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Pete's Cavallino Rampante Italian Aerobatic Team Sabre


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Thanks for the questions guys

  1. I have doused layer 1 with resin. I have let it dry and will then apply layer 2. I did a shroud of peel ply draped over the top and pinned down each side to keep the fibreglass sheet flat, which sort of worked. The problem is that you can get bubbles. The peel ply does however soak up the excess resin, and keep the weight down.
  2. I don't put all the layers on at once because the resin wouldn't soak through 3 layers of cloth properly. I don't bag it No, thought it might not be a bad idea to do so. Dirk can no doubt advise.
  3. As to dispensing with the parcel tape, this was recommended by Paul Janssen the pioneer of lost foam for PSS. His site has been taken over by Maarten Werner. The method is described on his site here - **LINK** I think as he was using polyester resin which would had attacked, I think, the foam, whereas I am using epoxy resin which doesn't react. I do find, however, that the tape helps you pull the goo out in one go at the end. It also leaves a smooth inside surface, which admittedly is not what you want. So the jury is out and Dirk is the professional expert on the subject? What say you sir?
  4. I use Copydex to glue the sheets of Blue Foam together but it is difficult to get now and expensive. What is the best glue for this chaps?
  5. I use 3M77 to attach the cloth to the parcel tap but that is also expensive, any suggested alternative?
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  • 2 weeks later...

Thanks for all the great tips Dirk. Yes, shame you aren't in England but that is the disadvantage of being in slope free Belgium.

Anyway, all the cloth is now on, and I have done a top layer of epoxy/microballoons. And yes there were wrinkles - next time maybe follow the Tinck method. Must look back on this as and when.

This is before the acetone went in - what an almighty mess. This time I used thick smooth resin friendly gloves but the goo stuck to the gloves - any tips Dirk? Went everywhere....

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And without foam

 

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Edited By Peter Garsden on 29/01/2020 20:40:35

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The only problem with a fibreglass fuselage is that you have to make the formers fit afterwards from the inside which is a difficult fitting job.

I decided to use the same cradle (F15) for the taiplane bellcrank, F9 and F10. Getting them to fit was a labour of love. Try as you may you can't accurately replicate the shape of the fuselage. Anyway it is done now and everything glued in position. I used epoxy mixed with fibreglass powder to strengthen the joint. The fin seems to fit so it is a case of leave to dry.

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Fortunately the cradle seems to be more of less square ready for the pivot.

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F10 from the rear

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After fiddling around a lot I decided to cut a hole in the bottom of the fuselage at the rear in order to gain access to position F9. You can see that I had to join the formers together before I glued them in once I had sized each half to fit each side. I also added some 1/64" ply reinforcement across the join.

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Well finally I have formed the outside fairings for the tailplanes, and the bellcrank, wires and tubes.

I was wary of which order I put the bellcrank on the tube, and bent the wire. I have a strong vice, unlike some and was able to anchor the wire in the vice to bend it to the right angle using the very handy template. The secret is not to put the brass tube in the vice as it will squash and be unusable.

I found that the bellcrank will slide over the bend in the wires even after both sides are bent. This was welcome because I should have slid the spacers (made of circuit board) over the tube before bending the 2nd wire.

I decided not to use a brass tube for the rear pivot hole which I am sure will be fine. I think there would be enough space if you are careful with the pillar drill to form the hole for the tube

Before gluing in the brass tube, I made a slot in the balsa fairing then filled it afterwards with balsa. I also coated the wire with Vaseline to stop it sticking to the tube and make sure it stayed free.

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I have also formed the fin and tailplanes using my handy sanding disc which saves so much time. I also used it to form the farings which are not a perfect fit to the fuselage but are the same height as each other. I had to put filling pieces in to fill the gaps underneath and at the end.

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I'm going to cut out the rudder later when everything is fitted. We will need to fit in some filler pieces around the fin for the concave fairings either side. I will probably cover it with the film prior to gluing as well.

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I can see light at the end of the tunnel. I must admit that usually fibreglass fuselages are quicker, but in this case, because I have had to fit a number of formers to hang other bits on rather than for strength it has taken longer than usual.

I am only using F1, F4, F7, F9 and F10. I am omitting 2, 4,6, and 8. The problem is that I am having to fit the former whole rather than in halves for the fuselage so I am gluing them together and reinforcing the joint with some 1/32" ply for strength to take the strain when they are shoe horned into the inside of the fuselage. I am also roughing up the inside of the fuselage which is smooth from the parcel tape to provide a good join for the formers.

They are only 1/8 ply so I am adding short stringers to increase the gluing area.

