General Aircraft Owlet

[Tim Hooper]

Cleverrrrrrrr......

tim

[Lindsay Todd]

It's the computer Tim, I'm just clever enough to correct my mistakes before you guys see them. Had a nice treat today when my cut parts from Slec turned up.

I have a few additions to make to a couple of formers as I have tweaked the design a bit since committing the drawings but only small additions and will only take a few minutes to add cut outs to the formers. That has actually been a benefit of working the design through in 3D as it did show up a few areas that needed further thought in how the construction should roll through. the shapes were correct but the visualisation had not accounted for how sheeting would be best applied, viewed in 3D and it all became quite straight forward with a few minor tweaks. I have the chance to do this over the next week or two now and then can think about making a proper start about mid July. As usual great job from Slec on the parts and interpreting my drawings. Linds

[Stephen Jones]

Looks a good subject to me Lindsay .

And something similar to a model a designed in my twenties and similar to something i am currently designing now and will certainly make for a good club model .

Watching with interest .

Steve

[FastFlyer Smyth]

Looking forward to this one Linds.

[Lindsay Todd]

Hi Steven, strangely I had designed something similar many years ago in my student days built out of bits and had an H tail, very stable in the air as I recall so this one has all the elements for making a great sport scale model and should not take too long to get it together once things get started. I have a bit of a back log of designs to get through in the coming months so looking forward to getting started very soon. Linds

[Lindsay Todd]

Airframe design work now just about completed and at least as far as the 3D Cad work it all seems to go together as intended.

A little more research has brought to light some more posters from the marketing department showing the rear cockpit fitted with a night instrument training hood and a nice picture of the cockpit instruments.

Just as well Weston is coming up now, time to get some bits and pieces together. Linds

[Stephen Jones]

Posted by Lindsay Todd on 07/06/2015 17:16:07:

Hi Steven, strangely I had designed something similar many years ago in my student days built out of bits and had an H tail, very stable in the air as I recall so this one has all the elements for making a great sport scale model and should not take too long to get it together once things get started. I have a bit of a back log of designs to get through in the coming months so looking forward to getting started very soon. Linds

Hi Lindsay,

Yes i have vague memories of mine being based on something i may have seen in a book or a film .

I do recall it being green and black and i think a German trainer ,i don't know why but i am also thinking a connection with the film the great escape .

Steve

[Lindsay Todd]

Hi Stephen, I think the aircraft in the great escape was a Bucker Bestman, or very similar but I know what you mean there is something similar in the tadpole like fuselage shape. I should have a photo of my original design so I'll see if I can track it down. I do remember it being yellow and a tail dragger that had lousy ground handling as there was no prop wash and just a fixed tail skid but was a dream in the air. I think I was about 18 at the time and built from my dad's wreckage so could have been made up of all sorts, but that's probably why I like designing my own model it was driven out of necessity and scrounging bits on a student grant. Linds

[Lindsay Todd]

At last I have a bit of a bench in the new house and can make a bit of a start

First job cut out and sand, mark up all the fuselage bits

Ace job by Slec so this did not take too long although I had made a couple of extra stringers and a couple of additional bits so it wasn't all plain sailing but nice to have a set of bits to get stuck into. All formers and fuselage crutch frames are in light ply and load bearing parts from marine ply such as motor mount and front uc plate.

First real job is to laminate the motor mount two parts and the forward u/c plate two parts together from 3mm marine ply and leave to dry.

Fuselage inner crutch can also have the ply doublers glued in place, 3mm marine ply for the u/c plate doubler which is aligned with a similar hole in the crutch and 3mm light ply behind, the 3mm gap will locate former F2.

Its a start at least and things can move forward quite quickly once these parts are dry. Linds

[Lindsay Todd]

Bit more done this evening with the front U/C plate glued into both sides of the crutch which effectively sets the width and at the same time I added the wing bolt plate which also spans the crutch, also marked up the position of the two formers so assembly is pretty straight forward, just keep things square.

