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Paul's CAP 20 L build 2018 MB

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Paul C.19/01/2018 21:42:15
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346 forum posts
104 photos

Starting with a place holder where I can record my build of Peter Millers CAP 20 L, I actually started early January but have not posted anything until now as I needed my laptop to do the typing. Using my tablet with the predictive text would result in disaster . Will kick off tomorrow with some picks and how I am getting on with the build, 'health warning ' I will blunder through this build in my own enimital way and end up flitting from one thing to another so please do not take this as 'the way to build the CAP' Peter has an excellent post on the build my posts will be my ramblings on how I did it.

Paul.

Gary Vinten 120/01/2018 11:38:23
507 forum posts
323 photos
1 articles

Will be watching 😉

Peter Miller20/01/2018 12:16:16
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8825 forum posts
1009 photos
10 articles

looking forward to seeing this one

Paul C.20/01/2018 19:57:43
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346 forum posts
104 photos

Sorry for the delay but have just made my first cock up, typed a few paragraphs and managed to lose the lot when I tried to find a photo, all part of the learning curve I suppose [cut and paste from word now].

This is my first venture into a build, have enjoyed reading so many that I thought I should bite the bullet and have a go myself. This is just me building one of Peters CAP 20 L not a particularly good builder and even worse when it comes to film covering so you have been warned.

Right then, engine ASP 52 FS somewhat on the large side but when inverted only the top of the cly head and exhaust will stick out, inverted engine will need remote glow [found this out when I built Ballerina], big engine up front will require servos etc moving back as far as possible to get the COG right and it’s just got to have a nice ally spinner on the engine.

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Paul C.20/01/2018 20:01:33
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346 forum posts
104 photos

20171212_102603.jpgCommandeered the wife’s baking paper to trace the formers etc , scan and print all of the wing ribs checked to make sure they sized correctly.

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Paul C.20/01/2018 20:05:52
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346 forum posts
104 photos

I have a scroll saw and used it to cut out the formers for the fus but used the Stanley knife on the lite ply parts

just making my own kit really

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Paul C.20/01/2018 20:15:08
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346 forum posts
104 photos

Needed to work out where to position the inverted engine and get the tank centred with the carb not forgetting to get it as close to F1 as possible. Surgery to the engine mount will be required [T mounts]

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Paul C.20/01/2018 20:39:10
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346 forum posts
104 photos

One problem I had with getting the engine as close as possible to F1 was sorting out the throttle linkage as the tank was in the way and no room for a clevis, I ran the outer cable down the side of the tank and ran a heavy gauge piece of wire through with 90 degree bend parallel to F1. Wire is stiff enough not to flex and long enough not to pop out of the throttle linkage, used this on Ballerina and seems to work ok.

Paul C.20/01/2018 21:03:52
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346 forum posts
104 photos

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Now these mass balance weights on the rudder and elevators got me scratching my head, Peter routed out the balsa and inserted lead. The only lead I had was the stick on square block type, I found that it I cut off the sticky back it was 1/8 thick so I opted for building up a laminate of 1/16, 1/8, 1/16 balsa with the lead inserted in the middle.

Cocktail sticks are shown on the plan to use when attaching these to the rudder and elevators, never used these before but the strength added to the joint is amazing. Commandeered all of the Christmas stock of cocktail sticks to the workshop, have used them when laminating blocks of balsa on the cowl and the back of the fus. You never stop learning in the hobby.

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Paul C.20/01/2018 21:37:05
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346 forum posts
104 photos


Decided to build the fus first probable wanted to get the engine, tank position and servo radio positions sorted asap. Got all the sides and formers cut out, used contact adhesive on the ply to balsa side, had a tin of the slow stuff but I think the cold snap got to it so had to use the usual instant. Used 5 minute epoxy on the ply formers the cold weather turned 5 min to about 2 hours to go off, my wooden workshop at the bottom of the garden is not the warmest place in the world a good gas fire is vital to fend off hypothermia. I wonder if a Mass Build starting in January is such a good idea we may be the cause of the demise of forum members embarking on the project.

