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Bistormer 60" (A Barnstormer with more ribs)

Barnstormer with more ribs

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Danny Fenton22/01/2014 17:57:39
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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

Danny Fenton22/01/2014 21:22:43
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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...

bs 26.jpg

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

Danny Fenton22/01/2014 22:09:39
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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.

bs 27.jpg

bs 28.jpg

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

bs 29.jpg

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

cymaz23/01/2014 08:24:03
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Too bad about the cold Danny, gets well soon. Whiskey might help, it'll numb the pain anyway if you take enough cocktail

Tony Bennett23/01/2014 08:32:39
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did you say "it will do" smile o

you must be ill sir to accept something that is not perfect. cheeky

though it looks blinking perfect to me.

get well soon young man.

Nigel Day23/01/2014 08:50:04
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1158 forum posts
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'Slapping epoxy everywhere'.

Won't do much for the weight will it? smiley cheeky

Nigel Day23/01/2014 08:52:13
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Please forgive me Danny but I'm new to this type of modelling.

Accuracy issues aside, what's the practical effect of the .5 degree angle difference to the construction?

Btw, the notes and images are very useful, many thanks. I'll be doing my wings some time in March I think.

Edited By Nigel Day on 23/01/2014 08:53:25

Danny Fenton23/01/2014 09:40:49
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3945 photos

Thanks Cymaz I am not sure SWMBO will let me near her whiskey even on medicinal grounds wink 2

LOL Tony I know once you let the standards slip, you may as well go whole hog!

Hi Nigel, the build becomes more difficult if bits don't fit properly. If the designer intended there to be 4 degrees of dihedral then he will have designed the cabanes and all the wing mounting geometry for this. I agree a 1 degree difference does not appear much but I do like to get things spot on and its annoying when you have cut your parts very accurately to supplied templates only to find they do not follow the drawing accurately. I have had to take a mm off the underside of the dihedral braces which obviously weakens them ever so slightly.

I was joking when I said slopping epoxy everywhere, bit of an in joke as Tony alluded to, I am very fussy usually though this model is pushing my OCD to the limit wink 2

I will do the bottom wing in the sequence I think they should be done and you can then see which you prefer Nigel, are you doing the 60" version?

Cheers

Danny

cymaz23/01/2014 09:47:28
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Danny its a good job you don't have my 72" bistormer. Flies sooo beautifully on an OS91 BUT on the lower wing one half is 1 inch longer than the other.

Happy dayslaugh

Danny Fenton23/01/2014 09:49:25
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9108 forum posts
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ARGHHHHHHHHH!!!!!!!! must go lie down......

Nigel Day23/01/2014 10:19:54
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213 photos

Thanks Danny. I WAS joking about the epoxy. Seeing your build so far I can see you're very meticulous.

As a newbie I'm trying to get a better feel for what errors and discrepancies make a material difference to the strength and appearance as opposed to simply offending the builder's sense of perfection.

Most of the time I also want to get it exactly right but it's useful to know when 'good enough' is enough in cases where adjusting or redoing something either isn't an option or would be a real pain.

Yes, I'm about to start the 63" B'stormer. I'm currently poring over the plans and the blogs from Tony, Phil and Jeff to see what mods, if any, I want/need to make. I'll be going electric.

It's the placement and fitting of trays and hatches which is making me think the most. Without the experience that you guys have I can't easily visualise where openings & fittings are needed, when to build them, and what mods to make to the basic plans.

This is all good stuff and one of the things that looks as though it'll make building even more interesting and fun.

Edited By Nigel Day on 23/01/2014 10:24:11

kc23/01/2014 11:26:03
6032 forum posts
168 photos

I have always found that David Boddington's hand drawn plans are accurate and informative. Much better than many CAD plans.
Is it possible that the main drawing is by Boddo yet the template has been done later by someone else? ( there have been several succesive owners since Boddo)

Nigel. Regardless of who drew the plan I always go over the plan comparing former widths etc with fuselage side & plan view. Dividers or plastic vernier calipers or just a ruler will quickly reveal any errors and studying the plan before cutting wood will save time & material.

Edited By kc on 23/01/2014 11:28:49

Biggles' Elder Brother - Moderator23/01/2014 11:34:48
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Nice work Danny - coming along well and looking good.

This is a great blog BTW - just the sort of detail new builders need and its providing great insights into building techniques.

Picking up on Nigel's point: new builders shouldn't be discouraged in any way by any "issues" being flagged up - there will always be challenging areas in any build. The real point is that with the Mass Build approach you get a "roadmap" provided by a more experienced builder of how to cope with those little problemettes. And that is exactly what Danny is providing here.

You ask a really difficult question when you say "how do you know when an issue is problem and has to be addressed and when it will be good enough and can be left". I suppose in the end that one comes down to experience. And this is one reason why we encourage new builders to do blogs - not just experienced builders. That way you can ask questions about your build - you can ask "Is this OK or do I need to change something?" or even "help, how do I fix this"!

I think one of the things that really characterises an experienced builder is the way he may be doing X, but actually at the same time he's really thinking about Y that he won't be doing until next week. He's constantly asking himself the question "What will be the knock consequences of what I am doing now?" and he's thinking out problems on future aspects of the build all he time. Notice Danny says at one point something like "I was thinking about how I was going to do the cabanes". He's not doing them now - but he's thinking about how what he is doing now will impact on that stage later. I know that when I'm "in a build" I'm constantly (and I mean constantly - often when not even in the workshop!) thinking about "how am I going to do this or that" and "this or that" is often well in the future.

