Finishing for first class results

Hi There,

With Johann currently tackling his second attempt at a moldable plug I thought I would post some pictures of my method , which is by no means the only way of doing things, but works for me.

Although 2k paint sometimes sticks in the molding of the plug , this is most likely due to problems with the release agent and not the paint. B.T.W. this type of paint 2k has been very successfully used in all the team built Shongololo's of Evans building groups, and is still my favorite when spraying a plug and polishing it, or the mold surfaces of a hollow molded glider.

After the blue foam plug is nicely sanded to shape and layed up ,with in this case 3 x 163 gr cloth layers, I sand it smooth with 180grit paper, especially glass cloth join lines.

Then the whole plug is layed up with a layer of 104 or 86gram fine cloth, I add a small amount of micro balloons to this resin layup , this aids in filling pinholes. You will see that although the foam is blue the resin/balloons make it look whiteish.

The plug is now wet sanded with 220grit , the surface becomes smoother and any imperfections are filled and repaired.

The product shown left is an epoxy based finishing resin , it is a two part and seals the surface well and is easy to sand.

Its available in most good hobby shops.

I make a mix of this and add microballoons , this finishing layer is screeded onto the plug and gives a high build smooth coat , as you can see, this is then waterpapered with 480 grit wet and a few drops of dishwashing liquid in the water.

This surface seals the foam from any solvents and provides a good surface onto which you can spray.

My larger plugs were finished in a similar way

but instead of the ZAP finishing resin I finish with a 2 part polyester spray filler (but care is needed as this stuff eats the foam , if it's exposed.)

I trust this may be of help to modellers out there.

Note 2K paint contains ISOCYANATE (a Cyanide derivative) in the harderner which is bad for you, so always wear a respirator and protective clothing.

Happy building.

Thanks for all the support and guidance especially from Evan and Mike. It seems like this has turned into a bit of a process....
I have not had a chance to respond to your e-mails, but I'll get there!
Evan, we managed to get the coating that you recommended for the plug. We tried several places and between only selling the paint in 5l tins at R1600.00 we finally managed to get a litre. I hope it is the correct one! the trade name is SIGMAGUARD HS which is described as a two component high solids polyamine cured epoxy coating and comes in a green grey colour.
The curing times seem to be a bit of an issue as it is described as 20 hours min between coats and 10 days for final cure.....
That means we will only cast our moulds in January......
Vic has given up on us and has proceeded to build a fuse out of balsa. (He has the time and it's his preferred building technique anyway) It may be a blessing in disguise as we can use the prototype to iron out all the gremlins. We'll post some pictures as he progresses.

Meanwhile Daron and I can dream about our future composite plane and colour schemes whilst we wait!


Mmmmm Daron likes black and yellow....

Hi there Mike, Evan & Vic

Thanks for the support that you have provided so far. I must say that some things you mentioned are so logical that I can't believe we never thought it thru such as casting the otherside of the mould without removing the Plug.


Plug number 2


Anyway, The new plug has been shaped and layered up with one 50g cloth and one 200g layer. We have re sanded and got back to shape with minor blemishes.
Should we put on another layer of glass, as I noticed the previous plug developed small pressure indentations during the final sanding and polishing phase?

Our wings are progressing well with some help from Vic Oxley who is an old hand at constructing built up wings. He has kindly undertaken to construct the wings for us. We would love to try bagging, but without a vacuum pump and the suitable knowledge, we will leave this process in abeyance for the time being.
Vic has been building and flying in our area for the last thirty years or so!


Vic Oxley hard at work in his workshop


The foam cores have been cut and he has elected to build a balsa covered wing which poses a bit of head scratching as regards the fixing of the wing to the body.

The thought has been to cut the"canopy" opening down to the bottom edge below the wing so that the wing can be bolted down to the lower section of the fuse and the enlarged canopy will be shaped to the top of the wing profile. It may help to have a removable wing and we are looking to put a centrally placed servo for the ailerons....
We're getting ahead of ourselves!

