Fokker Dr1

[John Olsen 1]

Hi Guys, I just purchased a set of the plans by A Lunt for a Fokker DR1. (Plans service 1213. ) They are good plans, but fairly ambituous. I presume there was probably a magazine article when they were first published, but I have no idea when that was, or for that matter which magazine. I wonder if anyone can tell me where it was first published so that I can have a go at tracking it down the relevant issue, or a photocopy or scan of it at least. A few photos of some of the bits of structure might help clarify things a bit.

 

It goes without saying that I would also love to hear from anyone who has built this model. It uses aluminium tube for some parts of the structure, and I am wondering whether it might be possible to substitute carbon fibre tube or rod for at least some of this.

 

regards

John

[Ernie]

Hi John, I've got an E111 half built in the workshop Its from a Proctor kit...

The round steel tubing is replicated with hardwood dowel. Of course it is difficult to make the joints between the tubes, especially as there are brass lugs in the joint to give fixing points for wires.

 

The joint is made with a wee jig, that allows a half circular cut to be made in the dowel.

Its a bit difficult to explain, I can take some pix if you are interested

 

ernie

[John Olsen 1]

Hi Ernie, yes, the DR1 uses dowel for the fuselage, that looks straightforward enough, and I can make a suitable jig easily enough, there is a milling machine here. The trick with that sort of thing of course is to get the length just right since it is kind of hard to put any back on. The DR1 uses curved aluminium tube for the outline of the rudder, elevator and ailerons, any ideas on how to make a clean accurate bend in such tube? We used to anneal dural for bending by rubbing soap on it, then heating until it went black, that was the right temperature to anneal it so it would bend easily. You didn't have to treat it again, it would age harden after working it. I don't know if that would apply to the sort of tube they are selling these days.I might experiment with a bit.

 

I am also wondering if the straight pieces of tube could be replaced by carbon fiber rod or tube, which might be stronger and might also take epoxy glue better.

 

I think the Dr1 might also have had wire bracing in the bays of the fuselage too, but since they would be concealed by the covering I would not be too worried about trying to put them in. I'd be more into semi scale than the full thing. Well, the one I just finished is a Hangar 9 DVII, which makes up into a nice looking model but is not a super detailed scale model. If I do the DR1, I would put in more detail than that, but not to competition winning levels. Something that looks nice while it is flying.

 

regards

John

[Ernie]

Hi John,

 

I usually laminate tube rudders etc.;from very thin spruce strips. I make a template, and then spring a layer of spruce around it. A wee smear of aliphatic, then another layer, till I have,say,5 layers. Then I sand to the required section ( usually a D) cos its easier to fix ribs, etc to a flat surface, and at the end of the day it's covered

It's light, and very robust.

 

The E111 certainly has internal bracing wires. I've put them in as far bach as can be seen if you squint into the cockpit

 

Are you filling the cockpit with all the dials etc?

 

ernie

[John Olsen 1]

Hi Ernie,

I haven't thought about the cockpit yet, I'm more at the feasibility stage. I need to finish restoring my 45 year old "Powerhouse" before I get into anything else. How many dials would a DR1 have had?

 

The spruce idea sounds good, laminations seem to end up very strong and not prone to warping, plus it would glue to other parts better than the aluminium. It certainly does need to be light back there, since the nose is very short.

 

regards

John

[Lew Weaver]

I built this way back in the 70's and used dowel for the fuselage and Ali tube, as per plan.

 

The model flew well, I passed it on to a clubmate and it can still fly these days.

 

The only problem was it's tendency to noseover on landing

 

A wee video of it's maiden flight -

http://www.youtube.com/watch?v=j_Iep9-HwSs

[Ernie]

Hi John, The spruce does work well...It also keeps the tips good and light...which especially helps as you have a mammoth six of them.

 

There won't be many instruments, rev counter, oil pressure, altimeter, compass. They were'nt completely standardised at that time, so you can use a bit of artistic licence. There is stacks of info available.......Red Baron and all that stuff

 

ernie

[John Olsen 1]

I have to confess that I rather like flying the Red DR1 in the Phoenix flight simulator, although I probably would not make a red one myself since it is such a cliche. They are of course pretty well designed to nose over. I would need a bit of practice on the SuperStick trainer that I just gave my son before I try flying my D VII or anything as ambitious as the DR1. When I was last flying models this radio control stuff was all a bit new fangled, and well out of reach of us youngsters. My best models were all free flight in those days.

