Pete's Cavallino Rampante Italian Aerobatic Team Sabre

[Peter Garsden]

So to the fairings or more accurately fill in the curve of the fuselage over the wing.

First I made some paper templates for the lower sheeting

1/64" Ply is the only way to go as it is flexible enough. I covered the bottom of the fuselage with clear film I use for the plans - it is florist wrapping which is ideal. I should actually have used cling film which would have been better because it is flexible.

I then applied a coating of Cyano to where it meets the bottom of the fuselage and pushed both sides into place. The important thing is that it must follow the dihedral of the wing

I then had to make wedges of 3/16 scrap balsa to support the side sheet of 1/64" ply and push the front and back down to follow the wing. I used my profile tracer I have shown earlier in this blog to map out the curve for each support piece which worked really well. I now have to make another paper template to follow the side pieces, which will also be of 1/64" ply

[Peter Garsden]

This is my exhaust as mentioned on Phil's blog. It is not as effective as the A4 Skyhawk because the exhaust is larger and not as recessed. The test, I suppose is when it gets into the sky!

This shows the advantage of a fibreglass fuselage - thin walls.

The disadvantage usually quoted is weight, but I think we are going to end up with the same weight as the prototype ie. about 4lbs.

Edited By Peter Garsden on 03/04/2020 08:03:34

[Peter Garsden]

Well I think I am done, finally. Have put some panel lines on the yellow mainly to break it up as recommended by Phil. Looks OK. Why am I always first to finish? Good and colourful scheme. I just weighed it at 4lb 71/2oz, which is heavier than I wanted. I did have to add 125gram/4oz of lead in the nose, however. I was aiming for 4lbs so whether mine will cope with 12mph we will have to wait and see.

It was sunny outside just so did a plane on the grass pose. Problem is, flying is banned at the moment so I will have to wait for a sunny day.

Edited By Peter Garsden on 04/04/2020 18:49:53

[dan h]

hi pete

looks fantastic great job

[Phil Cooke]

Great job Pete - it looks the business! A great coloursheme - I really like the gloss red and blue against that antique cream!

[Callsign Tarnish]

What's the final weight Peter and have you calculated a wing loading?

[Martin Gay]

Hi Pete,

As a ballpark figure, there is something like three square feet of wing area on the model.

That will give you a wing loading of about 23.6 ounces per square foot. Pretty good for PSS.

A weight of 3.5lbs will give a wing loading figure of just over 18 ounces per square foot.

Martin.

[Peter Garsden]

Thanks Martin, just what I needed. At that wing loading it won't be a light wind version!

[Martin Gay]

Anything above 20mph on the Orme should be fine. Below that and your Canberra will be flying!

[Harry Twist]

Hi Peter, looks fabulous.. looks like its going fast when its standing still! Well done on the completion, stunning colour scheme.

[Peter Garsden]

Maiden Flight - Sunday 5th July 2020, Mermaid Pool, Leek, Staffordshire, England.

It was a blustery day up at 1,500 feet above Rudyard Lake near the Roches in Staffordshire England. The wind was blowing at between 25mph and 35mph. The D60's and D80's were going a storm, so I figured there was enough wind to try out the Sabre. This is where they hold the Scale Day each year in August. There is a good landing area to use.

PSS models generally do not fly well here. Whilst it is a good slope for sports models, PSS models do tend to just hang there and not really perform well. The Orme is a much better test, and there is a fly in this weekend, so we will have to see.

This model has an all moving tailplane so it is difficult to judge angles. I got Martin to launch. As you can see from the video I needed more down. I adjusted the sub-trim and launched again. This time it soared away. It still needed a bit more up elevator. I have adjusted it at the clevis now ready for next time.

It is difficult to judge but it seemed difficult to gain height even in that wind. The all up weight is 4.5lbs which is about 8oz more than most examples (about 23oz per square foot). I put this down to heavy Glosstex covering, which I reckon added 1lb. Whilst it flew well, the fuselage seemed to wobble from side to side a bit. It was not overly sensitive on elevator as would suggest a c of g too far back. It was however very sensitive on ailerons as most swept wing models are.

I landed and decoupled the flaps from the ailerons. I had them mixed in. This seemed to give a much better and less twitchy aileron response.

I used a closed loop rudder with long tubes from the fuselage. I have tightened up the cables in case that is what the problem was. In other words the wind catching the rudder and throwing the model around in the very strong wind. The rudder is now a lot tighter.