With these in place the formers can be glued in place starting with F2 which sits in the slot behind the U/C plate

The remainder can be added one at a time, just use a square to keep things straight as its still all a bit flexible

F6 locates onto the end of the ply crutch as does F1 at the front

and final job for tonight is to glue the wing dowel plate into the slot at the front of the wing cut out

Good progress, tomorrow will start on the stringers and longeron's now I have a structure to work from. Linds

[Stephen Jones]

Nice Watching with much interest ,

Steve

[Phil 9]

Lindsay can I ask what cad program you use

[Lindsay Todd]

Hi Phil, lucky to have autocad through work but have used others and even the basic ones are well up to the job, I have a couple I have used to be honest and these days files get flipped between a few depending on what I am doing and where I am. Have also be known to get out a pencil and paper too

[Phil 9]

Thanks Lindsay. I just started to play about with cad.for a build but I may have to revert to a pencil to finish it off. This is an interesting build can you please post the details of how the rudders will work when you get to it

[Lindsay Todd]

Bit more progress on the Owlet starting with a bit I missed which was fitting the nylon U/C mount onto the front U/C plate, this is simply drilled and bolted on and is a commercial unit from one of the trade stands J Perkins brand I think and will carry the nose leg held and steering arm. Much easier to fit before gluing into the crutch frames of course.

With that job done I decided to finish off the motor mount. I have tried to be clever here and that is always dangerous but by adding some triangular section to the sides I have created a slot that runs over the crutch frames but sits square at the correct angle. The frame can then be slide up and down the crutch frames to get the correct position of the motor relevant to the front of the cowl so can accommodate different motor lengths and sizes a little easier.

Seems to work ok and can now be put to one side (not decided on motor yet!)

Next job is to get the 6mm square longerons in place down the fuselage, these extend from the nose former F1 back to F5 but not glued any further at this stage as we have quite an angle change at this point. A couple of elastic bands keeps things together whilst the glue dries.

Next job is to add the cockpit formers F4 and F4B these are glued onto the top longeron checking they are square and vertical, a 6mm square longerons are then glued between F3 and F4 and F4A and F4B. I'll trim these flush when dry.

Starting to take shape now I think, more soon. Linds

[Stephen Jones]

This looks like a very clever and well thought out build .

I am taking notes .

Steve

[Lindsay Todd]

Oh you've done it now Stephen, I find this stage usually goes ok. Grafting the tail section on gets a little more complex but I'll cover that next, glue still drying but hope to get the basic skeleton fuselage together by end of the weekend. Linds

[Lindsay Todd]

Further build update and time to make a start on the rear fuselage. This is started by building the 6mm square tapered lower longerons into a sort of ladder frame, flat on the plan. When done mark the positions of the rear formers onto the frame, Add the 6mm square cross braces ensuring the first and widest one sits exactly behind the location of F6 as this will glue onto the back of the former.

Next job is to make up an angle jig so that the formers can be glued onto the logerons at the correct angle so that when the rear fuselage is glued to the front all the formers will be vertical. Measure off the plan and use a scrap of ply.

Use the jig when gluing formers F7,8 and 9 onto the longerons

When dry we can then align and glue the rear fuselage frame to the front fuselage at the rear of F6. To do this we need to align the fuselage and use the jig to ensure that F6 sits at the same angle as the formers on the rear longerons, do this by adding packers under the front of the fuselage till the angle at F6 matches the jig and the the rear longeron frame can be glued to the rear of F6.

A couple of old battery packs act to weigh the parts down and stay flat whilst the glue dries.

Top lomgeron can now be added between F6 and F8 and side longerons from F6 to F9. I also added a 3mm triangular brace from the lower longeron to the rear of F6 for added strength.

The side longerons are trimmed between F5 and F6 due to the angle change in the fuselage, a separate 6mm square length is cut to size and glued in place, this will be later strengthen with triangular gussets that will tie the front and rear fuselage together further.

