SCORPIO_2727

Building the Optica deserves a new thread. Ok, kdc? Louis, a smart decision to shy away from building the Optica. I've started to build mine. The instructions leave a lot of gray areas. Building the prop shroud/duct can be likened to building a house from a stack of cards. One level on top of the other. The duct ribs (12) are airfoil in shape, of 3 pieces each rib. Thus the levels. Now in hindsight, I could have left the ducting ribs in 1 piece. Have 2 level built so far, the tailpiece yet to do. The biggest problem I can see coming up is the 1/16 balsa sheeting of the duct, inside and out. The instructions just say sheet the ducting. Imagine a semi-symetrical wing over 36 inches long, wrapped around in a 12 circle. The inlet is the problem. Balsa grain crossway between each pair of the 12 ribs would give me a circle with 12 "flat" sides. Wrapping a piece of balsa around the inner and outer circles in one piece would be next to impossible, due to the airfoil shape. Even with liberal use of hot water and ammonia. ANY SUGGESTIONS, PLEASE. The full size craft duct is circular and that's what I want. Yes, Louis, I spotted the no dihedral on that plane for sale. Will post photos asap. Glen

kdc

There are several ways I can think of to make balsa bend easily.

1 Make 2 laminations of thinner balsa or use 1/64 ply with the outer grain the short way. It is easy to make 5 inch diameter cowls from bent 1/64 ply so a 12 inch ring should be easier. An inner former (removable or integral ) is useful.

2 cover the balsa with solarfilm or masking tape or brown paper or glass cloth on the OUTSIDE BEFORE you attempt to bend. ( wood always bursts on the tension side -outside- before the compression side gives way ) Solarfilm, paper or tapecan be removed afterwards. Try an experiment and see how well this works!

3 Wrap the wet balsa around a former first and allow to dry before even trying 1 or 2 above.

4 Instead of balsa what about something like Depron over (or in ) a cylindrical former covered in glass cloth & epoxy? I am sure there are techniques like this used in free flight or something

kdc

In case anyone has not followed the previous thread all the way through the latest info is that the Edgeley Optica plan should now be avail from Magicalia www.modelflying.co.uk together with most other Encanta/Highbury/Nexus/Argus plans.
They will soon have an online catalogue. Meanwhile you could email orders to [email protected] or phone direct line (44 )01296 730691 with your order 9.00 am to 3.00pm GMT

The 81 inch span Optica plan was by J Wright and was published ( in England ) in the Winter 1988 issue of Radio Control Scale Aircraft.

SCORPIO_2727

Hi, Keith. Have taken on board your suggestions. Suggestions # 1 & 4 have given me ideas. The airfoil inlet duct (inner) can be likened to the flare on a coffee cup, ie bigger radius at the front lip than the bottom/back, whereas the outside sheeting glares inwards at the front lip. Forming the 12 inch circle, no problem, but to flare that same circle bigger at the front to follow the airfoil is my problem. Re suggestion #1. Lamination. Strips of balsa at 45 degrees to the ribs. ie starting at the top rear of one rib, across the middle of the next rib and down to the bottom of the 3rd rib, and so on. Suggestion # 4= Depron. The use of blue foam, etc, between the 12 ribs and then sand to shape, finally covered in light cloth and epoxy. I have to remember the ducting framing is rather fragile and won't stand much stress when it comes to pull and grunt. Thanks for your expertise, Keith; I needed a hudge to get the gray matter working, rather than sitting on my thumbs, pondering the problem and failing to see a solution. Glen

kdc

Before reading your reply I prepared the following message:-

"Not having seen the drawing of the component, I did not realise at first that there might be dual curvature to contend with.
As there is dual curvature involved the answer may be to use shipbuilding techniques like planking. In this instance diagonal planking may be the best option. In this technique a narrow strip is applied at an angle of perhaps 30 to 45 degrees, so the effect is to twist the plank rather than bend it in two directions.
Also the strongest way to do this is double diagonal planking which is two layers at opposite angles -i.e. 2 strips at about 90 degrees to each other ( like plywood ). (as used on Vosper MTB,s both full size and models, also Albatros planes I think ) The second layer is applied after the first has fully dried and been sanded. Joints are staggered of course.

