Purbeck 1/3rd Scale DG800 Build Thread

[Simon WS]

Simon,
Epoxy certainly isn’t water soluble.
I tend to use Meths to clean brushes etc., but I think Acetone should work too.
I tend to use low viscosity (runny) epoxy, applied with a 2” roller, but have never tried to glass up to a living hinge so far.

Yes, I'm aware that epoxy resin isn't water soluble Peter having used about 20 gallons of the stuff on my ASG29! (I was referring to the G4 stuff I'm now using...) I also use very low viscosity epoxy from Easy Composites with slow rate hardener with a roller and I've never had problems before - it was a combo of the very light glass fabric/warm conditions/live hinges/planets aligning etc...

The G4 is definitely much easier to use on a number of levels - productivity is much higher because it cures in about 90 mins and is fully cured in about 4 hours. I've done the second wing now all in G4 and it is a vast improvement on the first half epoxy/half G4 one

I've noticed the same thing about common interests John. You will notice that the orientation of the Kettle (Suzuki GT750) changes in the photos - I've taken advantage of it just becoming MoT free and took it out for a spin!

Here's a quick garden fly - current weight 7.3 Kg






Simon

[catwok]

Lardy??? That's called built in inertia... looking Simon hope to see it flying before the end of the season (I'm still waiting for a good westerly)

[Geoff Pearce]

Lardy??? That's called built in inertia... looking Simon hope to see it flying before the end of the season (I'm still waiting for a good westerly)

Things don't change, still waiting for a good blow !

[roo Hawkins]

Looking good simon. It is making me think about wanting to maybe start a build myself. Especially after the Fox. Looking at your build may encourage me to start maybe? ??????????????????????.ROO

[Simon WS]

Thanks Joser. Using G4 is really simple. Just lay the dry lightweight cloth on the surface and then paint (or use a foam roller on large surfaces) the G4 on top. It will bleed through the cloth and stick it to the surface. When I did it I did apply sanding sealer and let it cure before the G4 to avoid it soaking into the balsa or obechi but I have heard of people doing it without that step - comments from others? If in doubt I think I would be inclined to do a test panel without sanding sealer, weighed before and after and see what the weight gain is.
When the G4 is cured I find the easiest way of trimming off the overhang is just to rub a bit of sandpaper on a block across it and it will neatly cut the excess off.

I think AEB has used G4 quite a bit - any comments John?

Simon

[Peter Balcombe]

Simon/Joser,
I agree with Simon in that it is a good idea to seal the balsa prior to adding any glass as this prevents a lot of epoxy soaking into the wood and adding weight.
I always apply my epoxy using a 2” foam roller as this is very straightforward with modern less viscous resins.

[john greenfield]

Simon/Joser,
I agree with Simon in that it is a good idea to seal the balsa prior to adding any glass as this prevents a lot of epoxy soaking into the wood and adding weight.
I always apply my epoxy using a 2” foam roller as this is very straightforward with modern less viscous resins.

Peter
G4 is not epoxy and it is used very differently. Do not seal the wood first as it significantly reduces the bond of the cloth to the wood.
Lay the glass cloth onto the surface to be covered and smooth out with your hands so it is laying reasonably flat. Starting in the middle put a very small amount of G4 on the brush (dip it no more than 1/4" into the pot of G4) and start brushing very lightly whilst supporting the cloth from pulling with your other hand. Using very light strokes spread the G4 as far as it will go. Once the first couple of brushes of G4 have been laid down the cloth will be stuck to the surface sufficiently to avoid the need to support it from pulling with your hand. At this stage, all you are trying to do is get the minimum amount of G4 onto the model to hold the cloth down. Any wet or glossy areas mean you have put too much G4 on. You are not trying to fill the weave at this stage and an excess of G4 will cause the cloth to float off the surface and run the risk of sanding through it later. Using a roller will put too much G4 onto the surface and just add weight.
Once the whole surface has been covered let dry (45 to 90 mins) and then trim the edges with 320 grit wet and dry used dry. This will feather the edge to nothing. Repeat the process for the other side of the part you are covering.
Once dry and trimmed brush another LIGHT coat onto the surface spreading the G4 as far as it will go. Depending on the openness of the weave of the glass cloth this may be all you need before painting but if the weave is still a bit open apply a third LIGHT coat.
Final flatting down before applying paint should be done within 2 to 3 days of applying the G4 as after that it is very hard to sand.
In short, think of putting G4 on as more like painting, and not applying epoxy.

AEB

[Peter Balcombe]

My apologies John.
I’ve not actually used G4 before.
Peter

[roo Hawkins]

Hi simon how much g4 are you using and what weight cloth are you using. Just wondering how far it goes may have to use it myself. Roo

[Simon WS]

I used 25g cloth Roo and although I didn't do it like John suggests (because I had already treated the surfaces with sanding sealer) it went on beautifully anyway (and much easier than epoxy). I only bought a 500g tin of G4 but I have done 3 x 2.5m wing surfaces already and there will be enough to do the tailplane (without sanding sealer this time!).
I bought the G4 from eBay and the 500g was only £12.49 delivered - but in retrospect I should have got the 1Kg tin of G4 for only another £5. It is very cost effective, even though I have done it "wrong"!

Simon