare OS70FS and it seems a shame not to use it 3. (O.K. - I cant count), my eyesight is a bit dodge on dull days and bigger models are easier to see before I crash them. First I had to do a quick sanity check to make sure everything fits: So scan the plan (or bits of it) to A4, Print to PDF, Print from PDF increasing the size to 115% - seemples Side View. I intend to mount the engine inverted. Allowing for parallax,its actually a very good fit. There is about 10mm between the carb and the Firewall. Top view. Plenty of space which is very reassuring. I thought it would be too narrow Bottom view - I can offset the mount slightly to the left and add a little right thrust using shims. Plenty of space. That's the prep and sanity check done, got enough balsa and ply in stock to make a decent start. The next build type post should be in January. Looking forward to it More to come Martyn Quote Link to comment Share on other sites More sharing options...
FastFlyer Smyth Posted December 7, 2015 Share Posted December 7, 2015 Subscribed Quote Link to comment Share on other sites More sharing options...
Craig Thomas Posted December 8, 2015 Share Posted December 8, 2015 Looking forward to this one. Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted December 8, 2015 Share Posted December 8, 2015 I shall be watching Quote Link to comment Share on other sites More sharing options...
Martyn K Posted January 3, 2016 Author Share Posted January 3, 2016 Happy New Year in case you are not following my Aurora Build I made a start on the 1st January - cutting parts - no nailing of bits together yet (just kidding) and am starting to accumulate a reasonable kit. My Ballerina is scaled up by 15% and will house an OS70 FS Surpass. As this is a Mass Build and hopefully to encourage newbies to the building scene I'll add a little more detail than I usually do. I will describe the way I do things, they are not necessarily the best - in fact there are almost certainly better ways - but they suit me. Feel free to ask questions if its not clear why I am doing things the way I do. As this is a scaled up version of Peters original, I will be making some structural changes - mainly because the model will be larger and have more mass, I'll explain where and why I have changed things as I make progress. So making a start... I have scaled parts up by simply scanning 1:1 to A4, drop the colour depth to 2 channel (black and white), printed the result to PDF then from PDF printed at 115%. Great for small parts but wont work for a full wing.. All the formers and R2B have been printed in this way and need to be transferred onto the wood we will use. For small parts, I tend to use pin prick technique. This involves pinning the artwork to the underlying wood and using a map pin or similar simply prick the outline and any inner holes etc that will need to be cut. For larger parts like these formers I use Carbon Paper and then carefully draw around the curves freehand and use a pen and rule for straight edges. Where Centre lines are shown draw these as well - they are useful references. The 4 ply formers (lite and birch) were marked out and cut out. I am fortunate, I use a Band Saw for the outside edge of birch ply parts and a fret saw for the inner holes (except F1 inner - use a hole saw). Lite Ply formers are cut using a Stanley knife with a new blade. Dont try and go through in one go - it normally takes 4 to 6 cuts to cut through 3mm Lite Ply Ready for cutting.. The balsa formers have the grain running transversely - across the width. 1/8" balsa is specified. These formers carry more load during construction (I think) - as the fuselage gets nearer completion the load is shared by more components. Balsa varies vastly in density, You need to select wood that is of a medium density for the formers and straight grained. No knots or stains. Balsa at 10lbs/ft^3 can be tested by pressing with your thumb nail. There is a knack to it and experience is a wonderful thing but you should be able to mark it by pressing gently. You will see a nail nick in the wood but it should not be too deep. This is the density you are looking for - its better to weigh it using the above chart as a reference until you get more experience. Most wood is 3" or 4" wide. You will need to make it wider for the formers so will need to glue 2 sheets together. Cut the balsa to the correct former width. Sand the edge to that 2 pieces but up to each other neatly. Join on one side using masking tape Flip over and glue the pieces together. Lay it down flat and weigh the balsa down until the glue dries I use PVA glue for (almost) all my wood to wood joints. I have tried Aliphatic but never really got on with it. Cyano has its uses, but I find the joints using Cyano can be a bit brittle. Joining other materials - such as Plastic to wood etc, I use 24 hour Araldite and learn to be patient.. More to come Martyn Edited By Martyn K on 03/01/2016 22:31:09 Quote Link to comment Share on other sites More sharing options...
