Jump to content

Woodpecker


Recommended Posts

Well its about time for another quickie, this one a collaboration with my mate Paul Rice. This is what happens when you can't go flying because its too wet or too windy and the crayons come out and you start doodling. At least on this occasion I can't be blamed completely for the shape or indeed the odd name its been given. Anyway here it is , building has been started and well into progress, in fact now covering parts. Will be available as a V Tail or more conventional and we have even designed in a power pod conversion for flat field use.

What do you think of this?

06apr16.jpg

Linds

Edited By Lindsay Todd on 20/05/2016 09:07:36

Link to comment
Share on other sites

Very simple design with basic 6mm balsa box structure front end and open lattice rear frame with spruce longerons and ply plates for reinforcement. Wing span about 66inches (1676mm). and short of having to cut some ribs and sides has been pretty much built from the scraps box. The basic design was based on a fun slope sport scale-ish layout but we added the removable power so it could be a take anywhere model hopefully. Not sure on the weight but should be pretty light and their is certainly plenty of wing area. Power in the 300 watts 3cell 2200mah Lipo range I hope. more pics and info to follow when I get a chance. Linds

Link to comment
Share on other sites

  • 2 weeks later...

Well time to do a catch up build bloq, bit of an edited highlights as its been a fast build of two prototypes

As usual build starts with cutting out fuselage sides from 6mm sheet, to widths were required to get the depth required, glued together and then marked for position of the formers

img_8716.jpg

img_8713.jpg

This is the first set of formers, ruff cut to check sizes and fit, final version will have cut outs in the corners for 6mm square strengthening doublers around the fuselage edge. When happy 2nd side can be glued straight on top.

img_8719.jpg

Rear lattice follows very similar layout to my previous designs, however main longerons are from spruce rather than balsa, cross and diagonal braces from hard balsa and ovals from 0.5mm ply to reinforce and also add a bit of character. These can be made up separately from the front fuselage and then glued to the front later once the forward section is together. Just need to keep a check on alignment.

img_8715.jpg

Once the rear lattices are glued to the back of the forward fuselage the frames can be bent and glue together and the tail together with two triangular plates and clamped till dry

img_8720.jpg

Both prototype fuselages in process an ready for some sheeting to be applied

img_8723.jpg

Linds

Link to comment
Share on other sites

Next job was to get some 3mm balsa sheeting around the forward fuselage

img_8741.jpg

Extra sheeting added from the rear of the wing seat back to the lattice frame, also note the wing bolt fixing plate has also been added

img_8921.jpg

Ok so time to make a start on the wings. At 66inch and no dihedral it could be made in one section but I opted to make two wing panels and join together. Nothing complicate hear with double 6mm square spruce spars, 3mm balsa ribs and 6mm leading and trailing edges. Start by pinning down the lower spar square to the centre line, add and glue ribs into position, cut a length of 6mm strip for the leading edge and again for the trailing edge of the aileron cut out and glue in place, then add the top spruce spar.

img_8744.jpg

img_8745.jpg

Once complete, repeat for the second panel and when dry cut away a 6mm x 6mm slot into the first 3 ribs behind the main spar top and bottom to both panels. The wings can then be glued together a spruce spar doublers glued in place top and bottom. When dry the leading and trailing edges can be sanded to shape ready for sheeting.

img_8750.jpg

Also trim spars flush with end ribs , Note ailerons are made from 6mm leading edge glued onto 2mm sheet plan profile with riblets added on top. Ply plates are added for horn fixing top and bottom and diagonal riblets also added for torsional rigidity

img_8930.jpg

The wing is held in place to the fuselage by two 6mm dowels glued into the leading edge extending back to the main spar which has a 6mm sheet facing plate with corresponding holes for the dowels to glue into. This was done by positioning the wing onto the fuselage, checking for square and the drilling through the fuselage former into the wing to ensure correct positioning and dowels glued in place. Once done the wing can be sheeted with 1.5mm balsa, leading edge back to the rear edge of the main spar top and bottom, and 25mm strip at the trailing edge with 6mm wide cap strips over remaining ribs. The centre section is sheeted out to the fourth rib.

img_8939.jpg

To hide those wing bolts a small D box was added to the fuselage former and shaped to match the wing profile

img_8914.jpg

img_8920.jpg

Wing tips are from 6mm sheet glued on end rib chord centre line with 6mm sheet ribs top and bottom aligned with spars and sanded to shape

img_8934.jpg

Linds

Link to comment
Share on other sites

When it came to the tail surfaces we have two options. My own preference was for a V Tail, so no rudder. The assembly is made up from 6mm balsa strip cut to size and then sanded to a 60 degree angle on the centre. To reinforce and 6mm sheet strip was sanded to the same profile and glued into the joint, the assembly was further strengthened with glass fibre cloth and epoxy laminating resin.

img_8925.jpg

The tail is mounted onto a similar balsa sanded v section on the rear on the fuselage. I used an incidence metre and a level to ensure maintaining the 1 degree of incidence between the main wing and tail plane that I required but will be glued in place later. The elevators are simple 6mm balsa and sanded to profile. The control horns will be short torque rods will ball joint connectors to a single traditional pushrod with 2mm wire connections to each side.

img_8946.jpg

The more conventional tail is on Paul's version and follows a very traditional lightweight structure that will have some additional thin ply reinforcing a little later. The fin locates into a mounting plate at the front and into the tail stock at the rear of the tail plane in an attempt to keep the open structure element of the design.

img_8940.jpg At this stage the basic airframes are largely complete and now undergoing some thoughts re finishing

img_8949.jpg

img_8955.jpg

more updates soon as we hope to have them on the Orme in two weeks! Linds

Link to comment
Share on other sites

It's odd PV as a few people have said it reminds them of the Colditz Glider

colditz-glider.jpg

In reality it has a few similarities but not really that close so maybe its just that mental perception of what we think something is like until you put the two side by side. Maybe its the built out of scraps thing that fundamentally makes them have some synergy?

