Topic: 1/4 scale SE5a

Just put knife to wood this eve building a 1/4 scale (I use the term "scale" loosely).
Basing it on the DB plan but with modifications to the structure and wing fitting.  2 piece wings with top centre section permanently fitted, bottom centre section fits as per normal but will be removable via the wing bolts. Wing ribs are lightened lite ply, front section of fuz lite ply also.  Intended engine will be Honda GX31, if that proves inadequate there will be plenty of room for either a G38 or perhaps a XYZ 26cc.
Bespoke undercarriage more on the lines of the SE5a as the one on the DB plan is rather basic.  Covering will probably be Koverall and painted with WBC, guns will be home made, I have a pair of flair wheels from my dead Pup, servos will be tower pro 5010.  I'm in no hurry to finish this and may halt the build to do another Rafalroo and if I get the right engine a Lowley but I want it done finished for next season.

Mudders signing in, all present and correct...    

I had hoped to pile into this project today but I have taken on some outside work, lots of documents to alter and format so I have only had a few minutes here and there when stopping for a coffee.  I worked on the docs last night till 1:15am and will do the same again tonight to get it out of the way as fast as possible.

So far I have the front of the fuselage cut out and also just laminated up F1 from 2 pieces of curved ply, my LMS stocks some real rubbish but I will use that up before going into the excellent Slec materials.

BTW, Slec yesterday, they could not be more helpful and will let you dig through all their stock to find just what you want and a nice bunch of people to boot 

I got a little done today in between real world stuff.





I had cut 18 ribs from the 2mm lite ply several weeks ago, a couple of days ago I lightened them up a bit more, 18 ribs weigh 3 3/4oz, they feel light but not sure if all added up it will be heavy    I'm known for building tanks 

Signed in ready.

Looking forward to seeing this.

Agree completely about SLEC. Whenever I go its good to go into the mill and select your own wood in your own time.

Have you cleared the workshop, coz I am sure I can see some floor...

Subscribed

Subscribed. My next build after the Moth will be something 1/4 scale and I am an SE5A lover. look after those plans 

Simon

I'm in too

Ian.

Have you cleared the workshop, coz I am sure I can see some floor...

Trick of the light mate 



I could not spend much time on it today but got a bit down this eve.  The firewall is laminated from 2pieces of 1/8" ply with outer grain running at 90 degrees to each other, I did that as the ply I had was warped to hell it was from my LMS not Slec.  Once planed to size and perfectly square I prepped the gluing area with a junior hack saw.



This was epoxied on and held square with a weight.



Once the firewall and bulkhead behind the wing seat were dry I pulled the rear end in and glued the cross pieces.



It's all lined up on a pencil line on the board and checked for upright with a square and held where needed.    for when it comes off the board in the morning, there is a lot of tension where the clamp is but it's done to the plan, one bit I have not modified 

Looks like the Honda will fit in completely enclosed





Again I got very little done, SWMBO wanted to go out and look at holidays, she found one she liked AND BOOKED IT, one trip, booked it    and I get to go to  :colm:  as you can tell SWMBO is the main £ earner, I have started to work but only 16 hours a week and from home  

I'm just developing up the patterns for the formers which hold the turtle deck.  This being a kit plan rather than a construction plan they are not shown on there but as I'm making many other alterations anyway this should not be a major hurdle.  I must admit, it's been so many years since I have developed a pattern for this type of thing I'm scratching my head a bit, not good since I used to make patterns for complex ducting bends, lobster backs etc and hoods over open fire places.  Kinda writers block   (where is my Gordon Whitehead scale modeling book).

SWMBO is out tonight so I got a bit done, the formers for the rear stringers are cut and have the backbone in place.  Nothing is glued, I will mark out the rest of the stringer positions with a string line, remove them, cut them and remove unwanted weight into a hoop rather than a solid 1/2 circle.
I'm not sure what to do the stringers with, I think 3/8" X 1/8" balsa may be to weak but I suppose I could use hard balsa, failing that I can rip up some tree wood as I did the back bone but do it 1/8" X 1/8", it's very light but pretty strong.  I imagine I may have to add weight to counter the Honda but I would rather build light and have to add it rather than heavy and find I need weight up front if you see what I mean.

What do you think?  BTW I forgot to get ANY 1/8" or 3/16" balsa when I went t Slec the other day    another trip in order I think  :cigarsmoking:





BTW the hole in the side of the fuselage up front is for the dip stick, I will make a little hatch for it 

Just weighed it, inc the 6 little clamps it's 1Lb 6oz, I expect it will pack on the weight soon 

If it helps the fullsize had 7 full length stringers, 2 of which ran a nats above the main fus structure, so you could omit them leaving 5 full length stringers. In beetween them was 6 shorter stringers which stopped at the third former (as you count from the leading to the rear). I would use balsa, thats how the Pup is and you have a good strong spine there already, the others just hold it out to shape.

