60" Depron Lanc

[funflyerColin]

Hi all,

I'm new to these forums so i thought i might be able to get some help on this build as i haven't attempted a build like this before, i've build from plans using said materials but never done a conversion in size and depron before.

The plan is for a 74" lanc from Outerzone that i've reduced to 60", have got the main section of the fusalarge done minus any lightening and sheeting to top and bottom using 6mm depron top will be 3mm and bottom 6mm. Tailplane has been cut out but am not sure on this yet 6mm. I'm tempted to do this with 2 x 3mm with a balsa core. My next problem is the wing, I was thinking 3mm top and bottom skins with 6mm ribs.But how would i design the spar to include the diheadral on the outer panels. You guys make this type of build look soooo easy weather i over think things i don't know. Here's a few pic of what i have got done so far this is 2 weeks of a couple of hours on it per day slooow.

Edited By funflyerColin on 30/11/2013 22:47:20

Edited By funflyerColin on 30/11/2013 23:07:10

[funflyerColin]

Hello can anyone give me some guidence on a couple of questions on this build?

With regards to the wing i have now cut the ribs out of 6mm depron but do not know the way forward on the spar and dihedral braces. Sandwich 5mm carbon tube between 2 depron full length spars? or put hard balsa spars in and 3mm shear webs? any other ideas would be welcome.

On the tailplane athough i have cut them out of 6mm depron i was thinking maybe sandwich balsa inbetween 2 sheets of 3mm depron to give more rigidity?

Again any help would be appriciated heres hopeing

Thanks Colin

[riverlandgirl.]

Hi there Colin

There are others on the forum who know a lot more about it than me, ( check out Simon Chaddock's threads, He's got it all sorted), but for what it's worth, I've been useing a single, full depth timber spar in my polystyrene wings, which has proven satisfactory. An I beam type spar with shear webs and wide, thin horizontal spars top and bottom would be very strong. I would avoid carbon rod, as the glueing area is very small and the spars can creep. I hope this helps.

[GrahamC]

Colin, Without having seen the plan... I think that I would use a 6mm square wood spar top and bottom, and include a sheer web for 3/4 of the wingspan. I would use a ply dihedral brace both sides of the spar.

I use the 6x6 pine wood available in B&Q for things this. They have a good selection of small cross sections, and the 6x6 is less than a quid for 2.4m

I'd also bury a piece of carbon in that tail by opening up a channel in one of the layers. Score it with a scalpel and then pick out the channel with a screw driver

hope that helps.

[funflyerColin]

Hello riverlandgirl. and Grahamc thanks for the advice will bare what you have said in mind. Trying to keep this as light as possible and don't really want to use any wood in it if possible apart fron a bit of balsa, plus a bit of ply for the motor mounts and still thinking about electric retracts. maybe maybe not.

I used to be indecisive but i'm not so sure now .

[Roy Mundy]

Hi Funflyer I have just found your build blog and will watch with great interest.

I wish you luck on your build and if I can help with anything I will certainly do my best.

I am new to building with depron and have posted my first build blog on here, I am typing this on my iPad and can't seem to paste a link in here but if you search for 42" Curtiss Hawk 75a Depron Scratch Build (1st ) you will find it

i have had lots of help from Depron Daz and Electriflier who are fantastic with depron.

I can't see your plans fully but on my build I had a cross section of the wing including the dihedral which helped me a lot. I cut this out and made this piece the main spar, which I inserted a carbon rod, I then built the wing in the traditional way all from 6mm depron, this will be skinned top and bottom in 3mm depron.

take a look at my build (it's my 1st) as I have included lots of photos. I hope this helps.

good luck with your build.

regards

Roy M

 

Edited By Roy Mundy on 01/12/2013 22:30:59

Edited By Roy Mundy on 01/12/2013 22:32:46

[funflyerColin]

Hi Roy, i've just been over to have a look at your build thats a great build you have got there. Thats the type of spar set up i have been trying to work out, my only problem is that i don't have a front view of the wing. I think if i measure the thickness of the ribs in the center section and then from the dihedral break to the last rib i shoud be able to get the spar shape and length right . I have also got to work out the amount of dihedral it needs, the original calls for 3 1/4" at the tips so will measure that out on the bench and come back to 60" to get my dihedral. Thanks for the help it all helps now to cut the rest of the ribs out.