Thanks for all your positive comments and support.
Kind regards
Johann & Daron

Johann & Daron

It all starts somewhere......
It was about messing around on the Internet, browsing to see what planes were around, when we happened to come across the Jart web site. After looking around the local builders and seeing Adrian's build thread it made us believe we too could build this plane..... how hard could it be?
The fact that neither of us had built a scratch plane (balsa or glass), other than damage repair, did not deter us.
We sourced some Iso board and shaped the plug... so far so good
Then read up on all the epoxy and paint coating specs.....
glassed and painted....
( not without mishaps)
And we were the proud parents of a Plug!!!!
All shiny and smooth.
This was then laid up as described by Evan and others

My daughters got so exited when they saw their Dad busy with blue paint that they volunteered to help....

This only lasted for 5 minutes until they discovered that it was all gooey and did not come off.

The splitter board came off with no problem.

And......

It STUCK.....

I'm trying to get over it!

I must admit it's hard not to just give up.

I'll give it a day or so to come to terms with my short comings...

I suppose it's part of the learning curve and life's rich tapestry of experience.

We'll post some more pictues of our next build....

Progress - down the twisty road now!!

Wings out of the bag, root ribs had to be ditched as I forgot about trimming to the fuselage angle before adding the ribs....

I used a rubber polising wheel on the dremel to dig out the foam. You can go right up against the skin without damaging it and it eats up the foam no problem.

Then I mixed a strong cotton flock mixture (with no cabosil to allow it to run) and

poured it in the gap. The leading edge was dug out to about 50mm to seat the alignment peg - a 5mm diameter length of music wire fitted with an alignment tool - just an old printed circuit board with two holes drilled through it.

A bit of paint, some articulation and a new twf pnf toy is born!!

Articulation

Side on -

Full turn!

Look Ma, no elevator- no aileron ................ no Brakes!!

Just two servo's to fit (DS8711's with plenty amandla) and a ledge for the canopy and were are done.

ps - anyone else done a twf Jart in SA?

Fuz

No I have'nt just been sitting around but trawling the internet for acticles and advice on fibreglassing techniques. Also been shaping the fuselage and finally got enough confidence to do my first fibreglass project. All done now and expoxied, in the process of micro balloons and sanding to get to some resemblance of the finishes I see produced by the Jarters. I think the fuselage is a little plumper than it should be as I did'nt allow for the thickness of the glass etc. Looks cool though. Pic's to follow. Also got a wing and stab from Adrian so that should shorten the final programme.

Wings!

Some progress with the wings at last.

I 3M77éd the aramid leading edge cloth on again, this time with copious 3M. Added a vertical grain balsa subrib at the end of the joiner tube to spread the load out to the skins.

Then I added a strip of peel ply to the mylar leading edge with double sided tape making sure the peel ply extends +- 25mm past the mylar leading edge. This way, once you put a strip of bias cut glass onto the aramid and place the mylar just short of the leading edge the peel ply gives a beautifully "pre-finished"leading edge. (As per Mark Stockton's

Tabooish build thread at http://www.rcgroups.com/forums/showthread.php?t=634176 )

Well, no more excuses, the layup on this one is all glass, 1 of 25g veil cloth, 2 off 163g and a half span strip of 163g all on the bias.

Much anticipation later, burnt out the old switch on the vacuum pump, replaced on the fly and out came the wings, sheer magic, biggest bagging job yet, check the leading edge! (all untrimmed and not yet sanded at all)

It Flies what else?

Well finally the second Jart had its maiden flight, this last weekend at Volksrust, a group of us went down for the weekend. On saterday afternoon the wind had swung easterly and really picked up so we moved to the eastern point and I decided to give it a go.

This Jart is light it weighs just under 1kg and is fitted with two nice MG digital no name brand servo,s which I am trying for the first time.

The launch was uneventfull and she only needed a few clicks of up, this one is a little faster than my first one which has an MH32 airfoil . I also programmed in some flapperon which helps slow down for landings.

Anyway the first flight was a blast and on the sunday I tried a second flight in lighter air which resulted in a nasty tipstall and flick , you need to keep the speed up on these gliders, so due to the lack of good lift I safely landed.

I guess it's on to planning Jart number three .

Cheers

Mike

Ps I highly recommend you get yourself one they fly great.

