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Bistormer 60" (A Barnstormer with more ribs)


Danny Fenton
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Well I will be soon start cutting wood for one of these. This one will be electric for a 6 cell A123 battery pack. I will endeavour to make it look a little more like a 60's home built aerobatic bipe if possible, but the inline engine cowl may make it interesting as most homebuilts of that period utilised flat four cylinder configurations.

I think there are many similarities between the Bistormer and the Barnstormer and the construction techniques that Barnstormer builders are detailing should suffice so I think it will be okay to divert from plans a little.

First off I will have to alter the drawings to suit the motor I will be using, as the bulkhead distance needs to be set.

Cheers

Danny

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  • 2 weeks later...

Hi Chaps well enthusiasm on the Apache has kept me away from starting this but finally got an hour tonight after little Roisin went to bed.

I would first of all like to ask if anybody else is building one of these? Secondly and if you want more information to just holler out!

Thirdly there are errors in the written instructions, which means the plan and instructions leave you in a state of uncertainty. Alright for me cos I will just blunder along and fix whatever goes wrong but might be frustrating for somebody with less airframes under their belt.

Firstly the wing joiners were made. The nomenclature or labelling on the plan matches the cutting sticky back sheet, however the instructions have the upper and lower ply joiners the wrong way around. The long ones go on the bottom wing, with the added centre section.

The basic idea is that the trailing edge 1/16 is laid down on the plan. (protected with Balsa Cabin Plan protector polythene sheet). As well as the two lower spars and all the ribs. The spars are packed up off the plan by the thicknes of A. the forward sheeting and B. by the capping strip thickness. these are 1/16, so the scrap pieces of packing are 1/16 balsa.

The forward upper and lower spars are cut from 1/4 balsa, speciafically chosen that is heavier at one end than the other. This often happens and its not usually hard to find a piece like this when sifting through stock at the shows. The heavy/harder goes towards the root. All the spars are cut from this stock, so are consistent.

The lower rear spar is another area for confusion. On the cutting list, it is shown as 3/8 x 1/4 but the slot laser cut into the ribs, and mentioned in the build notes is 3/8 x 3/16 anyway the laser cut ribs are a given so the spar must match. Again I cut these using a SLEC stripper. Talking of this tool its at least 10 years old and still has it original blade. Usually cuts first pass too wink 2

I set the ribs onto the forward spars, but leave the rear spar floating, The ribs are all the same and the rear spar ends up a fraction out from the plan. This doesn't matter. Once all the ribs are dry fitted in place the spar will allign itself.

The leading edge is made up of massive chunks of 1/2 thick x 1" logs! I don't like that so will be using two laminations of 1/4" The end result will be the same.

Hopefully the pics will match the lyrics party

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Cheers

Danny

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Thanks Tony, its going to be slow going as I am not getting time at the bench. Just come upstairs at 11:40 and have managed to cut and fit the trailing edges. But that's it for tonight. Never mind you have to eat an elephant slowly or so they say.....

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Before the ribs could be secured, the root rib angle has to be set using a simple balsa jig. This is to allow for the dihedral when joinging the two panels.

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Not the only way to do this, and indeed if you look at BEB's recent Dawn Flyer build blog you will see he does it differently to me. I like to sand the top sheeting with a chamfer to fit the rib and lower sheeting angle. Each to their own wink 2

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Her is the fit of the trailing edge sheets.

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And as close to multi tasking as you will find me, two wing panels at once.

This model will be virtually stock, and only have ailerons on the lower wings.

Cheers

Danny

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I am not building this model but the pictures are very enticing....maybe I will change my mind!

Danny, you said " I set the ribs onto the forward spars, but leave the rear spar floating " perhaps you could clarify this for any newcomers building this or similar wings. I take this to mean you pinned down the front spar to the board ( with spacers) along the marked position but left the rear spar unpinned to find its own position fore & aft as dictated by the slots in the ribs. Then you pinned the rear spar down to the board ( with spacers) Is that correct?

I think others would be interested to know whether you cyano each rib in position so the glue dries before the next rib is fitted or whether you glue them all in with PVA and let all the ribs dry together overnight.
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Hi KC I am glad you are enjoying following along. You are spot on with your description (clearly better than mine ) as for the ribs, I set each one vertical and use thin CA wicked into the joint. I let it dry before moving on to the next. I am very impatient lol I use Titebond II for the areas that require more time to position.
Thanks for pointing out my lack of clarity, thats the trouble with posting late at night
Cheers
Danny
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That's good to know KC. I am using a lot more medium these days, especially where ply is concerned seems to give a better bond.

Hi Colin, I am not sure how quick it will be, I am hoping that it won't be too long, I seemed to spend all evening tonight trying to work out what the instructions are supposed to be telling me. TBH I wish I had screwed them up and done things my way. Sorry Eddie but I think the instructions may need amending in places..... eg do the wing retaining before sheeting the top leading edge GRRRRRR!!! wish I had seen that one coming.