 

That is a good video Lew, or should I say film. I guess it might be super 8? The model looks great. These days with a four stroke engine it should really sound the part too.

 

regards

John

[Lew Weaver]

John

 

You are correct it was super 8 film which can nowadays be converted onto a DVD. I think it had a Veco 61 in it.

 

I remember after building the fuselage from dowel I re-inforced the joints with steel pins.

 

The noseover on the movie after landing was edited out.

 

It nearly always nosed over on grass but it was OK on tarmac

[John Olsen 1]

Well, I don't know if anyone is still reading this thread, but I took a bit of time off my other projects and made a start on a rudder, using the tube technique as per the plan. It is not quite finished yet but seems to be working out fine. I have found some carbon fibre based stuff a bit like thin blotting paper, I think I might use some very tiny patches to reinforce the joints where the aluminium tube butts against balsa or dowel, as these look to be the most vulnerable points...it is quite a light piece of construction, as of course it needs to be on this type of aircraft.

 

regards

John

[Ernie]

Hi John, I think the type of covering that you use is very important on an aircraft of this type For example, silk can add a huge amount of strength to a built up structure.

 

I would use solartex, maybe you should cover just the rudder, and see if it is strong enough. Also, how are you fixing the rudder horns?

 

ernie

[John Olsen 1]

Hi Ernie,

 

The Ultracote is the most readily available around here...how does that compare for strength? I've just used some to cover the rudder and elevator for my vintage "Powerhouse", it seemed to go fine on there but has not had any real test yet since I don't have enough to cover the rest of the airframe. I made a tactical mistake...saw the stuff in the local store, bought a roll of each colour to try out, not knowing how much was on each roll. So when I went back someone had gone and bought the rest of those two colours...they have ordered more, but being at the ends of the earth it takes time. (I'm in New Zealand.)

 

Yes, I am treating the rudder as a sort of dummy run, it is small enough that if I decided I could do better I would not be wasting too much material.

 

(The Powerhouse is vintage because it first took to the skies in about 1967, powered by an Ohlsson and Rice .29 which was old even then...I still have it now, but plan to use a younger engine when the rebuilt Powerhouse flies again, this time with radio. Quite a lot of the structure is still the original, especially the fuselage and quite a lot of the wings. )

 

regards

John

[Ernie]

Hi John,

 

I'm not sure about ultracote, but I do know that for strength and appearance that a fabric finish is essential. The last thing that you need is your triplane to look like a toy

 

ernie

[John Olsen 1]

I guess you are probably right. The ultracote is all gloss so far as I have seen...even a matt would be more authentic, but a woven finish would be best. I will have to make enquiries and find out what is locally available. Or else maybe resort to mailorder or see what my Boys have access to over in Sydney. (I have two adult sons over there.) At least we can get real silk here these days, it used to be unobtainable when I was a boy, and the available nylons didn't shrink as well with the dope. Of course I dunno if you can get dope any more!

 

I didn't answer your other question...the plans show the horn going through a small plywood piece glued on the back of the main rudder post, which is 3/16 dowel. The actual horn is shown as dural, it is double sided as per original, and he shows a dummy wire tensioned with elastic inside the fuselage. I wonder why not just attach it to the other side of the servo horn?

 

The dowel needs slotting for the hinges, I have just tried on a spare piece and it is doable, although probably should have been done before making up the rest of the rudder. Well, we live and learn. I just weighed it, at present it is 9 grams, plus or minus 1 gram since that is the resolution of the scales. That is less the horn and its mounting block, and of course less covering. It seems acceptably rigid, hard to tell about strength, at least not without breaking it.

 

regards

john

[John Olsen 1]

There has been a bit of quiet progress here. I have the skeleton of the lower wing well started. I made a mod to the plan here. The leading edge is sheeted with ply, as was the original Fokker. The edge of the ply, which is 1/64 inch thick, goes in a zigzag shape, eg on the ribs it finishes well forward while between the ribs it goes further back. This leaves a triangular piece unsupported between each pair of ribs. I checked and according to the sources, Mr Fokker had that piece pinned to the spar (which is a box section and does not itself reach the surfaces.) So I decided that some half ribs between the leading edge and the spar would support that triangular piece in much the same way as Fokker did, and it also supports the thin ply better when attaching it to the leading edge. The half ribs don't show so will not offend any scale purists.

