A-7 Corsair Build Thread
05-06-2005, 05:14 PM
#51
Senior Member
My Feedback: (1)
Join Date: Oct 2002
Location: Bossier City, LA,
Posts: 543
Likes: 0
Received 0 Likes
on
0 Posts
RE: A-7 Corsair Build Thread
Years ago I watched a couple of guys do that at a Shreveport meet with A-4s, the hook was ripped off the plane. I think the hook was desigined to be the weak link
The A-7 is a cool jet thought, hope it makes it to kit form.
Good Luck!
Kevin
The A-7 is a cool jet thought, hope it makes it to kit form.
Good Luck!
Kevin
05-06-2005, 05:40 PM
#52
Junior Member
Join Date: Aug 2003
Location: Houston, TX,
Posts: 9
Likes: 0
Received 0 Likes
on
0 Posts
RE: A-7 Corsair Build Thread
Strykaas & Seanreit:
1. My stated reasons for A7Bldr and his colleagues to consider incorporating an operational tailhook in their jet was simply for marketing purposes as no other manufacturer, to my knowledge, is doing it at this time. The idea will either appeal to them or it won't. I can handle rejection!
2. Just because you buy A7Bldr's jet with an operational tailhook doesn't mean that you are obligated to use it, right?
3. "Catching the wire" would not mean that you have to engage in extremely hazardous maneuvers on final approach in order to land exactly on top of the wire; just a simple, normal landing anywhere downwind and just let the plane roll out.
To my way of thinking, if someone is going to build a scale model of an aircraft that has the capability of making an actual arrested landing, then why not strive to develop an arresting system to SIMPLY add to the REALISM of the features and capabilities manifested by the full-scale aircraft that is being modeled?
I hope these remarks ease your concerns and clarify my original exhortations to A7Bldr, et al.
1. My stated reasons for A7Bldr and his colleagues to consider incorporating an operational tailhook in their jet was simply for marketing purposes as no other manufacturer, to my knowledge, is doing it at this time. The idea will either appeal to them or it won't. I can handle rejection!
2. Just because you buy A7Bldr's jet with an operational tailhook doesn't mean that you are obligated to use it, right?
3. "Catching the wire" would not mean that you have to engage in extremely hazardous maneuvers on final approach in order to land exactly on top of the wire; just a simple, normal landing anywhere downwind and just let the plane roll out.
To my way of thinking, if someone is going to build a scale model of an aircraft that has the capability of making an actual arrested landing, then why not strive to develop an arresting system to SIMPLY add to the REALISM of the features and capabilities manifested by the full-scale aircraft that is being modeled?
I hope these remarks ease your concerns and clarify my original exhortations to A7Bldr, et al.
05-06-2005, 11:13 PM
#54
RE: A-7 Corsair Build Thread
Bushpotato, thanks for your interest in this build. The first plane to fly I’m sure won’t have any ordinance attached or leading edge devices, but will incorporate flaps. Once we are happy with the flight characteristics, we can add more of these things.
We think this plane could certainly haul a lot of ordinance as the full scale did, with its wing size. An arresting hook wouldn’t be too hard to incorporate as well, but that’s all in the future.
We're still quite aways off from flying.
Sean that German website was unbelievable! Quite an inspiration. I've got aways to go to match up to those guys...
Back to the fuselage build:
After the fuse plug was set in place into the parting board, I used modeling clay to fill in small gaps around the plug. The entire plug and board were waxed several times and PVA applied. For the first application, we (I had help) brushed on an Epoxy Tooling Gel coat, then a layer of 2 oz cloth and progressed on up to 10 oz cloth to increase the thickness of the mold. We used some thickened resin (mixed with milled fiber) to build up the areas around the little buttons on the parting board.
Jim
We think this plane could certainly haul a lot of ordinance as the full scale did, with its wing size. An arresting hook wouldn’t be too hard to incorporate as well, but that’s all in the future.
We're still quite aways off from flying.
Sean that German website was unbelievable! Quite an inspiration. I've got aways to go to match up to those guys...
Back to the fuselage build:
After the fuse plug was set in place into the parting board, I used modeling clay to fill in small gaps around the plug. The entire plug and board were waxed several times and PVA applied. For the first application, we (I had help) brushed on an Epoxy Tooling Gel coat, then a layer of 2 oz cloth and progressed on up to 10 oz cloth to increase the thickness of the mold. We used some thickened resin (mixed with milled fiber) to build up the areas around the little buttons on the parting board.