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grandsons old jenga blocks always come in handy

Paul C.20/01/2018 21:52:44
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346 forum posts
104 photos

Needed a canopy so contacted Vacform, never used this company before but the service was spot on, used PayPal and the canopy was made and sent to me in a few days excellent service. I ordered two as my previous performances when cutting and trimming canopies is dire. Needn’t have bothered as the quality and fit was excellent, even I managed to cut it out accurately. I made cardboard templates of the fus where the canopy sits few strips of masking tape, drew a line on the tape which matched the canopy mould lines exactly. Commandeered wife’s nail scissors which worked fine for the thickness of the canopy sheet, just thought I have not returned the scissors best do that before I am found out.

Paul C.20/01/2018 21:54:22
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346 forum posts
104 photos

more to follow

Gary Manuel20/01/2018 22:00:49
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1370 forum posts
1143 photos

Paul / Peter.

Any chance of explaining the need for "mass balancing" of the rudder and elevator?

I understand that it's something to do with reducing flutter but I don't understand why it would apply to this model and not most other models.

I have a 30% Glenns Cap 232 which has them fitted but I never really understood why.

Paul C.20/01/2018 22:16:16
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346 forum posts
104 photos

Hi Gary I think that this is one for Peter from my view it was on the plan so I followed accordingly . I have seen mass balance used on models before usually on large moving surfaces and probably on the faster flying models but as I have said Peter is the one to answer your question. A few years back I remember one club member flying a model that suffered serious elevator flutter at speed this ended up with the elevator parting company and the model totaled can't remember what the model was but am sure it was a semi scale type.

Cheers, Paul.

Peter Miller21/01/2018 08:21:14
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8825 forum posts
1009 photos
10 articles

Mass balance is used to prevent flutter. The idea is to move the CG of the control surface close to the hinge line.

I would check where the control surface balances.

One of my models (Dancing Girl) suffered from very serious flutter on the elevators due to a sloppy unsupported snake. Just for the experiment I fitted mass balances on arms extending forward of the hinge line. The model was then dived to terminal velocity from a great height while I waited for the tailplane to disintegrate. IT never even twitched. I did change the snake after that.

Not sure if the CAPs really need it but it seemed a good idea at the time.

In passing, we were doing a lot of modifications to Scottish Aviation Twin Pioneers in Aden. One mode was to add lead to the front of the elevators. That was a real pain. Glad I wasn't on that mod. The one I was doing was just as bad in its way.

Peter Miller21/01/2018 08:22:51
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8825 forum posts
1009 photos
10 articles

For your throttle connect, This may help

ballerina const 036.jpg

Paul C.21/01/2018 09:08:54
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346 forum posts
104 photos

Nice one Peter, I have not seen any cable for a while in my LMS will check it out on my next visit. What sort of connector did you use on the throttle arm is it something available from model shop.

Paul.

Peter Miller21/01/2018 09:36:36
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8825 forum posts
1009 photos
10 articles

That is Bowden cable. You can buy it direct from Radio Active. The people who make tanks and engine mounts among other things. Also from Pegasus model in Norwich and I am sure other places too.

The Brass fitting is a metal pushrod connector fromSLEC (SL063-R) abut again similar items will be available from Pegasus etc.

McG 696921/01/2018 09:38:26
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1841 forum posts
781 photos

Hello Paul,

Very neat build and instructive blog. I just love the little 'mass balances'.

One thing I did notice though. You really seem to "commandeer" a lot of your LotH's stuff - baking paper, cocktail sticks, nail scissors, ... - and even manage to forget to bring them back. surprise

I just presume you like to live 'dangerously'... wink

Cheers

Chris

 

Edited By McG 6969 on 21/01/2018 09:47:37

Paul C.21/01/2018 09:45:44
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346 forum posts
104 photos

Peter, thanks for the info I will check them out.

Chris, fortunately she never enters my workshop so I think I am safe for now wink

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