Verhees Delta

[Max Z]

Hi all,

I have been hesitating whether I should share this project with you, it is a bit uncertain if it will ever fly properly. And yes, I know, I have started other build blogs that I did not finish yet. But this one kept itching me, so here goes anyway.

The model in question is a 1/6 scale model of the Verhees Delta. You may never have heard of it, but it exists and according to it's designer Bart Verhees is very successful. Bart is a Dutchman like myself, but he lives in Belgium. And to make it even more European, he has a French CoA and thus flies under a French registration. Bart built his Delta himself, and has been trying to get other homebuilders interested for a while, but I do not think any other builds have been started yet. The plane is constructed entirely out of aluminium sheets, mostly with single curvatures only. The U/G is a tandem type, and consist of a retractable nose wheel, a tail wheel in a streamlined pod and a small wheel at each wing tip.

I have not been able to find any 3-views of the plane, only the main dimensions for span and overall length. I have never seen the plane up close, but I did see it whizzing past overhead close to where I live. Apparently mr. Verhees flies his delta to all sorts of meetings, and has been visiting the PFA rallye at some point.

This is my cad-rendition and a couple of pictures of the real thing:

Max.

[Max Z]

Structural details (to be sheeted completely with 1.5 mm balsa sheet):

Edited By Max Z on 01/07/2016 16:23:58

[Max Z]

So I got the parts cut and made a start with the construction today. The results sofar:

The housing for the tail wheel, which will have a trailing arm and a shock absorber element:

Max.

 

Edited By Max Z on 01/07/2016 17:52:13

[McG 6969]

Hi Max,

I'm taking a chair to add in the classroom, well two actually, as Gaston - sorry Guust - sees himself already at the stick of the Verhees Delta...

Hakuna matata

Chris

BRU - BE / CTR PDHV Control

[Max Z]

 

Sorry Chris, no cartoon characters in a scale model.

The wing/body all framed up:

Max.

Edited By Max Z on 03/07/2016 11:53:37

[bouncebounce crunch]

Share, share, share, Max.

Everyone will want you to have success, but, we do all have failures too just like full size.

No shame at all in failing either, aeromodelling is up and down, just millimetres making a good flyer or a wreckage.

By the way, all looks great with what you are displaying.

bbc

[MattyB]

What a delightfully eccentric little aircraft, and it seems to fly well too - 270kph (168mph) from 50hp is very impressive! Perhaps a little aesthetically challenged, but beauty is in the eye of the beholder and the low cost and high performance of this design does seem to make up for the looks.

Info on the Wikipedia page...

 

 

Nice building skills too - are you going to release a plan? The structure looks ideally suited to adaption for Depron as well for the many people who now prefer that material to balsa for small models. I think it should make a great model if you can get through the first few flights unscathed - my only worry is that anhedral which might make it unstable in roll. Maybe a paper dart or balsa chuck glider for CG position might be wise?

 

I take it this will be electric powered - what powertrain have you chosen? At 75cm span I am guessing a small 3S pack, 5-6" prop to address ground clearance issues and a fairly high Kv motor?

 

Matt

Edited By MattyB on 04/07/2016 11:59:47

[Max Z]

MattyB and BBC, thank you for the encouragement. Matty, I like your wording "aesthetically challenged" You are right of course, I have to fight to resist beautification of this one, especially the sharp corner on top of the fin/cockpit!

The span of the 1:6 scale model is about 700 mm.

I plan to use a NTM 35-30 1100 KV 380W motor, probably with a 10x6 prop, I haven't done the calc yet, so far it is just past experience with similar models. If need be a larger motor in the 35 series can be installed, but it will be a challenge for the CofG. The battery will be a 3s lipo, but space is at a premium so I will have to find one with minimum height. I had figured that it should be well forward to get the CG right, and located the carrier plate above the retractable nose wheel. Calculations have shown since that it should be at the back of the cockpit space, but I still cannot drop it behind the retract unless I do a complete redesign of the beasty. We will see.

Ground clearance is really not such an issue, theoretically I can swing a 11" prop because of the stilty nose wheel that I need anyway to position the plane with the appropriate take-off AoA, like the full size one. Remember; rotation is not possible.

Max.

 

Edited By Max Z on 04/07/2016 12:28:31

[Max Z]

Correction: I will have to allow for depressing the nose wheel, 10" is probably the max. prop size. I will try a 9x6 or 9x7 first to see if it cuts it.

[MattyB]

Ah, yes - I had forgotten it does not rotate (there is a nice description of the takeoff roll and general flight characteristics on the Verhees Delta home page), so can see now you should be able to get away with a bigger prop than I had thought. Lipo position does look a challenge though with that large wheel well; at such a small size I might have been tempted to make it a hand launch/belly land ship. Makes you wonder where the heck the pilots feet go in the full size - there must be a lot of wheel amongst the pedals!

