Foamboard Ki-45

[Graham Davies 3]

Hi All,

 

Following Eric's Me110, and in conversation with both Eric and Richard Wills, my interest has been piqued by the possibilities foamboard may present. For some background, I suggest taking a look at any of the fantastic Flite Test 'how to' videos. Richard and a number of others have all built P38s, and the video for this really covers pretty much all of the techniques FT use:

 

 

So, what do I want to achieve, and why?

 

This modelling technique has been taken to the nth degree by FT and in the past, I think we've tried to use Foamboard as a substitute for balsa. I think the 'all foam board' and 'balsa substitute' approaches don't suit many of us, but using foamboard and a few of our more traditional materials and techniques may result in some great models.

 

So, I reckon if this works we get quick to build, cheap and effective models that allow us to 'try' designs and ideas before committing scarce and expensive balsa, and significant amounts of time. 

 

I have a Zero canopy, and like the Ki45's lines. It will suit a sprayed colour scheme, and let's face it, I can 'do' japanese insignia! 

 

Let's get started...

 

Graham

 

 

 

[Graham Davies 3]

Right, The model is going to be made using Flight Test's 'maker board'. This is similar to the foamboard you can by from Hobbycraft, and a similar price, but is easy to remove the paper cladding. This is necessary to curve the board, but also saves a huge amount of weight. One thing to notice, if you leave it on with the intention of painting directly onto it, it's quite waxy and I suspect may be a struggle to paint. It also separates rather easily so may end with the model quickly looking tacky.

 

The board are 40"x30', but are split with the paper complete on one side (effectively 2 sheets of 20"x30"). For this reason, and the size of my Zero canopy, I'm going with 60" span. I have a pair of 3536 1200kv motors, which would be fine on 3S. However I only have 2200 packs which would result in short flights, but also may not help balance. As such I'll use my 3700 4S packs. The model is likely to be very light, so power won't be an issue.

 

It will be a 'fling and flop'. I want to learn about how to make use of this material and the associated techniques without complicating the issue with undercarriage that our rough strip will test...

 

Build next

[Graham Davies 3]

Starting with the wing, and following FT's techniques, I cut wing profiles and joined the lower skin along the centreline.

 

The spars are 2 foamboard spars created by glueing 2 thicknesses of foam boardand spacing them based on TLAR (Peter's That Looks About Right technique!). The spars support the top skin so are necessary to create the wing profile, so this needs to be born in mind. I used 1/16" dihedral braces and set the dihedral. I felt that whilst reasonably strong, the foamboard spars could crush in a bending force, so added a stiff 1/4" balsa spar for 2/3 span onto the forward spar.

 

Oh, most adhesive is hot melt glue using a dirt cheap ebay gun. Suggestion, buy 200mm glue sticks or you end up trying to change sticks mid way through a glue run, risking the glue hardening before joining the parts. I used brown gorilla glue to set the balsa spar.

 

Here's the wing whilst the spar sets.

 

 

The top skin is then curled by drawing it over the edge of your table. It's easier with the top skin still on at this point as it helps create the curve. Note I have cut in the ailerons, but these will be removed later. As I have decided to remove all the paper, I won't be using the paper to hinge in the way FT do. I will make separate ailerons and fit them with mounting tape before covering with Brown Paper. Or something else, when the time comes!

 

I then added the top skins wing at a time. This is a bit fiddly as I needed to add the glue one spar at a time to ensure it was still fluid. Excuse the workshop mess. but this is the wing now as a one piece lump of foam. I added a balsa leading edge as I think it helps to get a smoother profile and will avoid dings. My balsa was rather hard, but in the grand scheme of things won't add much weight and makes the wing very rigid.

 

 

I am using some cowls I 3D printed. This is another new thing for me. I spent NO time on this! I found some 'roughly right' radial cowls on thingiverse. These are for a DH Beaver. The air intake is wrong, but hey, the model is made from foamboard! I sized them to 120mm diameter and printed a pair. They look pretty good and weigh very little.

 

 

I created the motor mounts by insetting 'u-boxes' of light ply into the wing. These are glued to the mainspar, both skins and along the underside. They are pretty solid. I will use a 1/8: ply plate to mount the motor onto. I made a couple of foamboard discs that fit inside the cowl. One will support the cowl, the other the nacelle cladding. Had I thought; I wouldn't have poked the cowling on when I took this photo!

 

 

The top and bottom are then clade with some foamboard with a few slots cut towards the front to create the compound curves. I really enjoyed this bit. It was like working balsa with the grain going both ways! I'm not going to lie though, I didn't half get in a gluey mess...

 

 

Short of trimming the nacelle cladding and finishing the aileron areas, that's the wing done. I will weigh it at some point, but it feels pretty light

 

Graham

 

 

 

 

 

[Graham Davies 3]

Fuselage:

 

Took a bit of head scratching. I didn't like the idea that FT use of many laminations of foamboard used to stiffen the fuselage. I thought about using some balsa to reinforce, but eventually decided to keep it simple and simply have a go.

