Sparkie-RCU

My Feedback: (10)

The parts are vacuformed over with .030 PETG plastic but here is the cool part. The polypropylene coating the plastic is received with is not removed before forming.
(nothing sticks to polypropylene )
I have made three bombs with the mold so far and never used any mold release.
I have I have developed a better way to use the molds now that I have a few under my belt but I'll show the first method.

Spread a coat of resin in the bomb half and lay the glass cloth inside smoothing it out with your fingers.
apply resin to the inside with an acid brush working out all the bubbles you can.
( it's easier to tell since the mold is clear)
Give it overnight to set up and use compressed air to remove the bomb half.
Trim the edge of the fiberglass to match the edge of the mold line. It's easy to see because the surface becomes "not smooth".
Match the edges of the bomb mold with your finger and either drill holes or make marks so alignment can be done with the halves in place.
Apply glass cloth strips to the edges of one of the halves and put the halves together.
Using a long stick and a bent acid brush , apply the rest of the resin to complete the seam.

The better way is to trim the edges of the first ply at net trim ( edge of the mold ) while it is still wet.
Then apply the second ply offset by about 1 inch.
Offsetting the overlap becomes the seam doubler without adding weight; however there is the task of dropping in a round piece to strengthen the tip of the bomb.

Sparkie-RCU

My Feedback: (10)

I used 1/16 plywood to make the fins and used resin to bond them in place.
So there is the bomb ready for the Dauntless.

The bomb on the left was the first one , too heavy at three ply's and the seam needed allot of work.
The bomb on the right is very light weight because I experimented with lighter cloth.
The seam looks great but when you pinch the sides it flexes like a soda bottle. I, m sure it would fracture if it hit the ground, I may use it as a non droppable detail piece.

I'll have the mold halves on the website as soon as I write some instructions to go with it and figure up how much it will cost to form the molds and box them up.
Part of the problem is glass cloth availability.
I've been working with glass cloth that has been around the shop for a long time and I have no idea what the weight or weave is.
I suppose it doesn't matter because bomb toughness is really up to the guy doing the lay - up.

Sparkie-RCU

My Feedback: (10)

Good day for paint

Sparkie-RCU

My Feedback: (10)

The landing light servo is piggy backed to the retracts so a manual switch was necessary.

warbirdmustang

My Feedback: (21)

I love this plane! Great job so far, it's on mu bucket list also. I really like the weights you are using, both the ones that look like lead, and the ones that look like nylon. Could you possibly go into how you made those?
Thanks,
Bryan

Sparkie-RCU

My Feedback: (10)

I run a plastic shop as a side line and I was picking up an order when I spotted a small stack of plastic near the dock.
Short story, they gave me 6 blocks cut the same size, very handy.

The lead bars was poured into a mold I made with high temp silicone ( the red stuff a the automotive store. )
If you take a shot at it here is a tip.
Use bees wax on the master and give the silicone 3 weeks per half inch thickness.

Sparkie-RCU

My Feedback: (10)

Lots of good ideas here on RG universe but few answers (ref post # 37 )
I have read conflicting reports about the GT-80 being a good motor for this model. One thread described the flight as "struggling for power" others say over powered. suggested props are either $40 per blade or very hard to find.. I guess I'm on my own here. So I'll post what I have learned elsewhere.

Sparkie-RCU

My Feedback: (10)

Muffler.
Copper tubing used to route the exhaust to the scale position, silver soldered and supported to the muffler. This looks like a great idea and I can't take credit for it although the example I'm copying had the tubing mounted to the fire wall. I'll let you know how this version works out.

Sparkie-RCU

My Feedback: (10)

Ignition
My GT-80 "advisor" is a scale masters participant and has flown with his motor for years so for me he is my go to guy. I would give him credit but I'm unaware of that his connections are in the hobby and I don't want to ruin any deals he has made so he will have to go indentified.
He said "the G-80 is a great motor if you like to taxi" his explanation was that the magneto system works well at high idle but becomes unreliable where we want it. The fix is an electronic ignition.
This modification makes the motor lighter and from what I have seen in the threads this does not help the CG of this model. Anywhere from 4 to 8 pounds has been reported to balance the plane. Not this one but that is a whole separate post later.