Regards

Colin

[Roy Mundy]

Good Luck Colin,that should work out fine. Cut it out in paper first it will give you a nice template. I would do each wing in paper as you described then draw a line and work out your dihedral from the line, then join the paper wings in the middle with tape, you can then glue the template directly onto your depron ready to make your one piece spar with dihedral included.

good luck

Roy

[funflyerColin]

Latest pic have glued in the fuzalarge formers and sanded to a reasonable shape not egg shaped on top as plan shows. Now starting to cut the wing ribs. Roy i tested the idea of the wing section and dihedral by drawing on the bench it came out a treat thanks, now i've got to put it onto paper for the template will have to cut it out of depron in 2 pieces as my sheets are only 39" long wings are 60". No problem though will scarf join in the middle.

[Roy Mundy]

Your doing a grand job That will work a treat and be really strong once you have put in the carbon rod.

Good luck and enjoy your build.

regards

Roy

[funflyerColin]

Hi all slow progress as you see in my limited space excusse the mess, really must get these other projects finished. Tailplane now has carbon spar inserted and L shaped ply joiners for the fins. Cut out the depron spar and and started to cut channel for the carbon spar which is being glued at the moment. Dry fitted to see how it looks.

[Tony Bennett]

looking great there sir,

i must give depron a try after seeing all these great builds going on at the moment.

[Monz]

Looking great so far! Keep it up this is going to be a stunner

[funflyerColin]

Thanks Tony it's my 1st larger depron build, and the guy's on here are great with any help which i need plenty of keep over thinking things. Yes do give it a go i still like my balsa aircraft as well.

regards

Colin

[funflyerColin]

Thanks Monique hpoefully i can do it justice.

regards

Colin

[Simon Chaddock]

funflyerColin

You certainly picked a complex plane for Depron! Looks fine so far.

Just remember Depron has quite a bit of strength. Being so light it is easy to forget that its strength to weight ratio is actually equivalent to balsa although it is a bit more flexible (good for crashes!).

Up to a certain size you can build an all balsa wing but above that you have to consider reinforcing it with hardwood or carbon.. It is exactly the same with Depron. You can build an all Depron wing (and surprisingly large if you use the material carefully) but above that size you have to consider reinforcing it.

My own preference is to use hard balsa but only as the top and bottom spar flange with Depron in between.

This is the construction of my 60" pusher.

As the Depron wing skins are relatively thick (3mm) I arranged that the balsa spar flanges are flush with outer surface of the wing to give the deepest possible spar.

Note the spar is tapered (both in depth and width) to virtually nothing at the tip corresponding to the reducing bending forces.

In addition as the wing skin is carrying a substantial part of all the load the ribs only support the skin and need no bending strength themselves. They can be quite thin but should be closely spaced.

The centre joint was achieved using a shaped internal balsa/Depron/balsa dihedral brace.

This wing appear rather complex but it actually uses very similar techniques to conventional balsa construction but the end result is a great deal lighter.

Completed it weighs 6oz (including the aileron servos) but is remarkably strong.

No load

26oz load at the centre supported only by the tips.

This load is twice the weight of the rest of the complete plane (including the battery) and puts the wing under a bending load equivalent to pulling an 8g manoeuvre.

How much do you expect your Lanc will weigh?

 

Edited By Simon Chaddock on 07/12/2013 00:37:21

[funflyerColin]

Hi Simon thanks for the info on your wing much appriciated. Mine is also 60" the spar as you see it is almost full length apart from the last 2". I have cut a slot along the length of the spar and inserted a depron tube, with the dihedral bent out of 3.5mm spring steel 4" both sides and glued into the carbon tubes. Hoping this will work. The spar is full depth and the ribs will be slotted onto it, so will be flush with both top and bottom skins. As to the weight i have absolutely no idea as i haven't built any this way before, apart from a few small foamies from plans but hopeing 4 blue wonder motors will be enough for this either 1300kv or 1500kv.