 

My strategy is to use a 'u box' fuselage. If you imagine a straight line from tailplane forward, this will be the top of the U-box. I will then make a curved deck onto this, There will be a few formers to shape the box accordingly, and a lower cover will be added when all the controls etc are in place. That gives me the opportunity to add some balsa longerons if the structure does not seem rigid enough. It will be a one piece model so the wing will add considerable strength. 

 

I joined board to get the length I needed, and glued a foam doubler around the wing seat. I then glued to a foam 'crutch' that forms the top of the U'box. I have left the paper on this as it will be within the structure so won't benefit from brown paper adding to the stiffness. I have then drawn in the sides, and have the basics of a fuselage. It seems pretty stiff, and weighs very little.

 

This is from the top:

 

 

And here from the bottom. You can see the doublers. I will cut the profile from these and have a nice big gluing surface.

 

 

Right, that's up to date!

 

Graham

 

 

 

[Eric Robson]

Hi Graham,

it is a super fast way of making an aeroplane but a word of warning. I stripped the paper off both sides of the fins and covered them in brown paper, they were flat until I painted them ,I painted both sides but this morning they had both warped. I did not have this problem with the Lightning that was painted maker foam but after a while the paper started lifting. I may have to use foam board which has the paper attached with a stronger adhesive. On yours with the single fin and rudder it may be better to laminate two pieces of maker foam.

Cheers Eric.

[Graham Davies 3]

Hi Eric,

Yes, I'm keeping an eye on this. I am still undecided how to do the tail feathers. I'm leaning towards some balsa to stiffen them, possibly a trailing edge stiffener to take mylar hinges.. I may still use two laminations. It's so light, I'm not worried about tail heaviness, but I don't want the thing to fall apart! I will almost certainly use two laminations for the fin as I think it will look better.

 

Next time, I may get some Hobbycraft board for areas where I don't want to strip the paper. I could then 'roll' the tailplane leading edge. Anyway, I'll see what I can do when I get to that bit!

 

Graham

[Graham Davies 3]

Morning all,

 

A bit more progress.

 

I made up the tailplane and fin with foamboard edged with some medium balsa. This will hopefully reduce the tendency to warp. They are a lot less stiff than a conventional tail, as you'd imagine without any diagonal bracing. However, they seem OK. 

 

 

The upper rear deck of the fuselage was created with some formers and a rolled piece of foamboard. Quite satisfying, although hard to avoid a tramp's ribcage. The model is intended as very much 'is what it is' so won't be worrying about this.

 

 

The canopy is one of Richard's old Zero ones. I cut it in half and made a removable front section.  This will be the battery hatch. This is not easy as the stuff is so floppy, retaining a flat datum is really hard. Next time I will use a bit of 1/16" balsa to face the lower crutch and retain the rigidity. It's done now and is reasonably stiff once complete, but will need some fettling to improve the shut line.

 

 

 

I've since laminated some foamboard to carve to shape for the nose. I'm now starting to cover the wing with PVA/ brown paper. I need to get this done so I can join wing and fus. However, it's going to be a big and unwieldy lump once that's done, so need to get as much out of the way as possible before then.

 

It still weighs very little!

 

Graham

[Eric Robson]

Hi Graham, 

you may be able to reduce the hatch to just lifting the front canopy off, this will make the forward part more rigid. When I made the Me 110 I built the battery box well forward but the tail end turned out so light I had to cut it out and move it back as it turned out  nose heavy.

Eric.

 

[Stephen Belshaw]

Very interesting Graham, is this the FT foam board with brown paper covering that you are using? I ask because I have a stock of it so could be tempted in to having a bash at something like this at some point ........

[Graham Davies 3]

Thanks Stephen.

 

It is the FT makerboard. Same stuff, but the paper is now white. Fun stuff to use, but a few things to be mindful of. The paper is quite easy to separate, so if you leave it one, you'll need to find a way to seal open edges or you model will soon look tatty. I would also be reluctant to glue anything load bearing to the paper. It sands OK, but any highpoints on your paper rip it apart. 

 

It's certainly going to result in a light model. I reckon this model will be under 4lb. Not bad for a 60" span twin!

 

Graham

[Graham Davies 3]

Wing is covered now. As Richard Wills once said; you can't see what's under it once it's covered. It looks like any other model wing now...

 

[martin collins 1]

Fantastic Graham, watching this with interest, i love Jap WW2 aircraft, they had some great looking designs and the colour schemes are very eye catching. There are many i would like to build and this may be a way of doing it. Keep up the good work, can`t wait to see the finished `Dragon slayer`. Just built this as a plastic kit, it seems many things will be possible with this technique and flying weight.

Edited February 3, 2022 by martin collins 1

[Graham Davies 3]

Hi Martin,

 

Thanks for your comments, and the great picture.