Jim
05-06-2005, 11:17 PM
#55
RE: A-7 Corsair Build Thread
After the first side (female mold) had cured, I removed the entire thing from the building board and flipped it over to the lay up the other side. The edges were trimmed with a cutoff wheel and belt sander to smooth things up. Then the whole thing, including a 2" flange had to be waxed and prepped again. This thing keeps getting heavier...
Jim
Jim
05-07-2005, 08:25 PM
#56
RE: A-7 Corsair Build Thread
OK, after making the other side mold (just as the first) I popped them apart and cleaned them up for use. With this up close photo, you can see the button molded into one side and the receptacle in the other. When you lay one mold half on top of the other, they just 'clunk' into perfect alignment.
Jim
Jim
05-07-2005, 08:42 PM
#57
RE: A-7 Corsair Build Thread
After cleaning and prepping the molds with wax and PVA, I sprayed a coat of K-36 into each mold half. After about 1/2 hr. I layed in more West epoxy resin with cloth to complete the layup.
The layup consisted of 1 layer 2 oz. cloth, then 1 of 6 oz. then 1 of 4 oz cloth.
Between the last 2 layers I put in some 5 oz. carbon in the nose gear area, main gear area, and horiz. stab former area for additional strength. Also, since this plane has large, fairly flat sides, I laid in a piece of 3/32"X4"X40" balsa sheet. This was 'captured' under the last layer of cloth (4 oz.). This adds amazing strength for the weight added.
I then covered it all with peel ply and breather cloth (paper towels). It was then inserted into a vaccum bag to cure. The last photo shows it with the peel ply pulled off after cure.
The vacuum does a nice job of squeezing out any and ALL excess resin. Also it helps to ensure those sharp corners (like the wing saddle) turn out nice.
Jim
The layup consisted of 1 layer 2 oz. cloth, then 1 of 6 oz. then 1 of 4 oz cloth.
Between the last 2 layers I put in some 5 oz. carbon in the nose gear area, main gear area, and horiz. stab former area for additional strength. Also, since this plane has large, fairly flat sides, I laid in a piece of 3/32"X4"X40" balsa sheet. This was 'captured' under the last layer of cloth (4 oz.). This adds amazing strength for the weight added.
I then covered it all with peel ply and breather cloth (paper towels). It was then inserted into a vaccum bag to cure. The last photo shows it with the peel ply pulled off after cure.
The vacuum does a nice job of squeezing out any and ALL excess resin. Also it helps to ensure those sharp corners (like the wing saddle) turn out nice.
Jim
05-07-2005, 08:47 PM
#58
RE: A-7 Corsair Build Thread
Before the resin has totally cured, I popped it out of the bag to trim the edges (seam line) since the vacuum bag folds the cloth over onto the mold flange. I used a utility knife and dipped it into alcohol to aid in cutting. It cuts easily and cleanly.
Jim
Jim
05-08-2005, 05:39 AM
#59
RE: A-7 Corsair Build Thread
I sprayed a coat of K-36 into each mold half.
And it's also the first time I see someone not joining both half molds when molding fuselage sides... My guess is that you'll join them when molding the second half ? But it won't be possible to "vacuum bag" the second half
... Or perhaps will you join them once molded and cured ? But that's pretty difficult to do, you have to go through the openings (wing hatch, nose, ...) to apply some cloth to strengthen the joint ... Interesting...
05-08-2005, 03:13 PM
#60
RE: A-7 Corsair Build Thread
Strykaas, yes I do take precautions with the K-36; I have a lot of respect for it. I would like to find a safer primer to use, however.
I laid up both Lt and Rt sides identically and trimmed to size. After cured, I roughed up the center joint area about 1" width. I used a 1.5" wide joiner tape for the bottom joint and a 1" joiner tape for the top (nose area). I appled the tapes on one half using a a mixure of epoxy resin and cavosil (filler). After letting this sit for awhile, I found that it was adhered quite well and wouldn't slip around much.
Back in the vertical fin area, I merely applied a bead of Aeropoxy (or equivalent) on to each half seam.
I then brushed some resin onto the other mold half center joint and laid that mold half on top of the first. I had to make sure the tape didn't get folded over or caught between the 2 halves.
I used plenty of spring clamps to make sure the 2 molds were helf together tightly.
Using acid brushes and my fingers (with gloves on) I was able to wet out all the tapes to both halves, by working through the wing saddle area and exhaust area.
