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Design & Build Dornier Do 24

A bit of a challenge

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McG 696903/04/2018 18:54:41
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2710 forum posts
1015 photos

Thanks a lot, Robert.

Spending all that time to answer my question is just great. surprise

My center section is quite less complicated (I hope), but I see now that spars can also be 'butt' jointed if the dihedral brace is spreading the loads further away. The original Baron (1970), the Svenson plan and the JVM one were showing that construction, but - to be honest - I was a bit afraid to misinterpret what I saw on the drawings.

By the way, regarding the wing 'front dowel' of my Vicomte, if you remember you gave me the advice to use a front vertical bolt as you did with your Taube. Advice confirmed, Robert. I'll do Vicky's wing that way. yes

Thank you again for your time.

Cheers

Chris

Robert Parker03/04/2018 20:34:08
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916 forum posts
1175 photos

Glad to be of assistance

Regards

Robert

Robert Parker05/04/2018 20:56:36
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916 forum posts
1175 photos

Hi All,

The pace has slowed a little especially today as the sun was shining and I needed to get some jobs done outside the house, (brownie points from Mrs P to be cashed in on flying days, hopefully).

Ailerons have been cut out and made and I have started fitting the dihedral braces as well as hinging the rudders.

dsc04250.jpg

The ailerons are quite wide at the root so i decided to have a change of plan regarding the servo choice and beefed it up a bit, I was going to use the same as I have in the tail.

dsc04251.jpg

I had to slow down a bit as I had to get some more ply for the braces and ordered the servos for the wing, I settled on Corona DS339HV with metal gears, not used these before but they seem to have a high torque and only 32g. I was considering Hitec 225's but they were heavier and less torque.

Anyone have any comments on these servos?

Tomorrow, I will continue with the braces and make some holes for the cable runs, rushing ahead and not thinking ahead it is not going to be easy with the centre section around the nacelles and those close fitting ribs.

That's all for now regards

Robert

Erfolg06/04/2018 22:27:58
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11429 forum posts
1216 photos

I am sure that the servos you have selected will be fine. I am also sure that there are many other servos that would be pretty much similar in performance.

Hmm, does it really matter at all, I ask myself. Being brought up on Waltron and equally dodgy Linwood et all, i find it hard to get excited.

Many, if not all my models make do with 9g servos up to about 54" span, some fly quite fast.

IMO, yours are very well specified, nothing to worry about.

Robert Parker15/04/2018 18:09:27
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916 forum posts
1175 photos

Hi All,

It's been a bit of a busy time for me lately, and today I have finally managed to get back to the building board and hoped that once checked the wing / fuselage connections for alignment I could start sheeting the underside of the wing. However, a slight problem presented it self to me when I sat the wings in place, see below, this was over come with the aid of a 2mm drill and a bit of waggling. All of the connection pieces have been cut and I have started sheeting the centre section.

dsc04253.jpg

Always nice to see this part I can finally get to see it coming together. I was even more pleased when I did a wing tip to rear centre line to wing tip measurements and had a difference of only 4mm difference smiley, With this model there is relatively no adjustment just relying on the metal connections.

dsc04254.jpg

With the wing clamped at the rear and packing pieces in place to give the incidence. I thought I had a major problem on my hands when I saw that the front connection was wrong sad. I checked my drawing and measured from the back of the cockpit to the leading edge and it was right. So I marked up the wing and went back up to my workshop.

dsc04256.jpg

All marked up and drilled out in no time not so bad after all.

dsc04259.jpg

Wing servo's fitted

dsc04261.jpg

Centre section sheeted except for the trailing edge which I will do tomorrow evening. The wing connections are loose fitted at the moment.

That's as far as I have gone next I will sheet the outer panels.

That's all for now

Regards

Robert

McG 696915/04/2018 18:21:49
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2710 forum posts
1015 photos

Glad to see you back at the 'board', Robert.

I still don't understand how you manage all those different measurements and how you 'correct' them, but hey... that's why I'm still an apprentice. blush

Keep up the good job, please. yes

Cheers

Chris

Robert Parker15/04/2018 19:04:52
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916 forum posts
1175 photos

Thank you Chris for yous comments.

With a conventional aircraft the measurements I have mentioned above, usually are wing tip to tail and to wing tip and if all is well the difference is zero, if they are different then the wing needs to be adjusted on the wing seat and I tend to sand the leading edge slightly to maintain a good joint. Whilst the wing is in position it is worth checking the wing to stabiliser to see if they are parallel to each other when viewed from the front.

