Wolfgang Matts Arrow

[Andy Green]

Lovely job Sam, looking forward to seeing the complete model.

A

[Sam Wragg]

Thanks for the kind words, I was wondering that I may be being too long winded in my explanation in the build of Arrow. I will also endeavor to answer any questions as i go along to the best of my ability.

Gorilla Glue.... I have found that as soon as air gets to it, the glue starts to thicken in the bottle from the top down. To try and slow this process down I squeeze as much air as possible out of the bottle then put the cap back on and store the bottle upside down. As for spreading it thinly i make a scraper out of 1/16 balsa cut to the width required and use this to thinly spread the glue.

For wing skins i spread the glue on the skin dampen the foam core with a damp sponge and apply the skin.

Lifting Veneer... Personally i would discard the wings & contact Steve Dunning or your preferred supplier and get some new cores cut. Because if you haven't got the outer foam shut you could induce twists into the wing core and also with the cost of balsa sheet it would be false economy in trying to retrieve the wings.

I hope this answers your questions

Back to Arrow.

When i left off i highlighted the saw cuts in the Mdf template. This is the reason why.

If you look at the image you can see where I have marked out for the ply cross webs. I then re-position the Mdf template and use a Jigsaw blade to form my slot through the template

I carefully saw the slot down to the bottom skin (not through it) and then blow all the debris out

I then cut a piece of card to the same width of the slot and trace the outline of the wing onto the card

I cut out the outline then trace round it onto the card to produce the outline of the underside skin (mirror image)

I then cut out the outline. locate the card in the slot and trace the outline of the top skin

I then cut the template about 5mm past the outline of the top skin. This is done for a reason and will explain further as I go along.

Using the card I make 4 off 1/16" ply webs. I carefully rounding the edges with sand paper so as it makes it easier to slide the ply webs into the slots cut in the wing

Position the webs into the slots and mark out for the bearers.

Now you can see why i left the ply webs long.....It gives you something to grip when you remove the ply webs

Beach bearers and ply webs all marked up accordingly waiting for the next stage.

Sam

[Sam Wragg]

Final stage

 

Now everything is cut out the final op before assembly is to cut out the bearers in the ply webs

Before using a Fret saw i drill 2/3mm holes in the corners for the blade to drop into

Now the assembly begins

Using my Mdf template i cut out the 1/16 balsa floor

Using my template as a guage for the floor lining

Floor glued in position using Gorilla glue

Side walls lined with 1/16 balsa

Prior to this I Pre-formed the wheel lining by steaming the 1/.16 balsa linings and using a tie wrap to form the bend leaving the balsa to dry out

Sides lined

Wells lined.

Trail fitting of the Bearers

Check to see if the retracts are flush then mark out the ply webs to the outline of the surface

Ply webs now ready to be trimmed

The complete assy glued in position. For this operation I use Laminating epoxy resin as it penetrates the surrounding area and gives a better bond.

Next stage is to produce a balsa in-fill for the spring on the wire leg.

Glued in position.

Marking out the balsa in-fill prior to gluing in (using laminating epoxy)

At last the finished Wheel well sanded flush.

The next stage is to mark out the position of the Aileron servo boxes.

Sam

Edited By Sam Wragg on 22/01/2015 15:11:22

[Martyn K]

Fantastic

[Jack Banner]

Neat, methodical work. Excellent.

I am looking forward to seeing the Aileron servo boxes too!

[Sam Wragg]

Thanks for the kind comments. Bashing balsa is a lot easier than precision machining steal castings weighing up to 400 ton (and cleaner).

Not looking forward to the servo boxes because mistakenly i discarded all my jigs a number of years ago simply because i couldn't see me building again due to the emergence of Artf models + I'd lost interest in the hobby.

Thanks to Classic Pattern I'm like a kid in a sweet shop again.

Decisions decisions? Arrow is designed with flaps but todays radios allow for mixing, so is incorporating the Flap system necessary? I suppose i will have to decide whether to keep Arrow as designed or simply use mixing. this decision affects the amount of servo boxes required.

[David Oxilia]

Sam,

fantastic work as always!

If I may weigh in with my personal biases... given the amount of work and effort you are putting into this classic build, I'd suggest going with the flaps. I built some in to a later simpler Prettner model that didn't call for them originally, the Calypso, but am happy with having built them in. They do help in bleeding off speed on landing and give you the extra amount of lift to really slow the model down. Plus, you can do some cool things with them aerobatically.

Servo wise what I used was one center mounted servo for the flaps on two "traditionally aileron" torque rods into the flaps. The pushrod is simply a forked assembly going to the servo and each torque arm. You can also install the servo on its side for absolute linear deflection on the surfaces to insure they are both moving the exact amount otherwise you end up with roll effects. Two identical "half-H" bend pushrods can also be used wire wrapped and CA'd or JB Welded at the pushrod end leaving one of the wires longer than the other for a ball link (or Z-bend) connection.

