Rich, if you haven't got some WBP varnish yet, I use the 'Ronseal Diamond Hard Floor Varnish', I get mine from the B&Q store.

It is a polyurethane based varnish and perfectly safe on all the foams I have used.

Originally Posted by eflightray

Rich, if you haven't got some WBP varnish yet, I use the 'Ronseal Diamond Hard Floor Varnish', I get mine from the B&Q store.

It is a polyurethane based varnish and perfectly safe on all the foams I have used.

I haven't got it yet - I'm making a trip to b and q tonight ... I'll put some in the basket! Had trouble finding water based. Cheers for the info
Rich

Originally Posted by eflightray

Rich, if you haven't got some WBP varnish yet, I use the 'Ronseal Diamond Hard Floor Varnish', I get mine from the B&Q store.

It is a polyurethane based varnish and perfectly safe on all the foams I have used.

Hi eflightray, is the ronseal varnish you speak of water based? is it possible to thin it down with water before applying to the plane?

noticed its quite pricey, do you reckon this would work?

Originally Posted by richie967

Hi eflightray, is the ronseal varnish you speak of water based? is it possible to thin it down with water before applying to the plane?

noticed its quite pricey, do you reckon this would work?

Yes, the Ronseal one is water soluble, and pricey. I have not tried to thin it down, I usually just give a model one final coat, (satin clear), it doesn't seem to add much weight and certainly adds to the skin strength.

The Wickes one does say 'water based', so should be Ok, though obviously do a test first, on bare Depron, painted Depron, and over any decals etc you may want to use. Some decals will wrinkle from the water base.

Depron can have a surface coating that makes paint pool, or separate, (a bit like painting over a greasy surface). A light sand, or a good stiff brush action applying a primer or paint usually works. I have used matt white emulsion paint as a primer, and the artists acrylic paints for finish colors.

Originally Posted by eflightray

Yes, the Ronseal one is water soluble, and pricey. I have not tried to thin it down, I usually just give a model one final coat, (satin clear), it doesn't seem to add much weight and certainly adds to the skin strength.

The Wickes one does say 'water based', so should be Ok, though obviously do a test first, on bare Depron, painted Depron, and over any decals etc you may want to use. Some decals will wrinkle from the water base.

Depron can have a surface coating that makes paint pool, or separate, (a bit like painting over a greasy surface). A light sand, or a good stiff brush action applying a primer or paint usually works. I have used matt white emulsion paint as a primer, and the artists acrylic paints for finish colors.

Cheers for the info, I plan on using it on Standard polystyrene, and standard EPP. I'll coat a test piece, then lay soaking wet brown paper on top - then paint the top, wait for it to dry, then add a final coat of Vernish. Should make for a nice skin. And should reduce the twist of non reinforced EPP wings.

R

Watch out for shrinkage causing a twist or bend. Where possible do the top and bottom of the wing at the same time, smallish sections are best, don't go for big areas in one go.

My scratch B-17, 100" span, has white foam cores with heavyweight tissue paper and thinned PVA glue skins. Another material is news paper, preferably without the print.

Originally Posted by eflightray

Watch out for shrinkage causing a twist or bend. Where possible do the top and bottom of the wing at the same time, smallish sections are best, don't go for big areas in one go.

My scratch B-17, 100" span, has white foam cores with heavyweight tissue paper and thinned PVA glue skins. Another material is news paper, preferably without the print.

Just Checked out your b-17, and might I add it is remarkable, a beautiful aircraft! If I lived closer, I would offer to do some air to air filming form my UAV!
R

Okay.... so i took the plunge and ordered £140 worth of bits for this plane...

Power System:
Turnigy L5055B-600 Brushless Outrunner 600kv
ZIPPY Flightmax 5000mAh 4S1P 30C
Hobbyking YEP 100A (2~6S) SBEC Brushless Speed controller
TURNIGY 8-15A UBEC for Lipoly
Hobbyking YEP ESC Programming Card

Prop and Data
I have also ordered 2 14x12 APC Thin electric props. Here are the Estimated Figures ..

around 65A, 7200 rpm and 2500 g of thrust on take-off,
7 m/s RoC,
70 mph top speed,
more than 40 minutes on eco cruise.

I have had help in the power systems forum choosing this setup.. Fingers crossed it'll work!

Servos
I am going to use 4 x Futaba full size servos for the plane. I already have these. Considered buying 4 Hitec full size new servos - but decided against it on this occasion. The Futabas should be okay.

In other news,
I bought the Wickes Water based varnish (i don't think its polyurethane, couldnt find it anywhere to buy) and some normal underlay paper to cover the ailerons. I covered the EPS Polystyrene Ailerons with the varnish, soaked the paper and laid it on, then painted a coat on top. They are currently drying. U had some old brown paper lying around as well. And am using this paper for the ailerons, Iam aware its a bit heavy. But will be using the lighter stuff for the wings.

They are currently drying standing up on their ends...They've been drying for 2 hours, but still dont feel that rigid, maybe they need longer before becoming stronger.

In other news, I have cut the large hatch which i will use to access and place all of the electronics. this needs to be well planned. Currently planning on where the rc, ardupilot, light module, video rx, gps etc will sit.

Tail is almost ready to be covered, its been quite difficult using traditional building techniques, i think i will simply order the tail in EPP next time!

The gear will be going on next...

Rich

My Next challenge is how to hold the wings on, I have drawn a diagram, does anyone have any better suggestions for holding the outer wing panels on?

