Line Rake on vintage model?

mccoyboy Thu Apr 15, 2021 5:47 am

I have been building the Mercury Mamba from the plan down loaded from Outerzone.

https://outerzone.co.uk/plan_details.asp?ID=4409

It wasn't until I completed the wing and covered it that I realised that the plan shows no line rake. I then checked for engine and rudder offset but to my surprise there is nothing shown.

Should I put some line rake in and cover again (bit of a pain) or will it be OK with some motor side thrust and some offset rudder?

**944_Jim** Thu Apr 15, 2021 6:57 am

I love that plane, and wish to build one some day. What size engine will you be using?
Concerning line rake, engine and rudder offset, I think if you find a similar model with those numbers you should be ok to carry them into yours. If you want to get really serious about line rake, then checkout flying-lines.org. They have a set-up article discussing this in some detail. However, the link escapes me now. I'll try to find it later today.
In a pinch, get the model completed, with about an 1/8"- 3/16" rudder offset, keep the engine at zero offset. It can be shimmed easily enough later if needed. Then set up the plane and hang it by the two control line.lead-outs as they are already established. You want the plane to hang just a bit nose down, tail up.
This simulates the line pull as if the plane is flying, except for the offsets built in to the ruder and engine. Then your first flights would be on short lines, short tank, rich running engine to observe for any turn-in. Increase engine speed first, then line length if it flies well.

Links:
http://flyinglines.org/orin.basiccl.html
http://flyinglines.org/mckay.trimming.html

duaneh Thu Apr 15, 2021 7:32 am

I hadn't heard of this model, so I followed your link to the plans. Thanks for that, it's an interesting plane.
Actually, it does have line rake designed in. Rake is measured from the leadout location through the CG. Bellcrank location is not a factor. The CG shown is ahead of the leadouts, as it should be. Make sure the model balances where shown, and do the hanging test that 944 Jim described, then fly it. I bet it will be fine.

mccoyboy Thu Apr 15, 2021 9:43 am

Hi 944_jim,
Thanks for the reply and your thoughts and it does make perfect sense to finish the model and do the hang tests first and go from there. I will probably add a bit of rudder as you suggest.
I was going through my scrap box and realised I could build this one with the balsa I had and then it became a bit of a challenge for myself...can I build it completely without making any purchases?
With this as my goal, I have decided to build it as a radial mount and use the electric set up I already have but it will be also be easy to put on a Cox radial should the model be a winner!

Hi duaneh,
Thanks for the explanation regarding line rake, it makes a lot more sense now and as you state there is line rake there after all! Glad you found the link useful.

I took some pics along the way but did not get round to posting them but I can do so if anyone is interested? If so...should I post here or start another thread?

**944_Jim** Thu Apr 15, 2021 10:46 am

Check my previous message....I just dropped the links there.

If I remember right, OZ also has an electrified version by a guy in Europe. He also has a YouTube video of the same plane.

Here it is, for consideration:

https://outerzone.co.uk/plan_details.asp?ID=5661

Post pics here (if you have been a member longer than the cook-off period). I'd love to see the build...we all love/appreciate build logs!

mccoyboy Thu Apr 15, 2021 12:42 pm

Hi 944_jim,
Thanks for the link; it will be very useful.

I did see the plan for an electric version and printed it off planning to build it but when I set about gathering the wood things just would not come together.

I was not planning on building but there was another week of lockdown, the weather was awful and so I needed something to occupy me. I knew the week would be up before any materials arrived and so it had to be done from what I had lying around.
The only suitable power available was the electric set up on the Ace+ trainer. I could also use the undercarriage. I thought about it and the simplest option seemed to be to build the i.c version with the wood I had and fit a radial mount for electric/ fit a different undercarriage.
It seemed to be destiny when I tried a new in packet belcrank that had been in a drawer for more years than I remember and it fit exactly as the plan, exact shape and all.

mccoyboy Thu Apr 15, 2021 12:58 pm

First task was the ribs.

mccoyboy Thu Apr 15, 2021 12:59 pm

Then I cut the rest of the parts to make a kit : I even used an old kit box to keep the bits in...I love a kit!

mccoyboy Thu Apr 15, 2021 1:05 pm

Then it was time to start the wing which was straight forward. However, there was no way the belcrank would fit beneath the sheeting and I had to remove some of the width of the spar to lower it.
Given that the ply belcrank mount is glued to the spar and between the ribs with gussets I figured this was not going to be a big deal.

mccoyboy Thu Apr 15, 2021 1:10 pm

With the wing finished I moved onto the fuselage:

I left out the hardwood bearers and replaced with a radial mount.

mccoyboy Thu Apr 15, 2021 1:15 pm

A dry fit of parts to get an idea of how it will look:

A good deal of sanding / shaping still needed!

**944_Jim** Thu Apr 15, 2021 5:16 pm

Looking great, McCoyBoy!

It looks like you put the lead-outs in the factory position, so I believe you will be just fine with regards to line rake as long as the CG is where it belongs.

The wood for this one should be cheap enough that IF you build it again, you can really dial it in or even put in a sliding/adjustable lead-out guide.