Joiner success!

Just opened up the second carbon joiner and it's much better!

The tube is 12,5mm id and that takes 159 tows to fill completely so this time I cut 100 which is just over 60%. I also had an extra 20 in case this was too loose after coating with resin. As it turned out I used the extra 20 so my carbon content is just over 75%. It took all my weight on the joiner with the wire in the vice to get the tows through - very slowly!

My method for wetting out was to keep the wire hook in place and place the tows on a plastic sheeting covered bench, pour out about 80% of the resin and roll it with a ribbed roller. Turn over and add the rest of the resin and roll and roll and roll....

Evan just mentioned to me today that he dunks all of the carbon tows into the resin container (whilst keeping the looped end on the wire pull through) and squeezes out the excess which sounds much quicker!

New joiner is 65g, old one was 57 g, better fit and finish plus more strength!

On to the wings next time.

Time to do it again!

In the time honoured Jart tradition of learning new and fun stuff - sometimes you have to do it again!

The aluminium tube used to make the carbon wing joiner rod took a lot longer to dissolve in caustic soda than I had thought. Thanks Mike for the suggestion to put Dremel grooves on each side almost right though - even then it took two days to get through the grooves!

The calculation I used was 40% carbon 60% resin (very pessimistic) and when wet out it was way too easy to pull through the tube. I increased the carbon to 50% by area and it was much tighter so I left it at that.

Clearly not quite enough carbon as you can see - next time it's 60% carbon and if that isn't a really tight fit then add a bit more!

Just to make it a full house the motor I installed to power my vacuum pump had a faulty nameplate. It says it's S1 duty rated, i.e. continuous running but this was incorrect leading to massive heat build up and bad smells! It was set to run for half an hour then wait an hour as the vacuum regulator switch is giving problems. (It was not pressing foam but a wing mould so the very high vacuum was ok).

Oh well, the wing is next, just after the vacuum pump is re-built and a quick trip to the Berg next week!

Anyone know where to get a proper vacuum switch – Festo’s one is nearly R1000 while Joewoodworker.com’s sells one for only $25 but won’t ship to South Africa!?

Hot Jart

Well I got a chance to do a little final decorating , this is often determined ,by the colours I am spraying , as I line up a few plane projects for spraying at the same time .

Yesterday I mixed up some bright red 2k to finish off the yellow Jart and also spray up some mylars for a thermal ship which has been sidelined for some time.

First off I decided on a pattern and started masking with some plastic tape which gives nice sharp lines.

Next I masked and covered the entire plane , if there is any small overspray, this can be polished off later.

I layed down 2 x coats of 2k red and let it flash off, which is quick with the fast harderner.

As soon as its touch dry I remove the masking , carefully lifting the plastic tape. It all came out

rather well and with the red paint still pliable there is no chance of flaking or chipping which happens if you de-mask after a couple of days cure.

Final touch a JART sticker and now I will cut the ailerons and elevator and start the plumbing.

Wing progress

Bit slow on the wing progress, hope that I don't have the same problem with the paint that Evan had (see earlier posts by Evan re Eskom induced delays) as my stab and wing mylars were painted at the same time!

The joiner tube is a bit large so it needed filing down. The reason for the size is that the carbon joiner needs a fair amount of carbon in it and the aluminium tube is quite thick walled.


This is the joiner tube area after the first application of epoxy-cabosil-cotton flocks-micro balloon mixture. Some voids still need filling.

The aluminium tube with its carbon tows ready for insertion after resin application.



I am using the standard Reed specified S6062 at 7,95% thickness. For the stab I used an aramid leading edge but this was a bit tricky as I did it at the same time as the bagging! Not as per the experts and it was made even trickier because I only 3M77éd the stab halves together. Epoxy dissolves the bond after a short time...

For the wings Í discussed the layup with Craig (thanks!) and also used Joe Wurts' spreadsheet (http://www.charlesriverrc.org/artic...vacbaglayup.htm) which gives some comfort that things won't just break apart in mid air (as opposed to the more common/acceptable ground breakage!).

All the glass for the wings has been cut and is just waiting for the final sanding of the joiner tube areas while I debate whether to put on an aramid leading edge....

