RC Gliders, Sailplanes and Slope Soaring Discuss rc gliders,rc sailplanes and slope soaring in this forum. Thermaling techniques, airfoils, tips, etc

A better airfoil for a enlarged Super Sinbad?

Reply

Old 11-23-2015, 07:02 AM
  #1  
foodstick
Thread Starter
 
foodstick's Avatar
 
Join Date: Mar 2005
Location: ankeny, IA
Posts: 5,547
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default A better airfoil for a enlarged Super Sinbad?

I have some slightly enlarged plans for an old tow glider called the Super Sinbad. If you have seen one you know its has nice lines to it. Years ago I built the fuse and tail so that it could use a Gentle Lady wing. It would probably still work but I just don't think that wing will look right...
With the electric power out there now I think the NEW eventual goal is a power pod on the planes wing. I have been kicking around the idea of using a much better airfoil than the design used in the 30? 40s?

Is their another flat bottom airfoil out there that would be a smart replacement ? I admit I don't know anyone that has flown this design..but I am guessing the airfoil is far from being great.

This fuse has been on my shelf forever and its such a nice looker, I really want to get it airworthy over the winter.
foodstick is offline  
Reply With Quote
Old 11-24-2015, 02:51 PM
  #2  
jetmaven
 
Join Date: May 2002
Location: Fl.
Posts: 370
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

I did something similar some years ago .
Im sure there are a thousand different opinions but for the sake of simplicity I chose a
Clark Y . It's been around forever . Yet to fly and I'm thinking about aerotowing it.
If the picture is upside down , I apologize in advance . When I click on it , it come out right side up.
I give up .
Attached Thumbnails Click image for larger version

Name:	image.jpg
Views:	194
Size:	1.24 MB
ID:	2132340  
jetmaven is online now  
Reply With Quote
Old 11-24-2015, 06:17 PM
  #3  
foodstick
Thread Starter
 
foodstick's Avatar
 
Join Date: Mar 2005
Location: ankeny, IA
Posts: 5,547
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Well it looks like your air foil choice works inverted any how ! hahahha

I do like that era of free flight gliders. I can't even imagine the thrill and risk you felt taking something like these up high and just letting them go....
foodstick is offline  
Reply With Quote
Old 11-24-2015, 07:48 PM
  #4  
jetmaven
 
Join Date: May 2002
Location: Fl.
Posts: 370
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

If you click on the picture it opens right side up . I have no idea why but it does .
This design was an updated Albatross .
jetmaven is online now  
Reply With Quote
Old 11-25-2015, 09:25 AM
  #5  
speedracerntrixie
My Feedback: (29)
 
speedracerntrixie's Avatar
 
Join Date: Jun 2010
Location: Sacramento, CA
Posts: 6,656
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Eppler 205 was the go to flat bottom airfoil some 25 years ago. The Airtronics Saggita and Top Flite Antaries both used the 205 and were baseline sailplanes of the era.
Attached Thumbnails Click image for larger version

Name:	image.png
Views:	188
Size:	300.0 KB
ID:	2132445  
speedracerntrixie is online now  
Reply With Quote
Old 11-25-2015, 10:25 AM
  #6  
BMatthews
 
BMatthews's Avatar
 
Join Date: Oct 2002
Location: Chilliwack, BC, CANADA
Posts: 12,337
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

I think it becomes a "be careful what you wish for" sort of deal if you modernize it too far.

The whole point of using many of the sailplane airfoils these days is to expand the speed range. But a Super Sinbad fuselage of any sort is a nicely shaped parachute in comparison to the broom handle fuselages used on modern RC sailplanes. So the top end speed is going to be limited by this. Or you'll have to dive so much to make it happen that you lose out.

It's a bit more of a fuss to cover the wing but I'd want to go the other way and use a thin moderately undercambered airfoil to enhance the low speed side of things so it just seems to hang up there. It would become pretty much a light wind sort of model but then the drag of the fuselage sort of sets the bar at that level already.

Also when you say "enlarged" just how much of a size increase are we talking about here?
BMatthews is offline  
Reply With Quote
Old 11-25-2015, 01:36 PM
  #7  
foodstick
Thread Starter
 
foodstick's Avatar
 
Join Date: Mar 2005
Location: ankeny, IA
Posts: 5,547
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

You know, I am not even sure how much the guy I got the plans from enlarged them? This will give you an idea..



I do have a 2 meter Sig riser wing another friend gave me.. maybe I should just strip it, cut it up and make a dihedral wing.., and reshape the tips to a rounder shape....
Attached Thumbnails Click image for larger version

Name:	IMG_5124.JPG
Views:	1120
Size:	1.60 MB
ID:	2132478  
foodstick is offline  
Reply With Quote
Old 12-06-2015, 08:23 AM
  #8  
da Rock
Senior Member
 
Join Date: Oct 2005
Location: Near Pfafftown NC
Posts: 11,511
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Originally Posted by foodstick View Post
You know, I am not even sure how much the guy I got the plans from enlarged them? This will give you an idea..



I do have a 2 meter Sig riser wing another friend gave me.. maybe I should just strip it, cut it up and make a dihedral wing.., and reshape the tips to a rounder shape....
Gentle Lady wing was a good idea. It would have looked different. The Riser wing isn't going to look worse. Rounding the tips would help. However, the original Sinbad had a straight wing, no polyhedral and was not a high aspect ratio at all. So... you got some thinking to do about the wing planform which ever way you go.

Does your present fuselage match up to the root chord of the wing you're planning to use? The aspect ratio of the Sinbad design is quite different from what a Riser/Gentle Lady wing brings to the airplane. In fact, I'd guess truncating the modern wing at the polyhedral break might still give more AR than the Sinbad model had. The yaw stability might be a problem with a 2m wing on that sucker.
da Rock is offline  
Reply With Quote
Old 12-06-2015, 08:37 AM
  #9  
da Rock
Senior Member
 
Join Date: Oct 2005
Location: Near Pfafftown NC
Posts: 11,511
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

The E205 actually is a good idea for sure, from experience. I've used it on a straight wing "oldie". Well, it was actually a straight wing with slight LE and TE taper that was E205-E193.

What gave us fits was getting the AOI correct. Incidence seems to have more effect when the wing is carrying a bulky fuselage that probably isn't exactly low drag. I'd suggest having your rear wing rod be adjustable in the fuselage.
da Rock is offline  
Reply With Quote
Old 12-06-2015, 09:33 AM
  #10  
foodstick
Thread Starter
 
foodstick's Avatar
 
Join Date: Mar 2005
Location: ankeny, IA
Posts: 5,547
Gallery
My Gallery
Models
My Models
Ratings
My Feedback
Default

Hmmm, full flying tail might be smart ....

One change I have made to the fuse was the original plane had the leading edge at the back of the windshield...years ago when I was messing with this I extended the wing saddle to allow the wing to be out forward an inch or two.. right where the windshield comes up in center..

I am really tempted to modify the riser or gentle lady wing as I doubt I would be building/flying two meter anytime soon. I would GUESS the riser wing airfoil is better? the gentle lady wing is my absolute first rc aircraft wing.. I know there is some glue and repair inside of it !

hahahhahaha

I really do want to see this classic bird fly next year. to long on the shelf !
foodstick is offline  
Reply With Quote

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service