Mat

Thanks for that Mat, I have been doing some research on the SE5a online and have found some great pictures



I'm only building a sport model so measurements from full size are by eye, if it looks right it's good enough for rib spacing etc. but nice to have the correct amount    I'm gonna have to get some more materials, I stuffed right up when I went to Slec, took me 4 months as I kept changing my mind as to what to buy then when I did get the courage to go I got it wrong.......... had a fluffy day 
I still have my  for the Honda having enough grunt, I know it will have enough for general puttering around at the club field but as mentioned in another thread that extra grunt is so nice for high stall turns and getting out of the way of unexpected situations.

Been doing house work today so only got a couple of formers marked and cut whilst having a fag  :cigarsmoking:





The top 1/32" ply sheeting will overlap the fuselage sides as per DB kit, from memory this looked ok on the stock one I owned some years ago, these things were tatty anyway  and it is as I said a "Sport" model.  I purchased 12" X 48" of ply.......... I need over 12" wide 

I'm still making a lot of this up as I go and it is different from the stock DB kit.  I'm not sure what to do about the Vickers, do I just do a short barrel and glue on the front or a complete gun (1/2 of which will never be seen) and have it mounted as per original    much simpler to have just the 1/2 gun   

Right 1/2 a gun it is then  

It's unlike me but I'm trying to be aware of weight at all times, cockpit waist height bit (whatever it's called) is structural so needs to help hold the fuselage from twisting so I laminated up 1/8" lite ply grain cross fuselage and 1/16" birch ply grain running for and aft, very stiff but still pretty light.  Former in front of that is laminated again from 2 X lite ply and again 90 degree grain, the former with the lump to take the gun exit will have the cabane support rigging so it laminated from 1/8" birch ply and 1/4 balsa they both need to be more than 1/8" as the ply will join at these points with angle change.  Next former forward also from 1/8" ply as that to has rigging attachment points.
All formers have excess material removed whilst remaining sufficiently strong for the rigging, the added bonus of this is the engine will have a good airflow past the head as the air can come in the radiator slats, past the engine (may have to force through the fins with ducting) and can exit the cockpit and floor just behind the firewall.





As much as I would like to carry on playing with the SE5a today I can only grab a few minutes here and there as I have "work" to do  

looking goooood.. That Honda looks like it was made for it...

looking goooood.. That Honda looks like it was made for it...

It fits in well however I had to drop down the position of prop shaft to a non scale position but there is not much scale about this build anyway 

Shaun,

It's looking good.   You want to have a close look around the Vickers mounting / fairing if you want to get it reasonably right.  I seem to remember being frustrated by my Flair version which had a simplified, straight top decking which just didn't seem to work out right.

Alan

I know what you mean Alan, I plan to do it something like the picture below.



I think a 1/2 gun will do for me, I can always (but never will) cut it about and alter at a later date.  I may have a rudimentary cockpit, you know me maybe stick a old watch on the dash board  

Thinking about the wing joiners, I have some 6.7mm wound carbon tube which appears to have about the same amount of bend judging by hand flexing as a piece of 4mm piano wire and weighs 1/4oz apposed to the 1-1/4oz of the piano wire of the same length, that's an 8oz saving .  I have 12" lengths which is enough to span 2 ribs in the centre section and 2 in the wing panel.  Quick and dirty method of drilling the centre section to take the joiners (whatever they are made of) would be to drill a slightly over sized hole (correct size in the wing) slide the wing onto the centre section, prop up the wing to the correct dihedral and glue on ply washers with the correct size holes to the ribs.  It's a dirty way of doing it but affective I think, what do you say peeps?

Is the carbon tube suitable to use as the removable wing panels joiners?  

I'm thinking of using the normal method for a DB to make the cabanes i/e/ piano wire.  As the centre section of the to wing will always remain in place I see no reason for making up the joiner from front to rear cabane which looks ugly.  After flexing the undercarriage I made for the Pup which was MIG welded I cannot get it to fracture and it remains flexible on the welds which I was surprised about.  I'm thinking the cabanes can go up to the top centre section and terminate via a 1.6mm steel plate which can bolt through the ribs.  Easy to get the lengths correct this way and will make cladding the piano wire easier as there will not be a big lump of soldered wire wrapped joint other than the thin diagonal braces.

Other more complex/more bending and easier to get wrong method I thought of is to bend the top of the cabanes to run inline with the ribs and once the incidence is set screw on saddle clamps but that would be a fag  

Input please  

Nobody have any thoughts on piano wire Vs Carbon fiber tube or cabanes attachment methods I have mentioned 

Sounds like something the professional sailplane builders could answer...

Oh well I carried on with the bits I can do for a little bit today, at this stage it weighs 1Lb 8 1/2oz





all a bit boring I'm afraid as I have not made much progress and it all looks the same but now all parts are glued rather than just dry fitted    I thought I wold have a go at laminating the fin and rudder, seems ok  

Looking good NFG 

I like the lamination method for tail feathers etc, I did the same with the D.VI. it's a great solution 

Mud 

Looking good NFG 

I like the lamination method for tail feathers etc

Me too!   

