Scottish Aviation Pioneer by Chris Reid C of G Position

[alan p]

Looking for confirmation of the CofG position on a Scottish Aviation Pioneer by Chris Reid . Been built with slatted wing and fixed flaps,  as built  max chord at flaps is about 12".

As can be seen slatted CofG is well forward. 

Would be grateful if someone can confirm position as shown on plan.

 

[MattyB]

That does seem extraordinarily far forward… Can you post a picture of the completed wing for us to look at? It might help us understand why that is where it is marked in the plan…

[Simon Chaddock]

The Scotish Aviation Pioneer had extreemly large full span slats.

 

Depending on how they are modelled it could explain the very forward CofG position. 

Edited September 19, 2023 by Simon Chaddock

[alan p]

Go to the RCM&E home page click on Plans, forward to page 6, bottom of page 6 is the build article and photo's of the model. Photo attached from the article showing complete model. I think size and position of the tail plane might have some bearing on CoG position.

[MattyB]

10 minutes ago, alan p said:

Go to the RCM&E home page click on Plans, forward to page 6, bottom of page 6 is the build article and photo's of the model. Photo attached from the article showing complete model. I think size and position of the tail plane might have some bearing on CoG position.

 

Following your instructions, I found the page...

 

https://www.modelflying.co.uk/scottish-aviation-pioneer/

 

Seems pretty clear from that write up that you should have confidence in the indicated CG position, even though it does look a little weird on the page - the plan position is at 25% of chord, but that is including the area of the slats which aren't shown on the initial image in this thread:

 

" The battery on my model was secured behind the cabin using Velcro pads and a strap. This makes it a moveable feast, so that you can alter its position to set the C of G, which should be at 25% of the wing chord measuring back from the leading edge (or, if you’ve built your wing with slats, measured back from the front of the slat)."

Edited September 20, 2023 by MattyB

[alan p]

Thankyou Matty and Andy, as mine has a cowl built a lot lighter than the articles large lump of plywood battery position may be a lot different.

Thankyou both for your replies👍

[Chris Reid]

As the original 2007 designer of Pioneer, I did not build mine from the published plan which had several errors not on my original drawing.  Looking at my published copy today, I am not happy with the CG positions shown.  I did have a CG issue on the first flight as I had not included the wing slats as part of the wing chord.

Thus if I built one today, I would set the CG at max 33% of the chord back from the leading edge including the slats. This will be safe.

Chris Reid.

[Basil]

On 20/09/2023 at 11:19, alan p said:

Thankyou Matty and Andy, as mine has a cowl built a lot lighter than the articles large lump of plywood battery position may be a lot different.

Thankyou both for your replies👍

Hi Andy, been getting to grips, or trying to, re the Pioneer.Looking at building it!!!!!. If I could be so bold and ask some questions. I have many issues to solve in my mind before starting, one big one is the construction of the cowl and attendant electric motor mount on the nose. Can you give me any info re this please?. Perhaps you would prefer a PM.  I will send a PM at some stage. Thank you in advance 

Bas

 

[Basil]

Can anybody throw some light on the construction of the cowl/Fuse interface and the construction  of the upturn/flange in the rear of the cowl. In desperation I have bought a plastic (PP/PE) in the hope off cutting off the 'Flange' from the preformed funnel, but being plastic at a loss to make a firm fixing.

Some tips on making the cowl as a whole would not go amiss as well.

Thanks in anticipation.

Bas

[Guest]

Baz,this is how I did mine on disc sander,dropped table to requred angle and away you go.

Hope this helps.

Jim

[Basil]

Thanks JIm,  thats the interface , have you any tips about the cowl proper, particularly the 'Swept' bit at the back.

Bas

 

[Guest]

Baz

Not sure what you mean by interface?    The interface as you call it is the swept up bit at the back,the rest of the cowl is just a tube made up of two balsa dics wrapped with 1/64th ply,soft balsa ring on front end to produce curve.

 

Not great a tech. drawing but here is a rough sketch of how it goes together, 16yrs is a long time to remember exactly how i did it,hope this helps

[Basil]

Thanks for getting back. yes you have interpreted what I meant by interface . Thanks your first reply addressed just that. What I am stuck on is how to make the rear rim of the cowl, the bit that extends outward  from the rear of the cowl , about 1/2 " all around. It appears to be a ribbon of thin ply at an angle of around45 degs, supported by some angled 'Brackets' around the circumference of the cowl. I hope my description is identifiable !!!! 

Thanks Bas

[kc]

1/64th ply is a good material for such work,  but just shrinking  a plastic bottle over a wooden mould might be easier.  Or you might even find a part of a plastic lemonade botle that was already near to the right shape - checkout the base of some bottles in the supermarket!

[kc]

I reckon a competant woodturner ( look for a local club ) could turn a wooden shape for a mould in very little time.   Then a plastic bottle or glassfibre used to mould a cowl.   To remove the moulding from the wooden shape would probably need cutting ( perhaps underneath ) but for an electric model a removeable top half might be needed to insert the Lipo so a horizontal cut could work better.

A two piece balsa cowl with just a solid balsa rear ( painted black to look like a recess ) might be easier for a anyone who likes balsa work better than glassfibre or plastic moulding.

 

It might be best to work out how the motor and Lipo can be fitted and the CG achieved before making a cowl.

 

[Guest]

Bas

have another look at my sketch,   Tjhe first ring on the left is a ring of balsa with the 45 deg. angle as per my pic on the sander and the tube just glues to the ring.

I dont have the plan anymore but the ring will be around 4/5 inches in dia.

Another little pic to let you see what I mean.

The 45 deg angle is on the balsa ring,no ply ribbons.

[Guest]

This is pic of my model back in 2007

 

[alan p]

 

Hi Bas

Photos of my cowl construction 1/4 ply for the rings, 1/32 ply sheet and balsa. Obviously for a I/c engine but can be altered for electric

Alanp

 

[Basil]

2 hours ago, Basil said:

Thanks for getting back. yes you have interpreted what I meant by interface . Thanks your first reply addressed just that. What I am stuck on is how to make the rear rim of the cowl, the bit that extends outward  from the rear of the cowl , about 1/2 " all around. It appears to be a ribbon of thin ply at an angle of around45 degs, supported by some angled 'Brackets' around the circumference of the cowl. I hope my description is identifiable !!!! 

Thanks Bas

Sorry Jim, this was supposed to be addressed to you. Bas

[Basil]

1 hour ago, Jim Carss said:

Bas

have another look at my sketch,   Tjhe first ring on the left is a ring of balsa with the 45 deg. angle as per my pic on the sander and the tube just glues to the ring.

I dont have the plan anymore but the ring will be around 4/5 inches in dia.

Another little pic to let you see what I mean.

The 45 deg angle is on the balsa ring,no ply ribbons.

Thanks Jim, it begining to fall into place. many thanks. bas

[Basil]

22 minutes ago, alan p said:

 

Hi Bas

Photos of my cowl construction 1/4 ply for the rings, 1/32 ply sheet and balsa. Obviously for a I/c engine but can be altered for electric

Alanp

 

Many thanks Allan, some clear pictures of the cowl construction.This together with the other posts has given me some ideas, direction and inspiration. Many thanks. I have never had to make a cowl before.

Ta !!!!!!

Bas