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It is impossible to get the exact shape so fitting has to be done. I use my very handing shaping tool then matching it against the formers and sanding with my disc to the line.

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Amazing how you can use up off cuts, I think from the Skyhawk wing seat doublers.

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The stringers will point forwards as will the reinforcement doublers so you will not see any of this from the wing seat.

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This is F7 (behind the wing), which I have inserted to provide a mounting for my wing seat plate and guidance for my rudder wires. I will be redrawing the wing seat plate to span the fuselage. I am not using the F11 wing set bits because they won't fit into the slots due to the curvature of the fuselage. The wing seat will be quite stiff enough with front and rear formers going in.

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F1 from the rear showing some 1/4 square I have glued in to hold the battery box - there is no keel on my fuselage which would have cradled the box at the front. I will feed in the box after F4 has been glued in.

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F1 from the front - because of the curvature of the fuselage it would go in from the front which would have been easier. I had to push it in from the rear. I then used a syringe full of epoxy mixed with fibreglass powder to fill in the join with the edge of the fuselage and provide a fillet.

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I thought hard about how to secure the wing retaining bolt plate. I didn't want to just glue it to the side of a curved fuselage, which is mainly why I installed F7 so I could butt it onto the side as per the plan. I don't have any ply doublers so I glued in a support of 1/4 x 1/4 to F7 for the rear to sit on and fashioned some pieces of 1/2 balsa for the sides to rest on. I made it so I could slide it in and out.

I made the dowels for the front of the wing. To mark the position I spot glued some short pieces into F5, brushed some black acrylic onto the ends and slid the wing in which marked the hole positions, then drilled them out with ever increasing size drills as usual, then offered the wing up. I had to file away some of the fibreglass seating but it is a good fit.

I was then able to drill holes in the rear trailing edge from top through the wing and then the ply plate in one go. I put one in first, attached the bolt to hold it then drilled the second. Never been able to do that before. More accurate.

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There was a slight bubble in the rear wing seating which I cut away. I cut too much away so have patched it with 2 layers of glass cloth as the foreground shows. Next job is touching up any holes in the fibreglass with filler.

Edited By Peter Garsden on 21/02/2020 16:13:52

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So to the tailplane. I intentionally left the gluing of the tubes into the tailplane halves so that I could attach the wing, then line up the tailplanes with the fin temporarily slid into position. One everything was lined up, I pinned them into position and left them to dry. I have now filled the holes with some 3mm balsa scrap

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Finally, I glued the front nose intake pieces together, first of all drawing the lining up lines onto the wood to make sure they would sand down correctly.

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To get the right side profile, I made a cardboard template from the plan, which was very helpful.

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In this picture you can see the elevator and rudder servos in situ. I used up some scrap 1/16 sheet. I don't have a lot of 1/4 but have loads of 1/16 so laminated 4 sheets together using cyano then made up some curved supports out of 1/2 and epoxied in the tray once I had cut out some holes for the 1/4 birch hardwood to take the servo support screws.

As I said on another blog I am using the old faithful hitec 85mg for the elevator which has never let me down. The torque is about 3kg so hopefully more than enough for the 4mm carbon rod with a 2mm insert I will be using. It is now priced at over £20. I remember not long ago before Brexit when they would be priced at below £15.

I reckon that the load on the rudder closed loop system I will be using is less, so I am using a KST metal geared which is a bargain at £11 and 2kg of torque - **LINK** KST servos are excellent.

If you look in the picture you can see that I have added a piece of 1/16 ply to take the other closed loop wire. Incidentally it is a lot cheaper if you buy pike fishing trace rather than use a model supplier.

I am away skiing and it is blowing a hooley so using the time to catch up on my blog.

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Dirk deserves so much credit for inventing all sorts of extras and the hatch under the fin to gain access to the all moving tailplane mechanism is no exception. So, again, I copied Dirk's hatch using 2 pieces of Sullivan snake inner, and a screw with 1/64" ply to provide guides and a home for the screw with a piece of 1.5mm balsa underneath

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It was difficult making holes close to the bottom of the fuselage in F9 to take the plastic inners, but I used a small manual drill I have.

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Dirk deserves so much credit for inventing all sorts of extras and the hatch under the fin to gain access to the all moving tailplane mechanism is no exception. So, again, I copied Dirk's hatch using 2 pieces of Sullivan snake inner, and a screw with 1/64" ply to provide guides and a home for the screw with a piece of 1.5mm balsa underneath

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It was difficult making holes close to the bottom of the fuselage in F9 to take the plastic inners, but I used a small manual drill I have.

