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May 27, 2014, 02:36 AM
RJPIoW's Avatar
Build Log

1/4 scale Vans RV-9 from 4 sheets depron

I have just maidened this new build and am more than happy with its performance. It flew straight off the board needing no trim changes.

The wings are made of folded depron over formers using templates for the lower surface. The fuselage is depron skins over formers. I opted to stiffen the fin, rudder , tailplane and fuselage with 25g glass using foam safe superglue, but I think it would have been stiff enough without.

The Hobbyking donkey was more than powerful enough with 4 cells

I have posted a video of the maiden flights

Vans RV 9 (2 min 47 sec)

Last edited by RJPIoW; May 27, 2014 at 05:54 AM.
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May 27, 2014, 09:52 AM
Registered User
Very nice. Do you have pictures showing how the wing was built?
May 27, 2014, 10:36 AM
RJPIoW's Avatar
Yes I have wing build photos, I tried to make it as accurate and as simple to build as possible , and because the real airfoil section details didnt appear to be published I used a NACA 23013,5.

I had planned to post stage photos of the whole build and a set of plans as well, I just need a few evenings to clean it all up ready.

May 27, 2014, 10:38 AM
Registered User
Sounds great. Thanks!
May 27, 2014, 12:03 PM
3d and EDF, some scale
MustangAce17's Avatar
Building one for sure when plans are out ! Awesome job, I love the RV's and this scale is perfect
May 27, 2014, 09:00 PM
Retired CAD guy
birdofplay's Avatar
That is a beauty !

Vans RV has always been a fav !

I flew the Factory rv6 in 92 in Oregon.

If you have plans I will be glad to cut it for you.

Come to think of it I still HAVE full sized plans of the RV6.
Just never had the nerve to build it.
Bought a tired old Cherokee PA28-180 instead.

RE the HK donkey motors.
IF yo have one with Pierced Holes in the CAN
PLEASE make sure that it has clearance from the COILS !
Mine did NOT and quickly ATE into the COILS and it needs to be rewound now.
Lots of smoke was exciting ... sigh .....
Spacers and a GRIND OUT of the Backside of those pierced holes is MANDATORY !


Hoosier Cutout Service.
May 28, 2014, 12:08 AM
RJPIoW's Avatar
I originally built the wings with scale flaps and ailerons, but during the initial flights I realized that this model was so lightly loaded that it landed very slowly anyway. Flaps needed some down elevator trim and the plane flew at a very slow walking pace. For this 2nd outing I converted the flaps to additional ailerons linked in using my Hitec gear, this increased the roll rate. I also moved the Lipo rearwards to take the CG to the point where inverted flight needs very little down stick

Up to now I have been a bit lazy in an effort to get this beauty airborne and I reused an old pair of aluminum undercarriage legs, these will eventually be replaced by a composite scale set that I am making with wheel fairings as well.

Spins seem very controllable and I completed several snap rolls without problems.

Sorry about the quality of the videos they were taken using a muvi camera taped to my glasses !

The gear fitted was
HobbyKing Donkey ST4010-820kv fitted with an APC 13x6.5 prop
2650 4 cell Lipo
Hobbyking SS Series 60-70A ESC
Hobbyking 5V 5A UBEC 2-5S Lipoly (7.2-21v)
7 off TowerPro MG90S servos
Hitec Aurora9 and HobbyKing 2.4Ghz A-FHSS Compatible 8CH Receiver (Hitec Minima compatible)

My only disappointment is the noise generated by the fuselage structure the same motor mounted in a n 18% SU-31 is very much quieter.

I am working on updating the plans to as built and will post the build photos very soon.

2nd set RV 9 flights (2 min 7 sec)

Last edited by RJPIoW; May 28, 2014 at 12:34 AM.
May 30, 2014, 05:29 AM
RJPIoW's Avatar


I am traveling for work at the moment so I havent had a chance to get these 3 x A0 pdf's printed for checking, but here are the 3 plans made cleaner that I used for the prototype.

I will also publish the assembly drawing, and my photos of the build, probably this weekend.


30may Edit - rv9-1 A0-3 updated glass rootbrace added, tip shape corrected RJP
Last edited by RJPIoW; May 30, 2014 at 05:30 PM.
May 30, 2014, 08:55 AM
Registered User
Great job on the plans and the build. I suspect the model flies better (more aerobatic) then the full-size version. Getting the weight of a 1/4 scale model down below 5# is a great accomplishment.
May 30, 2014, 05:34 PM
RJPIoW's Avatar
Originally Posted by BrianRickman
Great job on the plans and the build. I suspect the model flies better (more aerobatic) then the full-size version. Getting the weight of a 1/4 scale model down below 5# is a great accomplishment.
Thank you. I think that it is fun to fly because of both the power and the light weight/low wing loading, and yes its far more aerobatic than the real thing !

In hindsight I believe I could have achieved something less than 4.5lb, with a bit more care.

I found a couple of omissions/errors in sheet 3 and have now posted a corrected version

May 30, 2014, 06:34 PM
3d and EDF, some scale
MustangAce17's Avatar
May 31, 2014, 12:52 PM
RJPIoW's Avatar
Wing assembly from the plan:

Cut out 18 off 6mm depron ribs, I used a 3mm ply template.

Cut out 2 off 6mm depron wing spars

Glue the ribs to the spar and then the 2 off 6x1 CF spars one on top of the wing spar and one on the bottom, I used Por for all of this. I have reinforced the 2 central bays on each wing by cutting out the vertical depron web and gluing in 3mm liteply with gorilla glue – I was concerned that the depron web was not strong enough in compression.
Last edited by RJPIoW; May 31, 2014 at 01:28 PM.
May 31, 2014, 12:54 PM
RJPIoW's Avatar
I attached the 5 wing lower templates to my building board, using UHU Por to glue the templates down, spacing them with one directly under every other rib, and of course the back edges in line.

Cut out the wing outer surface I cut them 10mm too big on the chord to allow some adjustment. I attached sticky tape to the outer surface for the first 6 inches either side of the fold line with one piece straddling the fold line, and used a wooden broom handle as an inner mandrel for the fold. Once the fold is induced you can flatten the depron to get a minimum bend radius for the leading edge. I actually put them under a heavy board over night.
May 31, 2014, 12:55 PM
RJPIoW's Avatar
To ensure a warp free wing I glued the bottom of the wing skin to the templates using UHU Por. I put Por over the whole template length and had to remove the residue when the wing was completed, there was no damage but you could get away with spot gluing along the template length I would imagine. I made sure the leading edge was in its correct position and let the excess material hang out the back at the trailing edge

Having marked the inside of the skin with the rib positions there was then a bit of a race to get Por onto the ribs and wing skin and then glue all in place. I used a piece of paper as a moving shield along the wing width between the skin and the ribs, getting the 1st rib positioned and stuck, then moving the shield to do the next etc.
Last edited by RJPIoW; May 31, 2014 at 01:00 PM.
May 31, 2014, 01:03 PM
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I cut the foam wedges that support the trailing edge using a hot wire and a 14mm high piece of aluminium strip, but you could sand this to shape.

I then glued these wedges in place butting up against the ribs.

The 2 x 2kgcm servos that operate flap and aileron were mounted inside the wing using additional ribs to hold the servos and lengthened servo cables.

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