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Mar 09, 2019, 02:17 PM
An itch?. Scratch build.
eflightray's Avatar
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Discussion

Started a replacement Lancaster


This could be a long term project.

After the demise of my previous Lanc last year, ( attack of the killer hedge ), the salvaged parts, everything except the body, wings, tail, kept staring at me, pleading me to make them a new home.

I started drawing up an A20 Boston/Havoc, then realised it looked too much like my B-25 but with only one fin, and only two of the motors. To use up those four motor it just had to be another Lanc. Well they do look ....... special.

So, another scratch build, and genuinely starting from scratch as there were no usable drawings of my original, but then that's the fun of making it up as I go along. Though I may later regret using the word 'fun'.

I don't do detailed build threads, just a few pictures occasionally, the rest of the 'design' is still in my head.

So here she is so far --

Ray.
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Mar 09, 2019, 03:06 PM
An itch?. Scratch build.
eflightray's Avatar
Thread OP

The continuing problem of being a cheapskate, and not wanting to buy more stuff.


At the start of the build I realised I had run out of 1/4" balsa sheet, I normally use it for full depth wing spars.

Then to add to the problem, my usual 1/2" balsa sheet for the leading edge was short. But I did have plenty of 1/8" balsa sheet.

So, thinking out of the box, (box of balsa ), I decided to try multiple 1/8" spars, and no leading edge, just wrap the Drepron sheet right round.

Why not ?

Here's another picture showing how the multi-spar arrangement will eventually work. Going to be a lot of 1/8" sheet striped down into 1/4" and 3/8" wide strips. This is just a try out, no glue yet, but I feel it will make a strong and light wing.

Ray.
Mar 11, 2019, 04:38 AM
Registered User
AMcC's Avatar
Nice going Ray. I'm about to venture into the world of large depron models so I'll be watching your progress. regards
Mar 11, 2019, 07:48 AM
An itch?. Scratch build.
eflightray's Avatar
Thread OP
Thanks AMcC, here's the original Lancaster if it helps with any ideas ---

Another Lancaster, balsa and Depron, 98" span.

A few things are changing, the fuselage on this one starts with an inner 6mm Depron box, then the part formers added outside, then the skin.

The wing design is also changing. The original had 1/4" balsa spars, and a balsa leading edge, this one will be more like an early free flight model wing with multiple small spars, no leading edge, the skin will wrap around the front.

Many ways to end up with the same thing, and hopefully just add more lightness.

Ray.
Mar 14, 2019, 05:26 AM
An itch?. Scratch build.
eflightray's Avatar
Thread OP
A couple of additional photos.

The wing spars are now all glued in plus some bottom 3mm Depron sheet added to get the trailing edge position. The wings have come out quite stiff considering I am only using 1/8" balsa for the spares

I'm trying a new adhesive to me, 'Unibond 100% Power Glue 0% Solvent. Seems to work quite well. Not a contact adhesive like UhuPor, and has a longer time to 'grip', so fitting the sheeting should be easier. It still has a fairly short dry time.

Now to sort out where the wire runs will go, 2x ESC to motors, plus the aileron servo and retract leads. I like to keep things separate to reduce any cross-talk. I cut plenty of holes in the ribs, but not necessarily where I want them, now i'm starting to consider the assembly. All needs sorting before the final sheeting.

Experimented with a 3mm Depron wrap-around leading edge, works well, and with probably a little glass cloth should be quite durable.

Ray
Mar 20, 2019, 11:00 AM
treefinder
springer's Avatar
Ray, the unibond glue sounds like a non foaming Urethane. Do you wet one surface for bonding? (found that in the fact sheet for it). How do you like it so far, and how long does it take to cure?
Mar 20, 2019, 02:53 PM
An itch?. Scratch build.
eflightray's Avatar
Thread OP
So far I have used it for balsa to Depron, Depron to Depron, and the carbon arrow shaft spars to Depron, all have been very successful.

Didn't know about the 'water', doesn't mention that on the bottle. Will set up a quick test, dry and wet.

