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Author Topic: Baron Knight II Coupe by Dave White  (Read 2763 times)
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billdennis747
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« Reply #125 on: January 24, 2020, 06:32:56 AM »

Caley, next time finish the entire model except for the pylon, covered, doped, motor in. Then build the pylon in the right place for balance
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crashcaley
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« Reply #126 on: January 24, 2020, 08:31:05 PM »

Bill, Seems I forgot to "Post" my reply to you, so what I wrote is gone.

But I will heed your advice.  Gotta remember that this is a complex model, and really the first one for myself.  Even scale models seem easier than this.

What I am doing is covering the aft portion, which includes the fin, stab and fuselage behind the motor peg with a tissue I picked up years ago.  I am guessing it is 10 grams a square meter.  The grain seems to be good, though it is pretty delicate if it runs into a stick or other solid poking object.

The fuselage forward of the motor peg is getting "Easy Built"tissue, which is fairly heavy at 62 grams a sheet (guessing about 40 grams a square meter).  The wing is going to be with "Easy Built Tissue" as it is the only tissue I have that allows me to create my rainbow wings.

You have to remember I am not competitive, and therefore, getting the model to exactly 70 grams is not a great necessity for me.  This is just a learning build, especially after so many years away from the hobby.

Anyway, I hope the tissue weight difference will compensate a little for my error on the pylon.
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What's stall speed?  Undecided
crashcaley
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« Reply #127 on: January 27, 2020, 08:10:27 PM »

I'm still working at things, and learning.

Example:  I was wondering about tissue over 1/4 mil Mylar, so i went online and read some.  I read one, that I now regret I didn't read more.  It said to pick you favorite glue stick, and after applying the Mylar to the wing bones, glue stick the tissue on.  I never noticed until hours after I finished that the whole thing, when viewed in good light, looked like it had some kind of skin disease.

I then went back and read a little more, and found that you could use dope to apply the tissue over the Mylar.  Well, being very skeptical now, I went ahead with a test piece, and sprayed the Gorilla glue on a piece of balsa sheet, then carefully  pressed the Balsa sheet onto the Mylar, that was sitting flat on the work bench.  I then applied dope over the Mylar.  Surprisingly, not very much dope is required to stick the tissue to the Mylar.  Not only did the Mylar go down flatter, but no more diseased look

I also discovered that you need to set the wash in or wash out on your wing tips.  Guess that is done during the Mylar application, as the Mylar can be shrunk with a modeling iron.

I also learned it is better to do a panel at a time, when applying the Mylar.  I did the inboard and outboard of each wing half at the same time, and that lead to difficulties trying to stick the Mylar flat.

Why all this experimentation?  For some reason, no matter how I try to dope on my tissue, it will not stick.  I've put down two coats of 50/50 dope with DUCO glue on the under cambered wing bottom.  And applied 50/50 dope to the upper surfaces.  Supposedly you can just position your tissue on the bones, and brush thinner to soften that dope, and it is supposed to stick.  Can dope be too old.  Mine is about 15 years old.  But like I said, it refused.  I fought with the tail surfaces, and eventually got those two things covered.  The fuselage also gave me a migraine with its refusal.  And the wing was just impossible.

I continued on today putting all the fiddly bits on, including timer, and weighed the entire setup, even with the icky wing, and it came in just over 72 grams.  That's quite an accomplishment for me, as i tend to build flying bricks.

I did find that I could remove the Mylar/tissue combination without much fuss, so the wing bones are awaiting trial number two.

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What's stall speed?  Undecided
Jastafuhrer 13
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« Reply #128 on: January 28, 2020, 05:16:56 PM »

Is it nitrate dope?  Butyrate dope has low adhesive properties.

In my experience the old recommendation to apply a couple of coat of dope to the frame work before applying tissue is just not enough, especially if it's been thinned.  It'll need at least 4 coats, or until there is some shine on the wood.  I think this is one of the reasons some builders use glue stick, tissue paste, or white glue to apply tissue - because it's faster.   I build mostly with carpenter glue so I still attach tissue with dope for the simple reason that it's very easy to remove tissue later with acetone or lacquer thinner without the fear of loosening joints.
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crashcaley
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« Reply #129 on: January 28, 2020, 06:05:25 PM »

Jast,  It's  Randolph non-taughtening Nitrate Dope.  I did two coats of 50-50 plus DUCO glue on the undersides of the flying surfaces.  It seemed to have a shine.  And I did the same with the 50-50 dope everywhere else.  I watched a video done by, I think it was DUCO GURU, and that was the process he used.  I've done that for years, and never had a problem.  Maybe it is my thinner that I am using.  From what I understand, Acetone can be used for this purpose.  Maybe I had a cheap batch of acetone that after many years of sitting around, became ineffective.  Will have to purchase more, but try to get the quality kind, if I can figure that out.

I started my wing again.  My previous experience is sure coming in handy.  Doing each wing panel separately worked very well.  Then I used my Monokote covering iron to heat shrink the Mylar, and ensure good seal around the edges.  I used shims on the wing tips to set the washout.  All I did was seal the edges, then I shimmed the wingtip, and held things down with magnets.  Worked really well.