The carbon tube idea seems OK - the idea about big holes and washers is very practical, in all probability the easiest way to get the best accuracy and more than good enough but ............. I've never liked that sort of approach, it just seems .......    No valid reason, it's just me 

Looking forward to seeing the instrument panel Shaun

Alan B

Looking good NFG 

I like the lamination method for tail feathers etc, I did the same with the D.VI. it's a great solution 

Mud 

It's threads on "proper" builds like yours Mudders that give us ruffens ideas beyond our station  all the fine detail stuff you guys do does help peeps like me to raise our own bars (but jus a lil bit)

You want to have a close look around the Vickers mounting / fairing if you want to get it reasonably right. 

Alan

Is the picture below what you were talking about Alan    I just wrapped some paper round the  formers to give an idea of what it will be like once the ply goes on.

The carbon tube idea seems OK - the idea about big holes and washers is very practical, in all probability the easiest way to get the best accuracy and more than good enough.

Aha, some input, one thumbs up is good enough for me, washers and tube it is then 

Looking forward to seeing the instrument panel Shaun

Alan B

What's the punch line  If it gets anything it will be real rough, I cant see it when I'm flying it and when it's on the ground I'm yarnin 

Centre section top wing is dry fitted and has taken a long time, in my quest for lightening the heavier cheaper materials I'm using I have made a mistake can you spot it considering the method of attaching the cabanes I had planned?  Centre rib 1/8" lite ply others all 1/8" birch ply as this area takes a bit of grief picking the airframe up by it.





The 5 ribs weighed 3 3/4oz, I managed to loose a bit and got them down to 2oz, the whole assembly in the pictures is 4 3/4oz inc the longer than they need to be carbon tubes.

I will goto the LMS tomorrow and get the piano wire to make the cabanes then start on the bottom wing centre section and undercarriage mounts.  I would also like to get the undercarriage made as I always think its getting somewhere when it's up o it's wheels.

Not much done today, I had 2 drinks last night before I went to bed just to chillax a bit and woke with what I thought was a hand over, turned out to be a migraine 

Jig is made holding the top wing centre section in place, just got to decide on a method of attaching the section to the cabane tops 

As I removed to much material from the outer ribs I'm now thinking just bend the tops of the cabane wires and soldering on like a "P" clip made from steel and screw that upward to a ply plate which I can glue between outer and 2nd rib........... what do you guys think......... MORE INPUT please 

Can you make a doubler rib and glue it on the inside of the outer ribs to put the strength back

Block in between the upper and lower spars and attach the cabane struts to that would be my way of thinking

Ian.

Can you make a doubler rib and glue it on the inside of the outer ribs to put the strength back

Could do but for the 1/2 hour and a bit of ply I would make a new one if needed but I like your line of thought 

Block in between the upper and lower spars and attach the cabane struts to that would be my way of thinking

Ian.

Trouble is Ian there will be the 7mm carbon wing joiner between the spars so that may make it hard to screw/bolt through tat bit 

I'm thinking now that I will fit ply and recess the underside say 3/4" long by the dia of the cabane wire (8swg) and sue a flat piece of steel strap with 2 screws to hold the wire in.  This will mean the wires will have to be made exactly the correct length, no room for error but will mean the top section can come off for servicing if needed.  I'm reasonably confident once my head stops pounding using my vice and a hammer I can get it right.

Is the picture below what you were talking about Alan    I just wrapped some paper round the  formers to give an idea of what it will be like once the ply goes on

Yes that's the sort of thing.  IIRC the Flair one doesn't have the humpy bit (technical term) so when you let the gun in to the top coaming it has to point up at an extreme angle otherwise the barrel doesn't clear the coaming.   Impossible to make it look right.   Yours is looking good    

Thinking about your cabane mounting - unfortunately I haven't come up with any bright ideas :( but I'll stick with it.

Alan

Yes that's the sort of thing.  IIRC the Flair one doesn't have the humpy bit (technical term) so when you let the gun in to the top coaming it has to point up at an extreme angle otherwise the barrel doesn't clear the coaming.   Impossible to make it look right.   Yours is looking good    

Thinking about your cabane mounting - unfortunately I haven't come up with any bright ideas :( but I'll stick with it.

Alan

I like comments like that, kinda makes you feel you are in the right direction but as for letting in a whole gun  I'm undecided as yet but can change until the top ply goes on 

With the tail end of the migraine today it physically hurts to look at the cabanes trying to think of what to do, I hope tomorrow will more productive 

In that case, hard fill between the spars above and below the tube, thin ply shear webs either side, U shaped steel bracket at the top of the cabane that the spars sit into, bolted on. Simples.

Ian you mean with a bend like the pic below?  This way is nice as you wont see any fixings but will make the ctr section less serviceable.

Hmm the piano wire cracked at the 90 degree bend, appears this stuff is particularly brittle    I refuse to go back to my not so LMS for more wire so will weld 1mm steel plates to the top of the cabanes to bolt through the blocked/webbed spars as Ian suggests.  Makes perfect sense to bolt to the spar where all the load is taken, I don't know why I did not see this before    what a numty  

Just about to go over to my dads to borrow his MIG to squirt the little plates on.



As you can see the wire snapped off where I was trying to put a 90 bend on it    but there is enough meat left to get a good couple of MIG tacks on it  



I will of course put thin ply plates either side of the spar before bolting through with 2 X 2mm bolts.