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Bistormer 60" (A Barnstormer with more ribs)

Barnstormer with more ribs

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Nigel Day23/01/2014 20:15:32
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1160 forum posts
213 photos

Thanks Danny. I don't think that Phil changed the position of the bulkhead (F2?) but I have a feeling that he increased the height of it. That might have been for the top hatch though.....

I'll make sure to check my dihedral templates. The others that I've checked seem OK but you've made me a bit more wary of relying on them all.

Many thanks for the info and guidance so far.

Danny Fenton23/01/2014 20:34:03
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9451 forum posts
4261 photos

Hi chaps, thanks for all the comments its great to hear everybody chipping in.

KC George likes the 5055 and 5065 motors so do I. They come in loads of different windings (KV) so you can tune the prop cell count etc to the power that you want. However in this instance I want this aeroplane to stooge about so 100 watts to the lb rule will be adequate I reckon. The motor I have gone for is an old one I had lying around, it is around 500kv and will work nicely on 6 cells A123 (5 cells lipo) and turn a 14 x 7 ncely. It should deliver draw around 6-700 watts of power. It wont be as efficient as some of the newer motors, but in this application it will be fine. Georges motor (4Max) will be good for a model of 15lbs. I don't know how heavy this one I am doing will come out but I would be a bit dissapointed to be far over 6 lbs.

Redesigning front ends. This is something I usually do right at the beginning of the build, but haven't in this instance. I have this nagging feeling in the back of my mind to stick a Laser in it. I have never had nor operated a Laser but I should. Anyway I am sure the feelings will pass, bit like the flu wink 2

This is a drawing I did for a Brian Taylor Hurricane:

270909dsc_1670.jpg

If you look closely you can see the motor and a new box structure that lies inside the original bulkhead but extends forward. This is a way around making a new bulkhead of the correct shape, just extend a box forwards.

These are drawings using a similar approach I did for the TN Spitfire:

both of these are using the 5065 Turnigy motor, swinging a 20 x 13 three blade prop.

Nigel I think you are absolutely spot on, take the ideas you see and try a few, some you will like some you may not. Pick n mix modelling wink 2

Theres no right or wrong way

Cheers

Danny

Danny Fenton23/01/2014 23:09:39
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9451 forum posts
4261 photos

Right a couple of snippets to show you, nothing exciting and you older hands can go back to sleep, nothing of interest, move along......

The glue I use for slower jobs is Titebond, I seem to alternate between Titebond original and titebond II I find the latter dries a bit quicker but other than there isn't much in it, well not to me anyway.

Titebond seems to come with a silly nozzle so I usually decant it into this smaller bottle with a long tip for ribs and small areas etc

bs 30.jpg

But for sections like wing leading edges I use the normal huge nozzle, lather it on then using the Palette knife scrape it off again, this leaves a nice film ready for the wood. Seems wasteful perhaps, but in the grand scheme of things its not much.

You will also notice the pins I am using, there has been a bit of chatter on the forum regards pins and the glass headed ones shattering causing an impaled thumb. Well I present to you these nifty pins. They are available from lots of good model shops, and if you really shop around you can be trendy "like what I is" and go for pink smile d You will notice these are all the rage on the US forums. I got mine from Al's.

bs 31.jpg

Here are said pins in action holding the upper centre section sheeting still. Had a bit of a mishap with regards the sheeting. This model is eating 1/16 sheeting like the proverbial! Anyway I try and always use stock from the same supplier. The reason is one outfits 1/16 is another outfits 1/16 less a bit. It is almost as if they are passing metric 1.5mm as 1.6 but with 1.5 the sheet should be 1 metre, the 1.6 it should be 36" So anyway I mixed the wood as I ran out of the stock from SLEC and dove into a pile I got from elsewhere sad Just means you may have to sand the area where the two meet a little to bring them level.

bs 32.jpg

Next up, if you wanted to cut a sheet of 1/4 perpendicular to the grain, who would reach for a knife? Not saying that is wrong, but you may find this method easier and a lot less fuss. Mark the length and lay your set square across the wood. Gently rest the saw against the square and cut. You will get a lovely neat and accurate cut. TIP Never use your best saws on anything but balsa, and for ply use the cheaper saws as the resin in them seems to chew blades.

bs 33.jpg

Next up we attached the leading edges. You may recall instead of using 1/2 balsa I used laminated 1/4 This worked very well. But first of all how do we hold the wing to work on the beast?

These blocks of foam have wedges cut out and will hold almost any wing so you can work on the leading edges. Cheap to make too,

bs 34.jpg

I use good quality tape that neither leaves a residue but has good grab. This blue tape from 3M is not cheap but I wont use anything else. It is also an excellent tape for masking.