For the ailerons, well, nowadays there is little to it simply using one servo per aileron. The question is whether to mount them in boxes vertically or on ply plates horizontally with a recess in the wing to accommodate the servo. The former is easier (I build mine out of 3/32" or 1/8" balsa but 1/8" poplar can also be used) and results in rotary movement of the servo arm (which is fine). The latter also allows you to exit a servo arm out of the ply plate for linear movement and is a little cleaner under wing at the expense of a little more weight and build time. Again, personally, I go with straight-up pockets for the ailerons and a center wing opening for a side mounted flap servo on a 1/8" light ply tray and hardwood arms for the servo mount flanges. One can build the pockets outside of the wing (4 sides and a floor to separate the walls) and produce the hole on the inner wall for the lead and use a pair of 1/4" x 3/8" HW braces at each end for the mounting. A simple X-acto blade can be used to make the wing cutouts using the box as a template. I like to use Estes rocket tubes in the core for the lead tunnels but paper or simply foam (of it is cut clean) suffices.

She's not far from the finish stage!

David

[Sam Wragg]

Hi David

As always wise words and sound advice, I think I was suffering from retract well fatigue. A few days away from the board has given me fresh impetus. I kinda new what I was going to do and feeling fresh again I'm going to crack on with the build.

My decision is to use 4 servos to control each surface. I have identified and purchased my choice of servos. For the Ailerons I will be using JR Ds3401 and for the Flaps, Savox SH-0256. These servos have enough pulling power and will allow to be installed vertically & flush with the wing surface.

Sam

[Sam Wragg]

Before I can start on the Wing servo boxes i have to make myself a pair of Vee Blocks,

Datum edge marked on

Finished pair of Vee's. Note the drilled and chamfered hole in the base of the Vee. This is for securing to the bench to prevent movement

You're all probably wondering why I have to make these replacements to the ones I discarded some while ago first of all? ......... all will become clearer at a later stage

With some outside Calipers(made by yours truly as an apprentice) measure the depth of the servo (allow for the thickness of the wing skins)

You can now determine the the minimum thickness of the wing were you cannot exceed when determining the position of the servo

Using a cardboard template (allowing for the 1/8 Balsa lining) mark out the servo positions.

Continuing with the Router theme I make another Jig

Jig made out of 9mm Mdf

With the wing sat in its shut on the bench set Jig level in its required position

Rout the servo box to depth

With the rebates routed out Lay the wing on the bench and set the Center line of the wing level

Using my Scribing Block (again made by yours truly as an apprentice) determine the position of the Servo wire run.

Transfer the position to the Root and mark out

The next stage is to determine the the run of the servo cable(s) through the wing

Center line of the hole for the servo cable marked out.

With the center line of the wing still level on the bench screw the Vee Blocks in posistion ready to drill the hole for the servo cable.

For this operation I use a straight length of 3/8 Aluminium tube and file on a cutting edge at one end.

Cutting tube laid in position

I only drill 1" deep at a time to prevent clogging, then withdraw the tube and remove the waste material and then carry on drilling 1" at a time.

Bulls eye ! !......the tube exits exactly where i wanted it to.

I know it may seem long winded but the extra effort is worthwhile when it comes to the final assembly

[Sam Wragg]

Now that the servo recesses and cable runs are cut into the wing panels I can now start on the servo boxes. There are a couple of ways to do this operation, this is my method.

First cut the well floor to fit the recess using 1/16 balsa

Place the floor lining into position(not glued) then make a cardboard template of the sides and cut the 1/8 balsa to fit. Using super glue tack the balsa side to the to the balsa floor whilst in situ. Doing it this way allows you to achieve a perfect fit of the servo box

Servo box withdrawn from recess with surface marked out. (JR servo)

Savox servo

Align servo to the required position

Bearers position marked out

Same with savox

Modified Router with 1/8 ply fastened to the base with guide edge glued in position

Machining slots for 3mm light ply Bearers

Machined slots

Light ply bearers glued in position with thin super glue wicked into the joints (on the inside)

Access for servo cable cut in.

Final trial fit before gluing in using Gorilla glue.

Finished wing panel. All that's required before joining together is drilling the access holes for the retract air lines.

Sam

[SR 71]

Fantastic Mr Teacher sir, again a super lecture, and again a lot of information learnt

Thank you Sam

[Sam Wragg]

Unfortunately Work Work Work has got in the way of Arrow, so finally this week end we have managed to find time to crack on with the final stages of the build.

 

Time to join the wing panels.

Wing Panel with the top surface laid flat then raised 5mm up at the root then weighted with wedges holding the wing center line true in position awaiting the opposite panel to be offered up

Wing panels aligned and glued together using 15 min Epoxy.

Sam

Edited By Sam Wragg on 01/03/2015 17:51:46

[Sam Wragg]

In the initial stage in building the fuselage it became apparent we was going to have Fuel tank issues as the tank specified was clearly intended for competitive flying giving you just enough duration to fly a schedule.

Experience dictates that fitting 14oz tank is the correct size using a 60/90 engine for everyday flying giving roughly a 10min engine run.