Started!

Finally, after ages of planning, reading and thinking I've just got a fresh Jart stab out of the bag, very chuffed as it's my second bagging attempt and the wow factor when you open a "To Dad, From Dad" present inside the bag is superb!

The leading edge and trailing edges just need trimming now.

Craig Goodrum and Evan Shaw's composite courses at AMT made it go pretty easy so it's on to the wings which came out great (thanks Mike for the template tip! - use thick Formica and a home-made feather cut).

The wings are going to be two piece for ease of transport. I discussed the wing joiner rod with Craig and I'm going to use the tows-in-a-disappearing-aluminium-tube idea. Pictures to follow as it's being done.

Thanks again Mike for your help and Reed for the generosity with the free plans for this beautiful plane!

Vic

About to start

Got the plan from Reed awhile ago and been threatening to start. Finally had chat to Adrian and see that I have a lot to learn and a long way to go. Anyway have made the decision to plunge headlong into this build. Going to get pdf printed and buy some foam and get started. (My son is on 6 weeks holidays and if I get going maybe I can entice him to get his hands dirty)


Here goes.

Jart 3 Canopy

Some good progress this last weekend on this build, I managed to join together all the big pieces,and it is now a Jart.













I fill the join lines and the wing shoulder gusset with micro balloons and some cloth on the wing and tailplane join lines.

After carefully cutting out the canopy, I make two small pieces in the mould, I dont spray the mould , the yellow in this case is pigment in the resin, these are the rough pieces on the wing nearest.











These pieces o about 4 layers of cloth are cut so that they fit on the inside of the fuselage and being flexable and more or less the right contour,
are easy to position and epoxy in place.











In this photo the lip is epoxied in place and the pegs hold two pieces of ply , which will be drilled to accept two small self tapping screws which hold the canopy on.










In the final picture the tear drop canopy has been sprayed black and the rest final coats of yellow.

Next I need to cut out the ailerons and elevator and wire up the servos.

At the moment it weighs 740 grams and feels lightish but battery , radio gear and balancing will change all that.

Hope this one flies even better than the red one.

I have done a slightly different canopy shape, but still starting ahead of the leadind edge so that I can still fit in a fair battery pack and full size receiver in its protective foam.

Some stripes next to tell the top from the bottom , important when doing rolls as these things roll , at a rate nothing short of a frenzy.

Jart 3

Nothing like practice, Jart 3 the white fuselage popped out the moulds no problem. If you build a glass model that you think you may want several of , its always a good idea to pull a mould, especially off a smaller model .If one crashes (does that ever happen to you) you can simply make another.

I am pleased ,I had made a mould , as my RED jart flies great so it is a well proven design. It also allows a fair amount of experimentation , with different lay-ups.

I am sure ,Glen from Durban will appreciate this as he is busy with his Jart using the lost foam technique, and the accompaning sanding and sanding.

PS. for the very sharp eyed, you will note I had in fact previously built a white fuselage so this is in fact Jart 4 , that one was traded to a licensed Jart Plan owner for 4 sheets of blue foam a fair swap I think.

JART no 2 and 3

A little Jart building at last, I sprayed up my moulds a nice rich yellow some months ago and put them aside to finish other projects . Recent outings with my red Jart have really been fun so time to get cracking on number 2 Jart, you cant have to much of a good thing ,you know.

The fuselage came out nice and strong and is now ready to be cut for wings, tailplane and canopy.

The yellow wing is blue foam with 1 layer of 104 gr glass then a lengthways 100 gr UD carbon and finally a 163 gr glass at 45 degress, it all feels nice and stiff and now needs to be trimmed and cleaned up on the leading and trailing edges.

The current weight of these two parts is 680 grams , but it still needs assembly of a tailplane and radio gear. they fly great at about 1.2 to 1.5kg in a fair blow.


With several "white" model projects on the go I always keep my moulds waxed up , and if for some reason some mixed 2k is available I go ahead and spray any excess paint into the next mould , so white it is . These fuselages are also perfect for using up all those off cuts of glass , these I sort and store in seperate plastic bags by glass weight and shapes.

