I won't say the job I did is up to par with those who have worked with Mylar for a long time.  I still have a few tiny wrinkles here and there that won't disappear.  I just didn't want to press my luck, and either pop the edge seal or melt through the Mylar by trying.  But I do have a nice surface, probably 50 percent better than the last try.  All I need to do now is take my time doping down the tissue.  Then maybe I will have the courage to show the finished product.
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What's stall speed?  Undecided
flydean1
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« Reply #130 on: January 28, 2020, 10:47:19 PM »

Caley,

Acetone and possibly lacquer thinner could thin the dope, but on recommendation from some really experienced builders, I never mix brands.  I use Randolph thinner for their non-tautening dope.  Strangely enough, Sig thinner will work for both their nitrate and lite-cote butyrate dopes.

When I buy either Sig or Randolph (my preference), I buy twice as much thinner as dope.

I use hardware store lacquer thinner to clean brushes.  You probably already know this, after a thorough washing in thinner, you should also wash the brushes in warm soapy water, rinse out all the soap (squeaky bristles) and let them air dry.  I have a brush that is over 40 years old, and still has all its' bristles, which is more that I can say for myself Grin Grin
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applehoney
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« Reply #131 on: January 29, 2020, 09:50:35 AM »

I just leave the brush in the tightly sealed dope jar ready for use whenever next needed.
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crashcaley
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« Reply #132 on: January 29, 2020, 11:20:17 AM »

I gotta purchase some of that Lacquer thinner stuff then for cleaning my brushes.  As for cleaning brushes, I wish mine in the thinner, then twirl it against the glass side.  I then brush everything I can off on a paper towel.  And yes, a trip to the sink with some warm water and soap does a nice job of finishing the process.  I just don't have a jar big enough to plunk my brushes into until they are needed, so they have to be cleaned each session.

Process on the wing covering is slow.  It's amazing just how little dope is needed to wet the Mylar.  Then I just position the tissue over, and lay it down.  The Mylar with dope, then just sucks the tissue tightly.  I gently brush out as many bubbles and wrinkles as possible, then let dry  The "Rainbow" wing has five colours on it so far.  10 to go.
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What's stall speed?  Undecided
crashcaley
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« Reply #133 on: January 29, 2020, 07:32:52 PM »

I'm pretty much finished with the model.  Just have to CG it.  Funny, but i swore there was a CG mentioned on the plan, but now I cannot find it, if my life depended on it.  Sometimes things need to jump out and bite you, so you notice them.  Bill, what is the CG, please.

The wing is better the the first, but the covering still leaves something to be desired, as compared to what I have seen at the flying field, people using tissue over Mylar on their flying surfaces.  I guess it just takes time to develop the technique to do it correctly.  But I am pretty happy.

I erred on a previous post, saying the model was about 72 grams.  I forgot to add the timer, the rubber o-ring and motor peg bobbin.  The bobbin is created by myself from 1/32 ply and aluminum tube.  I've done this for previous models, and it not only helps the rubber unwind better, but also seems to make inserting the rubber into the model easier.  But I am going to modify the covering on the fuselage just a tiny bit, by adding a clear window in the area just behind the motor peg.  Probably will cost me another few hundredths of a gram, but at least I can peer inside while fumbling with getting the rear motor peg through the bobbin.

And finally, what you've been waiting for.  Put on your slum glasses, as this may be cruel and blindingly unusual punishment for some.

EDITED:  for those wondering what the long rectangular object is under and behind the fuselage, that is blue foam that I used to hold my stab when not flying.  It helps prevent warping of the stab.
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Re: Baron Knight II Coupe by Dave White
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OZPAF
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« Reply #134 on: January 29, 2020, 07:46:47 PM »

That is extremely colourful Caley - even with Sunglasses! It looks very neatly built as well. I think you should hang it on the wall! Smiley

John
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applehoney
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« Reply #135 on: January 29, 2020, 10:37:13 PM »

Nicely done, Caley !

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billdennis747
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« Reply #136 on: January 30, 2020, 03:49:23 AM »

Looks very nice! So it's about 76g all up? The CG needs to be about 60% back from the LE - I hope that doesn't put the weight up!
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vintagemike
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« Reply #137 on: January 30, 2020, 07:49:08 AM »

Whats wrong with it? looks bloody good to me!
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crashcaley
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« Reply #138 on: January 30, 2020, 08:24:10 AM »

Bill,  As I said, this was a learning build, and not one that will ever win a contest, if it were to be flown in one.  Not knowing about the pylon position thing, you are correct.  I did need a lot a nose ballast, 7.5 grams  But hopefully it will fly as well as my Souper Coupe, that came in at nearly 90 grams.  I got that one to fly for 90 seconds.  There's only half an inch of play on where the pylon can go back, unless I put it farther back than the sheeted part of the fuselage.