For example, take the question "does 1 degree error in the dihedral brace matter?". Well in terms of it being a dihedral brace, no not at all. In term of the job in hand - joining the wings - it matters very little (Danny's OCD apart wink 2). But an experienced builder isn't thinking about those things - he knows he can sort that. What he's thinking about is that a 1 degree difference here, at the wing root, will mean that out there, at the wing tip 30" away, he'll be a whopping 12mm out of position! Now suppose the inter-wing struts are on the plan at 300mm long - the gap they go into will now be 312mm. This isn't going to work! (I don't know if the Bistormer has inter-wing struts - but you see my point).

OK, this can be fixed - but it shows how a very small error in one part has bigger consequences further down the line.

The thing to remember though is that, in my experience, there are very few of these challenges that can't be fixed, worked around, or modifications implemented to cope with. The difference between a new builder and Danny is; Danny already knows he has an issue in the future because of what he is having to do now. A new builder would probably just carry on, unaware, then eventually some time later make the strut to plan size and then look puzzled when it was half an inch too short! He'd then make another one longer - and make a mental note not to fall for that one again. And being an "experienced" builder is in reality for most of us the painful process of many years of making such "mental notes not to do that again"! smile

BEB

Danny Fenton23/01/2014 14:55:38
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9108 forum posts
3945 photos

Hi Nigel, I am more than happy to help any way I can re hatches etc and mods for electric. I am torn between doing the fus next or the other wing. My head is still mulling over what to do with the fus, as I am going electric too, the entire front end is over engineered. and to make matters worse the structure utilises "rails" as you have no doubt seen. This doesn't translate well to bulkhead mounted leccy motors.

Also the ply fuselage doublers are there to transfer massive vibrational loads that are simply not present with electric so could be modified to save some weight. With regards to weight, I am not trying to save weight because its electric, I am trying to save weight because of the flying characteristics that I want from this model. I really enjoy flying a Cirrus Moth that I renovated for my friend Chris, and I would like this to float around with the moth. The wing section is not really right for the role, however if I keep it light I may be able to slow it up enough wink 2 we will see.

I noticed BEB answered your thrust line and motor moving question in his DF thread. All valid points, however I may be moving the motor down on mine. You may already have noticed if you have been studying the plans that the leccy motor mount would have to be higher than the available bulkhead on the BiStormer, so mods have to be done. Either the motor gets lowered or the bulkhead raised I am still musing that one.

I also do not like massive down and side thrust, I think it looks awful on a model and am happy to play with the rudder and elevator to compensate for power settings. After all that is what you do on the full size.

BEB I really must thank you for such a clear and concise post, you even make me sound like I know what I am doing, the choccy biscuits will be in the post wink 2

You have, as always hit the nail on the head, and put it so eloquently. I guess we do always keep in our minds, what impact will this decision have later on. There are no struts on the Bi Stormer, though i am still really struggling to decide whether to build this vanilla or to try and make it look period in a semi scale kind of way. Which would then mean struts.

Re the dihedral, I cadded the head on views and worked out the amount the dihedral would change at the tips if it was only 3 degrees, and it would have meant 1.835 inches under one tip with the other flat on the board.

My brain is churning modelling stuff like this over ALL the time, good job driving is second nature. My wife wonders how I can drive for hours without any form of entertainment music/radio etc. Well now you know teeth 2

KC I think you are right the drawing does seem accurate, its the sticky printed templates that are out.

I will be more vigilant and compare my parts to the plan from now on!

Thanks for all your feedback and comments, it does make doing these blogs all the more rewarding.

Cheers

Danny

kc23/01/2014 17:50:41
6032 forum posts
168 photos
Recently I have electrified a couple of models intended for glow. In each case I decided it was better to move the engine bulkhead forward so the Lipo came as far forward as possible to help make CG position without lead.
To me putting the bulkhead forward is much better than using standoff type mounting. What are your thoughts Danny?

Danny Fenton23/01/2014 18:01:28
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9108 forum posts
3945 photos

Hi KC, I agree. The first few conversions I did were using threaded rod as standoffs. Worked fine but was a waste of valuable real estate under the cowl. A bulkhead further forward is a much better solution thumbs up

The BiStormer may be odd in that I am probably going to use A123, with these there is no need for a hatch as they can be charged in the model. We will see how I feel when I get closer.

Of interest I converted a pupeteer a few years ago and was able to shorten the nose by nearly 2 inches because the motor and battery could be positioned much further forward than an ic. Thoughts of the C of G is always tugging at the neurons wink 2 we do not like lead!

Cheers

Danny

kc23/01/2014 19:29:32
6032 forum posts
168 photos
As the nose normally narrows in, moving the bulkhead forward means a change of width and height of the bulkhead. I simply mark the new position on the plan and measure height & width at that point, then make the former a similar shape but to the new dimensions. I am sure that Danny will know this method but it may not be obvious to newcomers.
kc23/01/2014 20:00:11
6032 forum posts
168 photos
I suppose the bulkhead position has to be determined after the motor is selected. DB suggest a 4 Max motor and they suggest their PPO 5055 which is 1580 watts and has an 8mm shaft. Seems massive to me -- again whats your ideas Danny?
Nigel Day23/01/2014 20:04:02
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1158 forum posts
213 photos

Thanks kc.

That's just what I've done. So far the dimensions on the plan match the inside of the lines drawn on the patterns/templates - but then I've only measured less than 1/4.

Nigel Day23/01/2014 20:11:22
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1158 forum posts
213 photos

Nicely explained BEB.

As you say, these blogs are a great source of ideas and information for a newbie when doing the model. I've learnt a lot from following the (at least) 5 different Barnstormer builds going on currently.

I'm currently reading three of them and am starting to understand the decisions and rationales of the various builders for the decisions they've made. I suspect that I'll 'pick and mix' from them when I build and 'wing it (sorry)' a little too. All part of the learning experience.wink

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