Foam board Lancaster build

[Kevinbennett126]

6th December
** WARNING **
When I printed the Lancaster plans at 75% I did it "print-to-fit" on A4 paper.
As a check on sizes, the outer wing sections should be about 20" (510mm) long
Check you have this right or adjust the other measurements to suit.


In this thread ….
http://forum.flitetest.com/showthread.php?4374-foam-board-Lancaster-bomber

I talked about the foam board Lancaster that I built and a couple of people asked if I could share the plans, I don't have a complete set of drawings but its not that difficult to do so I've started this thread to explain how to do it.
I crashed my original Lanc so this is a chance to build another and share the experience with others.


This is not a beginners project, neither will it be a 'blow-by-blow' account of how to do it.
But if you've built one of the FT swappables before (especially something like the Spitfire with a folded leading edge ) and you have some idea of what your doing with a scalpel and glue gun, then it should be fairly straight forward to do.

I built the first one in a bit of a rush and with little confidence of it actually flying. But come the day when it was finished and the weather was calm enough, my friend and I decided to maiden it.
Because the final build is quite heavy, and the foam being fairly delicate we decided to run along with it on about half power and see if it felt like it might fly rather than risk a test glide.
We had the CofG in what we thought was about the right place and the thing seemed to balance ok, so John held it while I opened up the throttle. He started to run and almost straight away the thing was up and away.
Just glided out of his hands and into the sky – flew like a bird.
First couple of flights were a bit fast, I wasn't sure how slow it would fly or what the stall characteristics were like. But eventually slowed it down and was able to get a reasonably scale speed fly by.

So lets get started …..

First you need a set of Lancaster plans from this site ..
http://www.outerzone.co.uk/plan_details.asp?ID=2860
I printed these out at 75% - this gives a wing span of about 1400mm (55&#8221

Also a copy of one of the FT plans and study the build video would be useful too.
I used the Spitfire build to work from because I could see how to do many of the Lanc parts and I'll be making reference to that here.

I started with the wing center section. This is simply a straight (i.e. no trailing edge curve) version of the main part of the Spitfire wing.
See Picture 1 for details, there's three score lines, one for the leading edge and two for the top of the wing 'curve'.
The wing spar is made up of two pieces of foam glued together – just like the Spitfire wing, so the slots need to be wide enough for two foam tabs.
Score the lines and fold over the leading edge as they do in the Spitfire video.
The foam board I use is not 'Dollar tree' and is tougher (probably 'Elmers' I guess) so I have to make a good job of creasing the leading edge fold to make it work without tearing the paper.
Cut out two center section spars as in Picture 2 and put all the above to one side for the time being.

For the outer wing sections, print out the wing plan from the PDF. Lay this on some foam board and draw round it - Picture 3
The nice thing about the Lancaster is it has straight leading & trailing edges which makes this all very easy, and this technique could be used for other planes with similar wing shapes.
Then add the score lines as in Picture 4 – don't forget to transfer the aileron from the plan too.
It should be obvious that it now includes the lower wing surface and cutouts for a spar.
You need two of these – one left & one right, I use the same paper pattern and turn it over (you only need the outline) that way it pretty much guarantees they will be the same size & shape, but do make sure you have the leading/trailing edges the right way round!

That's enough for now - more to follow later

 

[ClearSkiesCalmWinds]

This is great Kevin. I'll be following along with build and cutting mine along the way. I'll be sandwiching a aluminumn spar 1/16x1/2xthe length of the Foam spar for strength. Picked up this tip from NerdNic's nnMIG3. I use it for strength and speed assurance. Thanks for the share. Clear Skies, Calm Winds. Cheers.

 

[ClearSkiesCalmWinds]

View attachment 35298 View attachment 35299 Hope this helps.

 

[ClearSkiesCalmWinds]

View attachment 35301 View attachment 35302 Some more pics.

 

[unstoppablecarl]

This is exactly what I wanted to see. I can't wait for the rest.

Are you planning to draw up plans? or just the photos with dimensions like you have posted so far?

 

[Kevinbennett126]

@ClearCkiesCalmWinds - thanks for the pictures, its looking good! Love the twin glue guns at the ready

That's a nice idea with the alloy spar - I might steal that idea and include it, will certainly give more confidence when it loops or rolls.

 

[Kevinbennett126]

This is exactly what I wanted to see. I can't wait for the rest.

Are you planning to draw up plans? or just the photos with dimensions like you have posted so far?

