GP-4 Experts

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

Michael Wilt

New Member
Joined
Jan 3, 2021
Messages
1
Is there anyone out there who knows the GP-4 ? I am currently puzzling through the plans, modeling much of the aircraft in CAD to be sure I am interpreting the plans correctly. I have some specific questions.

Mike
 

jmodguy

Member
Joined
Feb 9, 2011
Messages
14
Location
Indiana
I am building a GP4. What do you need? I will tell you if it about retracts, I won't be much help. Mine is a fixed gear taildragger. There is a GP4 group on Yahoo the name is gp4@groups.io
 

Victor Bravo

Well-Known Member
HBA Supporter
Joined
Jul 30, 2014
Messages
8,595
Location
KWHP, Los Angeles CA, USA
Wow that's really interesting!

Careful attention to detail and aerodynamic tuning will result in you suffering only a very very small loss in cruise speed, but you will enjoy a large gain in useful load and reduced systems complexity.

I can't wait to see the progress on this!
 

jmodguy

Member
Joined
Feb 9, 2011
Messages
14
Location
Indiana
Thanks for the kind words everyone :) I have recreated the wing in Compufoil and will be cutting the ribs on a cnc router. I figure that will get me a cleaner/truer airfoil than the traced blueprints. Cowl will be similar to a James style used on RVs. Will use individual plenums on the cylinders to keep the air where it needs to be. I have a set of Vans leg spats and wheelpants to clean the gear up. Tailwheel fairing will be home brew but clean and will flow into the tail stinger.
Here's a couple pics of my Kitfox I completed in July. IO-340 (I built it), 80" WW STOL prop, AV Weld mains, T3 tail shock, SDS IGN/FI system. 1013 lbs and 2600'/min and more climb! Custom FWF including cowl.
IMG_2882.JPGIMG_3615.JPGIMG_3726.JPG
 

Toobuilder

Well-Known Member
HBA Supporter
Log Member
Joined
Jan 19, 2010
Messages
5,086
Location
Mojave, Ca
You say "SDS", but theres a lot of Robert's hardware in the Kitfox picture.
 

TFF

Well-Known Member
Joined
Apr 28, 2010
Messages
14,345
Location
Memphis, TN
Is there any structure difference in the fuselage since you moved the gear to the engine mount?
 

jmodguy

Member
Joined
Feb 9, 2011
Messages
14
Location
Indiana
I reinforced the lower firewall by not cutting the nose gear tunnel notch in the lower firewall crossmember. Also added a double layer of 1/2" ply triangles on the corners under the skin where the engine/gear mounts to the lower fuselage. Merged the GP4 engine mount with the RV6 gear mount structure and added a couple extra tie points along the lower firewall. As for the tail, I added 6 layers of CF to the inside of the skin just aft and below the horizontal. Also added some CF to tie the H stab to the upper longerons. Some in the yahoo group were worried about the tail falling off so I had a structural analysis done of the tail just fwd of the h stab and it is more than strong enough to support the conventional gear configuration.
 

TFF

Well-Known Member
Joined
Apr 28, 2010
Messages
14,345
Location
Memphis, TN
What is your glue? I assume you will cover with glass and resin; when do you think you will get to that step, and how long have you spent to get it to now?
 

jmodguy

Member
Joined
Feb 9, 2011
Messages
14
Location
Indiana
What is your glue? I assume you will cover with glass and resin; when do you think you will get to that step, and how long have you spent to get it to now?
T-88 for the”glue”. 😂 Yes on the glass and resin question. Its not too far off but I need it to get warmer. No idea how many hours. It went pretty quick though, I used to scratch build rc planes and this is basically the same but bigger parts. Maybe 18 months to get to its current state.
 

redwitch

Member
Joined
Mar 16, 2021
Messages
6
Fixed gear taildragger GP4? You MUST share some pictures with us! Please.
Are you familiar with taildraggers, or just decided to choose this option? It is tricky with such big power and the rudder is very small on this one....
 
Top