Martyn K Posted January 3, 2016 Author Share Posted January 3, 2016 Wing Ribs This is a parallel chord wing which simplifies construction considerably. Rather than cutting out all the variants shown on the plan, I simply used R2B from which all the other wing ribs can be cut. My preference to cut wing ribs is to make a master Then simply cut round it. The wing rib is about 12" long and at first glance it looks like I will only get 6 ribs per sheet. However, by being careful, I managed to get 9 ribs per sheets. I am still cutting these out - I always cut a few spares just in case To cut wing ribs out using this method (rather than the sandwich method that others will advocate), press down on the rib and with a new blade in your scalpel carefully cut around the rib. Cut the verticals for the spar slots and then remove the wood after the outline has been completed. The cut thumb happened on the Aurora - however - it is very easy to slice the top of a finger so take care. More to Come Martyn Edited By Martyn K on 03/01/2016 22:23:09 Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted January 3, 2016 Share Posted January 3, 2016 Great start Martin and excellent detailled blog. Following with interest! BEB PS happy New Year to you! Quote Link to comment Share on other sites More sharing options...
AndyD Posted January 3, 2016 Share Posted January 3, 2016 Martyn what sort of weight are you aiming for at 115%,im doing 120% electric and thinking about 7 pound wth mine,ive got to be careful as my motor batt setup a bit on the heavyside. Quote Link to comment Share on other sites More sharing options...
Martyn K Posted January 3, 2016 Author Share Posted January 3, 2016 I am hoping for about 4.5 - 5lbs (dry - but I am fitting a 10oz tank) - must try and keep it off the Christmas leftovers. 7 lbs seems a bit heavy for this though - I would have thought an upper limit of 6lbs to keep the character would be about right for 120% M Quote Link to comment Share on other sites More sharing options...
AndyD Posted January 3, 2016 Share Posted January 3, 2016 i shall try for 6ish but just my batt and motor weigh 2Ib 10oz,wait an see,im going to leave my batt hatch untill last possible as i think the hatch might be under the pilot.great build shall be watching with interest nicking all the good ideas. Quote Link to comment Share on other sites More sharing options...
Andrew Price 2 Posted January 3, 2016 Share Posted January 3, 2016 Following with interest, Martyn. Thank you for the extra detail, some useful stuff already. Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted January 3, 2016 Share Posted January 3, 2016 Always good blogs Martyns, loads of pictures and commentary John Edited By john stones 1 on 03/01/2016 23:34:46 Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted January 4, 2016 Share Posted January 4, 2016 Hi Martin, Subscribed & will be following with interest. Please keep detailing as much as possible as I will be back nicking your ideas for the wings of my Bella Ballerina HD. Peter & kc suggested to move the dowel hole in F2 upwards by 6mm (& doing the same to the R1 rib slot with a depth of 50mm) for increased strength. Are you not doing this on yours? Happy cutting Chris Brussels, Belgium Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted January 4, 2016 Share Posted January 4, 2016 Martin, Also, if I remember well the balsa former's grain was drawn wrongly on the published plan & should be vertical just like the ply formers. I didn't wrote this down in my notes though since mine will be Depron anyway and of course my neurons could be flashed out by my extensive glues-testing... May I suggest you a quick check with Peter or kc about this? Happy checking Chris Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted January 4, 2016 Share Posted January 4, 2016 This has been mentioned. Grain should always run up the longest dimention Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted January 4, 2016 Share Posted January 4, 2016 Thank you Peter, for confirming me the 'normal' condition of my neurons (at least, at this point of the build) ... Chris Quote Link to comment Share on other sites More sharing options...
