Improving the TF GS Mustang Cowl
11-24-2007, 02:22 AM
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RE: Improving the TF GS Mustang Cowl
All,
A interim milestone.
Here is the cowl plug with the parting boards attached and bottom half sprayed with PVA. The second photo shows the lower cowl coated with epoxy tooling resin and ready to be laminated in the morning. The tooling resin averages about 1/32" thick.
After the lower cowl mold has set, the horizontal parting board (it's one piece) will be removed and the top cowl mold will follow.
As you can see, the raised thrust line and extending the cowl has created a very smooth curve from the chin scoop down to the front of the wing.
A interim milestone.
Here is the cowl plug with the parting boards attached and bottom half sprayed with PVA. The second photo shows the lower cowl coated with epoxy tooling resin and ready to be laminated in the morning. The tooling resin averages about 1/32" thick.
After the lower cowl mold has set, the horizontal parting board (it's one piece) will be removed and the top cowl mold will follow.
As you can see, the raised thrust line and extending the cowl has created a very smooth curve from the chin scoop down to the front of the wing.
11-24-2007, 08:55 AM
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RE: Improving the TF GS Mustang Cowl
Thanks for the update . The cowl looks great ! When I got my ARC I saw how disjointed that lower cowl area was . Your's is so much better . Eagerly awaiting your product !
Marc
Marc
12-27-2007, 03:14 AM
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RE: Improving the TF GS Mustang Cowl
I'm seeing the light at the end of the tunnel ...
The top and bottom molds are done and they both turned well. All that filling and sanding of the cowl plug really paid off!
I'm now finalizing the cloth cutting patterns and optimizing the layup schedule using just the top cowl (since it's easier to work with than the lower cowl). After 5 trial parts I've got it about optomized. Looks like the rear edge of the cowl will be 0.015" thick (give or take a little) which is what I hoped for.
At the same time I've been working out the details on how I want to mark the location of the exhaust shrouds in the top cowl and how to make the recesses for the air filter covers in the lower cowl. I think I have both techniques adequately tested and ready to try. The filter covers themselves will be 1/32" laser cut plywood and have been ordered. At the same time I'm working on the new exhaust kit for the cowl.
By this weekend I should have a full cowl made that I can trial fit to a fuselage to make sure the thrust alignment is OK. Then I can cut it apart to get the contour of the upper and lower firewall support formers.
There are a couple of decisions to be made in a few days that I'll be asking for help on.
The top and bottom molds are done and they both turned well. All that filling and sanding of the cowl plug really paid off!
I'm now finalizing the cloth cutting patterns and optimizing the layup schedule using just the top cowl (since it's easier to work with than the lower cowl). After 5 trial parts I've got it about optomized. Looks like the rear edge of the cowl will be 0.015" thick (give or take a little) which is what I hoped for.
At the same time I've been working out the details on how I want to mark the location of the exhaust shrouds in the top cowl and how to make the recesses for the air filter covers in the lower cowl. I think I have both techniques adequately tested and ready to try. The filter covers themselves will be 1/32" laser cut plywood and have been ordered. At the same time I'm working on the new exhaust kit for the cowl.
By this weekend I should have a full cowl made that I can trial fit to a fuselage to make sure the thrust alignment is OK. Then I can cut it apart to get the contour of the upper and lower firewall support formers.
There are a couple of decisions to be made in a few days that I'll be asking for help on.
12-27-2007, 01:20 PM
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RE: Improving the TF GS Mustang Cowl
Tony, glad to hear things are progressing. Heres a question for you, could this be modified ...easily into an "A" model P51? or could that be an option you could put out? I imagine that a different chinmold and a crb scoopp would have to be made. Realise I have never made a mold before .....[:'(]
12-28-2007, 11:16 AM
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RE: Improving the TF GS Mustang Cowl
Ram-bro
In answer to your question if my new cowl can be converted to an A model ... maybe. See the attached sketch in which I overlaid the best fit A model outline over the new cowl. It all depends on how close one thinks it comes to being realistic.
At this point I'm too involved in getting all the associated details worked out for the Merlin cowl kit that I'm not able to really think about any conversion like this. However, you could do it by cutting away the shaded area of the lower cowl and then spot gluing blue foam into that area. The foam would then be sanded to form the new contour. After glassing over the area the foam is then sanded (or dissolved) away. The intake could be done the same way.
This is a fairly simple process that I can help you with if you decide to go that way. PM me if you have any questions.
In answer to your question if my new cowl can be converted to an A model ... maybe. See the attached sketch in which I overlaid the best fit A model outline over the new cowl. It all depends on how close one thinks it comes to being realistic.
At this point I'm too involved in getting all the associated details worked out for the Merlin cowl kit that I'm not able to really think about any conversion like this. However, you could do it by cutting away the shaded area of the lower cowl and then spot gluing blue foam into that area. The foam would then be sanded to form the new contour. After glassing over the area the foam is then sanded (or dissolved) away. The intake could be done the same way.
This is a fairly simple process that I can help you with if you decide to go that way. PM me if you have any questions.
01-07-2008, 01:51 PM
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RE: Improving the TF GS Mustang Cowl
Hi Tony!
How much you want for one of piece of art cowl?
I go start assemble my TF 1/5 P-51 in some weeks and i really like of use one of your cowls....
Thanks
Doug
How much you want for one of piece of art cowl?
I go start assemble my TF 1/5 P-51 in some weeks and i really like of use one of your cowls....