As to the corrections, today it was either move the wing connection in the wing or move the one in the fuselage, way too late in the build for that so I had to modify the wing rib slightly. I did for a passing moment consider a new rib but again that would be extremely difficult to do, my solution with the drill was the only easy way around it and the "old" slot will be filled with epoxy when the wing connections are finally fixed.

Regards

Robert

Erfolg17/04/2018 21:02:39
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11429 forum posts
1216 photos

I do not think you received a reply with respect to servos, particularly ones that are deemed to be suitable.

It may provide reassurance something that BEB either produced for the mag or maybe a contribution on this site. From memory BEB used a classic (IMO) relationship F =0.5 Roe*V^2*S*Cl, this was used to determine the force on a aileron (probably a typical one), then moments were taken, about the clevis to find a value that the servo would need to produce, for a specific speed he had chosen.

Again from memory, BEB concluded that the forces for many models was typically modest, in that the old servos of the 70s could provide the necessary force. Which is what experience from the period indicates. I guess what it also hinted at that the Radio link in that era, could have been more of an issue, than the servo output. Particularly when you recognise that a single central servo would often drive both ailerons via torque rods and some dodgy hinges.

In short, in my opinion, it matters a lot less than many would suggest what or whose servo is used. It is reliability that for most applications matters the most, as of a group, most have broadly similar performance. Even the reliability aspect seems to be much better today, than in the past.

Robert Parker18/04/2018 19:03:04
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916 forum posts
1175 photos

Hi Erfolg,

Thank you for your reply regarding my servo choice, I only asked it as I usually prefer to use Hitec servos, but the Corona ones were a lot cheaper than the Hitec ones and I have not yet, at present I'm having to watch my expenditure, got a lot on this year with one thing or another, houses do swallow money at an alarming rate along with changing cars.....etc etc

Regards

Robert

Robert Parker24/04/2018 20:57:53
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916 forum posts
1175 photos

Hi All,

Thing have not been going my way recently with the Dornier, to the point that on Saturday I was ready to scrap the wing and start again sad

I had managed to create a warp in the centre section trailing edge / flap area and had regretted cutting out the flaps before the build. The warp was too much to ignore and would have had an influence on handling especially in the prop wash of two motors. So I thought I'm not too far into the build really, I'll start again.

I'm glad I decided to leave the scrapping until Sunday, sometimes things look a little better after a nights sleep. Refreshed and looking at the problem in a fresh light I set about removing the offending warp or least reducing it as best I could. with knife to hand I set about freeing the glued parts and clamping a good straight (1" x 2" hardwood) edge to the underside and wetted the sheeting and re-glued the joints and left if for 24 hours to dry.

Yesterday, the clamps came off and the wing was checked and a big improvement was found and only a slight presence still remained which I should pull out with the top sheeting.

This evening, I have sheeted the underside of the two outer panels so the wing looks less fragile than it did.

Now I've got that out of the way I can start the nacelles, let the fun commencewink

That's all for now

Regards

Robert

McG 696924/04/2018 21:23:50
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2710 forum posts
1015 photos

Glad you could resolve it, Robert.

It's sometimes 'weird' that after leaving things alone for a while or after a good night sleep, ideas or solutions often come up out of the 'blue'... smiley

Didn't you tell me that regarding Vicky's wing front dowel or horizontal ply mount decision... ??? angel

Well done & cheers

Chris

Robert Parker28/04/2018 09:49:05
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916 forum posts
1175 photos

Hi All,

Just a photo of the completed sheeting to the underside.

Progress has slowed considerably mainly due to my work taking me further away from home and having to travel at least 1 1/2 hours each which has gone well over 2 hours due to roadworks by the time I get in unwind have tea etc the evening has gone before I know it.

dsc04282.jpg

At least the wing is less prone to mishaps now sheeted and the warp removed.

Over the weekend I intend to make a start on the nacelles hopefully once I've finished doing other jobs that need doing.

That's all for now

Regards

Robert

Robert Parker29/04/2018 16:46:44
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916 forum posts
1175 photos

Hi All,

Nacelles fitted with a little adjustment

dsc04283.jpg

dsc04284.jpg

Front shot showing the centre motor nacelle is raised by 1/4" (6mm) as per full size to give prop clearance to the fuselage.

