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Design & Build Dornier Do 24

A bit of a challenge

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Robert Parker18/02/2018 19:30:13
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878 forum posts
1133 photos

HI All,

Tony, yes she is very curvatiuos indeed it took quite a bit of soaking the planking strips to flow around the framework.

Thank you Chris, elegance and hopefully gracious in the air when the day comes for the maiden.

Adrian, thank you I do think it is developing a wow factor.

I first came across the Dornier Do 24 in a flight simulator as an add-on I cannot recall which one, quite likely to be one of MS flight simulators.

I have made a start on the sponsons fairly straight forward as well as the block at the rear of the rear step of the hull.

i'm starting to think about covering the model and toying with using brown paper, but having not used it in the past. I have also read that it shrinks a lot and a little doubtful with it on the fuselage not wanting a "starved horse" effect but wanting a strong finish.

Any ideas or personal experiences??

Regards

Robert

McG 696918/02/2018 20:13:32
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2475 forum posts
976 photos

Hi Robert,

Unfortunately, I can't share anything about "personal" experience... blush

But Richard of Warbird Replicas uses brown paper a lot and maybe it should be worth to ask him about his experiences by sending a PM. Just a thought here.

Cheers

Chris

Mark Stevens 121/02/2018 03:59:48
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116 forum posts
48 photos

Hi Robert,

Loving the build so far - reminds me of my days when I used to sit and draw plans by hand too :

As for the paper covering method, I have used this on balsa many times, not with brown paper but with normal computer printer paper and clear PVA Glue (the sort kids use in schools) There is a slight shrinkage but nothing to worry about so long as you don't overdo it with the glue. You won't end up with the starved effect as it is water based glue. Just take care when applying the paper and rub out any bumps or blisters (pop them with a pin if you need to help this)

When it dries it is quite flat and tough over any open holes (a bit like the old tissue / dope method but better) You can easily rub down any overlaps or join edges with a little light sanding. To finish off, a coat 2 or thinned dope (very lightly sanded between each coat) gives a really nice finish for painting with no wood grain visible. A lot of people may point out the weight gain but it is barely noticeable.

I'm looking forwards to seeing more of the build.

Mark

Robert Parker21/02/2018 18:25:58
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878 forum posts
1133 photos

Hi Mark,

Thanks for the info on paper covering.

Build is coming on nicely, will keep you all posted.

Regards

Robert

Tom Sharp 221/02/2018 18:41:21
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3356 forum posts
17 photos

Mark, I would wonder if PVA glue might absorb water over time, being a float plane.

Robert Parker21/02/2018 23:12:51
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878 forum posts
1133 photos

Hi All,

Don't worry about a "float plane" she will be taking off from and landing on to the ground, take off's will be with the aid of a dolly and landing on her belly or should that be hull.

Last week I did consider getting a couple of glider retractable wheels but thought again when I saw the price of them surprise.

dsc09135.jpg

My own design Short Stirling just airborne on her maiden flight, the Dornier will take off from here and hopefully have a better maiden than the Stirling

Regards

Robert

Robert Parker04/03/2018 16:21:16
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878 forum posts
1133 photos

Hi All,

Progress has slowed a bit over the last two weeks.

I have finished the sponsons and made the three blocks for the nose, 2nd step and tail.

dsc04099.jpg

The nose block I have left the bottom until the bottom planking is on

dsc04100.jpg

I forgot to take any photos of the sponson build but they were straight forward

dsc04104.jpgThe 2nd step block in position.

dsc04103.jpg

Tail block

I think the fuselage is just about as far as I can take it other than to give it a coat of sanding sealer as it is getting the odd ding here and there.

So next I'll make a start on the wings.

That's all for now

Regards

Robert

Timo Starkloff04/03/2018 19:02:06
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339 forum posts
756 photos

You’ve met that complicated fuselage shape perfectly

Robert Parker05/03/2018 20:21:34
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878 forum posts
1133 photos

Thank you Timo.