I would suggest trying to get a 2 inch strip of 1/16 balsa to fit at 45 degrees first, if this wont conform, try 1 inch or ¾ inch etc ,then try some 1/32 . At a guess I would expect 2 layers of 2 inch by 1/32 would be quickest/strongest. (glue is heavy!) Maybe 1 layer balsa covered by fibreglass?

In any case it is said to be best to work on opposite sides at the same time to avoid pulling out of shape. Perhaps in this instance start at 4 places at 90 degrees."

So it is true ' great minds think alike!'

SCORPIO_2727

Keith. Am going to go ahead with the strip planking idea. Building the duct, in 3 stages/levels, is a pain. Going by the magazine instructions you sent me, I first glued the cockpit 1/4 inch ply spine to the ply engine mount. Mistake. Now the spine is in the road while building the duct. So cut a slot 12 inches long by 3/8 wide in the top of my building table, inserted the cockpit spine so I could build upwards. Now my building board has the semblence of a minature Stonehenge or Romas Colosseum, 2 levels, one to go. To keep everything square while building the duct upwards, I've used threaded rod tapped into the ply engine disc, (in lieu of an engine shaft); cut a ply disc the size of the 11inch prop plus clearences, set at the level of the prop. This holds everything square while I build upwards and during sheeting. Started this project with a lot of trepidation but now starting to enjoy the experience. More satisfaction than just putting an ARF together. One ARF plane in 50 odd years of modelling and that was given as a present. Now to that plank sheeting, working one for one opposite.

kdc

I cannot actually visualise the construction. It would be very interesting to see a quick picture on this site. A very unusual setup might become useful to other people for a completely different model too.

SCORPIO_2727

Will dig out the digital camera and try to post some pics of my "mini Stonehenge" construction. In the past, have tried to post pics here but have run into all sorts of strife.

kdc

I seem to remember that you need to use the ' Reply' button at the top of the page ( instead of the ' fast reply' section that appears under the previous messsages,) when submitting photos. Takes time too.

Look forward to seeing pics.

SCORPIO_2727

http://s149.photobucket.com/albums/s75/scorpio_2727/

Eventually got the photos to "stick"- used cyno. Joke The problem was not with RC Universe. That rectangular balsa block in the centre is only temp, holding the threaded bar (in lieu of engine shaft) vertical during duct construction. The two ply "wings" on either side are the attachment points for the 1/4 x 1/4 spruce wing spars. Another set of ply wings (rear sub spars) mount on the balsa ring where the pins are. The 12 tailcone ribs yet to be put in situ. Of course, the big ply disc comes out after framework is completed. Have yet to find out why the ply rings do not go full circle. That slot in the building table certainally came in handy.

kdc

Very interesting photos, I can understand the construction now.

Next time instead of mutilating your workbench you could always use the slot in a Black & Decker Workmate!

SCORPIO_2727

The ducting tailcone sub ribs are in place. Had to support these ribs with with cross-bracing around the "circle". (Weak without the sheeting. ) Have wrapped the balsa sheeting around the centre section, inner and outer. I do the inner sheeting first- to see what I'm doing. Have now just started on sheeting the inside inlet duct with 20mm wide planks (1/16 balsa) at 45 degrees as you suggested, kdc. Slow process but coming together. Planning ahead re sheeting the outer surface of the tailcone. A 13 inch forward ring, 5 inch back to a 11 & 1/2 inch rear ring. (All the inner duct is straight/parallel). The sheeting would require a curved flat profile to wrap around the 2 circles. Confession; cheated here. Spoke to draftsmen at my workplace who referred me to the machine shop. Just so happens they have a "plate and sheet development program" on their computer. Gave them the specs and 10 minutes later I was presented with the correct curved flat profile shape. Much better than trial and error using a huge compass made out of 2 bits of wood, a nail one end, pencil the other. Louis, the most important instrument in your photos is that plastic set square. My set square is indespensible. Glen

Vliegeniertje

I'll leave this your building thread and post in the other one

kdc

It would be nice to see a photo of the double diagonal planking method being used.

