Topic: Stearman - Ziroil 77" with Seidel 770ST radial

Day 11 - 40 hours
  Installed the last former to the fuz, this time dry fitting, I had to modify the ply sides to allow the former to drop in fully.

Sanded off the surplus filler, glued and clamped the 2 bulk heads together with PVA.

Didn't get much done last night having trouble sourcing the correct balsa from my local model shop, so if I can't find a supply there isn't much I can do over the weekend. 

Paul

What size wood do you need plenty in my shed
bert

Not too big and not too small, but just the right size 

Check out Solarfilm.co.uk
 
Bert

Day 12 - 46 hours

Started the cabains using 5mm diameter piano wire and a blow torch.  After a quick lesson from my mate Bert, not too difficult just heat the part until red hot and using pliers, a vice and a hammer, bend and keep checking and fit with the plans trying not to burn them too much.  One very important point do not touch the red bits they are VERY hot "Ouch".  Ill finish these off when I can fit the upper wing

Firewall, after gluing the 2 parts together making it about 10mm thick, I drilled out the center then using my laith and permagrit rounded off the edge, I also cut a groove around the center to help make a shelled for the carb, to help prevent warm air inhalation (A problem with radials) and suck air from the fuz.

Started the lower wing see pics, much easier the second time around.  I intend on leaving them pinned down for as fare into the construction as possible to help keep them flat.  They are made up in a similar way to the upper wing with some exception.  I am not installing the center ribs, to allow for dihedral, ailerons and servo mounts. Plus now I know what a rib shim is, this makes perfect seance now, it's to lift the trailing edge, off the board and make the ribs sit flat on the stringer. 

The fuz will need some of the rib removed to install the cabains and I need the lower wing finished before the upper wing can be fixed, to check level, the wing seat needs to be finished in the fuz before I can fit the lower wing.  So 2 steps forward and one back.

Question, Balsa lock? what is it and should I use it? I have bean advised to paint the finished wing with Balsa lock to protect it and aid in covering grip?

Paul

Balsa Lock is a white fluid painted on to wooden areas where you need extra stick from your iron on covering. once applied, let it dry (it'll go clear when dry), and when you apply the covering, the iron will heat it and make it sticky. I wouldn't paint all the wood with it, just the edges of where the covering film will go.

HTH
Mud 

Looking good

Balsa lock can be found on the solarfilm website

Enter site and you will see products on the front page just put mouse pointer over the balsa lock bottle and click on it and all info will be there

Its a mater of personal choice as to use it or not as different strokes for different folks

Bert
I think it might be worth flattening of the struts where they will meet the hard wood section in the wing. not by massive ammounts but just enought to stop them digging into the wood 

Looking good


Bert
I think it might be worth flattening of the struts where they will meet the hard wood section in the wing. not by massive ammounts but just enought to stop them digging into the wood 

Yes when I eventually come to fit the wings, I will grind of a flat to the eyelet for a snug fit.

Paul

Do grinding before fitting

on bench grinder

lots of vibration would be generated if trying to grind after fitment

bert

Hi Paul,

Still looking good and more movement in i week than i manage in a month 

On the way you have bent the wire ! by heating to cherry red then bending you will have taken most of the strength out of the wire wiser people than me on here will tell you if you can heat teat the wire as for the life of me i can't remember, but don't ignore it or it will bite you 

On the way you have bent the wire ! by heating to cherry red then bending you will have taken most of the strength out of the wire wiser people than me on here will tell you if you can heat teat the wire as for the life of me i can't remember, but don't ignore it or it will bite you  

Hmmm, Rookie error no 3 perhaps? I will look into this further kcman and perhaps do some tests on my own to ascertain the residual strength after heating. Thanks for the heads up.

Paul

Day 13 - 50 hours

Spent 4 hours not getting much done last night. 

So made up some more sheets for the lower wing, started building up the ailerons off the plan so to allow me to keep the wing pinned down and started to sheet the top of the right lower wing with PVA and remembering to ues packing balsa under the clamps to avoid any scaring and dents like the upper wing and that's all, too much time admiring my work and NOT BUILDING!, must try harder!!

Once the glue on the sheeting is fully dry (Tonight) I will release the first wing and ailerons from the plan and then do the same sheeting on the left wing, I hope this will ensure a strait wing.