Martyn K Posted January 4, 2016 Author Share Posted January 4, 2016 For Formers I (now) prefer the grain running across the Fuselage. I already mentioned that I think the formers carry most load during construction. What I find was happening was that as you pull the fuselage sides together, the formers would bow. The result was that I needed to add additional cross pieces to prevent this happening. When I saw the plan I thought I had been doing it wrong on all those previous models. When the formers are glued in place, the effect of the fuselage sides will add the vertical stiffness. It may be 'wrong' but this is how I am going to build it Chris - on your other point, I will be using 6mm dowel for the wing locating peg. AndyD - Target weights Trying to keep to the same wing loading, my Ballerina will have an area increase of 32%, which means to maintain the same wing loading, my target weight should be 93oz (5.8lbs) Yours - with a +20% scaling will have an area increase of 44%, which means to maintain the same loading, the target weight should be 102oz (6.4lbs) M Quote Link to comment Share on other sites More sharing options...
AVC Posted January 4, 2016 Share Posted January 4, 2016 Posted by Martyn K on 04/01/2016 09:30:51: Trying to keep to the same wing loading, my Ballerina will have an area increase of 32%, which means to maintain the same wing loading, my target weight should be 93oz (5.8lbs) M Hi Martyn The experts will correct me if I'm wrong, but as the surface and the size of the model increases, the wing loading can do it also (the so called "scale effect", so you can be more flexible on that target weight. Using an "extreme" example, a 1/6 scale Piper Cub has a wing loading of around 55-60 grams / square decimeter (sorry, I still measure this in the Continent money...) whereas the full size is around 900 - 1000 grs / sq decimeter, and it still flies deadly slow... My rule of (cut...) thumb is something around: - trainer / slow flyer up to 1.6 meters ws: 50-60 gr/sq dec - sport same size: 60 - 75 gr/ sq dec - scale same size: 70 - 80 gr/sq dec Obviously these thresholds don't apply for bigger models, so when building a big scale, I try to search for advice from the designer, or opinions from people that have built and fly it before. In any case, I always try to save weight in every step of the process, using PVA or aliphatic as much as possible, cleaning glue on all junctions before it cures, using epoxy only for critical parts, etc etc... Quote Link to comment Share on other sites More sharing options...
Martyn K Posted January 4, 2016 Author Share Posted January 4, 2016 Thanks for that. yes - that is a very good point indeed. I have to admit that I can think happily in linear metric measurements and weights and can visualise cubic metric measurements - 1000ml and square mm and cm etc - but I get very confused trying to visualise a square decimeter. Even though I know that a decimeter is about 4" long. Just a mental block that I have. M Quote Link to comment Share on other sites More sharing options...
AVC Posted January 4, 2016 Share Posted January 4, 2016 Posted by Martyn K on 04/01/2016 10:06:31: Thanks for that. yes - that is a very good point indeed. I have to admit that I can think happily in linear metric measurements and weights and can visualise cubic metric measurements - 1000ml and square mm and cm etc - but I get very confused trying to visualise a square decimeter. Even though I know that a decimeter is about 4" long. Just a mental block that I have. M I fully understand Martyn, I can easy move from linear decimal to linear imperial, and cc/ml to cubic inches is easy, but surfaces is a different subject: I can't get my head around so far (although I'm trying my best...) Quote Link to comment Share on other sites More sharing options...
AVC Posted January 4, 2016 Share Posted January 4, 2016 Is it any good?? Quote Link to comment Share on other sites More sharing options...
Martyn K Posted January 4, 2016 Author Share Posted January 4, 2016 Thanks I think a nomogram (remember those) with sq inches and sq dm on one axis and oz/gm on the other axis may be the way forward. Once you have made the visual relationship it should all fall into place. M Quote Link to comment Share on other sites More sharing options...
Levanter Posted January 4, 2016 Share Posted January 4, 2016 Martyn's builds and blogs are always extremely interesting. A great one to follow. Quote Link to comment Share on other sites More sharing options...
AVC Posted January 4, 2016 Share Posted January 4, 2016 Thanks Martyn for the advice on the nomogram, I'll see if I can find something to help me on the conversion. A very interesting building blog, btw, very detailed and well explained. I'll follow it with interest! Quote Link to comment Share on other sites More sharing options...
Martyn K Posted January 4, 2016 Author Share Posted January 4, 2016 Many years ago - probably about 40 - I bought a copy of this: and inside it has a wing loading nomogram... I'll print a copy and paste it to my shed roof. M Edited By Martyn K on 04/01/2016 10:50:44 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.