The V Tail prototype is now covered supporting a predominantly yellow solartex scheme, leaving the lattice frame uncovered of course and stained with a dark varnish as it is what I had left over from Dawn Flyer a couple of years back. Ailerons and Elevators covered red. Just need to work my way through the servo installation now and she is not far away from being ready for a test flight at least in her pure slope layout. We have also added a fairly substantial nose skid to the design. The engine pod is also in progress, I'll add some more photos to the blog soon Linds

Link to comment
Share on other sites

Well quite a bit of progress done including a complete re think on the name as it was just not working for me so we have settled on the new name of 'The Woodpecker' It also gave rise to a quite cute little logo insignia.

Model is now covered with Solartex and kitted out with two HS85MG servos for the ailerons and a Futaba 148 for the elevators which are connected via a single traditional pushrod with wire fork linked to the horns via ball link connectors.

A little work just to do in fitting the battery and setting final CG as far as slope soaring is concerned however I am also making a bolt on brushless motor which I will show a little later.

For now here's some pics

s3180004.jpg

Keeping up with the tradition of open lattice rear fuselage of Dawn Flyer and Flycatcher

s3180008.jpg

Nice big skid needed sweating and clamping to get the bend but does add a touch of character I think.

s3180005.jpg

Well you've got to have the correct pilot for the job don't you

Linds

Link to comment
Share on other sites

Well GeeW, Dennis gets the V tail, if we can find a Beryl she may well get the other. I know what you mean about the skid. I did or at least we (Paul Rice & I) played around with concepts but in the end this idea seemed to fit best and pretty simple to fit as it is just screwed into hardwood blocks and will have a fake spring on the front. The beauty of models like this of course is that if you don't like it then its easy to change, which is what its all about in the end.

Today I have mostly been playing around with a motor mount set up. The plan is to make this model multi task so flat filed options are a must so a power set up needed to be designed in. The hatch on the nose was the targeted space so a mount design was configured to support a brushless motor to provide adequate power for a hand launch flight.

s3190007.jpg

The mount was designed to set the thrust line at approximately the correct angle by fixing from a face plate set at a controlled angle. This angle was set by measuring the incidence and on the main wing and tail and setting the mount to give -1 degree thrust. to ensure we get prop clearance some long 3mm bolts and nylock washers are used to create a standoff that gives the prop about 6mm clearance at the front of the model. Its obviously all a bit finger in the wind at this stage but should not be too far away from the final settings required.

s3190003.jpg

The esc will mount inside the fuselage and the mount will be fixed with bolts onto the hatch opening with 3mm bolts and captive nuts so can be removed easily when not required. The trick will be to get the CG position correct for both options without to much messing about but a tray with fixings for different batteries to locate will hopefully resolve this issue and make transition a few minutes work only and something that can be done on site if required.

s3190004.jpg

The prop has about 6mm clearance, no power tests done as yet but that's a Parkzone 10x7 prop and would hope to get about 275-300 watts on a 3cell pack with a bit of luck through a 40amp esc but I can up spec if I need to. the motor is an 1100kv 35-30 size so should be up to the job. In fairness I have not weighed the model yet so I need to do that first and then see what power I can drag out of the set up but were not after vertical performance on this one. more soon. Linds

Link to comment
Share on other sites

  • 6 months later...

Its been a while since I updated this blog, the model has now flown way back in August at the Greenacres Fly In and whilst under power she performed quite nicely I just felt the gliding performance was too compromised. This was backed up on the slopes and a further problem also became evident with masking of the V Tail occurring at certain angles of attack resulting in loss of elevator effectiveness. Whilst considering various options I settled on the decisions to revert to a more conventional tail as per our second prototype which has had a better performance and also extend the wing for a better gliding performance from 66 inch to 80 inches and split in two halves with aluminium tube spars for easy transport. The model now also has larger ailerons as a result of the wing span increase and also a set of clip on struts. The result has been a significant improvement in performance as a glider. The option or question now is do I keep both wings, the short as a power model and the larger as a glider.

photo of the larger wing final version on the slope today

final woodpecker dec16.jpg

Linds

Edited By Lindsay Todd on 17/12/2016 17:50:24

Link to comment
Share on other sites

  • 2 weeks later...

Well finally managed to find a day and get some descent flying shots done of Woodpecker design, both prototypes flown one having a 65inch wing and the yellow and red with a two piece 80inch wing for better soaring performance. Both models performed beautifully and I guess I now have to get down to drawing it up properly anyway he are a few pics that my wife took on the day.

img_8811.jpg

img_8863.jpg

img_8812.jpg

img_8876.jpg

Linds

Link to comment
Share on other sites

  • 10 months later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...