Scratch-built "Cuda"
- Thread starter gsjames
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gsjames
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That's great, Dave! Thanks.
I found the coordinates for Kevin's KM7 section and made a quick overlay of it and Dr. Mark Drela's AG40d-02f section. The Drela section has a bit more camber but they are quite similar, so I figure that my build will be more than satisfactory for a sport model. Here is an image of the two sections. The Drela section is in blue and the McKiou section is in red. Of course, it is likely that my actual wing isn't even close to what I intended with the limitations of hot wire cutting, sheeting, vacuum bagging and sanding. But it will be good enough.
I found the coordinates for Kevin's KM7 section and made a quick overlay of it and Dr. Mark Drela's AG40d-02f section. The Drela section has a bit more camber but they are quite similar, so I figure that my build will be more than satisfactory for a sport model. Here is an image of the two sections. The Drela section is in blue and the McKiou section is in red. Of course, it is likely that my actual wing isn't even close to what I intended with the limitations of hot wire cutting, sheeting, vacuum bagging and sanding. But it will be good enough.
Gregory A Stewart
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I don't follow forums as closely as I used to, so just spotted your thread.
Great progress, looking forward to seeing the finished 'Cuda & flight reports.
Been flying RCRGs/BGs on & off since the late 1970s including a spot on the 2006 & 2008 US WSMC teams. I built a 'Cuda in the late 1990s/early 2000s (along with one each of Kevin's Stingray III & V).
The 'Cuda is a good primer model for RCRG duration, though not really competitive in current S8E/P & S8D/P (although it wouldn't be too bad for non-precision landing events). I even used my 'Cuda as a training model for a then junior in 2007 which he used to get a slot on the 2008 Junior team... & has since been on more teams than me, including this summer's WSMC S8E/P Silver Team.
While Kevin's build & instructions are a GREAT primer for this type of model, there are several things I suggest as tweaks / improvements...
1st, the pod is a significant weak spot & breaks easily on even ok landings. & It is designed for older RC gear than available today. After a few repairs / rebuilds I rebuilt my 'Cuda pod with the servos on-line, used 1/20 basswood for much of the pod sides with CF strips as additional reinforcement, moved the hatch to the bottom to minimize unsupported structure, & glassed the pod with .75oz fiberglass cloth. Nearly the same weight, MUCH STRONGER & MORE DURABLE, I STRONGLY RECOMMEND THIS!!! Details in this post & a few following in that thread:
www.rcgroups.com
2nd, I did the optional tapering of the balsa wing skins to 1/32" at the tips, CF strips instead of the included glass, & finished them & the tails with Esaki tissue to keep them light.
3rd, on my 2006 & 2008 comp models I used bondable Teflon tubing with .018" stainless steel pushrods, much lighter than the recommended while just as stiff if installed as per plan. Not sure where to get the bondable Teflon nowadays though!
4th on my 'Cuda I used Kevin's "sand a cylindrical recess in the bottom of the assembled inverted V-tail & glue 8t to the top of the tailboom" from his SR-III. Works, easy to do, strong, but as I later found out very draggy. I also did this on my OD 2005 flyoff models, but during a repair converted one to the bottom-mounting as similar to the 'Cuda instructions. My boosts with the otherwise identical model were 100'+ higher! I now do this with the rear of the airfoiled inverted V-tail slightly recessed to glue directly to the CF tailboom & a small, light balsa fill-in at the front. Will see if I can post some good pix of this.
5th, use a launcher (as shown) with guides that cradle both the wing & tail/stab separately & can be adjusted to have the surfaces exit the guides at the same time. This prevents wind pivoting the model as it leaves the launcher & allows good launches even in high winds... Can share stories & pix about this if you need convincing, but I consider this a must-have for these models.
Kept light & reasonably low drag, it is a fun model on plugged C6s, C11s, & D12s. Trim with C6s, then move up. & Of course even better on D7-E7-E6 reloads.
Greg in Mississippi
P.S. I'd call Chad Ring's model above "'Cuda Inspired" at best. Nice though!
Great progress, looking forward to seeing the finished 'Cuda & flight reports.
Been flying RCRGs/BGs on & off since the late 1970s including a spot on the 2006 & 2008 US WSMC teams. I built a 'Cuda in the late 1990s/early 2000s (along with one each of Kevin's Stingray III & V).
The 'Cuda is a good primer model for RCRG duration, though not really competitive in current S8E/P & S8D/P (although it wouldn't be too bad for non-precision landing events). I even used my 'Cuda as a training model for a then junior in 2007 which he used to get a slot on the 2008 Junior team... & has since been on more teams than me, including this summer's WSMC S8E/P Silver Team.
While Kevin's build & instructions are a GREAT primer for this type of model, there are several things I suggest as tweaks / improvements...