Sparkie-RCU

My Feedback: (10)

He told me about his struggle getting this motor to put out the power it should.
" it was like the motor had a governor on it no matter what prop you used the top speed wouldn't change."

After going through several prop sizes and pitches it was flown without the cowl and the was a marked improvement. It turns out the cowl would pressurize and cause the fuel pump diaphragm to restrict fuel flow.
The fix was to attach a fitting to the diaphragm pump cover and route a tube to a static air location inside the model. It worked on his model so the modification was applied to mine.

Sparkie-RCU

My Feedback: (10)

Choke, have to have it but I need all the servo channels for the other stuff I want it to do so the "scale score" has to take the hit.
keeping it simple, I soldered a brass rod to the brass portion of the choke butterfly giving me the hardware attach point I needed to rotate it.
The fuel tube allows the motor to move a bit and not break the torque rod assembly.

Sparkie-RCU

My Feedback: (10)

Tank
the answer is yes ( ref. post 37 )
a 50 oz. tank will fit in the model with room to spare. The photos below shows how I made a rack to secure the tank.

The rack slides on the floor and engages a lip on the firewall to secure the front. Two screws attach the rear of the rack. I have had to remove the tank three times for adjustments and to mod the ignition so the time it took to make the rack was worth it.

I put a brass plate between the tank and the rack and attached a wire to it .
This was because of the warning on the plans about the wing screw damaging the fuel tank.
With the wing mounted to the fuselage the screw is installed and screw turns was counted from the point it engaged the nut till it contacted the brass plate. The continuity tester was the indication.
The screw was shortened to the length that got me the maximum turns without touching the tank.
(17 turns)

Sparkie-RCU

My Feedback: (10)

The stand I made is PVC pipe. I used a heat gun , waste basket and dog bowl to make the curves needed for the ends. The pipe is coated with several layers of felt strips for padding.
This model is to be transported with the wing center section in place. This means I have two wing panels loose in the explorer. Having a stand to hold the model inverted at the field may be needed so I made the model stand serve two purposes. Fuselage stand, wing transport rack. Holds the wing tubes too.

redbiscuits

My Feedback: (6)

Subscribed!
Looking forward to seeing how the GT-80 pulls her around. I'm in the planning stages of building one.

Pecanpatch

Time for a Update [8D]

Sparkie-RCU

My Feedback: (10)

OK, but it is more like a rant than an update.
I ran this Zenoa GT-80 that everyone goes seems on and on about.
This may be a great motor but not out of the box!
I was told that it will run smooth on the stock magnetos but you better like to taxi the plane because the idle has to be high or it will die.
So I bought the electronic ignition upgrade.
I also bought a 24 X12 prop because it was middle of the road on length according to the prop chart provided. ( I asked here and got nothing )

At the field we got the motor started and the idle was nice and smooth but the model was not.
The electronic ignition adapter was off by .035 causing a 3/16 prop tip run out difference. I guess it slipped through the QC step.

As for the prop they said would spin at 7000 rpm .
All we could get out of the motor was 4700 RPM with a cylinder head temp that was unacceptable
What planet or state do they test these engines at . There is $30 I’ll never see again.
I have been on hold for two weeks waiting for the replacement adapter.
The next prop will be a 24x 10 .

Sparkie-RCU

My Feedback: (10)

Can’t believe this, seems that I just posted and the box with the adapter arrived.
This one has a machined face whereas the last one had a frosted / casted look to it.

Ham639

My Feedback: (13)

Hi Sparkie,

Here's a little info on mine if it helps.

I too am using the GT 80 (magneto version) swinging a 22 x 10 3-blade. I am getting almost 6700 on the ground and I'm still a little rich.