Next, finish off wiring and then top sheeting

That's all for now

Regards

Robert

Robert Parker22/07/2018 07:37:44
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916 forum posts
1175 photos

Hi All,

Due to several other things happening in my life (some unplanned) I have had to leave the Dornier, however, these other events have passed, well almost so it won't be too long before I get back to her. This dry weather has meant I have done a lot more flying and repairing than usual as well which has added to the delay. I have also been side tracked by building another plane a Uno Wot with my son and getting him to do the work but this has proved a lot harder than I thought due to his discovery of a game called "fortnite" and he wants to be on it all of the time. The Uno wot is at the covering stage so it will soon be finished.

Back soon

Regards

Robert

Robert Parker11/08/2018 16:20:14
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916 forum posts
1175 photos

Hi All,

And I'm back on the Dornier at last. Having spent a little time getting myself back up to speed where I left off. I have carried on with the top sheeting of the outer panels, fitted the placed the motor wiring in position and ordered a few bits and pieces, following on from my failed attempt to maiden my FW 200 Condor I have ordered a 4s 5000 mah battery for the Dornier / Condor.

dsc04872.jpg

1st off, one of my distractions which took a little longer than I thought it would, just waiting to maiden it and give it to my apprentice pilot to learn on.

dsc04873.jpg

I have now completed the sheeting to the outer panels. Cut cooling holes in the bulkheads for the ESC's.

dsc04874.jpg

Flap servos and motor wiring installed and RX battery pack positioned, this is a bit of an after thought as I am thinking of using two RX's to save on the amount of extension leads and save on the rigging time. A six channel Rx in the wing covering the ailerons, flaps and esc's and a four channel Rx in the fuselage for the rudders and elevators.

Can two Rx's be bound to the same Tx on the same model, not tried it myself but has anyone else?

I'm using a Spektrum DX9 with Spektrum Rx's.

Next, when my packages arrive I will continue with the electrics and sheet the centre section

That's all for now

Regards

Robert

McG 696911/08/2018 18:08:04
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2710 forum posts
1015 photos

Glad to see you back to the Dornier bench, Robert. yes

Unfortunately, I can't be of any assistance regarding your 'double' Rx bind... frown

Cheers

Chris

Robert Parker11/08/2018 20:19:38
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916 forum posts
1175 photos

Thank you Chris,

I have enjoyed working on her today with renewed motivation.


I have found out that you can use "double RX's" so happy days

Regards

Robert

Robert Parker18/08/2018 17:48:27
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916 forum posts
1175 photos

Hi All,

Managed to do a bit during the week and today.

Centre section is now fully sheeted, wing tips added and sanded to profile, ailerons cut out and hinged and flap cut out and made.

dsc04875.jpg

The top of the centre sheeting I fitted at 45 degrees over the flap area this is an area that I was concerned about the fragility of the ribs as so much was cut out for the flap, ailerons marked out they seem very wide but are to scale. plus wing tips added.

dsc04876.jpg

Flap cut out and made with temp hinge.

dsc04877.jpg

In hind sight I think a single servo would have done the flap.

Not fully decided about the hinging of the flap yet. Whether to go as per full size and have pivot hinges where they pivot out of the wing or to hinge as shown.

That's as far as I have go this week, next I'll look at the nacelles, I have had to re-make the parts as I seem to have over sized them some how.

I have managed to find some plugs on e-bay for the wiring to the motors and speed controllers to make it a bit neater. I bought a XT60 lead with a three way split and a three way "Y" lead if you can call it that, only problem they are coming from China and will take 4 weeks to arrive, I bought before I noticed that. Still plenty to get on with

That's all for now

Regards

Robert

McG 696918/08/2018 18:07:17
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2710 forum posts
1015 photos

Still following here, Robert.

Nice progress these last sessions.

Aren't you concerned that the two servos for the flaps might work 'against' each other if they react slightly differently? Daft supposition, very probably...

Keep up the mojo, young man.

Cheers

Chris

Robert Parker18/08/2018 18:17:29
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916 forum posts
1175 photos

Thanks Chris,

They take a little time to set up and some dry runs needed. I had a lot of "fun" with my FW 200 Condor flaps as there are 4 servos to set up still not quite right at full flap so I have reduced the throw a bit this seems to be ok on the ground.

dsc09892.jpg

That said each servo operated it's own flap.

Regards

Robert

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