Sun Ray biplane
 

Hello Everyone,

I just began scratch building a Sun Ray biplane which was featured in March 1975 RCM magazine. I can post a few pictures of my build if anybody is interested.

Wingspan: upper 51", lower 38"
Wing Chord: upper 9", lower 6-3/4"
Total wing area: 700 square inches
Airfoil: symmettrical
Wing Planform: constant chord
Dihedral Each Tip: no dihedral
Overall Fuselage Length: 50-1/2"
Stabilizer Span: 21"
Rec. Engine Size: 61
Fuel Tank Size: 12 ounce
Rec. No. of Channels: 4
Weight Ready to Fly: 120 ounces
Wing Loading: 24.6 oz./sq. ft.


Quote from RCM article: "This is a fast biplane, highly maneuverable and performs all AMA and FAI patterns, is good for open pylon, and makes a great all around sport plane for the Sunday flyer. She's extremely steady and stable in high winds, with easy stall characteristics and slow landing speed. The wide stance landing gear sets up good control in ground maneuvers, landings, and take offs. One of the most remarkable features of this airplane is it's ability to do sustained knife edge flight, and starting from straight level flight, will climb out and complete a 270 degree knife edge loop! The plane is completely predictable in all flight maneuvers."

I've already cut out several parts including the gull wing spar from 1/4" ply. I'm using notebook paper to trace parts on the plan. I taped a few sheets together for making a fuselage side template. The notebook paper isn't very transparent but I was able to see thru good enough to trace parts.

Next I want to make the wing ribs. I need to make 18 identical ribs for the upper wing and 24 identical ribs for the lower wing. Cutting these individually would take a long time. Anybody remember a method of stacking balsa blanks between two plywood rib templates and then sanding them to shape. I think you drill two holes thru the stack and bolt them together before sanding. Is that how it's done?

Anybody have a March 1975 RCM handy? I wish to see if the article has any helpful construction photos. My RCM plans only included a copy of the text. Real bummer the photos aren't included.

Found these Sun Ray pictures in another thread.


Mike

RE: Sun Ray biplane
 

Mike,

nice project. That's a good system to cut the ribs. Start with two identical ply templates to sandwich the oversized balsa ribs. You can bolt them together if you bore two holes through the stack but drilling nice round holes in balsa ribs is tricky unless done with a very fast rotation bit (i.e., a Dremel). I find a satisfactory method is to clamp the stack from one side of the ribs (e.g., bottom) and then contour the top ribs to template with a band or disc sander. You then flip the clamps over and repeat for the rib tops.

If you want to make some lightening holes in the ribs, I find that a Dremel drum sander works well. Make your hole in the templates and then sand through them with the Dremel. With a little care, you end up with a nicely bored set of ribs.

Keep the photos coming!

David.

RE: Sun Ray biplane
 

Clamping them sounds good. I'll try that.

Thanks

RE: Sun Ray biplane
 

Cool plane! Looks like a fun build. Save those rib templates, I may want to borrow them... :D

RE: Sun Ray biplane
 

For anyone else who is interested, Trenton RC Flyers has the sunray article up on their site.
[link=http://www.trentonrcflyers.com/pattern/articles/sunrayarticle.pdf]http://www.trentonrcflyers.com/pattern/articles/sunrayarticle.pdf[/link]

Hope that drums up some more interest in this unique looking ship. Enjoy gentlemen!

-Mitchell

RE: Sun Ray biplane
 

I tried the link but says the web page can not be found. I reported the problem and will try again later.

Thanks,

Mike

RE: Sun Ray biplane
 

I loved mine - great flying airplane! First airplane that I've built that would fly a knife-edge loop cleanly. I built mine in '76 or '77 and plan to build another one someday (maybe scale it up a bit).
Post some photos of your build!!

RE: Sun Ray biplane
 

I cant get the link to work myself anymore for some reason. I have the PDF saved however, so PM me with your guy's email addresses, and I'll send the PDF over e-mail. I think the file is too large to post on RCU, or I would just try posting it here. -Mitchell

RE: Sun Ray biplane
 

Awesome. I can hardly wait to see the article. Sending PM.