They need to connect to the middle wing piece,

My Plan so far..

Not over keen on that method you have shown. Personally I would go for a round spar in a tube to take the load, then drop a pin through for locking.

I use that method regularly. Carbon wing tubes are available, (tube in a tube), though some use aluminium. I have used fiber glass tube spars, (ex cheap fishing rods from Poundland), even hardwood dowel into paper tubes, (my B-17 and B-25).

It all depends on the loading. For none aerobatic slope soarers, I have even seen the wing sections butt jointed together and tape wrapped round. The tape actually grips over a large surface area so works. Your plates and screws will concentrate the load very locally.

The sketch you show is more valid for full size or bigger models. How it'll work for your model is a little iffy. A lot will depend on the strength of that spar you've got showing.

If you insist on this method slop in the mounting holes will be hyper critical. An all but undetectable amount at the joiner plates will result in the wing tips being movable over a good inch or more. And as the holes in the wing and joiner plates wear, and they will, this wing tip flopping tendency will grow.

I'm afraid that Ray has the better option for joining the wings. Using the joiner in tube sliding fit greatly reduces the effect of the clearance needed to allow fitting things together

If you want to persue your method then a few hints. The plates should be made from G10 epoxyglass board or aircraft aluminium. Then metal bushings in the stub of the one side and precisely reamed holes in the plates would allow a precision ground locking pin to pass through the plates and wing stub to hold everything in place. And to leave less room for slop the stub joiner plates should be bonded and fixed to the center section.

Originally Posted by eflightray

Not over keen on that method you have shown. Personally I would go for a round spar in a tube to take the load, then drop a pin through for locking.

I use that method regularly. Carbon wing tubes are available, (tube in a tube), though some use aluminium. I have used fiber glass tube spars, (ex cheap fishing rods from Poundland), even hardwood dowel into paper tubes, (my B-17 and B-25).

It all depends on the loading. For none aerobatic slope soarers, I have even seen the wing sections butt jointed together and tape wrapped round. The tape actually grips over a large surface area so works. Your plates and screws will concentrate the load very locally.

Originally Posted by BMatthews

The sketch you show is more valid for full size or bigger models. How it'll work for your model is a little iffy. A lot will depend on the strength of that spar you've got showing.

If you insist on this method slop in the mounting holes will be hyper critical. An all but undetectable amount at the joiner plates will result in the wing tips being movable over a good inch or more. And as the holes in the wing and joiner plates wear, and they will, this wing tip flopping tendency will grow.

I'm afraid that Ray has the better option for joining the wings. Using the joiner in tube sliding fit greatly reduces the effect of the clearance needed to allow fitting things together

If you want to persue your method then a few hints. The plates should be made from G10 epoxyglass board or aircraft aluminium. Then metal bushings in the stub of the one side and precisely reamed holes in the plates would allow a precision ground locking pin to pass through the plates and wing stub to hold everything in place. And to leave less room for slop the stub joiner plates should be bonded and fixed to the center section.

Hi both, based on both your feedback, I am going to go with the pin in the tube method - as if this is tried and tested - I would much rather something that is more robust. There are 2 aluminium square tubes with an 8mm internal diameter that run through the 50cm internal wing panel, and 25 cm into the outer panels. I have 8mm carbon tube running through both of these. So will fill the ends of both of them with epoxy, and drill a hole through and use a pin to fix it in place.

One of the rods is not quite a meter long, so difficult to locate where is is as the entire alloy tube is 1m long. So will order another one. I guess with the pin method, i'd slide the pin in, then tape over it to stop it coming out in flight.

Currently working on wing joiners, Tail and landing gear. The power system has arrived, the motor is pretty chunky - not one to power on in the lounge!

Some pics and annotations of current progress....

Tail almost complete...

This was my first time doing ply formers and covering with solarfilm... I have learnt a few lessons:

1. Do not mount v tail servos on underside, as control surface horn should be mounted close to pivot point. I don't have enough throw on the elevator. Even with long servo arms.

2. Check servo speed prior to installing. Left v tail servo quicker than right, even though same model Number. Could be to do with the elev-gear mix I have setup on the dx6i.

3. Create slices for hinges to slide into. Had to glue hinges on top and duct taped them in place whilst waiting for epoxy to dry. This resulted in solarfilm ripping when removing tape.

4. Make the tail assembly out of EPP and cf next time!

away on hols for a week now, but hope to add landing gear next sat, bolt the motor on and try a maiden in 2 weeks!

Not completed much since back form hols, but I have some questions relating to this build...

Servo position
As part of the build I wanted to ensure that this plane could stand out in the rain for a few hours without water ingress to the electronics. This is fine for the Fuselage and aileron servos, as the fuse will be covered and a small neoprene seal made, and the aileron servos are on the underside.

The problem I have just discovered, is that even with long servo arms, the servos do not give enough deflection of the tail.. I have attached 3 photos of the neutral, elev up & elev down throws. It doesn't look enough - travel has also been increased to max. I guess the control horn should be mounted as close as possible to the pivot point to get maximum throw - but as i mounted them on the underside, and the hinge is on the top side, this has meant that there isn't enough travel. Any thoughts on how I can have the servos on the undeside of the tail, but increase deflection?

The plane does feel very heavy, but my maths are correct and it will weigh 4.5kg when built (I think it may even come in a few hundred grams less). It doesn't even seem like its going to fly its so heavy. But i guess there is plenty of wing area - wing loading is 22oz/sq ft.

Adding landing gear tonight....

what will cover the main wing?