[MattyB]

One quick recommendation whilst I remember... Those NTM motors are ok, but their power handling capabilities are (like most motors on HK) extensively exaggerated! Looking at the figures for your motor of choice it looks like a 9x7 will give you ~200W at ~20A (well within the 3W/g rule of thumb for cheaper motors). Based on that and aiming for 100W/lb you are looking at an AUW of no more than ~900g - looks achieveable given the powertrain should weigh about 130g plus the lipo. Even if it came out a bit heavier then 80W/lb should still give it a fairly spirited performance - the low drag design and easy handling of deltas at slow speeds means landings should still be a breeze.

I can see fitting the lipo in could be a challenge though... maybe try the Zippy C's?

[Max Z]

Posted by MattyB on 04/07/2016 18:13:27:

Makes you wonder where the heck the pilots feet go in the full size - there must be a lot of wheel amongst the pedals!

It does not look too bad, see here. Remember it is not a cramped cockpit sideways, you can spread your legs into the wing root.

As for hand launching: I see it as a challenge to make it self starting, it makes it stand out from other delta models.

Max.

[Max Z]

Matty, one of the advantages of 3D modeling is that you can easily make an accurate volume calculation, so depending on the accuracy of your specific mass figure of the various woods you use you can asses the AUW fairly accurate. Coupled with having most components at hand, including the O/D retract strut, I now calculate it to be just under 900g, so according to your power train calc I should be ok

As for the Zippy's, I will look into those. As a matter of fact I just ordered a 3 Ah 20C one, which should only be 18 mm thick.

Max.

Edited By Max Z on 04/07/2016 18:48:49

[Max Z]

I have not posted on any updates for a while, the reason being that I spent quite a bit of time rethinking some of the installations and construction methods, but I am picking up the pace again. For a start, I decided to build the ailerons in isolation rather than as part of the wing construction. For that purpose I laid the top sheeting flat on the building board, and stuck the riblets onto that, added the slanted LE, did a bit of sanding and added the bottom sheeting. This gives a minor deviation from the intended airfoil, but I think it is acceptable. Last, I added the TE and shaped it.

The next decision was to move the aileron servos to the rear, no need to have them forward:

The last design change was to change the battery location. Originally I was going to use a 3000 mAh lipo lying flat over the retactable nose wheel housing. but even with the thinnest I could find this still left me very little space for the cockpit/hatch. After checking the expected motor current, which came out at approx 15A max (with a 9x6 prop), I decided that a 1500 mAh pack would have to do, so I lowered that to the lower floor panel. Hopefully I have enough space left for the Rx.....

Edited By Max Z on 11/07/2016 16:06:13

[Max Z]

This is what it looks like today:

[Max Z]

I installed the retract and the tail wheel to get an idea of the fit;

Same for the motor, which I installed on spacers so I could replace it with a larger size if needed (but I will have the battery problem again..):

[Max Z]

The tail wheel rests on a shock absorbing element (a section of heavy duty garden hose..):

That's it for now, more to follow.

Max.

[Ken Lighten]

Following your build avidly Max, right up my street!

[Ken Lighten]

Following your build avidly Max, right up my street!

[MattyB]

Great work Max, looking good. Looks like you have an electric retract in there, but did you manufacture the oleo leg yourself? Looks pretty scale. I think the move to a smaller battery is a good idea - a 3S 3000 did sound a bit heavy to me for that motor and prop. Are you going for a scale colour scheme, or a more easily visible one?

[Phil 9]

fascinating subject. maybe the plan could be published in the magazine ?

[KiwiKid]

Really intriguing project. Looks like something from the drawing board of Alexander Lippisch - he went with pointy tail option.

The production model was going to be jet powered.

[Max Z]

@MattyB: I did not actually manufacture the "oleo leg", but I designed it around a HK electric retract unit and a pair of O-rings as spring-elements. I made the design in 3D-cad and then sent it off to a 3D-printing firm who manufactured it in a tough kind of plastic using a powder fusion process. It is not strictly scale, but it functions more or less like the real one.

I am going for the scale colour scheme, I don't think a different scheme will improve visibility very much. With such a compact shape it will be hard enough to maintain orientation anyway. The problem will be to mimic the bare aluminium skin, HK sells a "bright silver" iron-on film which is supposed to do just that, but it is out of stock in the EU warehouse. I know there are other brands, but those are mostly chrome-like.

@Phil 9: I am considering asking the editor if he would like to publish the plan. It would not be too difficult to convert the 3D design into a 2D plan, but as always the devil is in the details, literally. I know, I did it before (my "Wiggo", published in july '15).

Max.

[Peter Miller]

This is interesting. I shall be wathching.

IT is also a bit like the Payen Katy. A French delta design.

This was another Payen design. This flew but failed to respond to the controls

Or I should say my model failed to respond to the controls, It flew about 200 yards ina steadyturn before gently diving into a field.

Edited By Peter Miller on 12/07/2016 09:13:41

[Peter Miller]

This is thelinkto the Wikipeadia Payen Katy.

**LINK**