Hi, thanks for the comment.
I don't have the enthusiasm (or time) to draw it up properly - sorry.
I'll carry on with the photos for the time being, there should be enough detail for the experienced builder to follow.
This is in no way a 'fine scale model' - just a quick and simple hack to get something that looks 'Lancasterish' flying, but it does look good up in the air.

Kevin

 

[ClearSkiesCalmWinds]

Hope it helps. These tecchniques were shared by Tim Brush (Beyondthewheelrc.com) Nick (nnMIG3) Balckbeltrrf (B-25 build). There are some great pics by Blackbeltrrf on tail support for simular setup. Clear Skies, Calm Winds. Cheers

 

[Kevinbennett126]

Part 2

If you've followed it this far then you should end up with a pile of bits like Picture 5
You need 2 servos with extension leads - I plan on mounting the receiver on the top of the wing in the middle – so extensions need to be long enough for that, 400-500mm
And you need to cut an access hole for the wires in the wing (central about 25mm x 12mm) and don't forget to cut & bevel the ailerons too!!

The underside of the wing needs trimming at an angle to match the center section. The easiest way is to fold the top half of each wing back on itself (i.e. open up the score lines fully) and follow the line of the edge to trim the lower part.
The top surface will need trimming too (to allow room for the dihedral) when we glue up the sections, but we'll get to that later.

Those who are smart will probably have noticed there is a slight problem where the spars meet.
Because this design ends up with effectively a swept back spar on the outer sections, the over laps in the middle don't quite line up.
One my first build I just put plenty of glue around this area and it worked fine! I looped and rolled it (gently) with no problems. But in this build I'm taking the suggestion from 'ClearSkiesCalmWinds' and adding some reinforcement.
In his B25 build he's using an alloy stiffener and I would do the same too if I had some thin alloy but I don't – what I do have is some fiberglass printed circuit board material slightly less than 1mm thick so I'll cut a stiffener from that. I'll have to 'bend' it a little where it meets the center section but I think that will work.
The dihedral angle is a ratio of about 3:20 – i.e. the outer sections are about 20” long and are nearly 3” high at the tips.
So my fiberglass spar will be full width for the center section, then 200mm at each end, this makes it 2 x 200 + 380 = 780mm long x 12mm wide. This takes it to about the mid point in each wing half. And the height at each end should be around 30mm. I shall sandwich this between the foam spars and probably use some 2 part epoxy to do it. I'll add a picture when I've made it and all should be clear.

( )

 

[ClearSkiesCalmWinds]

These are the pics of the tail support possibilities. View attachment 35467 View attachment 35468 View attachment 35469 View attachment 35470 These were provided by Blackbeltrrf's B-25 build.

 

[Kevinbennett126]

Part 3
Here in Picture 7 is my wing spar stiffener (two batteries to hold is flat for the photo). This will be sandwiched between the foam spars. Behind it is the center section with a 'dry fit' of the foam spar.

Picture 8 is an attempt to show it glued up between the foam.
The foam halves are 'handed' - have one with the dihedral angle to each side to match the foam spar in each wing outer as in Picture 7.

Picture 9 shows the sections laid out ready to glue up.
First of all glue in place the center spar. Make sure you have one half pointing left and the other half right, its not critical which half is which as long as you can match the out spars and inner spar together.
Block up each wing tip to about 75mm / 3” - enough to match the angle on your spar stiffener if you have one. Hot glue the joint between each lower wing and the center, try not to glue it to the building board though! I've also added some scraps of foam over this joint for extra strength.

Don't forget the spacer strips along the trailing edge, same as in the Spitfire build. The center strip will need to be shaved down to almost nothing but the outer ones will be ok just 'mashed' as they do in the video.

The rest of the spar can now be glued together, but make sure everything is lined up and the dihedral is equal on both sides.

A quick note about gluing.
I use three methods to glue plane bits.
Hot glue gun for quick and instant stuff like spacers or formers that need an instant fix.
Two part epoxy for bonding things like the wing spar sandwich which would be tricky (but not impossible) to do with hot glue.
And finally 'PVA' or white wood working glue, using this gives you plenty of time to adjust the fit until your happy that everything is in line. Now, I've heard mixed reports about using liquid glue on foam board, some say the paper will de-laminate but my experiences with it have all been good. Maybe its the type of foam board here in the UK.

So on the wings I use all three methods. Two part epoxy to make up the center spar, then hot glue it in place. Then when it comes to folding the leading edge over I will PVA it all together and leave it over night to set.

Picture 10 shows the complete spar epoxied and clamped to set over night.
Now for the interesting part …....