Some more pics --
Mar 20, 2019, 04:55 PM
An itch?. Scratch build.
eflightray's Avatar
Thread OP
Not a very scientific test, -

'T' type join with 6mm Depron,
1. - flat piece mist spray with water, - vertical piece glue on edge, -join together.

2. - same again, but dry.

The wet join took longer to feel 'tacky', took longer to grip properly, and after an hour still didn't feel strong. I wouldn't recommend using water.

The glue does take some time to dry, (probably half hour for safe handling), but to me that's acceptable for many situations, and it's ideal for attaching wing sheeting to ribs.
It give you time for putting glue on all the ribs and spars, and for positioning the wing sheeting.

UHU is too instant at times, but still the best for many jobs where an instant contact glue is required.

I will probably get some more Unibond as it does have some advantages, - it's not an instant contact adhesive, - gives time for positioning, - it doesn't smell, and once dry seems to hold very well, very slightly rubbery.

The 'get-out-clause', - it works for me on the materials I use, and the way I use them and the glue. Other materials and situations may vary.

Ray.
Mar 20, 2019, 10:16 PM
treefinder
springer's Avatar
Interesting results, maybe you have enough moisture in your air to get good cure, and any added is too much. I have overdone the water with the gorilla glue, and got a uneven cure that took longer to get it all "done". I suspect the humidity is higher in Wales than in Michigan this time of year. Half hour to handling strength is a decent time, I agree.
Mar 21, 2019, 01:01 PM
Ken Stuhr
Just an observation on your wing spar approach. The full depth sheet spars had the capability to handle the vertical shear loads due to the airplane's weight. With the multi-spars, this vanishes. Only the depron ribs every few inches carry the shear loads, and whether this will be enough is not clear to me. Might be smart to somehow fit a couple full-depth units right thru the center section out to your wing joints to carry the bulk of the shear.
Mar 21, 2019, 02:09 PM
An itch?. Scratch build.
eflightray's Avatar
Thread OP
Sorry, but I don't do 'smart', just tend to rely on 60+ years of building and flying experience

Ray.
Mar 31, 2019, 10:13 AM
An itch?. Scratch build.
eflightray's Avatar
Thread OP
Very slow progress, too many distractions, (garden and house work), plus hitting that 'wall' where you start to think "what the heck am I doing ..... ".

But I've been there, done that before, eventually.

Just a bit more 'skinning' to show, all the head scratching of wire runs and fitting paper tubes are hidden away.

The wrap around sheet leading edge has worked out quite well. very pleased.

I can easily see a quite large ultra light aerobatic model appearing using this wing method, once the Lanc is finished.

When you get the, 'lets build it even lighter' bug, there is no stopping you, (except age, sadly).

All the outer wing panel ribs are now also cut, all scaled down from the main rib, (15% Clarke Y).

Ray
Mar 31, 2019, 05:14 PM
Build straight - Fly twisty
Whiskers's Avatar
I am enjoying seeing this plane coming together although I must admit it induces a degree of envy of your building skills.
Onward and upwards!

Apr 07, 2019, 05:13 PM
Registered User
l33adm's Avatar
Hi Ray. Nice build and great methods. Love it. Please can you show the leading edge wrap arouns skin up close so we can see it? Thanks, Regards Andrew
Apr 08, 2019, 04:48 AM
An itch?. Scratch build.
eflightray's Avatar
Thread OP
A bit more done. After cutting out all those outer ribs, and all the spar notches and holes for 'things', my mind started to wander to the simplicity of ARF models.
But sanity ( ? ) prevailed and I got back to some gluing.

The outer wing is not glued to the inner yet as it's easier to work on as a separate part, (I have restricted room for building models). Once all the outer 'engine' nacelle is constructed I will do the sheeting. As for the wing tip, I'll make that up when I get to it, (i.e. can't think of any other excuses). Once it looks about right, then I can do it all over again for the other side. The fun of model building

So some more pics, plus a close-up of the leading edge sheeting and how I roll the sheet.

Ray.


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