Question - The lack of any real spare in this lower wing is giving me some concern, just 2 thin pieces of ply about 250mm long to join (Dihedral angle) the 2 wing halves and a couple of 1/4'' inch x 1/2'' inch balsa stringers and that's it, I was thinking of adding something like a carbon rod through the ribs for some sort of strength?  The upper wing has two, 1/2'' pieces of hardwood for mounting the wing, that provide quite a bit of integrity to the construction. Advice please?

Paul

Hi Paul,

On the way you have bent the wire ! by heating to cherry red then bending you will have taken most of the strength out of the wire wiser people than me on here will tell you if you can heat teat the wire as for the life of me i can't remember, but don't ignore it or it will bite you 

Yes the steel will be weaker kcman,
http://www.springerlink.com/content/g4n34r0140359284/

"Intense loss of strength for steel 18Kh15N5AM3 occurs after annealing at temperatures above 550°C. "

I will do some testing to see if the remaining strength is up to the job.

Paul

Don't forget that plan also shows aluminium can be used in this part

If you were making undercarriage bending would have to be done cold

Given that the eye end has got to be made small enough for a m6 bolt to go through it my personal view is that it would be very hard to do with a general purpose bender to get it to go that small

And doing it that small would probably over work harden the wire during bending and fracture anyway.

As it's made from 3/16" wire and it's not going to be expected to put up with movement like you would get in an undercarriage I would have thought it would be OK

The only real way is to test it but you must test it in relation to the stresses it would encounter in the given environment IE its not a undercarriage leg

Bert

The only real way is to test it but you must test it in relation to the stresses it would encounter in the given environment IE its not a undercarriage leg

Bert

My Intention barmybert is to put a 90o, cold and hot bend in the same piece of wire then stress it to destruction, to see if its up to the job. My feeling is it will be fit for purpose, however I'm not prepared to use the parts I have made with this question mark on them, so I will test first, Plus I like braking things. 

Paul

Question - The lack of any real spare in this lower wing is giving me some concern, just 2 thin pieces of ply about 250mm long to join (Dihedral angle) the 2 wing halves and a couple of 1/4'' inch x 1/2'' inch balsa stringers and that's it, I was thinking of adding something like a carbon rod through the ribs for some sort of strength?  The upper wing has two, 1/2'' pieces of hardwood for mounting the wing, that provide quite a bit of integrity to the construction. Advice please?

The spar is made up from the 1/4 x 1/2 balsa and the shear webs that fit between the ribs - it makes up into a strong structure

The thin bits of ply you mention are more than adequate for the job they do in joining the wing, all they do is tie the left and right spars together, there's no need to fit a carbon joiner


Mark

The spar is made up from the 1/4 x 1/2 balsa and the shear webs that fit between the ribs - it makes up into a strong structure

The thin bits of ply you mention are more than adequate for the job they do in joining the wing, all they do is tie the left and right spars together, there's no need to fit a carbon joiner


Mark

I appreciate the quick response, but do you think it would detriment the build if I put it anyway just for my piece of mind? As I'm not used to wings being this bendy!

Paul

No need for carbon.......remember this is a braced biplane......the wings do not need to be anywhere near as 'strong' as they would be in a canterlever monoplane

A carbon joiner is pointless, especially one put through the 'centre' of the rib.......the upper spar is in compression, the lower in tension, so the stresses right in the centre are minimal. To make the carbon joiner have any significant effect, you'd have to make it very large in diameter. If you really want to beef it up but add minimal weight, adding some carbon toes across the join on the top of the upper spar and the underside of the lower spar is the way to go...this puts the reinforcement as far apart as possible, meaning they give their greatest benefit.

Phil

Hi Paul

Have you seen Richard Rawle and Steve Hollands 1/3 super Stearmen with RC wing walkers? They are fantastic .

Alan

Paul

Watching this with interest, good job so far.

Alan mentioned the Richard Rawle's, Breitling wing walkers, this may be of use?

http://www.youtube.com/user/iceboxvideo#p/u/15/H8ZoWnwCzaA

Paul

Watching this with interest, good job so far.

Alan mentioned the Richard Rawle's, Breitling wing walkers, this may be of use?

http://www.youtube.com/user/iceboxvideo#p/u/15/H8ZoWnwCzaA

I can say with some confidence that mine will not be that good. 