Anyway hope I haven't put everybody to sleep, not necessarily the only way to do stuff but it is how I do it. Now where is my Lemsip.......

Cheers

Danny

Edited By Danny Fenton on 23/01/2014 23:14:55

Concorde Speedbird23/01/2014 23:13:19
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2732 forum posts
650 photos

6 pounds is very light for a biplane of this size, my 45" span Domino aerobatic biplane is 6 pounds, so I wouldn't be worried if it goes above 6 or 7 pounds. Keep up the good work.

CS

Danny Fenton23/01/2014 23:19:01
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9451 forum posts
4261 photos

Thanks CS, I am choosing the wood, and that I am hoping will make the difference. I think the Domino also has foam wings? It all adds up. But you are right it is a big model to keep under 6lbs. We shall see wink 2

Perhaps we should start a sweep, see who can get closest to the final weight?

Cheers

Danny

john stones 123/01/2014 23:39:34
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11443 forum posts
1516 photos

lovely building Danny.

like your use of highlighter pens and foam to hold wings

great tips yes

Barrie Dav 224/01/2014 08:17:40
1012 forum posts
14 photos

That's a beautiful bit of building there Danny. Why does a well built balsa model look so good?  Well, it is an art after all......

Has anyone had issues with using cyno for the main glue when building? I've always understood that it becomes brittle with time and the joints can come apart if subjected to a sharp knock (usual in my landings).

Edited By Barrie Dav 2 on 24/01/2014 08:21:46

Danny Fenton24/01/2014 09:04:13
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9451 forum posts
4261 photos

Thanks John and Barrie, and thanks for joining in. It makes it more interesting to get feedback.

I have not had experience of CA weakening over time, but would be interested to hear more?

Anybody else heard about this?

Cheers

Danny

Colin Leighfield24/01/2014 09:23:49
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5993 forum posts
2503 photos

I've not heard about time-related deterioration, but I'm aware that brittleness can be an issue, which perhaps makes joints more prone to shattering in an impact where an epoxy joint would hold together.

Perhaps it's one of those variable things related to the type of cyano glue being used? I have the impression that joints made using thin cyano "whicked in" aren't as robust as those using a medium cyano, but perhaps that's simply due to the volume of adhesive and effective surface area of the glued faces.

Like most people I suppose, I use thin and gap-filling cyano, epoxy, PVA, contact adhesive and balsa cement is still surprisingly useful. My Tucano wing panels are wholly glued together with Uhu Hart without the slightest problem, epoxy being used just for the centre join.

However, for a quick build with ribs in a built up wing panel or dropping intermediate formers into a balsa sheet fuselage, I use thin cyano all the time. The loads on those joints are well distributed and if there is an impact severe enough to shatter the joints, I doubt if there's enough left of the plane to be worth worrying about anyway!

Barrie Dav 224/01/2014 10:43:38
1012 forum posts
14 photos

I generally use Aliphatic glue and sometimes, where it's too difficult to use a metal pin, use a spot of cyno on a very small section of bare wood to 'pin' the former/rib etc. in place whilst the wood glue sets. I've done this for years and it speeds to building no-end. Thus the wood glue takes all the knocks.

Danny Fenton24/01/2014 11:12:54
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9451 forum posts
4261 photos

I always have trouble sanding aliphatic, Superphatic and most of the pva glues. Titebond is not too bad, but I find CA easiest to sand, must be just me because everybody else I know says differently wink 2 Whatever floats your boat I say thumbs up

Been musing over the next part to build, tempted to start the fuselage, but there are stil decisions churning over in my mind, so it might be wise to crack on with the lower wing while my neurons work on the fus wink 2

The wing is going to be almost vanilla. I will add ailerons as per plan, they look large enough. I am going to use a single servo and bellcranks because nobody ever does them and you may want to see how I do them? I am also going to top hinge the ailerons rather than use a central hinge that is shown on the drawings.

Cheers

Danny

Barrie Dav 224/01/2014 11:21:39
1012 forum posts
14 photos

Danny, the wings will be ok 'Almost vanilla' but not almost banana. Vanilla pods are generally straight (ish). smiley

kc24/01/2014 11:38:32
6417 forum posts
173 photos
Danny's photo of his bandaged thumb is the best advert for not using glass headed pins! Presumably the Als pink pins are plastic headed.
I am glad you agree 1500 watts is far too much. Could be an error? 100 watts per pound is considered usual for reasonable aerobatic performance on monoplanes, but do you reckon to allow any extra for the extra drag with biplanes Danny?
Danny Fenton24/01/2014 12:26:01
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9451 forum posts
4261 photos

Thanks Chaps, the thumb was a result from cutting sheet balsa, Never been so foolish before. Held the wood down with my thumb on the cut line crook Really slowing me down...... never had a glass head come off but I only use pins in soft balsa.

