Repairing a 3D Angel "Jigsaw"

[Edgeflyer]

This popular Sebart electric aerobat is an artf kit that suffered severe damage in a crash. I acquired it as a challenge and I just like salvaging formerly expensive planes on the cheap.

It's the Sebart Angel EVO 50. Front end is wrecked and the wing saddle area is likewise a mess.

The new fuselage parts would be no longer available, other similar spare fuselages from the sebart 50 series are over £100. My challenge having got the model with 4 good servos and the wings and rear of the fuse pretty much unscathed, for a very reasonable amount (i. e. less than the cost of new servos) is to effect reasonable repairs to a fairly tidy, flyable state at minimal outlay.

One of the big challenges is to get the wing mount and root ribs strong enough without losing the geometry.

So I begin by carefully working out an order to pull the bits together and strengthen some as I go while letting other areas be strengthened later when the structure is established.

These modern artf are very light and relatively very strong for their weight, but once the structure is disturbed they seem to disintegrate like a glass vessel.

The motor mount box is a bit sad but I am hopeful and if this doesn't work out I can redesign the front for a more traditional structure. Adding some weight will be unavoidable but given the power to weight ratio of the brushless setup, this won't be too awful

The wing joiner tube supports are completely out, so this will be a critical repair area.

I've managed to slot the assembly back in with superphatic to make an initial repair with a view to internal bracing when the rest is in place.

[alex nicol]

Watching with interest.

Ive had the misfortune of 'rekitting' a couple of artf's, the method I've used is to build a jig to hold/support the structure and cyano all the original parts in place ( no matter how small) once this is done it should be strong enough to handle unsupported.

Next step it to apply lightweight glass cloth on the outside of the fus over the glued parts. Warm the epoxy in the microwave before mixing to reduce the viscosity apply cloth and epoxy then cover with acetate sheet and squeegee any excess epoxy off and leave for 24 hrs to dry. once dry remove the acetate sheet. Done properly it'll leave you a very strong lightweight repair with a smooth glass like finish.

Good luck with your repair

[Edgeflyer]

Thank you. I did consider glassing over the repaired area. I don't want to remove the covering from the rear half, so I will have to have a step where the glass cloth starts.

[Colin Carpenter]

All credit to you for attempting this ! Looking forward to the reconstruction ! Reminds me of my Sebart Shark where the motor mount delaminated in mid air 😨 . I thought the spinner had come adrift , cut the throttle immediately and started a deadstick. As it got nearer we could see the motor hanging out the front of the fuselage . All the bits were in the bottom of the cowl so I was able to reconstruct it for a pattern. It was an early version bought secondhand . Never flown ! There were no gussets behind the mount and I rebuilt it adding some. The cowl had bits broken , but as a boat racer used to rebuilding grp hulls , this didn't present a problem. Flew perfectly when rebuilt. Colin

[Edgeflyer]

Thanks that encourages me that maybe it will fly again after all the puzzles are solved.

Next stage is to get the engine mounting box to a point where it can be reattached.

The top panel and one side are mostly missing and I think I need to establish a square structure first so my plan is to attach additional panels from 0.8 ply. There is room inside the cowl area.

So I've measured and guessed and drawn them on card.

Then fretted them from ply. Although one side and bottom are OK I'm inclined to cover those too to keep a kind of balance in the stresses.

Top and one side glued and clamped. The other side will go on at the same time as attaching to the fuselage front I hope.

It's quite interesting problem solving.

You also get an insight into where these artfs are a bit deficient, even though they are technologically very clever.

There are places where joints didn't have enough glue.

And places where its hard to imagine having the equivalent of a 50 size glow motor hanging off bits of 0.8mm ply.

[Colin Carpenter]

With 3 Sebart 30’s in the hangar and 1 foamie , I think the secret of longevity is to stick to Sebs power train , and to keep the speed down in the dive ! Not only did my Shark disintegrate in mid air , a club mates Angel 50 had the mount disintegrate on landing as it touched down ! A bit of mount reinforcement doesn’t go amiss ! But they are beautiful flyers ! Colin

[Edgeflyer]

The engine mount box assembled and glued into place

[Colin Carpenter]

Excellent work . I take it there's nothing left of the cowl ? Dumfries models may keep them ??? Colin

[Edgeflyer]

Yes electric models are good for repairing as no oil contaminates, however I've found these artfs use poor quality ply and balsa that splinter and crack easily. If this had had a glow engine, all the ply components would be delaminated by now.