1st, the pod is a significant weak spot & breaks easily on even ok landings. & It is designed for older RC gear than available today. After a few repairs / rebuilds I rebuilt my 'Cuda pod with the servos on-line, used 1/20 basswood for much of the pod sides with CF strips as additional reinforcement, moved the hatch to the bottom to minimize unsupported structure, & glassed the pod with .75oz fiberglass cloth. Nearly the same weight, MUCH STRONGER & MORE DURABLE, I STRONGLY RECOMMEND THIS!!! Details in this post & a few following in that thread:
RC Groups - View Single Post - S8E - models
RC Groups - the most active Radio Control model community: electric and fuel rc airplanes,rc helis,rc boats and rc cars. Features discussion forums, blogs, videos and classifieds.
2nd, I did the optional tapering of the balsa wing skins to 1/32" at the tips, CF strips instead of the included glass, & finished them & the tails with Esaki tissue to keep them light.
3rd, on my 2006 & 2008 comp models I used bondable Teflon tubing with .018" stainless steel pushrods, much lighter than the recommended while just as stiff if installed as per plan. Not sure where to get the bondable Teflon nowadays though!
4th on my 'Cuda I used Kevin's "sand a cylindrical recess in the bottom of the assembled inverted V-tail & glue 8t to the top of the tailboom" from his SR-III. Works, easy to do, strong, but as I later found out very draggy. I also did this on my OD 2005 flyoff models, but during a repair converted one to the bottom-mounting as similar to the 'Cuda instructions. My boosts with the otherwise identical model were 100'+ higher! I now do this with the rear of the airfoiled inverted V-tail slightly recessed to glue directly to the CF tailboom & a small, light balsa fill-in at the front. Will see if I can post some good pix of this.
5th, use a launcher (as shown) with guides that cradle both the wing & tail/stab separately & can be adjusted to have the surfaces exit the guides at the same time. This prevents wind pivoting the model as it leaves the launcher & allows good launches even in high winds... Can share stories & pix about this if you need convincing, but I consider this a must-have for these models.
Kept light & reasonably low drag, it is a fun model on plugged C6s, C11s, & D12s. Trim with C6s, then move up. & Of course even better on D7-E7-E6 reloads.
Greg in Mississippi
P.S. I'd call Chad Ring's model above "'Cuda Inspired" at best. Nice though!
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Greg, greetings from Memphis and the Mid-South Rocket Society. We launch once a month at Shelby Farms in Memphis, TN.
https://midsouthrockets.com/
Would be great if you could join us some Saturday.
https://midsouthrockets.com/
Would be great if you could join us some Saturday.
Gregory A Stewart
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Greetings back.
I've been well-aware of MSRS for the last couple years, even been on a few of the monthly Zoom meetings. & WHEN I get the info on where to send my membership payment, I'll be a section member!
Worked with MSRS earlier this year to find a local mentor for a near-Memphis TARC team I was mentoring remotely this last cycle. Happily Dave Mower stepped up & provided the hands-on mentoring, launch opportunities, & assistance the team needed to post successful qualification flights. Sadly, they didn't make the finals. But they learned a LOT!
I'll be up there to fly at some point. Currently getting back into the swing of building & flying, mostly focused on gliders (pure, electric, & rocket-boosted) along with a smattering of rockets, free flight competition models, & RC sport models. All spurred by FINALLY bringing a minimal level of organization & order to my model aviation build & storage spaces PLUS gaining / regaining access to several local flying areas.
Likely later in the fall, making no promises yet, but I have a large portion of my relatives on my dad's side in the Memphis area (literally hundreds of relatives!), so there's always a pull to visit!
Greg in Mississippi
P.S. The prelaunch pix of one of my older S8E/P models on the box-based RCRG launcher was taken at a local practice session of 2 of the US S8E/P team members who won 1st, 5th, & 12th & Team Silver a few weeks ago at this summer's World Champs. Flying with them was a true hoot!
I've been well-aware of MSRS for the last couple years, even been on a few of the monthly Zoom meetings. & WHEN I get the info on where to send my membership payment, I'll be a section member!
Worked with MSRS earlier this year to find a local mentor for a near-Memphis TARC team I was mentoring remotely this last cycle. Happily Dave Mower stepped up & provided the hands-on mentoring, launch opportunities, & assistance the team needed to post successful qualification flights. Sadly, they didn't make the finals. But they learned a LOT!
I'll be up there to fly at some point. Currently getting back into the swing of building & flying, mostly focused on gliders (pure, electric, & rocket-boosted) along with a smattering of rockets, free flight competition models, & RC sport models. All spurred by FINALLY bringing a minimal level of organization & order to my model aviation build & storage spaces PLUS gaining / regaining access to several local flying areas.
Likely later in the fall, making no promises yet, but I have a large portion of my relatives on my dad's side in the Memphis area (literally hundreds of relatives!), so there's always a pull to visit!
Greg in Mississippi
P.S. The prelaunch pix of one of my older S8E/P models on the box-based RCRG launcher was taken at a local practice session of 2 of the US S8E/P team members who won 1st, 5th, & 12th & Team Silver a few weeks ago at this summer's World Champs. Flying with them was a true hoot!