 

I completely agree; both with the interest in these Japanese 'birds, and in the possibilities this construction method offers. It is incredibly quick (or could be if I got on with it!), and it is certainly possible to create a decent semi-scale representation. The proof of the pudding will be in the flying. This model will certainly be light, which is half the battle. It won't be as stiff as a conventional construction, but time will tell if that makes much real world difference. If not, I've not exactly cost myself much!

 

Graham

[Eric Robson]

If it fly's as well as my P38 and Me 110, and it will! you will be pleasantly surprised how well they cope with winds up to 12mph , 

Graham, the wing looks like the original maker foam now but much better than what they used for covering,  at least it won't peel off as easy.

[Graham Davies 3]

Fingers crossed Eric.

 

Did a little more at lunchtime. I cut the wing aperture. SO much easier than with balsa/ ply! I also fitted all the servos, although that's less obvious. I need to do this so I can close up the fuselage although I will do that after the wing is fitted. This is because I'm going to add a balsa spine under the wing that will be a handgrip, and build the lower decking onto this. That way I can make a couple of fingerholes in the lower skin that will give a decent launch grip. I will cover the rest of the fuselage and tail this evening and then join the wings. I can then balance it, and sort out the canopy and hatch. 

 

Like you said Eric, I think it will be nose heavy, so will leave the hatch until I know where the battery will end up. I may be able to redo the nose and simplify the hatch then.

 

It still weighs not much...

 

Graham

 

[Eric Robson]

Is this what you had in mind Graham, to date they have not been used as there has always someone there to launch it for me.

What motors are you using on yours? mine has Racestar 3536 900Kv currently on offer from Banggood  just under £11 each .

I have an Aerotec Mosquito to build next 72" span. but I still fancy doing a quick build twin maybe a DH Hornet or Westland Whirlwind.

Kevin Branch lives near Harrogate. I had the Marutaka Black Widow that he built it is almost ready to fly but waiting for the grass to be cut.

Will you be at Wings and Wheels this year?

Eric. 

[Graham Davies 3]

Yes, exactly that! It will be a bit of a handful to fling without a decent grip...

 

I have 3536 1200kvs. A bit revvy for 4S, so I may get a pair of 900s whilst I still have a chance to change them. Once I fit the cowls, that will be that!

 

Graham

[Graham Davies 3]

Sorry, yes I will be at W&W. Becoming a Warbirds Replica's day out now!

[Graham Davies 3]

I spent some time yesterday trying to get the front into a nose shape. I have to say, it was a riot of laughs trying to hold everything together in free space and apply hot melt glue. At one point, I became a structural member...

 

I've redone the hatch, as Eric suggested. A brief CG check showed it is not going to need a forward battery, so I've made the hatch  into the canopy section.

 

The nose is far too long, and looks like a tigercat, but it'll do for this first foamboard attempt. I've got a bit further with brown paper covering, but not far enough to join the wing to the fuselage, Hopefully tomorrow. Then I can finish the lower fuselage before finishing covering. 

 

[Eric Robson]

Looking good Graham,

as far as builds go they don't come much cheaper or quicker

[Graham Davies 3]

Very true Eric. 

 

I chopped a few inches of the pointy snoot off this morning and laminated a new nose that is closer to the correct shape. Happier now!

[Graham Davies 3]

Morning all,

 

Not been getting much done lately following the welcome return of my two other loves; Televised rugby, and gigging with my band...

 

Still progress slowly continues.

 

I chopped the pointy snoot nose off and shortened and rounded it. It looks a bit better now. I had laminated some curved sheets over the front and these don't blend too well, but it looks OK from the top. I have also now completed the lower fuselage decking, and more importantly, unglued myself from it. I had a load of 'A must be completed before I can do B and C' type jobs. One was to connect up the rudder. This was because the rudder servo is fitted into the fuselage, and so I couldn't add the lower decking until this was done. I don't like exposed servos much. The elevator is fitted to the outside, but is under the tailplane so not visible. The rudder would have been much more obvious.

 

Now the lower decking is done, I can cover the fuselage before fitting the wing. It's going to be a bit unwieldy then, so I'll do that as late as my patience will allow. Once the wing is fitted, I'll build the launch grip onto the bottom of the wing, and build the lower decking around it. Then it will be ready to paint. 

 

This has been loads of fun...

 

Graham

 

 

[martin collins 1]

Thanks for the update, i will be tackling something similar in a couple of months so really interested in your build... Great job so far, have you got a colour scheme picjed out yet? 

[Graham Davies 3]

Thanks Martin, kind  of you.

 

Regarding colour, sort of. I'll be going with something like this:

 

 

 

 

But a bit 'in the style of' rather than particularly accurate. I have got some matchpots of emulsion and will mix up to get reasonably close and see how it looks.

 

Graham

[martin collins 1]

Nice, will be very eyecatching ?