Yes the cowl and canopy will also need extensive repairs. To buy new ones would cost more than the entire project so far so I'd like to persevere.

[Edgeflyer]

Next challenge...

The internal panel that supports the battery, rx etc does not look strong following the front end / wing root damage.

So my plan is to fibreglass over the area, followed by an additional panel and link these to the wing joiner tube..

After making a card pattern here is the 0.8mm ply panel being fitted. Fibreglass and resin will be placed then the ply bonded on top with more resin. This should compensate for the missing bits in the original plate.

The front bulkhead that mounts the motor will need similar treatment as the crash stress has caused some splintering of the top ply of the motor mount.

[Edgeflyer]

The plate fitted over FG cloth and resin

The wing joiner tube wrapped in FG cloth which spans the ply plates, hopefully this will be strong enough to take the wing stresses.

The front motor plate being FG coated. Screw holes temporarily plugged with bits of nylon screw, which will be drilled out when the resin is set. The cloth here is the wing joiner bandage type.

Beginning to work on finishing the fuse front sides.

Having put in all the bits, I've covered with lightweight cloth and resin to consolidate before more filling etc.

[Edgeflyer]

How it started

[Colin Carpenter]

Well Phil , that cowl doesn't look too bad from pic ! You've got half of it ! How come it's not in pieces if the woodworks that smashed ? Colin

[Edgeflyer]

Yes the cowl is not too bad. It must have taken a side swipe which took off the whole front and strained the wings and several fuselage formers.

The canopy however is poor. I may be able to get the shape from it and design something.

When the original owner comes maybe he'll tell the story of the crash. Something to do with gyro settings I think.

[Colin Carpenter]

Canopy is only an acetate material. Get some sheet and bend it with heat and glue and shape. Look ok I’m sure. Keep up good work. Colin

[Edgeflyer]

Having removed some covering for repairs, the new covering will need support strips where the joins come.

I've acquired a reasonable canopy to replace the original which is not really usable. It's the alternative colour scheme but I can work around it. Still needs a few repairs.

It came with a spare wing set in need of some repairs.

[Edgeflyer]

Final bits of the jigsaw glued in. Several had to be made from scrap.

Repair area on first side covered in lightweight fibreglass with epoxy. When the sides are both covered they will be filled and flattened.

[Edgeflyer]

After glassing the repair area both sides, they are sanded to begin to flatten, then low spots filled with epoxy /glass balloons mixed runny. Covered with Solartex backing to allow squeegeeing flattish. Sanding when set.

Work begins on repairing the replacement canopy.

I'm wondering what glue the factory uses to stick acetate to the ply framework. It is very effective. The acetate cracks and ply breaks but they never separate. Research suggests it may be Loctite 401, a high quality cyano type so I've ordered some.

[Geoff S]

You're doing a great job. Somehow repairing someone else's disaster is quite therapeutic - you've got everything to gain and little to lose except a few materials and time.

It'll be interesting to know how much heavier the repaired airframe is and how it affects the flight performance.

\geoff

[cymaz]

I admire your patience and tenacity

[Edgeflyer]

Final flattening of sides, checking fitting of wing mounting before covering the repaired sides. Canopy and cowl repairs and fittings next.

[Colin Carpenter]

Cracking job ! I would have purchased a new one !😂😂

[Edgeflyer]

Thanks for positive comments.

Having fitted the wings, I'm thinking a little more structure is required following the crash that, on hitting a wing tip, ripped out all the central wing joiner section.

First step an extra cross piece / former from 0.8 ply.

I quite enjoy fretting these and don't need a Cad laser cutter yet!

[Colin Carpenter]

Phil ! How’s it progressing ? Colin

[Andy Stephenson]

I have an almost perfect set of Angel wings that were rescued from a fuz write-off if any one is interested, no reasonable offer refused. Blue colour scheme.

Andy.