Paul

Day 14 - 52

Stress test - As most of you will already know, heating softens sprung steel but does not make it brittle as long as you let it cool naturally and don't false cool it with water or oil.  The sample I made needed over 50KG of pressure to bend and then I bent back and forth 20 tines without fracture, see pictures.  So in conclusion the parts I made would be up to holding the upper but would not be acceptable for under caridge.  Having said all that and done the tests I will be remaking with cold bends.

So not much time on the wing last night, just some sheeting to the top of the wing and one aileron, on the aileron when sheeting remember to sand before sheeting and overhang the sheeting to allow sanding back.  The first wing should now be ready to remove from the bench to complete the sheeting on the bottom.

Paul

OK it's a large chunk of humble pie for me

Went to shop and got 3/16" piano wire

Went to work and made a bender super robust out of man size metal

Found that it is possible to bend 3/16" wire cold

In working it cold to achieve a 6mm eye notice it got very hot during bending and when it came to cut of excess the properties had changed and made it very hard and possibly brittle.


Bert

No need for carbon.......remember this is a braced biplane......the wings do not need to be anywhere near as 'strong' as they would be in a canterlever monoplane

A carbon joiner is pointless, especially one put through the 'centre' of the rib.......the upper spar is in compression, the lower in tension, so the stresses right in the centre are minimal. To make the carbon joiner have any significant effect, you'd have to make it very large in diameter. If you really want to beef it up but add minimal weight, adding some carbon toes across the join on the top of the upper spar and the underside of the lower spar is the way to go...this puts the reinforcement as far apart as possible, meaning they give their greatest benefit.

Phil

OK then, thanks again for the advice, I won't waist my time with reinforcements. You just can't buy experience 

Day 15 - 56 hours
   
   Not had much time this last week, so just a small amount of progress.

Started sheeting the second wing and the first aileron, installed a lite ply servo horn mount and used balsa dust to secure inner joint of mount.

Wing sheeting this second wing was problematic in as much the sheeting was not as flexible as previous sheets and had to use lots of pins to hold it down.  The sheet nearer the center join has cracked along the grain resulting in a slight 50p shape, I think its ok as the glue is still well stuck, I intend on sanding smooth when fully dry.

Paul

'LITE PLY' servo horn mount?

Is this mount for a horn to be screwed to, or it it a 'pocket' of 2 pieces of Lite Ply that a glass board horn slides and is bonded into?. If it's the latter....fine, if not, then I'd seriously consider replaying said plate with decent birch ply. Self tapping screws, lite ply and load bearing areas do not mix

Phil

'LITE PLY' servo horn mount?

Is this mount for a horn to be screwed to, or it it a 'pocket' of 2 pieces of Lite Ply that a glass board horn slides and is bonded into?. If it's the latter....fine, if not, then I'd seriously consider replaying said plate with decent birch ply. Self tapping screws, lite ply and load bearing areas do not mix

Phil

Hmmm... Rookie error No.4, I will look in to this and make some modifications.

Paul

Day 16 - 60 hours

The lower wing is becoming a bit of a chore and is taking considerably longer than the upper wing. With the extra complexity and things not going smoothly I estimate this wing will take 3 or 4 times longer than the previous wing, even with the experience of the first one.

Installed balsa servo tray mounting blocks in one wing, started bending with wing tip sheeting, glued in some more sheeting.

See the split balsa sheet previously mentioned.  I intend on repairing this in situ, sanding and filling.

A couple of questions: Hinge installation? I have the hinges recommended, they are the flap plastic type with a metal pin for the hinge, like a standard house door hinge but smaller.  Is it ok to just glue into the balsa as plans?

Servo choice: No recommendation in the kit, I am intending on using a 4.6KG under sized servo for the ailerons, any knowledge on this would be helpful. Do you think this will be up to the job?  I am used to running 2 to 4 15KG servos on each aileron but this is not my usual type of plain, Some advice please!!

Paul

Hinges - YES

Servos - I'd avoid fitting mini servos on a primary control surface on a model of this size/weight/power. 4.5kg's per control surface is ample power wise, but you will run into problems durability wise. Small servos have small gear trains with minimal contact areas....subject these to high vibration and moderate flight loads and you run the risk of either wearing the servo (introducing slop) very quickly, or stripping it all together (Yes, even if it's metal geared servo....been there done that )

I'd fit a standard size servo, one per control surface, mounted on it's side in the 'fattest' part of the wing (just behind the main spar) and make sure the linkage between servo and control horn is a stiff as possible (use M3 not M2 hardwear). Connect a metal clevis to a heavy duty M3 ball link with steel M3 studding, and slide 3mm I/D carbon tube over the studding to stiffen................works a treat.