Looking at all the readily available tanks it was looking like 10oz was the maximum size that would fit simply because clearance was required for the fuel lines up at the bulkhead for the engine pump unit? In a flash of inspiration I remembered I used to use Mk & Tetra tanks. A quick search and I found that a 14oz Bubble-less Tetra tank would fit (just). This was obtained from Central Hobbies.

As you can see the tank just fits but a Well is required cutting into the wing to clear the tank.

To be Continued

Sam

[David Oxilia]

Sam,

Tettra and MK tanks are great. Good to see you found something that fits.

You should also take a look at the Hayes Slimline tanks carried by Tower (and others). They are specifically designed for the type of installation needed in classics such as the Arrow where there is a nose gear below the tank. They are also very resilient where pumped engines are used - they won't split (I duct tape them anyway). They make up for the shallowness with width and length but it is rare that they interfere with the wing.

They don't make a 14 oz slim but they have a 12 and a 16. Here is a link:

http://www3.towerhobbies.com/cgi-bin/wti0095p?FVPROFIL=&FVSEARCH=%3Cb%3Ehayes%3C%2Fb%3E+slimline+fuel+%3Cb%3Etank%3C%2Fb%3Es

Nice to see you get to the final stages of the build.

Cheers, David

[Paul Jefferies]

Rather than cutting a well into the wing, try to modify the shape of the tank. I seem to remember modifying a tank back in the day........ Use heat to soften that bit of the tank, you can use your thumbs to push it in but it will be quite hot so use a bit of cloth or some gloves as insulation. Push that corner in and then plunge it into cold water and it should stay "deformed". I think I used a heat gun but you need to be a bit careful as it would be possible to melt the tank completely! You may find that boiling water poured over the relevant area will get it hot enough.........

Paul

[Sam Wragg]

Paul great tip, Dave thanks for the link i will no doubt use for future planed builds.

I decided to rout a 5/8 deep recess to overcome the issue the tank fouling.

5/8 deep recess prior to lining with 1/16 Balsa

Lined recess.... Note 1/16 ply cross brace web sunk in 1.1/2" back from the leading edge to support the Wing Dowel

Problem solved. I can now glass the center section of Arrows wing

Sam

[Sam Wragg]

All work and no pleasure is slowing thing down now but beginning to see the end of the build now, all that is required is to manufacture the Belly pan and form the Wing fairings.

Belly Pan

A simple task of cutting some 3/8 Balsa sides (Tack glued on)

Note the 1/16 gap between the L.E/T.E of the Fuzz

Top sheeting in place (Gorilla Glue) then carved and sanded to profile before removing the belly pan from the wing

Completed Belly pan prior to covering

Wing Fairing

This was achieved by bonding 1/32 ply to the fuselage and Gorilla glue to fill any gaps using the wing to hold the ply in position then in-filled with 1/2" triangular carved to shape prior to gluing on using Cyano then filling using Model Lite filler

Arrow "in the flesh"

All that's now required is a bit of titivating before Epoxy Glassing the fuzz/Belly pan & Pro-Filming the Wing and Tail surfaces

Sam

[Martyn K]

Sam

That looks absolutely fantastic.. Really looking forward to see her fly..

Martyn

[Martyn K]

Sam

Are you planning to use Peel Ply when you glass the fuselage. I have been given a hint that polyester cloth works just as well.

**LINK**

and

**LINK**

M

[Sam Wragg]

Hi Martyn,

Over the years I have read up & tried many methods of glassing and come to the conclusion that unless you use the Vac Bag technique you can guarantee one thing........ plenty of elbow grease will be required, some more than others.

Nevertheless I have developed my own preferred method that seems to work but still not looking forward to undertaking with the only driving factors of that it strengthens the airframe and completely fuel proofs it.

If there's enough interest i will give a step by step account on my method as I go along

Sam

[Peter Android]

Sam , Please do so . your build blogs / skills are enjoyed by many captive - nuts ...........

[Martyn K]

+1 for that

Martyn

[Andy Green]

Would like to see how you do it Sam, so + 1 from me.

Andy

[Sam Wragg]

Right then fellow enthusiasts here we go,

First of all i don't want to come across that my method is the best as I know there are various methods that other modelers use and prefer. My way of glassing was learned over years of trail and error and every time I glassed another model I learned a bit more until I developed my own preferred method.

First of all the key element to glassing is surface preparation, time spent on this stage dictates the outcome of the final finish of the model.

Firstly I take my time and spend many hours filling any surface defect with lightweight filler and sanding back the surface using sand paper & sanding pads until I'm happy.

I'm only happy when i can hold the model up to the light run my fingers over the surface and can see nor feel any surface blemish

These are the sanding pads I use which are obtainable from Automotive paint suppliers and can be used Wet or Dry

What I find is that these pads follow the shape of the surface allowing for an even all over finish.

On average it will take me around a week to prepare the surface.

Sam

Edited By Sam Wragg on 30/03/2015 11:04:28

[Martyn K]

 

"On average it will take me around a week to prepare the surface."

 

I can see straight away what I am doing wrong..

M

Edited By Martyn K on 30/03/2015 14:40:12