Question:  Just how did you build the pylon without attaching it to the fuselage.  I tried, and could not keep it from moving.  Did you build things before covering.  I guess you could then carefully slice the pylon away from the fuselage sticks and sheeting.

At least I know what i need when I build a second one, and that is already started with the fuselage, and two new prop blades. 

I did run the prop on a few turns, and I need to find the balance point for the counter balance weight.  It shimmies just a little

I do appreciate your help, and everyone else's help and support during this build.  Whenever I get another done, I will post, and hopefully it will be a bit nicer than this one when it comes to weight, now around 82 grams.
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What's stall speed?  Undecided
faif2d
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« Reply #139 on: January 30, 2020, 09:07:16 AM »

I really have no idea why you beat your building ability up so much.  That looks gorgeous to my eyes!!!!!!!
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I used to like painting with dope but now I can't remember why!    Steve Fauble
billdennis747
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« Reply #140 on: January 30, 2020, 09:18:22 AM »

Caley, don't forget that the original French specification was 90g + 10g and since you aren't competing, another 3g of rubber might help. But they used to score five maxes and ROG!
I don't finish the pylon separately. Once I know where the CG is I stick on the central piece and finish the rest around it.
This model looks good in the air and nicely different from the modern identikit types
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cvasecuk
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« Reply #141 on: January 30, 2020, 09:37:48 AM »

That is lovely, and like all Coupes, if launched into good air it will max!
As Bill says, it was designed to the 100g rule so you have done well.
Ron
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crashcaley
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« Reply #142 on: January 30, 2020, 10:11:45 AM »

Didn't realize this plan was for the old rules.  I don't feel so badly now.  I will fly with just the 10 grams of rubber.  All I hope is that it does fly, even if it is only 60-90 seconds.

Bill, If I understand things, you build everything except the pylon, and determine their weights, then place them somehow to find where to put the pylon.  I guess this involves putting in the motor, attaching the prop, and putting on the stab, then sliding the wing back and forth until you get a balance.  I will try that for #2.  For now, I am taking a break from building.  #2 will probably be after the nice Boomer MkII P-30 kit that Dean gifted me.  Thanks Dean.  I'm already taking photos of everything for the introduction to the build.
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billdennis747
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« Reply #143 on: January 30, 2020, 11:12:27 AM »

Caley, yes I assemble the entire model ready to fly except for the wing, which doesn't affect the cg. I put a mark on the central pylon piece at 60% and glue it on to match the balance point, then finish it off
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« Reply #144 on: January 30, 2020, 11:28:43 AM »

What year was the Baron Knight plan published? My copy of the FFQ Coupe Survey says that the 100 gram coupe weight was brought in during 1971 and went back to 80 g during 1980?

Peter
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billdennis747
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« Reply #145 on: January 30, 2020, 11:36:05 AM »

Peter, yes of course. The BK was designed to 80g but I was just telling Caley that models like this (and a lot bigger!) will fly well at 100g!
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crashcaley
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« Reply #146 on: January 30, 2020, 11:45:45 AM »

Bill, As usual, I cannot interpret what is being said sometimes.  Never knew the wing didn't affect CG.  What you provided, sure makes the whole process easier.
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What's stall speed?  Undecided
billdennis747
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« Reply #147 on: January 30, 2020, 11:59:55 AM »

Bill, As usual, I cannot interpret what is being said sometimes.  Never knew the wing didn't affect CG.  What you provided, sure makes the whole process easier.
Caley, if the CG is approx 50% and the wing structure light and evenly distributed fore and aft, the cg won't move much with or without the wing
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crashcaley
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« Reply #148 on: February 04, 2020, 06:23:49 PM »

Bill,  Thanks for all the info on how to make things easier next time, which is happening right now.

I tend to cut out a lot more parts than I usually need, for just in case I get heavy fingered and snap something.  So I had about half the parts needed to complete a second BKII. 

The second fuselage is done, and I discovered that my problems with the tail wanting to be crooked wasn't my building problems, but the fact that the pieced together plan, even though it looked straight, was actually off a tiny bit.  I definitely need to find a copy of this plan that isn't pieced together.

I also realized another mistake, though maybe not a huge one.  While sorting my balsa sticks, and weighing them, and bundling them in .1 gram groupings, I noticed that for most, the sticks were not centered on the scale, but sometimes as much as 2/3 off to one side.  This tells me that one end of the stick is heavier than the other.  And I should have been putting the lighter end of the sticks towards the tail.  That probably would have amounted to a few 10ths of a gram at the tail, and about four times that at the nose, meaning less nose ballast needed.  And because I had been out for so many years, that little bit of info that was passed on years ago was forgotten

On BKII #2, the stab, Fin and sub fin are done also.  So I basically need to make another wing, this time pre-setting the washout required, and of course, make another nose block.  I already have two new blades, and bent four additional prop shafts.  I always figure, why do one, when you have everything out.  Why not make a production of it, that way copies are available for the next model that requires a similar item.
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« Reply #149 on: February 04, 2020, 10:38:48 PM »

Great Caley.  Enjoy the building. 
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