 

[ClearSkiesCalmWinds]

It's looking good. Hope to get my wings in shape this weekend. FT Minis are to much fun. Need to make time. Thanks for the share. Clear Skies, Calm Winds. Cheers

 

[Kevinbennett126]

6th December
** WARNING **
When I printed the Lancaster plans at 75% I did it "print-to-fit" on A4 paper.
As a check on sizes, the outer wing sections should be about 20" (510mm) long
Check you have this right or adjust the other measurements to suit.

I've added this message to the top of the thread.

 

[ClearSkiesCalmWinds]

Thank you for heads up! Mine is at about 20" 1/4 each. What spar did you go with is that copper? Clear Skies, Calm Winds. Cheers

 

[Kevinbennett126]

Thank you for heads up! Mine is at about 20" 1/4 each. What spar did you go with is that copper? Clear Skies, Calm Winds. Cheers

Thank goodness for that - phew! .... I could imagine all sorts of sizes of wings LOL.

I have access to off cuts of printed circuit board material .... copper coated fiber glass (FR4 is the proper name)
The spar was cut from 0.8mm thick sheet, which is flexible in one direction (forwards and backwards) but very stiff in the right way (up & down) - plus its quite light, I think mine is about 18grams total.
I did consider taking off the copper, but thought its more trouble than its worth.

I used 'standard' 1.6mm FR4 for the firewalls on the first Lanc - might do the same on this one, or just some 1/8" ply, not sure yet, I'll have a think about it.

 

[ClearSkiesCalmWinds]

Are you considering using metal gear servos over nylon? Clear Skies, Calm Winds. Cheers

 

[Kevinbennett126]

Are you considering using metal gear servos over nylon? Clear Skies, Calm Winds. Cheers

I always think my foam board planes will have a pretty short life .... so have only used the cheapest '9g' servos from Ebay.
The loading on them is very low - elevator movement is very low and there's one for each aileron so I'm happy to go with nylon gears.

Kevin

 

[Kevinbennett126]

Part 4
Again it would help if you've watched the FT Spitfire video build – this is pretty much the same.
Start with a 'dry fit' of the center section.
Gently fold it over and make sure it lays flat on the build board at the trailing edge. I had to shave the trailing edge 'packing piece' pretty low to achieve this.
What we're trying to do is make sure the bottom surface of the wing is in line with the trailing edge of the top surface …. i.e. if you put a rule or straight edge underneath the wing it should just touch the back lower edge of the top surface (for a smooth air flow)
When you're happy then glue it down. I use woodworking glue, you use whatever you're happy with. But whatever you use apply it the the leading edge fold, the first score line and top of the spar and servo.
I would leave the final score line until that lot has dried. Then you're not trying to fight too many levels all in one go.
If you're an 'ace' with the hot glue gun then go-for-it all in one go.
Try and make sure the center area of the aerofoil is horizontal (i.e. parallel) to the underside.
So looking from the side it should taper up from the leading edge, be fairly flat for the center part then taper down to the trailing edge.
When its set, glue along the final score line and along the trailing edge packing piece and stick down the trailing edge.

Picture 11 shows the center section done and one side ready to be folded over. Don't forget to glue the servo in and pass the wire through the access hole in the center section.
And you need to trim the edge to allow for the angle of the dihedral. More in the middle and tapered to the front and rear. Do this bit-by-bit (not like I did, all in one go !!) to make sure you don't take off too much. Keep trying the fold until it meets the center section ok.
Same as the center section, apply glue to the leading edge fold, the first score line and the spar & servo.
Fold over the top surface and hold till set. And if all is ok, then glue the second score line and trailing edge packing piece and complete the fold. Repeat the same for the other side.

This is the wing about finished …. so time to make a start on the engine nacelles.
You can make these as nice as you like - or simple boxes like mine, once the thing is in the air and more than a few feet away I don't think anyone will notice …. they will all be over awed that it actually flies

Cut out from the paper plan the side views of the engine pods. There's (obviously) two inboard engines and two outboard engines, so you need two pairs of each. Lay on the foam, draw round and cut out, see Picture 12. You'll need to tighten the radius on the top where it joins the wing to allow for the slightly more 'curvy' leading edge. Might be worth cutting them 'as the plan' then trim to suit your wing. Mine can be seen in Picture 11

Then from the paper wing plan cut out the tops for the nacelles – again two inner & two outer, see picture 13. Lay on foam, draw round, then cut out. The length is from leading edge to trailing edge for the inner pods, outer ones start from the leading edge and finish the same as the plan.
This does actually come out to be a little wider than the plan (because of the extra width of the foam on the sides), but that not such a bad thing if you're going to use 28mm dia motors.