Anyway not much to show for a good 2 hour stint crying 2

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Leading edge was fitted, and planed flush with the ribs. This is not how DB recomend, but I prefer to sheet over either a false leading edge, then add a real leading edge. It increases the gluing area for the leading edge sheeting and makes for a stronger D box section in my opinion. The leading edge upper sheeting is added as per the DB instruction sheet sad

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Looking through all the Barnstormer builds I haven't seen anybody show how the wing (in my case upper) is attached. On the Bistormer there are two ply plates per panel and these are fitted flush with the lower edge of the ribs. This may not seem strong but by the time the lower sheeting is added it will be plenty strong enough. Just to make sure at the front hardwood rails are fitted.

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And at the rear, though not required by the plan, I have added some 1/4 sq section to add a little support.

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To transfer the position of the holes from the plan to these ply plates, first the bit of the plan was traced and the two crosses transferred to the ply.

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The play plates are supposed to have 4BA nuts epoxied to the underside, I am opting for a slightly more modern (though not by much) and am fitting 3mm blind nuts. The 1/8 ply plates wont handle the depth of these so additional plates were made up from ply and the blind nuts nipped up tight.

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Voila!

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I usually cut play washers to go over the top, but in this instance I am going to simply epoxy these in place. The epoxy resin has been mixed with coloidal silica to stiffen it.

All that remains is to fit these small plates inside the wing behind the FITTED ply plates, would have been so much easier before the sheeting!!!

I am full of flu I am afraid, so had to call it quits for tonight, me and a lemsip are off to bed face 21

Cheers

Danny

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Danny could you explain a bit more about the photo of the T nuts being fitted - I assume it shows an allen key being used with a bolt to draw the T nut prongs into the ply and the collet or collar and thick ply are just used as spacers or washers. Have I viewed it correctly?

I have to say that whenever I have fitted T nuts this way they always loosened eventually so I now coat them with epoxy before drawing them into the ply with a greased bolt. Messy but it lasts longer!

Edited By kc on 21/01/2014 12:33:18

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Hi Tony, as I drank my Lemsip last night I was musing about the alignment. I think I am going to have to fit the cabane struts to the wing and adjust the fit on the fus to get everything straight. The instructions are actually making the build harder smile o

Hi KC, the nuts are glued as they are pulled into the play as well as coated on top. The procedure is as you describe. I usually use a small ply disk with a recess to keep them in place but this will suffice.

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Cheers

Danny

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Well I am persevering with the instructions, but I wont be following them for the lower wing. The sequence doesn't suit my building style at all crook

Added the lower leading edge sheeting, the capping strips to the tops and bottoms of the ribs, and the wing tips.

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Also completed the spar webbing. I would have done the webbing before any sheeting but my OCD says I must following instructions sad

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I have included this shot to give some scale, its not as small a model as it first appears, it has a good sized chord.

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I then cut the slots for the plywood dihedral braces and epoxied them in place, being very careful to align the lower surface with the spars.

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I know there has been chatter on the forums about epoxy stirers, and lots of people use coffee stirers, well I really find a palette knife gives really superb control, and lets you get epoxy where you want with precision. A quick wipe with acetone and its clean.

Cheers

Danny

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Just a note for those that have not come across the tool I am using to notch the ribs for the dihedral braces. Permagrit sanding blocks and tools were introduced a few years ago now and are a must for your building tool box. They do various sized blocks, files, and in this case slotters. They are a bit pricey but work very well.

Permagrit Tools

Cheers

Danny

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Some might say I am a little pedantic... don't say it Mr Hooper sarcastic....

Anyway I was expecting more of this drawing...

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When I extend the lines drawn on the plan I get 4 degrees which is the stated amount and matches the small jig for which there is a diagram. However the template for the dihedral brace (shown stuck over the plan rendition) shows as only 3 degrees. This amounts to 1 and 1/2"half an inch under the wing tip, as opposed to the stated 2" Thats quite an error in my books thumbs down

Maybe I am just used to Brian Taylor drawings where accuracy is king!

Off to go and put my "fudging" head on, before I can join the wings.....

 

Edited By Danny Fenton on 22/01/2014 21:23:32

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I marked and sanded the dihedral braces to suit and then went about correcting the angle on the root ribs. These were set using the template but were a degree out also. I fixed this by lifting one tip up of the bench and sanding the other with the sanding block edge sliding along the bench to keep things true and perpendicular.

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Its made the wing gap better, still not perfect, but it will do wink 2

The wings were then joined and clamped after slapping epoxy everywhere wink 2

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The wing is pinned to the bench, with one tip raised two inches as specified on the plan.

Thats it for now cold has got the better of me, off for another Lemsip.

When I say cold I mean near death experience ie man flu, for any ladies reading its obviously just a cold......

Cheers

Danny

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