SCORPIO_2727

All the duct sheeting is now complete. Phew, what a job, kdc. Before I did the final bit of planking on the inside of the tailcone, I took pics. Taking pics as I go along. Will post when I can. That 11inch plus clearance disc I used in the prop position, I kept moving up (finishing at the tailcone) as I built up/back. Worked a treat. Still have that 11inch plus clearance at the tailpipe exit. I wrapped the disc in clingwrap at the feathered end of the ribs to stop the pvc glue from glueing the lot together. Plus the disc supported the oh so wobbly ribs. Sheeted the outside of the tailcone first. Removed the disc, plus other braces. That programmed curved disc was spot on. Sanding and filling ahead of me now. Louis, 2 things I'd like to mention. First, I'm comleting the cockpit/ducting assembly first--I don't want to be waving big wings around. The wings and the rest can come later. Second; when doing your planking on the STRAIGHT tapers using 4 inch wide balsa butt-glued together, (over 38 inch long) put the glue joints different inside to outside. When I sheeted the outside of the tailcone, I had a many straight sided circle. Looked awful. When doing the inside of the tail ducting, I set the butt-joined balsa so the glue joints were in between the glue joints on the outside. Pulled everything back into a circle. I intend using a 3 bladed pusher prop, 11 inch with a rather coarse pitch. I have 3MM (1/8") clearance at each prop tip. When doing the cockpit, will have to work out the best route for the servo extension leads to the servos at the tail end-- have to get everything through that gaping 11inch duct without flapping in the breeze. Best way I guess would be to "bury" the leads in the duct vanes and out into the wings. I'm enjoying this!!! Glen

SCORPIO_2727

Here are some of the latest construction pics.





http://s149.photobucket.com/albums/s75/scorpio_2727/

Glen (the one with the sore thumbs from pushing in pins)

kdc

Very interesting photos of a difficult build.

( get some T headed pins for your next job! )

Boomerang1

Hi Glen,

Stumbled across this Optica on an electric website. May be of interest. - John.

http://www.flyelectric.ukgateway.net/optica.htm

BOB MOORE

Hey Glenn the web site Boomerange sent you is the one I tried to send to you but you couldn;t open itBOB

LowFlyBye

Glen-

Here are the pics per your request.

-Low

BOB MOORE

Het guys!! There is an Optica for sale in the USA. I contacted the seller(Owner) D Wallace and he sent me these pictures, Enjoy BOB Moore

Vliegeniertje

I can't keep up with you, having a real hard time finding parts like the transparant dome and the pushprop.

It's looking good [sm=thumbup.gif]

SCORPIO_2727

Low and Bob. Thanks for the pics. Am having colour photos produced of these pics. These are a lot clearer than colour photo copies. All my cockpit problems are now solved. I can see so much detail now. So will now make changes to my model to make same more scale like. I'll be like a young girl setting up her doll's house now. I'm waiting on servo extension wire to turn up to insert in each stage as I progress. Have been waiting 2 weeks for it's arrival. Strange how I can receive r/c goodies from the UK faster than I can from a mail order hobby shop here in Australia!!! Perhaps the pony express horse threw a shoe? Low and Bob, am now happy as a pig in mud. Many thanks to you both. Glen

SCORPIO_2727

Louis, I am sure I can help you out with your transpatent cockpit and prop. Just give me the width and height of your cockpit. As far as props go, what size/type (2 or 4 stroke) of motor are you using? Do you want a 2 or a 3 blade pusher prop and what size? People help me out on this thread so I can do likewise to and for you. Louis, all you have to do is ask. Would be my pleasure to help you out. Glen

Vliegeniertje

Glen, I'll post in the other thread so this one stays clean with building related "things"...