It didn't feel quite right, however, though it did fly. I only have the launch on video unfortunately.

I went back home and tried out the c of g on my new Vanessa Launch winch. I reckon it was about 5mm too far back, so I have added some more weight to the nose but have not tried it again. Watch out for the next post when it is sorted.

Oh and a big thank you to Brian for the pictures and video.

Edited By Peter Garsden on 09/07/2020 13:35:49

Edited By Peter Garsden on 09/07/2020 13:36:24

[Steve Houghton]

Pete,

Congratulations on your maiden. Glad it went well.

That's a really nice looking model - great work.

[Phil Cooke]

Great work Pete - somehow you are always the first to finish and fly the Mass Build subject ahead of the event! Impressive stuff!

I look forward to seeing your new model in action on a more suitable slope this weekend - lets just hope we get the winds for our sport!?

[Peter Garsden]

Last weekend - 22nd and 23rd May 2021 was the much anticipated first event since lock down at the Orme. Unusually for the end of May the wind was from the North West, which meant we were flying from the slope by the cafe, Difficult to launch and fly from due to the shape of the cliff at that point.

 

The landing area is narrow but is bordered on one side by the cliff and the other side by the rock strewn launch area. Also one has to avoid the car park and the road. Tricky n'est-ce pas? I flew 3 models and crashed 3 - not a good record. The Sabre crashed on launch rather than landing, but it is difficult launch because of its shape - low wing and fat nose. Nothing really to get hold of. Ironically my first flight landing was perfect - because it has flaps that I thought were unnecessary, but this jet flies very fast. So in a difficult to land area it helped slow it down a lot.

 

2nd flight was oh oh....the wind had dropped and more speed was needed on launch - it went up then down vertically, landing very close the edge of the lower ledge and a watery grave.

 

It had landed on its nose and one wing. Because I had built a strong fibreglass nose and the wing was balsa it took the hit and cracked across the lower sheeting. The top sheeting buckled. I thought the spars were intact and I was right. Just one web easily replaced had broken.

 

 

This is the underside of the wing. You can see that the break is at a point of weakness where the fairing ends.

 

 

The lower half of the wing showing that I have poured hot cyano around the area in that getting glue into the join would be difficult. It held, however, remarkably well.

 

 

This shows the same crack from the top. Helpfully it is not on the edge, so I laid over 2 layers of 25 gram cloth. I also replaced the webbing with 3mm instead of 1.5mm as the original had cracked down the middle.

 

 

 

This photo shows the rear lined with the 25 gram cloth (thank you John Hey for the tip - great idea).

 

It also shows, however, the block of balsa I added to the plan build, which I may remove. There was discussion on the blogs about what would make the plastic wing bolts snap - there are 2 - and it was thought that if there was little gap between the hard surfaces it would assist a snap. As the wing broke and the bolts didn't I wonder?

 

Does anyone have any theories? 

Edited May 26, 2021 by Peter Garsden

[Peter Garsden]

To get the shape of the 1.5mm balsa accurately, I used paper templates and pencil rubbings. Worked very well as, after fitting the shapes fitted nice and tightly.

 

 

[Phil Cooke]

Nice job Pete, Im sorry to see you having to repair your Sabre but it looks like you've done a great job and quickly after the event too!!

 

[Peter Garsden]

After a fateful crash at the same site as the above picture ie the NW Cafe Slope of the Orme, from whence the Warden in his wisdom and partly due to use allegedly upsetting the nesting chuffing Choughs (no jokes please), as a result of which I wrote the wing off, I have decided to make a new wing, this time in foam and veneer.

 

I think the C of G was too far forward because upon launch in admittedly a light wind, the model dived headlong downwards and hit the far cliff. Fortunately it avoided a watery grave, and Phil Cooke, God bless him, scaled down the almost vertical slope and retrieved it.

 

The problem is that I have made a fibreglass fuselage with wing fairings which is too rigid for the flexibility of the built up wing. It has now broken 4 times, so I am going to provide more reinforcement in the new wing with a diamond shaped piece of fibreglass wing joining cloth, and some plywood wing joiners.

 

Phil from Cloud Models skilfully cut me some veneer covered black foam wings to exactly the right shape which was helpful. I sent him the plans for the built up version.