 

[Kevinbennett126]

Part 5

The rear ends of the engine nacelles are tapered to a point. On the in side faces of the inner nacelles mark lines at about 10mm from the rear towards the front. Finish at about where the step is – see Picture 14.
Make sure you do them in pairs …. one left & one right.
Gently crease these lines with the edge of a ruler of any straight edge. You can then ease a nice curve in the foam to match the tops that you've already cut out.

Before gluing them up, use a straight edge to extend the top surface (the part that will fit under the wing) and mark at right angles to this where your firewall will be - Picture 15
For the motor size I used (2822 1450KV) this line is about 30mm from the engine pod front.
You can adjust this to suit whatever motor/firewall combination you have.
Its fairly important to get the firewall line square to the bottom edge of the wing, so try and keep this line at 90deg to the wing line.
There is no down thrust built in at this stage, my original Lanc didn't have any but you can pack the motor mounts if you feel it needs some.

Apply glue to one edge of the nacelle top edge, line up with the rear end of the side and fold it around, its not critical where it finishes. Then glue on the other side – see Picture 16.
Try and keep the top surface flush with the top of the edge of the side (we shall use this area to glue them to the wing later) and keep the sides square and parallel.

Repeat the above for the inner engine nacelles too.

Engine mounts.
On my original Lanc I used scraps of Printed Circuit Board material (1.6mm FR4) to make up a firewall with side 'cheeks' and epoxied them into the nacelles.
For this one I thought I'd try some 3mm (1/8”) ply.
See Picture 17 … cut a strip of ply to fit the inside width of your engine nacelles. In my case that is about 36mm. Cut off lengths of 50mm, 36mm and 2 at 30mm.
Glue these together to make a three sided bracket with the longest side on the front. Mark and drill for your particular engine mounting bracket.
Do a 'dry run' with the motor to make sure they fit and that the three phase wires will go through the hole. Although you can leave the motors attached, its probably easier to glue the assembly in to the nacelles without the weight of the motor.
Again I shall epoxy these in place, but feel free to use whatever glue you like best.
Apply glue and line up with the previously marked lines in the insides of the nacelles.
The top of the engine mount should line up with the extended line from the bottom of the wing and the front should be on the vertical line. Picture 18 should make this clearer.

 

[Kevinbennett126]

Part 6

Fixing the engine pods.
For the outer engine pods we need to add a spacer to the outside edges so that the engine will be 'upright' when mounted on the wing which is angled up with the dihedral.
Lay the outer nacelles on some scrap foam (we've all got plenty of that!) and draw around one side.
See Picture 19
Cut these out, but don't make them too wide or they will defeat the purpose. And glue them to one side of each engine nacelle, Picture 20 makes it clearer, make sure you have one left hand and one right hand. Once the glue is dry use something smooth to squash the spacer a bit at an angle that will allow it to meet the wing. I used a piece of rod and held it against the top of the engine pod and rolled it back and forth.
I also cut 'glue holes' in the tops of all four nacelles to allow me to melt some hot glue through once I'm happy they are in the right place on the wing.
The engine pods should now be ready to fix to the wings.

We need to mark on the bottom of the wing where the engine nacelles must be fixed.
So on the bottom of the wing mark a center line, do this by measuring from the joints where the outer wings are attached. Really we should go 'wingtip-to-wingtip' but the above will be close enough.
Then we can mark a line 150mm each side of that, this is for the inboard engines. Then from the outer wing joints mark a line 145mm out on each wing, this is for the outer engines.
To make sure I can line up the engine nacelles when I glue them, I mark two further lines 50mm apart on each engine center line. All of this can be seen on Picture 21.

Apply glue to the parts of the pods that will contact the wing, in the case of the inner pods its easy, all over the top of the pod will do – for the outer pods just apply glue to the new spacer and the opposite edge of the top. Line these up with the '50mm' guide lines, the 'step' in the pod should contact the leading edge and leave to set. On the outer nacelles, for simplicity the 'step' is square to the engine nacelle but the wing leading edge is swept back by a few degrees. Make sure the pod sits 'straight' with the lines you've drawn and not at right angles to the swept back leading edge.
Its quite important to get these all in-line with the center line of the plane or it might have a tendency to fly in circles …. oh and it would be nice if they all face forward too
Picture 22 shows how they should look.