Thank you chaps....I am about to embark on a test piece. Shouldn't be much different from the paper/packing tape technique, just with the all important slop omitted, we shall see!

Well I have to say I was expecting an intractable lump of glass, resin and aluminium but it worked perfectly!

I waxed and lubed the ali tube and then two wraps of clingfilm with an additional coating of Vaseline. I bagged it for about 5hrs, then left it in the foot well of the car with the heater on while I went for a drive. It slipped out easily and I was able to remove the clingfilm by grabbing the end with a pair of pliers and twisting it out.

No slop and despite this being a quick test piece and a little lacking in thickness, it'll be usable as a tube for the incidence rods.

Nice work on the no slop joint. It is a tricky process and I can imagine that you have added a few steps to achieve the good result.

Small folds brought about by the bagging process, might be able to cure this by wrapping the thing tape before bagging.

The small folds never bothered me inasmuch as they are extra material. I would rough sand them off just for looks. With your installation, there is no need to sand the folds. Since the sleeves are completely encapsulated by other layups, they do not need to be terribly strong. Just strong enough to hold there shape when installed in the spar. If you wanted to use the ali. tubes as joiners, those sleeves maybe good to go as is.

BTW, not everybody bothers to vac bag. If you wrap the lay up with Kevlar thread as Guitarcher suggests, you'd still get a good tight slop free fit and no vac bag induced fold line. Now I want to try it again.

160 x 12k tows for the semi-span joiners

Time to cut the cores for the inner panels.

I've made a new bow to handle the denser foam that I bought last week. Using some thicker nichrome wire
and reducing the bow width gave me a bit too much heat so I went back to the smaller dia wire. After a bit
of fiddling to increase the tension we're good to go!

All cores cut

I got a tiny bit of rippling on the first cut, but this was a result of having the core too close
to the drop arm.....perfect cuts after that!

I'll need to make up a couple of templates so I can accurately slice out the area where the
spar goes. I should be ready to bond it in some time next week, then the joiners, then the
wing skins. Maiden early in the New Year perhaps?

Nicely done.Its what’s hidden inside that matters

It's full of love inside Stuart....or did you want to see what the surface cut was like?

In the mean time it's been fill-sand-repeat. Just the last round to do now, I reverted back to using
normal interior filler as the dry micro balloons mix was still a bit too hard and was also tricky
to work with.

I've also decided to slightly reshape the canopy area to reduce its height slightly and also to
smooth the curve of it when viewed in profile. I'll hit this with the last round of sanding.

Originally Posted by miniphase

Time to cut the cores for the inner panels.

I've made a new bow to handle the denser foam that I bought last week. Using some thicker nichrome wire
and reducing the bow width gave me a bit too much heat so I went back to the smaller dia wire. After a bit
of fiddling to increase the tension we're good to go!

Nice bow, simple and effective auto tensioning system.

Nice cores too! What density foam, the reason I ask is if it's greater than 25psi I'd be very interested in where you obtained it.
Thanks
Curtis

So many curves...............so delicate.
You must have an array of specialty sanders.

Originally Posted by miniphase

It's full of love inside Stuart....or did you want to see what the surface cut was like?

In the mean time it's been fill-sand-repeat. Just the last round to do now, I reverted back to using
normal interior filler as the dry micro balloons mix was still a bit too hard and was also tricky
to work with.

I've also decided to slightly reshape the canopy area to reduce its height slightly and also to
smooth the curve of it when viewed in profile. I'll hit this with the last round of sanding.

For future reference this stuff is ideal for filling foam.Sands really well

https://www.ebay.co.uk/p/Woodland-Sc...d=161616835162

Curtis- Good to hear that you like the bow....I love its simplicity, it makes cutting cores a lot easier if you have less to worry about with the set-up.

The density of the foam is 250kpa which Google tells me is just over 36psi...it goes under the trade name of Hexatherm. Not sure if it's avaiable in the US though.

Kent- I thought I was going to have to make a few shaped sanding blocks, but I smoothed the filler over with a wet, flexible scraper before it went hard and then just curled the sand paper I was using it as needed. The sand paper is quite stiff and the filler is super easy to sand so it was a very easy process.

Stuart- I'll take a look at that filler, could be handy for projects where weight gain is an issue. I see there are a few Youtube videos on how to make your own....


I'm now thinking ahead to laying up the ply on the cores. The one problem area will be getting the leading edge to adhere to the curve of the core. The sample at the start of this build proves it can be done, but I need a way of making sure I can keep everything aligned as I vacuum bag it.

With this in mind I'm planning to make a jig to support the core and the skins. Before epoxying up the ply, I mask off a few area along the leading edge, the add the epoxy, remove the masking tape, add 5 min epoxy to these areas.

I can then put everything in the jig and the 5 min epoxy spots will locally bond the ply to the foam. I can then lift the while lot out, put it on the foam beds in the bag, seal the bag, clap the leading edge down, then the trailing edge and then apply the vacuum. Thus alignment of the skins on the cores will be maintained.....hopefully!

I think I may need to do a little test length of this method to avoid any upset!

So it is a 2 step process. First to fix the skins to the cores in the proper alignment, then vac bag. Not entirely sure that I am following every detail of this process, but will throw this idea out for your amusement.

You can take advantage of different cure rates in one session and no special jig. Mark a strip on the skins and the core as shown in the sketch. Apply thick 5 minute epoxy/microballoons to the skin and core in this strip and wipe it all off with a squeegee. This will leave just enough epoxy to bond. Then apply slow epoxy for normal skin attachment on the remainder of the skin. Stack up the assembly so that the 5 minute epoxy strip is in contact and block all materials in place. I use bricks. Let the 5 minute epoxy go off and carefully place into the vac bag.

Let the skins overhang the cores at the LE. They can be trimmed later. Just focus on getting the TE alignment right.

There are a lot of variations on this concept.

edit: added TE to skin

edit 2: replace 5 minute epoxy with double stick tape if you can tolerate the alignment process with the instant grab tape.

OK, this process has me a little concerned about getting the TE fully bonded in the right position.

If you broke it out into many steps, each step would be easier with a high quality TE as the result. It isn't really more work, just more wait cycles.

1. vac bag the bottom skin on to the core
2. sand the bottom skin at core for perfect alignment. Use tape to protect foam
3. vac bag on top skin with over hang at TE. cure then sand TE.

With the use of the foam beds, the final profile should be maintained.

In my mind, where the ply abuts the leading edge block is the critical point. If I can get this right in the jig, it's easier to close the ply around the core and the trailing edge will look after itself when I close the skins. As much as I hate CAD, I've drawn the core up with the ply skins on so I can accurately cut them to size and know they'll fit.

My biggest concern with adhering the skins around the spar area would be my ability to then sand a decent, 5+ metres worth of straight face to bond the leading edge block to.

Shall I make a little movie of my approach with a test piece? There's every chance it could reach its climax with me throwing it the bin and having a serious strop!