 

I have now attached the leading and trailing edge. I am just working out how to feed the wires through to the servos. There is a hole near the trailing edge which I am hoping to use and has been bored through for that purpose methinks.

 

 

One can see the handy masking tape method to stop the David Plane cutting off bits of veneer.

 

 

[Peter Garsden]

Apologies, I have made some progress but not taken pictures. Please see, however the servo mounts which I made by scooping out foam with my wire foam cutter then lining the hole with 0.8mm ply and gluing in the servo mounts I took out of the old wing. I am going to cover the surface with some clear plastic, iron on some film and selotape them on. The point is that as the Sable lands flat on the wing one cannot have clevises sticking out the bottom, so all control rods poke through the top of the wing. Note that I left a bit of wire pudding inside the recess, should I have to take them out again.

 

 

I also had to make holes for the flap servos. Phil from Cloud Models had already made holes for the aileron servos which came out in the right place as he had assumed that the servo would be placed as per the plan which I sent him. The flap wire holes, however, I made with a sharpened brass tube lined up by placing a ruler on top of the wing.

 

I then fed through the wires by gluing the ends to a piece of 2mm carbon rod and pulling it through.

 

Next job was to join the wing together. As the original wing kept breaking, I asked Phil to make me some 1.5mm ply braces which fit inside the wing through pre-cut slots. Perfect fit. I had to feed the aileron wire, however, through the rearmost joiner and glue everything into position with the wires fed through the top before it dried

 

 

Trailing Edge now glued on with epoxy and front part of wing sawn off to butt against the fuselage former with dowels yet to be recessed inside the wing in the correct place - that will be a challenge!

[Peter Garsden]

 

Wing location dowels to front leading edge of wing - a tricky job as I said. This is what I did.

1. Made up some short pieces of dowel to push into the holes in the fuselage. The dowel was slack because I had eased the holes for the last wing, so I wrapped the dowel in masking tape. I then spot glued the dowels top and bottom with cyano and pushed them in place into the fuselage holes leaving about 6mm protruding. 
2. I made sure that the front of the dowel pieces was sanded flat.
3. I covered the fronts with thick black acrylic.
4. I pushed the wing into place and the black paint gave me the position for drilling into the plywood you see at the leading edge.
5. I drilled ever large holes with a hand drill and the wing in the vice making sure it was vertical, and glued the dowels into position, having checked that they fit, which they do! Result.

Rear wing bolt holes

 

I used my usual method of sharpening a scrap piece of 6mm wing bolt to a point then screwing it into the screw thread of the captive nut so it was nearly home. I then placed the wing in position and marked one hole in the trailing edge. I then drilled it out with 3mm, 4mm, 5mm then 6mm drills. I then screwed one side into position, and did the same with the other bolt hole. Result.

A piece of ply - plan specifies 3/32 and I don't have any so I laminated a piece of 1/16 with a piece of 1/32 which I have in abundance. This strengthens the wing bolts and can be seen in the photograph. I cut it to size from the plan, and glued it in position then drilled through for the wing bolts.

 

Wing Reinforcement over Join

 

I found that the 2 inch wide bandage was not strong enough on the original wing so wanted maximum strength and made a mix of 2 inch wide wing bandage and a diamond shape to reinforce strength top and bottom. You can see the shape in the photographs.

 

You can also see the peel ply ready cut to shape - this will be laid on top and will soak up excess resin. Don't you find that if you don't you get bobbles of resin which would interfere with the balsa wing centre fairing which lays underneath, so it will be maximum strength minimum thickness and weight. Film will also adhere to it better.

 

Also shown is the paper template I used to get the shape right. Also shown are my amazing Kevlar cutting scissors which I got from a glass supplier. If you have ever tried to cut Kevlar and watched it destroy scissor blades you will know what I mean. £47 but worth every penny if you cut a lot of cloth. Heavy and brilliant.

 

Next job is resin. Bottom first then top letting it dry in between.

 

 

 

 

Edited June 28, 2023 by Peter Garsden

[Peter Garsden]

Nearly finished hopefully in time for the Lleyn meeting next weekend. Have been putting off the under wing fairing. I followed the previous wing and used 4 pieces of 6mm. For the front pieces I steam bent the balsa to follow the curve of the wing. I also adopted my usual method of adding masking tape to avoid marking the surrounding fuselage and wing. Now ready for covering.