Back in the narrow fin area where the Aeropoxy was, I used a narrow stick to ensure it was pushed into the right places. I'm sorry I don't have more photos of this process. I think I was getting too excited to see the end result!
Jim
I laid up both Lt and Rt sides identically and trimmed to size. After cured, I roughed up the center joint area about 1" width. I used a 1.5" wide joiner tape for the bottom joint and a 1" joiner tape for the top (nose area). I appled the tapes on one half using a a mixure of epoxy resin and cavosil (filler). After letting this sit for awhile, I found that it was adhered quite well and wouldn't slip around much.
Back in the vertical fin area, I merely applied a bead of Aeropoxy (or equivalent) on to each half seam.
I then brushed some resin onto the other mold half center joint and laid that mold half on top of the first. I had to make sure the tape didn't get folded over or caught between the 2 halves.
I used plenty of spring clamps to make sure the 2 molds were helf together tightly.
Using acid brushes and my fingers (with gloves on) I was able to wet out all the tapes to both halves, by working through the wing saddle area and exhaust area.
Back in the narrow fin area where the Aeropoxy was, I used a narrow stick to ensure it was pushed into the right places. I'm sorry I don't have more photos of this process. I think I was getting too excited to see the end result!
Jim
05-08-2005, 03:41 PM
#61
RE: A-7 Corsair Build Thread
The end result:
After allowing it all to cure, I anxiously drove in small wooden wedges between the mold flanges. With little effort the top mold half came off, then the bottom.
All the center joint seams were tight, with resin coming through, as well as the Aeropoxy area.
I trimmed it, washed it up to remove parting agent residue and temporarily taped on the inlet lip to see how she looked.
I was quite pleased!
Jim
After allowing it all to cure, I anxiously drove in small wooden wedges between the mold flanges. With little effort the top mold half came off, then the bottom.
All the center joint seams were tight, with resin coming through, as well as the Aeropoxy area.
I trimmed it, washed it up to remove parting agent residue and temporarily taped on the inlet lip to see how she looked.
I was quite pleased!
Jim
05-08-2005, 04:15 PM
#62
RE: A-7 Corsair Build Thread
This fuselage (70" long, 11.5" high and 8" wide) weighs in at 3 lbs. 4 oz.. It feels light!
It is plenty stiff, and anywhere it seems a little 'squishy' it will have a bulkhead that will take care of that. The in-laid balsa sheet was a great idea and will serve us well as the landing gear formers and any wing attach formers bond to it.
At this time the fuselage has been sent off to Cactusflyer in Phoenix for him to work on bulkheads, tail flying surfaces, landing gear, and engine installation. He has his hands full!
He has been producing CAD drawings all along on this project and has good input on how to best utilize the space inside the fuselage. I expect to see him posting on this build process next.
I have more to do and will post on that as well (top hatch building, canopy ,etc.)
We are having a lot of fun on this project,
Jim
It is plenty stiff, and anywhere it seems a little 'squishy' it will have a bulkhead that will take care of that. The in-laid balsa sheet was a great idea and will serve us well as the landing gear formers and any wing attach formers bond to it.
At this time the fuselage has been sent off to Cactusflyer in Phoenix for him to work on bulkheads, tail flying surfaces, landing gear, and engine installation. He has his hands full!
He has been producing CAD drawings all along on this project and has good input on how to best utilize the space inside the fuselage. I expect to see him posting on this build process next.
I have more to do and will post on that as well (top hatch building, canopy ,etc.)
We are having a lot of fun on this project,
Jim
05-08-2005, 05:12 PM
#64
RE: A-7 Corsair Build Thread
Stryk, things may slow down a little on the posting, but the idea is to NOT stop on this project. We said at the start we woudn't start a build thread til we had a fuselage in hand - and that's what we did.
As far as sanding goes, yes there was 'flashing' of epoxy protruding out from the seam.
A hard block behind the sandpaper cleans that up.
Jim
As far as sanding goes, yes there was 'flashing' of epoxy protruding out from the seam.
A hard block behind the sandpaper cleans that up.
Jim
05-11-2005, 06:23 PM
#71
RE: A-7 Corsair Build Thread
Well, Folks,
While I was waiting for Jim to finish sculpting the fuselage plug, I decided to draw the horizontal stab and cut the cores. I designed a pivot mechanism and control horn. The .375"" solid carbon shaft is supported by ball bearing and the bracket is made from plywood.