 

The ply is itself a bit of a problem, it is only available here in NZ in pieces 1ft (300mm) square, although it is made in bigger pieces. So I have had to do a join on each side of the lower wing. This is not easy to do, although worked out OK. The ply needs to be steamed to take the curve. I made a "jig" from a piece of 5/8 inch ply with a piece of bright mild steel bar taped to it....this is close enough to the curve to allow clamping the steamed ply to it while it dries and cools. Better than trying to clamp to the somewhat flimsy wing! It also makes a good jig for doing the joint. Once it has set to the curve, it is glued to the wing with slow epoxy and all hands to put rubber bands on to hold it in place. I've only glued one side, the other will have to wait until I come back from three weeks in Australia. I used 1/8 carbon fibre tube instead of aluminium for the leading edge and the rear spar, this works out fine, even if expensive. The ones that are bent will of course have to be alloy. I am hoping that the Aussies may have the ply in bigger pieces, at least 1ft by two feet, or even 1ft by four feet, although the latter would be fun to bring back on the plane.

 

With the slow epoxy, I am trying the West system lightweight filler, this makes for a glue that will fill gaps and make a fillet but is much lighter than epoxy thickened with the usual cotton fibres and talcum powder. The joint is still stronger than either the ply or the balsa, so this seems a useful thing to do.

 

I did manage to buy one roll of solartex in the white linen colour on a recent business trip to Christchurch. So I will finish off the rudder soon and cover it. Once there are enough bits to make it worthwhile I will take a few pictures.

 

regards

John

[John Olsen 1]

Lower wing...this half needs the rib caps, the tip, and the trailing edge, which is to be tube bent to the scalloped shape. (Fokker used a wire which the covering pulled in.) You can see the zigzag shape of the leading edge ply, but as you can see (or not) my half ribs do not actually show, although they do nicely support the leading edge ply. The other half is not quite so far on, the ply is not glued in place yet.

The delicate little rudder, awaiting the control horn, the hinges, a little more of that carbon fibre reinforcing and a layer of solartex. The vertical part gets trimmed back to the tube at the bottom.

regards

John

 

[John Olsen 1]

Well, I am just back from 21 days in the wilderness, Australia to be precise, so not much has happened on the Dr1, except that tonight I started putting the rib caps for the lower wing. A bit fiddly but no problem.The leading edge got put on the other half just before I went away.

 

However one benefit of my travels on the great desert continent is that I found a place that stocks 1/64 inch ply in 1ft by 4 ft sheets. Well, they did until I bought both the sheets they had, plus a 1/8 inch sheet to pack them with for the trip home. This is great because I won't need so many joins in the leading edge sheeting. I also have two 1ft by 2ft sheets that a local (NZ) supplier came up with. Now the main thing I am looking for is a source of 1/16 aluminium tubing in decent lengths, the only ones I have found are only 1 ft long.

 

As well as the ply, I brought home some SIG Koverall. This is a heat shrinkable cloth covering. It has no glue on it, you apply a heat activated glue to the framework, iron it on, then shrink it at a higher heat as is routine. Then you seal it with clear dope and then apply the finish of your choice. Sounds great although I have not tried it out yet. One benefit is that it is very much cheaper than any of the usual coatings, while being an actual lightweight cloth. (1 and 1/4 oz per square yard.)

 

For those who are familiar with the Phoenix simulator, the shop I went to in Canberra is about five minutes walk from Kambah Field, as featured in Phoenix. The locals are able to fly electric models and gliders there at suitable times. It is a rather strange feeling to see a place that you first saw in a simulator. Those kite eating lighting poles are actually there, as are the trees.

 

One other feature of Canberra not to be missed is the War Memorial Museum. They have an excellent selection of aircraft from both world wars and later conflicts, including a lovely Albatros that was captured when it force landed in the Aussie sector. There are not too many original Albatrosen about! They also have the actual control column from Freiherr von Richthofens Dr1, plus a few other bits from the plane. Maybe I should post some of my pictures in an album here!

 

I also managed to make it to a club flying day at the Sale, Victoria (Not Sale UK!) flying field for an hour or two. There was a good selection of aircraft there including a number of large jets.

 

regards

John