Regards Colin

[funflyerColin]

Hello, got a bit more done wing ribs all glued in place and had a got at bending some 3mm depron. Not very successful i know that it bends better one way than the other but you guys make it look so easy will persevere though. Also had a unsuccessful attempt at making some canopys using plastic bottles may have to have solid ones. Weighed the parts today wing comes in at 65g Fuz at 71g and tailplane components at 30g.

Also recieved some reteacts today Turnagy may be a bit heavy still not sure weather or not to use them.Hand launch still appeals.

[Depron Daz]

Hi Colin.

Yes indeed it does bend better one way, it's best to check each sheet if you have lots of bending to do, as some sheets can be grained one way and the next sheet may be the other way.

However, you are doing a fine job, so keep at it

Daz

[funflyerColin]

Hi Daz, thanks for that .I have also noticed that it seems like the depron has a brittle side if bent one way it does'nt snap but done the other way you get a snap as it breaks. Is it normal to get like wrinkles on the inside of the bend but nice and smooth on the outer?. Should the brittle/hard surface be on the outer side or inner?, sorry for all the questions. Have a few other jobs to do on it before i have to to the fuzalarge tops. By the way lovin your valiant and Vulcan , i have a 32" flat plate Vulcan would love to do a much larger on though.

Regards

Colin

Edited By funflyerColin on 09/12/2013 23:00:05

[Depron Daz]

Personally I won't use white depron on the outside as it is more brittle than the grey and a lot harder to bend IMO. You are right with the creases on the inside and smooth outer.

The grey is nice to get tight curves, and once all of the panels are glued on, I just take one the wife's old nail emery boards and sand across several panels to get a nice flat joint. The Vulcan was painted with emulsion but that put a lot of weight on it. The Valiant will be glass clothed and Eze-Kote'd, so it should be a lot tougher against any hanger rash for hopefully the same sort of weight once spray painted.

The Vulcan flies beautifully, and I'm hoping that the Valiant does the same, however I haven't done much on it lately, I get bored and just do literally 30 minutes on it now and then. Seeing that the weather is pretty pants, I guess there is no hurry.

Daz

[Simon Chaddock]

FunflyColin

Its coming along nicely.

Just remember that if you 'plank' you don't have to bend and as the joints are largely in shear they don't need to be perfect either!

Half the Cessna Skymaster built over the plan.

With significant double curvature it needs a bit of trial and error to determine the best shape for each plank.

Lifted from the board a start is made on the other side.

In this case the skin is grey Depron simply because when finished it was to be painted black.

Light weight filler for the seams.and with just limited sanding the contours are smooth and you can no longer see the joints.

Light, rigid and with no reinforcing it happily holds a 2200mAh 3s and 300W of power (150W front and back). About the same as 4 Blue Wonders?

I would recommend planking for any surface with significant curvature. I have yet to find another method that gives the same strength to weight.

[funflyerColin]

Hi Daz and Simon, thanks for the info at the moment i don't have any gray depron as white was easier to get hold of in full sheets. Most of my foam builds are all flat sheet no curves apart from sanding several layers down to shape, so hadn't bothered with the gray but will bear what you say for future use. i notice the you seem to mainly use UHU por as glue is it really strong enough as i am tending to use the Gorilla glue which i find is easier to sand. I did try the technique of using thinned light weight filler on my little combat Spit and was suprised at the results i got will be employing same on the Lanc if it gets that far.

Regards

Colin

 

Edited By funflyerColin on 10/12/2013 17:37:02

[Simon Chaddock]

funflyercolin

Used as a contact adhesive (thin film on both surfaces & let it dry for a couple of minutes) UHU POR is instant & very strong. Used as a normal glue it allows adjustment but takes some to reach full strength.

As you say POR is horrible to sand but the very fact it remains rubbery does give a Depron structure a bit more crash resistance.

It is worth remembering that sheet Depron is itself a sandwich. Its outer layers are denser & stronger than the centre. Sanding the surface can significantly reduce its strength.

You can get 'aero' Depron that does not have a skin so is about 25% lighter, rather more flexible but not as rigid.

[funflyerColin]

Thanks for the info haven't done much on the Lanc lately but hope to get some time on it over the Christmas break. Merry Christmas to all hope santa brings you what you wish for .