Cheers

Danny

Danny Fenton24/01/2014 12:30:34
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9451 forum posts
4261 photos

Hi KC I am pretty sure that this will have enough power, remember I just want it to fly like a 20's biplane, the emphasis will be on slow flying. If you go bigger on the motor the weight sneaks up. One of the factors I use when choosing a motor is the weight, often you will see a similar spec of motor but 200 grams heavier! I would expect 60 watts /lb will fly it but it would be marginal and no extra for getting out of trouble.

You are right the extra drag would be a factor on something draggy like a Pitts Special, but for slow aircraft it doesn't appear to matter much.

Cheers

Danny

kc24/01/2014 12:50:52
6417 forum posts
173 photos
I have found 50 watts per pound adequate for flying a vintage style model but a little marginal for takeoff when the grass is long. So 100 w per pound seems right for a Barnstormer or Bistormer - a biplane with no draggy bracing wires etc.
Those scalpels cut skin just like they were made for it!

Peter Miller's designs very often uses single servo ailerons with bellcranks. His way of putting both piano wires from ailerons into a brass tube together with a U shaped rod to the servo arm seems a very good idea. I believe he uses a RadioActive brand servo mount which helps mount the servo from the top. A good photo of this setup in the latest RCModelWorld February 2014.

Edited By kc on 24/01/2014 12:54:08

Danny Fenton24/01/2014 13:08:46
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9451 forum posts
4261 photos

Hi KC thanks for that, I had missed that pic in RCMW, I love the way Peter has charred the balsa around the servo bay when soldering, brilliant! I like Peter's designs thumbs up

Cheers

Danny

cymaz24/01/2014 13:44:35
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9182 forum posts
1181 photos

Danny , stick a laser engine in. It is crying out for one. You wont regret itangel

Edited By cymaz on 24/01/2014 13:46:34

Concorde Speedbird24/01/2014 16:44:37
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2732 forum posts
650 photos

Yes, it does have foam wings. It is the best flying aeroplane I have flown, stall is a non-event, so I wouldn't be worried about the Bistormer being well over 6 pounds. The Bistormer is more of a slow flying aeroplane though, rather than the aerobat Domino.

CS

Danny Fenton24/01/2014 23:50:56
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9451 forum posts
4261 photos

LOL CYMAZ I am recovered now.... and the Laser moment has passed.....

Thanks CS, I have no doubt it would fly well at 10lbs but I don't want that I want a floater and with a symetrical wing it wont slow down as well as Chris's Moths.

bs 35.jpg

First of all I worked out where the piano wire was going to run from the centre section out to the belcrank, and made suitable holes in the ribs involved. A Permagrit round file is superb for making the neatest of holes, forget drills in the scenario.

bs 36.jpg

I was asked previously of my exact process, well here you can see a rib being positioned, checked for exact upright then CA'd into position, before moving on to the next bay. Don't forget the root rib is not vertical!

bs 39.jpg

Considering the innacuracy of the wooden template this time I made one from card using old school protractor and ruler. It isn't held in place for the picture as I have only two hands, but you get the idea crook

bs 37.jpg

Two extra trailing edge ribs have to be made up per aileron, and also notice the small section of 1/16 under the aileron leading edge, I have used this to keep it stable for when I saw the aileron off

bs 38.jpg

One extra riblet at each end of the aileron.

bs 40.jpg

I was really unhappy with this bit, not a clever solution, but unless I have missed something I can't see any other way this is meant to happen. I have added a block per bay to build up the trailing edge spar to the the upper skin. With hindsight I shouls have slotted in some 3/16 x 3/16 and webbed the gap. But these blocks seem to be how the plan shows it. Any input guys, have I missed a trick here?

bs 41.jpg

The aileron was then seperated from the wing panel with my razor saw and set aside for later.

bs 42.jpg

The wing panel had a trailing edge fitted, I haven't shown it as I showed it on the upper wing, but the sheeting is chamfered to fit.

bs 43.jpg

Nearly there. In this shot you can see that I have added the spar webbing. Because I have done it now it is really easy to get a really tight fit against the ribs. Perhaps BEB could put me straight but to my mind if the joints are not close with regards webs then a lot of the D box strength is lost

bs 44.jpg

The last thing tonight was to fit the false leading edge.

Cheers

Danny

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