Thanks very much,

Mike

RE: Sun Ray biplane
 

Great to hear the positive comments from a former Sun Ray builder and flyer! I'm really looking forward to completing my Sun Ray and having some fun. More photos coming soon.

RE: Sun Ray biplane
 

Thanks Mitchell for sending me the Sun Ray article on pdf. There are many cool pictures in the article including some construction photos.

Side view picture from the article.

RE: Sun Ray biplane
 

could I get a copy on the plans?

chuck hochhalter

RE: Sun Ray biplane
 

PM me your email address and I would be happy to send you the article plans PDF I have... -Mitchell

RE: Sun Ray biplane
 

Mitchell has the plan on pdf or you can order a copy from www.rcmplans.com for $12.00 plus shipping.

I finished all the ribs! I only sandwiched 6 rough cut ribs at a time between the ply templates. That seemed easier than dealing with a tall stack.

Guess I'll make the ply fuselage doublers next and misc balsa fuselage formers.

Couple more pictures,

RE: Sun Ray biplane
 

Many more parts completed. Now the real fun begins, I'm ready to begin assembly! I will make all the other required parts as I need them.

RE: Sun Ray biplane
 

Looking great! If only my hand-made parts would ever look that immaculate, haha. I'll keep checking back to see your progress in the hopes that it'll get me off my duff to attempt my own build. The Sun Ray is just quirky enough to be my kind of model. Good luck with the build, not that you'll need it seeing the quality of your workmanship this far. Take care. -Mitchell

RE: Sun Ray biplane
 

Thanks! The parts are slightly oversize after I cut them with my Dremel scroll saw. Then I carefully sand them to match the plan. I used a straight edge and an xacto knife to cut the fuselage sides. Luckily so far I only messed up one part. I incorrectly cut bulkhead # 3. I didn't notice it should have an angle at the top.

Today I'm going to the hobby shop for a few misc supplies including an engine mount and spinner.

I hope you decide to build a Sun Ray too!

Mike

RE: Sun Ray biplane
 

This is a fun topic. Thank you for choosing it. I am subscribed!

Brian

RE: Sun Ray biplane
 

Thanks!

RE: Sun Ray biplane
 

Unfortunately I had a problem today when I mixed some 30 minute epoxy for the fuselage doublers. I had most of one fuselage side coated when it began to harden. Oh no!!! I tried to hurry and finish but it just started making lumps. Wiping it off was hopeless! That just made a bigger mess!!!

I don't know why my epoxy cured so fast. I hardly had 5 minutes working time. Maybe because it's old.

Oh well, I will let the lumpy mess dry overnight and try to sand it smooth tomorrow. Hopefully I don't have to make a new fuselage side.

RE: Sun Ray biplane
 

I salvaged the fuselage side! Luckily the epoxy dried hard (not rubbery) and was easily sanded. I began sanding with a little dremel sanding band and then block sanded.

After fixing the problem I have glued the doublers with some different epoxy. This time I used 20 minute finish cure epoxy. It's old too but seems to be okay. If anything it dries a little slow.

On with the build!

RE: Sun Ray biplane
 

I vaguely recall the Sun Ray as it appeared in the model magazine, but for those of us who require a little refresher, what's the wing span, wing area, and the size of the engine you'll be using?

Looking forward to seeing your model all framed up. Will you be putting wheel pants of your Sun Ray?

Interesting build,

Keith

RE: Sun Ray biplane
 

Specifications added to the opening post.

I decided to use my NIB K&B 61 with Perry carburetor. I'm preparing to send the engine to original designer Clarence Lee for PDP porting and blue printing. He offers this service for $28.50 plus $7.50 shipping as seen in Model Aviation magazine classified adds. I've heard these old K&B's with Lee's mods have very impressive performance.

Neat idea but I'm not planning to use wheel pants. Just some cool old Kraft Streamline wheels. Retracts would be ultimate!

Mike

RE: Sun Ray biplane
 

Mike,

I'm sorry for asking the wing span, when you had already posted that info. Lee's K&B engines are good ones, especially for your Sun Ray. You'll have plenty of power that's for sure!!
I suppose missing info can happen when responding to a build in the wee hours in the morning!!!

Keith

RE: Sun Ray biplane
 

You were right. I just edited the post to add the info. It wasn't there last night.

Mike