GP-4 Experts

[Michael Wilt]

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]

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

 

[billyvray]

Fixed gear taildragger GP4? You MUST share some pictures with us! Please.

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

 

[jmodguy]

Heres a few pics. Panel has a Dynon Skyview, Garmin SL30, GNS 430 and Garmin GMA240. Engine will be a modified IO320. Cold air sump, SDS EFI/FI system. Looking at 3 blade Sensenich ground adjustable cf prop. Made the rudder a little wider at the top to help with crosswinds n such.

 

[Victor Bravo]

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!

 

[billyvray]

That's a mean looking machine!

 

[Chris Matheny]

Beautiful. You actually made the tail somewhat appealing. That is saying a lot.

 

[TarDevil]

Nice work!

 

[jmodguy]

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.

 

[Toobuilder]

You say "SDS", but theres a lot of Robert's hardware in the Kitfox picture.

 

[jmodguy]

Yup. Got more support from SDS after I got it running so....

 

[Toobuilder]

As I suspected. Funny how often that turns out to be the case.

Nice looking pair of airplanes

 

[TFF]

Is there any structure difference in the fuselage since you moved the gear to the engine mount?

 

[jmodguy]

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]

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?

 

[terke]

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

What are your questions?

 

[jmodguy]

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.

 

[jmodguy]

To close this out the OP called me a couple weeks back and his questions were answered.