I am using the stock mufflers but I did cut out the baffles.

Idle has been smooth and no issues so far.

She weighs 45lbs and the 80 flies it fine.

Hope this helps.

Best of luck,

Chuck

Sparkie-RCU

My Feedback: (10)

Well that gives me a bit of a warm fuzzy and I appreciate the information but I’m almost ready to shelve this project until I can build up more patience with it.

I ran the GT-80 again with the prop everyone at the field said did great the Xora 24 X 10
We couldn’t get more than 5 grand out of it with a peak temp of 230 degrees. . . .un cowled!
I would imagine with the cowl the pistons would surely melt!
That was three weeks ago

I bought another prop . . .Xoar 23x 10
Took it to the field for some help with it and we got 65 grand RPM at 200 degrees
At idle after a brief pause the motor starts looking for an RPM to idle at ( fluctuates about 200 rpm)
After we ran about a half tank thru the GT-80 it started misfiring and dying.
I topped off the battery for the ignition system and we tried it again with the same result.
That was two weeks ago

Now
I just returned from running it up with another ignition system ( I bought to troubleshoot with )
And I’m getting about 6700 rpm but the temp is crazy high at 285.

So far I’m not impressed at all with the Zenoa GT-80, what I know for sure is you cant trust their prop chart.

Sunday’s plan is to take it back to the field and run it without the scale exhaust stacks to see if there is a performance difference.
Thanks Chuck for the baffle hint, I might have caused the problem all along.
Also
Could somebody please bring a temp gun to the field and give me an idea what temp I’m shooting for.
I have tested my weed eater, leaf blower and lawn mower and got 174, 179, and 190 in that order.

Ham639

My Feedback: (13)

Sparkie,

I have 10 flights now on my SBD. The 3-blade is working just fine, however I did fly with another Z SBD with a 24x10 2 blade and he was faster than I. The 3-blade does have a better scale speed though. My idle does fluctuate about 200 RPM from take to landing, my guess os the heat is causing this. Pete Goldsmith from Horizon stopped by to chat with me about my SBD and told me to check to see if there was a fenelic spacer between the card and header. If it doesn't this will cause the idle issue. Mine does not have it. It will soon though.

After this season, I will experiment with a 2 blade 24x10 and lean on the needles some more. Right now I'm just burning fuel to break in the motor more.

Hang in there, I do really like this bird. it's very honest.

Ham638

spd101

Gorgeous work guys!!!

Sparkie-RCU

My Feedback: (10)

Thanks Ham,
Mine does have the plastic spacer between the carburetor and manifold.
We considered a vac leak and tightened the manifold to cylinder joint because it showed signs of being wet but it didn’t help .
Access to the carb to manifold joint was not easy at all so it was not looked in to.
I have found a small leak in the Sullivan fuel filter during defueling that I have to address .
I don’t know if it is sucking air while at full power because I don’t want to get my face that close to it to see.
So for now I’ll clamp it , test it and run it.
Thanks again for the tip any help is appreciated
Your plane looks great!

Got a CG location you like?
I calculated the marking on the plans to be at 14% of mac but labeled 25 %

Ham639

My Feedback: (13)

Sparkie,

My CG is right at 5.5 and I am happy with it.

I would get rid of the fueler they will leak.

Ham639

Edwin

My Feedback: (2)

I've never had luck with fuelers, and the people I've helped with engine problems that had fuelers, the fuelers were the problem. If it doesnt leak now, it will later. I have 4 on a ATI B-17, installed by the builder. All 4 leak and have to be removed.
Edwin

Sparkie-RCU

My Feedback: (10)

Good to know, I didn't trust them either. I have a dedicated line to the tank with its own clunk.
Lighter in weight than the carburetor feed line so it will not interfere with the mission of the feed line.\

It’s the Filter to the carburetor that had drops on it while defueling.
Sullivan calls it a Crap Trap.