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Pete, your fuselage process reminds me of my MiG-15 1/10th scale that I started but never finished some years ago.

Here I was laying on the first fibreglass strips over the packing-tape-covered pink foam... and yes, Sir -- that same unbelievably godforsaken messy "is-ness" that you encountered from A to Z... foam dust, static cling, resin, gloves, brushes, fiberglass shards, silica dust, the works!

Note the extra strips lying there in the foreground...

 

It was my first attempt at doing anything in fiberglass... and after the resin dried I was dismayed by how dang HEAVY the fibreglass monster seemed to have come out... as in, I likely fell prey to the impulse to add more resin than was needed... something I had set out to AVOID, but maybe it happened anyway?

So... here's how the thing looked during the next step, rough-sanding the now-cured White Whale:

The leftover pizza and gin helped me to cheer up, as did the shiny insides that emerged when I cut the thing in half... turned out that I didn't even need to destroy the foam original plug in the process!

So I can fast-forward to NOW and your Sabre build is a real eye-opener. Lots of info about where and how next to proceed on this MiG-15 someday soon, especially with all these new Sabres out and about.   Love your detailed, info-packed build threads!

Edited By John H. Rood on 05/03/2020 18:47:59

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Excellent John, very interesting. Nice to see you without a scratch on your face. I have made 2 other fibreglass fuselages - the Tornado and the Alpha Jet, and both come out about the same weight as the balsa equivalents. Not weighed this one yet but it will be interesting to compare. This time I have put more infrastructure into the fuselage which may put the weight up certainly. Should probably have replaced them with balsa rather than ply - too late now.

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Well I am now doing the very tricky underwing fairings, which are very thin and have to follow compound curves - tricky indeed. The problem is that when balsa gets very thin it rips, unlike fibreglass.

So I used the tried and tested 40 grade sandpaper on the fuselage/wing and sand away until the balsa follows the shape then glue on and fill gaps with epoxy.

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First I did the front former which has the tricky triangular side bit. One then has to sand them hollow to follow the curve of the fuselage and wing. I used 1/2 inch then planed it down. I used a piece of dowel wrapped in wet and dry to get the concave curve effect.

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To make sure I got this the right way round I drew an arrow. In the end I cut it down the middle across the wing as it was easier to fit. This is 6mm.

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Following Dirk's excellent suggestion the rear piece rang the grain across. I made the wing bolt holes oversize, and finally added the rear pieces joined in the middle again to ease fitting. It is now drying to await sanding and planing. Note the cling film to stop the wing sticking in place.

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Well we are getting there.

Re the underneath fairings. I noticed that both front and back under wing fairings made from 6mm balsa had very fragile ends to them which would break off. I thus packed underneath them with Milliputty (2 pack mix together) and covered both the top and sides with 25gram fibreglass cloth. It is now a lot sturdier. I am still at bit apprehensive about weight but we must await a final weigh in.

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You can see the greenish wedge of putty and the glass fibre over the top.

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And the rear fairing

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I also decided to cover the wing bolt access plate with 25 gram cloth and water based epoxy (resin would have done). I am going to cover the wing and fuselage in heat shrink film (Glosstex by Solarfilm) but when I was unscrewing the wing bolts the screwdriver slipped out and put a ding in the balsa which I have now filled. The edges are also a bit delicate so I thought I would reinforce it. It certainly now is a lot stronger and ding resistant.

 

Edited By Peter Garsden on 10/03/2020 09:38:00

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I have also made my fin to tail triangular stock fillers ahead of gluing the fin in, principally because one has to sand them down to cope with the 3D complex shapes of the tailplane fairings and the curve of the fin. You can only do this with the fin out of the fuselage with sandpaper on a flat surface. I use coarse 60 grade.

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These are not yet glued in obviously. It is easier to make them in 2 or 3 pieces - other side is in 3 pieces.

And I have made a handy sanding tool, by stealing Dirk's intellectual property, except mine is made of wooden dowel, a piece of ply, and a metal rod glued in with epoxy. I think it will work well.

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I decided to cover the fin before gluing it in as it will be difficult enough to get the glue round the convex curves which bridge the join as it is. I lined everything up eg tailplanes before lining up and ensuring the fin is perpendicular before epoxing the fin in position and attaching the front fairing - also covered before gluing in.

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This photo shows the SLEC closed loop horn that I have glued in after roughing up the plastic for adherence. I also added some 1/32" ply surrounds to the slot which the horn fits in for extra strength, otherwise I fear that the horn would rip through the balsa if tugged hard.

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