The third Jart out of the mould is going to be white , and I laid up some ud carbon cross ways
were the wing and taiplane bond onto the fuselage.
Some nice red and blue striping would make this an attractive colour scheme?
go build your own Jart.

Glen Jart progress

I did tell you not to expect too much progress in the short term, but surprisingly, there has been a little.... Last Friday I was able to hand the "completed to this stage" fuselage over to Jacques for him to cut the wings,fin etc. Once this has been done, I will take the fuz back, blend in the wing fillets and fin, and prep for final spray of undercoat and colour. Did I mention that Jacques is planning to make his Jart a 2 piece removable wing option, so that transport to and from the slope is easier?


Again, many thanks to Mike May for his invaluable advice and motivation, especially during the epoxy and balloons/sanding stages.


Pictures of the project so far.....














Lots of carbon goodness for extra strength and vitalty.



Done at last - after lots of filling and sanding. Maybe my lack of glassing skills have something to do with it.

See what Mike Ma(y)de me do!

Well, it all started with Adrian B in Cape Town being reluctant to part with a blemished Jart fuselage and then followed by the non appearance of Santa down my chimney in December 2007, so it was decided that there was only one thing left to do! Seeing as the mysteries of composite construction were being unravelled to this newbie via another project I had embarked on (also coutesy of Mike May and the Sungazer event), I decided that, with advice from Mike only being a phone call away, that I would try my hand at this Jart thing. Please, dont expect miracles and hope to see this thing fly before December this year (2008), as I am a slow builder with LOTS of distractions. I checked the other day - I received my plans from Reed in March 2006! (does that tell you something).


By the way, this plane is being built for my flying buddy and neighbour Jacques, who will be assisting along the way.


Here is the progress (or lack of) so far....

Fuselage shaped out of isoboard foam, with first layer of very thin glass cloth added. Dont ask me details such as weight of glass cloth etc because I dont have a clue - I just do what Mike tells me to.....

More to follow in the coming months.

Mikes Jarts No 2,3

With the local gliding scene moving to the thermal competetions there has been a break in Jart activity.

The sucess of my red Jart has prompted me to build 2 more, my son has his eye on one , so I am glad I bothered to make a mould.

I spray the moulds and , during other layup projects I use the off cut glass cloth , that comes from wing layups were the roll is cut at 45 degrees and there are big off cuts. I then build Jart and other fuselages.

Will post progress of these two as I go

later.

Mike's Jart

Well back from Volksrust , and maidened the JART successfully, a group of us went down for 4 days and generally the wind seemed to really pick up in the afternoons.
The first day the wind was ok for Zaggi flying but just not enough for the JART.
Thursday produced better conditions on the south slope so I decided to give the Jart a go.
It went straight out and only needed two clicks of up trim, left and right was spot on.

The video shows the moment of truth , unfortunately the wind dropped after a few minutes, and the jart just could not maintain altitude , it landed about 20 mtrs down the slope but was unharmed.

In the afternoon later in the day the wind swung easterly and we flew the eastern point , great lift and the Jart was, in its element it does all the things everyone raves about , its smooth flying when it has a some speed is most impressive , it does not like to be slowed down . The landing was down wind in a bit of a rotor and it cartwheeled on landing , slitting the nose open. That evening I rejoined the split which was on the join line with some cloth and it was good to go.

Saterday saw us back on the Northwest slope this time and at about 14-00 hours the air looked Jartish ready, this flight went off all wobbly until I realised I had the max rate set on my dual rate switch for ailerons a quick flick and she settled down nicely.

This flight was excellent and I pushed the Jart a little more with rolls and loops, what made it really special was that for the first time Blake my son stood next to me flying his Zaggi totally unaided so he has pretty much gone solo. The landing was fast and smooth with only a little flare, right at the end to prevent the nose(pointy in case you havent noticed)from spiking the ground.....

conclusion its a lovely design looks great in the air and is a perfornance machine ,well worth building one.

PS I have already started no 2. and have completed the fuselage already,I will post a mini build thread as I go , not so much the construction but the enhancements to the red no 1.

cheers for now.