I'm really pleased with the results so far.

Now the fuselage is out of the way I can enjoy making the wings and then hoping that everything lines up with the wing connections

Regards

Robert

McG 696905/03/2018 20:31:56
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2475 forum posts
976 photos

Hi Robert,

I'm really pleased that you're "really pleased as well"... wink angel

You're having a great job done over there.

Cheers

Chris

Mark Stevens 107/03/2018 02:17:17
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116 forum posts
48 photos
Posted by Tom Sharp 2 on 21/02/2018 18:41:21:

Mark, I would wonder if PVA glue might absorb water over time, being a float plane.

Tom, not a problem once it's doped and painted, it is usually well sealed by then.

I covered this balsa tail fin for one of my Helis using exactly the same method as I described.

dscf0394.jpg

I actually got this tip from the model boat guys and have tried it out on one of my own boat builds, I used thin card instead of paper but still used the same PVA Glue. It works well as you can see, built in 1985 and she hasn't sunk yet. Probably more relevant for the Dornier being a Seaplane

active1.jpg

Mark

 

 

 

Edited By Mark Stevens 1 on 07/03/2018 02:24:16

Edited By Mark Stevens 1 on 07/03/2018 02:32:03

Robert Parker18/03/2018 19:02:48
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878 forum posts
1133 photos

Hi All,

I had a bit of a break from the Dornier over the past couple of weeks.

I eventually caught up on some repairs and alterations that needed doing to a couple of other models whilst the bench was free.

So with those out of the way. I made a start preparing for the wings this afternoon.

dsc04207.jpg

Routering out the ribs for the wing connection plates,

dsc04208.jpg

It took a couple of practices to get the depth right of for the router

dsc04210.jpg

I am having some reservations about the strength of the rib above the flap, hopefully the top sheeting will tie it in

dsc04212.jpg

A slight over sight on by me on not giving consideration to the dihederal on the bottom spar. So I cut off the bottom and will glue on top to take the brace

dsc04213.jpg

I had a bit of a tidy up ready for the build.

That is as far as I have got today.

I ran out of greaseproof paper, (it appears to be difficult to get hold of "clear", a lot seems to be brown) so using cling film for a change.

That's all for now

Regards

Robert

Robert Parker24/03/2018 16:51:23
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878 forum posts
1133 photos

Hi All,

I made a start on the wing centre section plus modified the ribs that take the nacelle side formers as I not too keen on the ply / balsa joint due to the length of the formers and the possible applied leverage stresses they might impose on the balsa ribs and possibility of material failure if knocked.

dsc02337.jpg

The nacelle side NSI above slots between the spars and is glued to the rib. So I have glued 2mm ply to the balsa rib to strengthen it, also I will have to put the dihederal brace behind the spars and not in front to alow the notch to work as this sets the angle for the nacelle in relation to the wing.

dsc04214.jpg

Centre section started and I have made sure that the central rib sandwich is straight and square as this will take the wing connectors. Unlike most other models there is no room for adjustment. A fraction left or right out at the centre would mean the wing tips are a mile out.

Next I'll fit the leading edge and when dry I'll start the outer panels.

That's all for now

Regards

Robert

McG 696924/03/2018 19:03:28
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2475 forum posts
976 photos

Really nice progress here, Robert.

It still seems a quite complicated build to me. Not for me yet, I'm afraid. frown

I hope to be able to start my 'simple' wing center section soon as well.

Cheers

Chris

Robert Parker25/03/2018 09:02:38
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878 forum posts
1133 photos

Hi Chris,

I agree it is not an easy one for me either.

I was hoping it would be straight forward, and it is compared to the fuselage. There are a few niggles to get around which are cropping up as I go which is expected being a design and build project. I took three attempts to get the Stirling fuselage right (drawing error, not spotted until build three)

The outer panels should be straight forward nothing complicated to them just to build in some washout.