Phil

Day 17 - 61 hours

  Aileron servos: I have NOW chosen standard size Futaba 3010 servos, I will probably use these through out the entire build as they are a good solid servo that I have used before.

Mounts: So after a couple of hours thinking, scratching my head and talking to builder friend, I have decided to make up servo covers/mounts.

I used light ply covers and hard wood blocks and bearers sanded to shape, "see pictures", not completely finished but you should get the idea.  My intention is to drive the aileron from inside the wing so have no visible linkage.

Paul

Day 18 - 64 hours

Just a little more gluing and sheeting plus put first wing bolt seat and second servo mount bearer.

Paul

Hi 
Ziroli recommended Servos are   Ailerons (2) 90oz BB , Elevator (1) 100 oz BB ,Rudder (1) 100oz BB Throttle (1) 50oz BB I have used the JR 579 which are 8 Kg about 120oz.
I built this model last year it is powered by the OS  FR5-300 Radial using the Microsen onboard glow system, covered with ceconite ( sold by Belair ) and sprayed in Army colours, weight 24lbs , I used Aluminium for the struts annealing the alloy when bending covered with aluminium Streamline tube,    Good luck with your build   Jon             le

Day 17 - 61 hours

  Aileron servos: I have NOW chosen standard size Futaba 3010 servos, I will probably use these through out the entire build as they are a good solid servo that I have used before.

Mounts: So after a couple of hours thinking, scratching my head and talking to builder friend, I have decided to make up servo covers/mounts.

I used light ply covers and hard wood blocks and bearers sanded to shape, "see pictures", not completely finished but you should get the idea.  My intention is to drive the aileron from inside the wing so have no visible linkage.

Paul

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Day 19-20 - 68 hours

Not had a lot of time of late hence my lack of posts

The main changes I have made are the installation one wing servo and aileron plus a bit more sheeting, made up and installed a balsa tube for servo wire (Didn't have a cardboard to hand) and addition of shear webs in first wing.


Thanks "me" for the servo info, the servos I have selected are close to the recommended spec plus I intend on using one on each elevator, so Im going to stick with them.

Paul

Day 21 - 71 Hours

The first of the lower wing halves are ready for some minor filling and final sanding.

I used a little light ply to bridge the gap in the wing/aileron as the stinger was cut through for servo push rod etc.

so now on to the second half of the lower wing, looking forward to seeing this joined and then back to the fuz and fitting wings.

Although I have a very small amount of cut parts left from the kit, just the rudder and fin, I am feeling like Im only about 40% of the way through the build.  Does that sound about write?

Paul

If that!!....I always think when the construction is complete and you're ready for covering....you're 1/2 way through

If that!!....I always think when the construction is complete and you're ready for covering....you're 1/2 way through

OMG!  That means I'm only 1/2 way through the half way mark, or 25% done.  I need a drink...

OMG!  That means I'm only 1/2 way through the half way mark, or 25% done.  I need a drink...

Whats the rush? Take your time, do the best job you can and enjoy every minute 

Mud 

Absoloutly..........

You say 71 hrs to date........so 280-300 hrs for a 77" scale biplane..........sounds like pretty good going to me

Day 22 - 74 Hours

Second half of lower wing going a bit more smoothly, compared to the first half (Learning as I go).
So, some more sheeting on wing using PVA, same on aileron and Epoxy on second servo box as before this time I made it correct the first time.

"Mud flap" and "P51P47"  I don't think I'm rushing but I don't have anything to compare to and I am doing the best job I can (perhaps I will do better next time), I am still enjoin the build even if this lower wing is hard work at times, I just didn't realize how much time it would take plus I can't wait to fly it 

Paul

I don't think I'm rushing but I don't have anything to compare to and I am doing the best job I can (perhaps I will do better next time), I am still enjoin the build even if this lower wing is hard work at times, I just didn't realize how much time it would take plus I can't wait to fly it 

Paul, you're doing a grand job mate

To quote one of our respected members

Building is the key, flying is the reward

Keep up the good work


Mark