Thanks for sharing. If I wasn't mid-build on too many planes, I'd parallel-build with you.

mccoyboy Fri Apr 16, 2021 7:51 am

944_Jim wrote:Looking great, McCoyBoy!

It looks like you put the lead-outs in the factory position, so I believe you will be just fine with regards to line rake as long as the CG is where it belongs.

The wood for this one should be cheap enough that IF you build it again, you can really dial it in or even put in a sliding/adjustable lead-out guide.

Thanks for sharing. If I wasn't mid-build on too many planes, I'd parallel-build with you.

Thanks. I know what you mean about a back log of projects! It would have been cool though to compare notes and if you do get around to building it in the future I would be very keen to know what you think of its flying ability.

mccoyboy Fri Apr 16, 2021 7:57 am

I decided to tissue the fuse and tail surfaces and film cover the wing. However, the tissue I had was purchased for some rubber power projects and was of the more expensive Esaki variety and so I decided, in keeping with the keeping it cheap from the scrap box, I would use film covering of which I have ample supplies.

mccoyboy Fri Apr 16, 2021 8:02 am

Then on to the fuselage. I have decided to cover the canopy and nose area in black tissue.

**944_Jim** Fri Apr 16, 2021 7:33 pm

OoOooOOOoOOoOoooo! That is so cute...I "need" to build one. Since the weather isn't supposed to be good this weekend I may clear off the build table by finishing one, two or more projects.

If you go to the doctor's office much, snag a meter of the exam table paper to test as a cheap alternative to Esaki. It is covered with DocSpan..."everyday, crepe" grade. Over here it is distributed by Tidi Paper Company. I've been pleased to use it. I will say it shrinks in both directions, so really humped-up ribs may need some additional (yet thin) "spars" to keep the "swag" from pulling down between the ribs on the curved surfaces... especially on smaller models. It works great on solid surfaces, fills quickly on open structures. But you have to be careful. I'll try to show how I goobered a prototype kit wing trying to get it to pull "along the grain" too much.
Maybe OhBee can post his latest white and green model, or the link to it. ISTR he did the entire plane with it.

OhBee Sat Apr 17, 2021 1:52 am

O D K!

OhBee Sat Apr 17, 2021 1:54 am

One thing I would add is gussets behind that radial mount. Maybe you did....can't tell from the pic on my phone!

OhBee Sat Apr 17, 2021 1:58 am

Mine could have benifited from a couple spars....but I love how the exam table paper worked out! This was my first build s

ince the 60's.

Ken Cook Sat Apr 17, 2021 7:22 am

While I'm a huge fan of dope finishes, they're a total waste of time on a 1/2A. A iron on finish enables the builder to twist the wing if desired. Dope will automatically do that for you 99% of the time the incorrect direction. It's not cost effective and it certainly isn't easier or more durable. While some claim iron on covering is heavier, I've debunked that myth on many occasions. The reality is that the rigors of 1/2A flying does not lend itself to use dope finishes. It won't hold up to the flip over landings or weeds, the accidental gravity surges that take place or the fact that we use higher percentage nitro. I'm not suggesting that those in favor shouldn't try it or use it, I'm saying that you couldn't of chosen a better way to finish your model using iron on covering. If your out at the field and you need to do a emergency repair, clear packing tape has you in the air in minutes whereas dope finishes, put it back in the truck. I keep a $20 inverter with me and my Monokote iron and if needed, I can do simple adjustments right at the field even repairs and back in the air.

getback Sat Apr 17, 2021 7:28 am

Mc , thats a very nice looking model you got there , goof job on the fing covering too , hope to see a flight report . Wink

fredvon4 Sat Apr 17, 2021 8:34 am

Simulated old skool dope finishes are easy with a product like SLC or it's replacements.

Super Lite Covering was sold by Phil Cartier until his supplier stopped selling it. His replacement product is slightly thicker but still usable.

Bobby Mears has a Combat Museum and switched to this method as it looks like a good dope finish.

see this article from Flyinglines

http://www.flyinglines.org/gp.col18.html

mccoyboy Sat Apr 17, 2021 10:02 am

Hi all,
Thanks for the replies.
I like both film and covering for different reasons.
I shall keep an eye out for a cheaper tissue for C/L fuselage use and save my Esaki lite for serious Rubber Power models. I will stick to film for wings ( or perhaps the whole model) for now as 'puncture' resistance is going to be important given my lack of flying skills!
Ohbee - that is a super finish you have achieved; you have obviously not lost any of your skills since the 60's. A lovely looking model. I did add gussets behind the radial mount and carved /sanded them to fair in and so they do not show up well in the pics.
I did sneak a bit of tissue into the build using some scraps of black Esaki to cover the nose and canopy.
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OhBee Sat Apr 17, 2021 11:52 am

No dope was used on mine at all. Varethane laquer on the paper,and krylon paint topped with minwax clear.....Sweet looking plane Mcoyboy! Should fly great!

NEW222 Sat Apr 17, 2021 11:58 am

Looks sharp, and a very nice bird at that!

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