Reards

Robert

Robert Parker02/04/2018 19:17:21
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878 forum posts
1133 photos

Hi All,

I have managed to make a start on the outer panels.

Having been hampered by carrying out more repairs to my Cessna and Chipmunk, the latter of which went in hard and in an identical fashion to my cherished Astro Hog although repairable unlike the Astro Hog, namely total loss of control on the final turn from base leg to final approach which has led me to ditch my JR PCM9X with spectrum module for my DX9.

So repairs completed to both aircraft and changed over radio.

Back to the Dornier and both outer wing panels started and wash out being built in.

dsc04238.jpg

To the left the repaired Chipmunk and my "old" JR PCM9

dsc04239.jpg

Tapered piece at the rear giving 4mm - 0mm washout.

As the top of the wing is straight from tip to tip each tip needs to be raised 31mm to achieve this. So when the ribs are dry I'm going to put a block under the tip rib and a 35mm - 0mm wedge under the trailing edge to maintain the washout and fit the top spars. I used this technique on the Cessna.

Next, to add the top spars and cut out the ailerons.

That's all for now

Regards

Robert

Tony Bennett02/04/2018 19:41:31
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5071 forum posts
129 photos

lovely work young sir.

you are crafting a beautiful aircraft there.

Tony B

Robert Parker02/04/2018 19:50:27
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878 forum posts
1133 photos

Thank you Tony,

I lost a bit of motivation recently hoping to kick start it back again. I have got the rest of the week off this week so I'm hoping to get a fair bit done especially as the weather forecast is so wet so I will have to build once the wife goes back to work tomorrow and kids glued to their ipads etc

So keep watching this space more to follow

Regards

Robert

McG 696903/04/2018 11:20:28
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2475 forum posts
976 photos

Great that you have your mojo back to the building board, Robert.

Allow me a question, if you don't mind? angel

I'm following (trying to) your explanations regarding the 4mm washout and the wing tip 'jig' to keep the top of the wing 'flat'. So here is the question: are your front & rear spars supposed to 'take' that 35mm bend? Or are both spars from the center section stopping at the rib doubler (where the clamps are) and the outer wing spars just being 'separated' pieces?

Apology for the daft inquiry, but I have the same problem with Vicky's wing center section and wondering if 'separated' spars would work correctly. question In Vicky's case, the 'double ribs' and spars are still held by the two dihedral braces.

Cheers

Chris

Robert Parker03/04/2018 17:33:28
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878 forum posts
1133 photos

Hi Chris,

I don't mind questions, the more the merrier. Glad to be of help if I can.

The lower rear spar of the outer panel butts up against the lower spar of the centre section, whilst the top spars runs straight over the wing panel joint and is spiced at the wing centre. Ply dihedral pieces to be fitted at the wing panel joint to provide strength.

dsc04248.jpg

Makes more sense in a photo. Photo above showing the panel break between centre and out wing panels,

dsc04247.jpg

Each wing tip has to raise 31mm(at the front spar) + 4mm at the trailing edge washout to allow the wing to be flat on the top edge

As for my "jigs" I have used some scrap pieces cut to size for the tips and places a 1m steel ruler across the wing to check that it is straight

dsc04242.jpg

I have also made a large "wedge" for the washout.

Top spars added and spliced and space left for the main dihederal brace along with the shear webing and leading edge.

dsc04240.jpg

Both panels made and shear webbing added to the centre section

dsc04244.jpg

Close up shot (the black line is felt tip pen) of the spar reduction splice joint, 6mm x 6mm reducing down to 6mm x 3mm

dsc04246.jpg

Front spars packed apart to allow for ply brace. The main 9 x 9mm spars run into the outer panels by 2 bays hope this works.

I hope this answers your question, sorry if it is a little long winded, but it has allowed me to show today's progress.

Regards

Robert

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