Once I cut the cores, it became obvious that this was going to be a THIN stab. Since I had some resin that was just waiting to get used up, we decided to do a composite horizontal stab. The reasoning was that since we would have to reinforce the part to house the pivot shaft a lot, why not make the whole thing fiber glass. I sheeted the cores with some fairly hard/heavy balsa that I had in the scrapbox. The next step will be to finish it with 1.5 oz glass and lots of K-36.
John
While I was waiting for Jim to finish sculpting the fuselage plug, I decided to draw the horizontal stab and cut the cores. I designed a pivot mechanism and control horn. The .375"" solid carbon shaft is supported by ball bearing and the bracket is made from plywood.
Once I cut the cores, it became obvious that this was going to be a THIN stab. Since I had some resin that was just waiting to get used up, we decided to do a composite horizontal stab. The reasoning was that since we would have to reinforce the part to house the pivot shaft a lot, why not make the whole thing fiber glass. I sheeted the cores with some fairly hard/heavy balsa that I had in the scrapbox. The next step will be to finish it with 1.5 oz glass and lots of K-36.
John
05-12-2005, 06:34 PM
#72
RE: A-7 Corsair Build Thread
Next, I mounted the stab plug on a stick so that I could paint it. After several coats of K-36, it started looking pretty good. I applied chart tape panel lines just to see how that would turn out. We are considering making the vertical fin composite as well. I got interested in doing the composite flying surfaces after seeing a Q-40 pylon racer wing the other day. An old racer buddy, Gary Schmidt, stopped by the field one day and showed me a wing that he and Jim Allen were making. These guys had the process down to a fine art with all the painting done in the mold....gorgeous! I think that I will stick with primer in the mold...............
Now for more K-36 and sanding...............
John
Now for more K-36 and sanding...............
John
05-13-2005, 11:25 AM
#73
RE: A-7 Corsair Build Thread
..Next, I cut the splitter plate and built a frame to hold the plug. The splitter was given four coats of clear polyurethane to seal it. I used the foam core shuck as a saddle for the plug and I placed MDF blocks at the trailing edge to support it at the proper height. The gap was filled with modeling clay and the whole thing given 4 coats of PARTALL wax.
John
John
05-16-2005, 07:11 PM
#74
RE: A-7 Corsair Build Thread
OK, Here is a weekend’s worth or work. After I polished the last coat of Partall, I wiped on some Safelease release agent. This stuff is really thin and it was applied with a paper towel and allowed to dry about 20 minutes. I mixed up some resin with milled glass and applied it around the edges of the plug. Just when this stuff was getting a little tacky, another batch was mixed to a thinner consistency and poured over the entire plug and splitter. I added a layer of 4 0z, 2 layers of 6 oz and 2 layers of 10 oz cloth, then a layer of mat. I have never used fiberglass mat before but I tried it here....Man that stuff soaks up the resin!
Once this lay-up was cured in the sun and over night, I pulled off the splitter...well almost. It seems that my urethane sealing was inadequate and it stuck! What a mess. After a lot of prying and cursing and sweat, it came apart. I have since read here on RCU that simple clear packing taper works well to seal the wood....maybe next time. Anyway after I scraped and sanded the remnants of the splitter from the mold, it was waxed and prepped for the other half to be laid up. In the picture you can see the area that stuck just in front of the leading edge on the flange. Now I applied the same mix of resin and milled glass to the other half........................
Once this lay-up was cured in the sun and over night, I pulled off the splitter...well almost. It seems that my urethane sealing was inadequate and it stuck! What a mess. After a lot of prying and cursing and sweat, it came apart. I have since read here on RCU that simple clear packing taper works well to seal the wood....maybe next time. Anyway after I scraped and sanded the remnants of the splitter from the mold, it was waxed and prepped for the other half to be laid up. In the picture you can see the area that stuck just in front of the leading edge on the flange. Now I applied the same mix of resin and milled glass to the other half........................
05-16-2005, 07:24 PM
#75
RE: A-7 Corsair Build Thread
Now, after this cured over-night (long weekend), I trimmed the edges and sanded them smooth on a belt sander....Man I hate the fiber glass mat! This stuff is like handling a cactus...next time I'll just use more layersof cloth instead. Anyway, I drilled seven .250" holes around the perimeter while pressing in a steel dowel pin after each hole was drilled. I prefer this method rather than the "bumps" that Jim molded in on his fuse mold. Once all the pins were done, I removed them and used wooden wedges to pop the mold apart. Now onto the lay-up and vacuum bagging!
Tailwinds,
John
Tailwinds,
John