That's it for now, more soon. Linds

[Lindsay Todd]

Got a bit more done this afternoon between DIY projects starting with adding the remaining longerons to the rear structure from F6 back to F8 and then fitting some triangular 6mm sheet to reinforce the joints of the longerons between front and rear structures

also fitted the angled top to former F5 using a little angled offcut to ensure the correct position

Finished this area with the remaining 6mm square balsa between F5A and F6

Next job was to fit the ply plate that sits across the fuselage at the rear of the wing and carries the position of the lower longerons from F6 forward. I cut these about 3/4 way through to help them bend and then glued to the ply plate, when dry trimmed flush with the ply plate.

Next job is to fit the wing seat. this is from 2mm balsa glued from the inside edge of the ply crutch frames from rear wing plate to front leading edge wing plate. Balsa is cross grain to help it bend and glued in sheet width sections cut to width from rear to front.

Quite an easy job and will give a good glue joint when the sheeting gets applied later

More soon. Linds

[Colin Leighfield]

You've got it all worked out Lindsay.

[john stones 1 - Moderator]

Coming together well Linds, like your sliding motor mount

John

[Lindsay Todd]

Well set myself a target for this weekend and just about got there I think. First job was to fit the cockpit floors using 2mm balsa sheet glued to the underside of the top side longeron and formers.

Next job was a bit of work to the area just forward of the leading edge fuselage sides. This is quite a critical area as it tapers in towards the cowl line and is made up of a 6mm triangular form that extends back from the front plate that the wing dowel will locate into back to a point inline with the front edge of the U/C plate so it tapers from the wig dowel forward aligned with the longerons. Next job is to glue laminates of 6mm to the sides, 3 laminates each side will be required again from 6mm balsa, these will be sanded flush when dry. These also add strength to the U/C fixing area.

 

Edited By Lindsay Todd on 02/08/2015 22:51:25

[Lindsay Todd]

Next job is even more critical and is fitting the tail plane support plate 6mm balsa part between F8 and F9. This of course sets the incidence of the tail so needs to be correct. Fortunately this is parallel with the top edge of the ply crutch frames so easiest way is to jig the fuselage so the crutch frame sits level and then test fit and sand if necessary so the tail support plate is also level, I did this with a small spirit level.

With the tail support all useful to check that it sits square in all directions of course as will avoid and sanding later to try and square things up.

Final job was to add a couple of 6mm square between F5 and F6 at the angle change just to help when I come to sheeting over the fuselage.

Now just leaves a general final sand to shape and can start to look at the next stage, control rods and some sheeting. More soon. Linds

[Lindsay Todd]

Little bit more of an update on progress starting with finishing off the front nose lower support by adding 6mm sections extending to former F1, this will give some gluing area to the cowl sides later. Also sanded the 6mm infill to shape

Next job is to add cross grain 2mm balsa sheet to the underside tail section from rear of wing all the way back

With the easy bit of sheeting done it was time to tackle the sides and this is by far the most time consuming phase as the shape dictates it is done in sections. It seemed the easiest approach was to start with the cockpit area using a section of 2mm sheet between F2 and F5 from half way across the lower longeron using the full width of the sheet. I soaked the outer surface to assist in it conforming to shape and then using pins, pegs and tape glued and fixed in position and left to dry

When dry I trimmed back the sheet to the front of F3 and down to the top longeron as the angle is to steep for the sheet to conform. This area was then planked with 6mm strips of 2mm sheet. Slow but the strongest solution and actually quite therapeutic once you get into it.

Obviously quite a bit of sheeting and planking to do over the next few days. Linds

[Lindsay Todd]

bit more work on the sheeting, due to the angles I figured it easiest to stick with planking method for some areas and larger sheet pieces for others. I have now just about finished the top decking and the upper sides around the cockpit area. At this stage the sides are sanded so that the edges are flush so that the sides can be sheeted reasonably easily.

Before I sheet the sides there are a couple of jobs to do. First is to fit a mini servo to the rear of the fuselage to drive the rudders. I have messed around thinking through lots of linkages thinking I would be saving the weight of a servo but I finally decided on the keep it simple method so a bracket to support a Hitech HS81 will be made up so that the arm will sit about 3mm above the tail plane support, this will require a clearance hole and will also need some consideration re access for maintenance in the future.

The servo will drive a pushrod that will run centrally through the tail plane, that will hopefully become clear later in the build. More soon. Linds