Thanks
Doug
01-07-2008, 08:28 PM
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RE: Improving the TF GS Mustang Cowl
Doug (and all)
The pictures below are of a complete cowl made from flawed test parts. As shown (including two heavy coats of primer) it weighs just 4-1/2 oz more than a painted OEM cowl. I'm happy with that. The current layup schedule provides a good rigidity ahead of the firewall and a nicely thin (0015 - 0.020" thick) rear section where the cowl goes over the fuselage.
Assembling this cowl settled a couple of questions I had about the configuration of the kit.
(1) It has to be joined in the mold. I had toyed with the idea of shipping the two halves to save on shipping. But joining it out of the mold is like trying to get two fish to ballroom dance together!
(2) Cutting the removeable cowl will be left to the builder. The good news is that the cuts can follow scale cowl panel lines. These lines (along with all the other cowl panel lines) will be shown on a dimensioned drawing included in the kit.
The air filter covers are laser cut 1/32" plywood. The recess so they can be flush mounted will be included in the cowl assuming I can make that work for production. If not, I'll have to make a new lower cowl. In the pictures a piece of 1/32" plywood glassed to the inside of the cowl was used. The cowl averages 0.028 there so it worked out well.
(Curving the air filer covers to the cowl proved to be dead simple after some research on the Internet. After boiling them for 2-3 minutes in a coffee cup in the microwave, they were rubber banded around a cylinder (a pop can or something slightly smaller) and left to dry for 24-48 hours. Worked perfectly.)
My major problem at the moment is trying to get good - much less consistent - layups in the near freezing weather in my unheated shop. So my task for the next two weeks or so is to get an area out there insulated and paneled so I can add heat. At the same time I'm looking for a cheap chest style freezer big enough to make into a warming cabinet for the cowls and my manifold kits.
Doug, the price of the first batch of cowls will be near $100 as promised. When I get caught up with all the orders, I'll look at whether that's a realistic figure or not.
The pictures below are of a complete cowl made from flawed test parts. As shown (including two heavy coats of primer) it weighs just 4-1/2 oz more than a painted OEM cowl. I'm happy with that. The current layup schedule provides a good rigidity ahead of the firewall and a nicely thin (0015 - 0.020" thick) rear section where the cowl goes over the fuselage.
Assembling this cowl settled a couple of questions I had about the configuration of the kit.
(1) It has to be joined in the mold. I had toyed with the idea of shipping the two halves to save on shipping. But joining it out of the mold is like trying to get two fish to ballroom dance together!
(2) Cutting the removeable cowl will be left to the builder. The good news is that the cuts can follow scale cowl panel lines. These lines (along with all the other cowl panel lines) will be shown on a dimensioned drawing included in the kit.
The air filter covers are laser cut 1/32" plywood. The recess so they can be flush mounted will be included in the cowl assuming I can make that work for production. If not, I'll have to make a new lower cowl. In the pictures a piece of 1/32" plywood glassed to the inside of the cowl was used. The cowl averages 0.028 there so it worked out well.
(Curving the air filer covers to the cowl proved to be dead simple after some research on the Internet. After boiling them for 2-3 minutes in a coffee cup in the microwave, they were rubber banded around a cylinder (a pop can or something slightly smaller) and left to dry for 24-48 hours. Worked perfectly.)
My major problem at the moment is trying to get good - much less consistent - layups in the near freezing weather in my unheated shop. So my task for the next two weeks or so is to get an area out there insulated and paneled so I can add heat. At the same time I'm looking for a cheap chest style freezer big enough to make into a warming cabinet for the cowls and my manifold kits.
Doug, the price of the first batch of cowls will be near $100 as promised. When I get caught up with all the orders, I'll look at whether that's a realistic figure or not.
01-12-2008, 08:25 PM
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RE: Improving the TF GS Mustang Cowl
Thanks guys. (8178 - you do realize you're dating both of us!)
As mentioned earlier the next important data point was to check the cowl alignment. So I slipped the mockup cowl on a new fuselage I just bought. (Being super conservative, I can't bring myself to take the plug off the original fuselage yet.)
I previously had made a fixture to take the place of the engine that I could mount the spinner on. This was built as accurately as possible and bolted to the OEM motor mount holes. This way the spinner could be used to check thrust angles and alignment of the nose ring with the spinner.
Putting the cowl on the fuselage was instructional. First of all, it fits the fuselage like a glove. There are no alignment issues - it fits just one way and one way only. What that means is that any extra thickness anywhere inside the cowl where it fits over the fuselage causes it to deform slightly. I found this out after I spent an hour chasing an alignment problem that turned out to be the extra layer of cloth I'd put at the lip of the cowl when the cloth I'd pre-cut came up short one layer in one spot. Sanded flush, the cowl alignment immediately improved.
At this point the only thing not verified yet is the spinner gap which is now faintly uneven - about 1/32" side-to-side. This may well be the result of joining the halves outside of the mold.
This cowl can't provide any more answers, so next on the agenda is a new cowl joined in the cowl.
As mentioned earlier the next important data point was to check the cowl alignment. So I slipped the mockup cowl on a new fuselage I just bought. (Being super conservative, I can't bring myself to take the plug off the original fuselage yet.)
I previously had made a fixture to take the place of the engine that I could mount the spinner on. This was built as accurately as possible and bolted to the OEM motor mount holes. This way the spinner could be used to check thrust angles and alignment of the nose ring with the spinner.
Putting the cowl on the fuselage was instructional. First of all, it fits the fuselage like a glove. There are no alignment issues - it fits just one way and one way only. What that means is that any extra thickness anywhere inside the cowl where it fits over the fuselage causes it to deform slightly. I found this out after I spent an hour chasing an alignment problem that turned out to be the extra layer of cloth I'd put at the lip of the cowl when the cloth I'd pre-cut came up short one layer in one spot. Sanded flush, the cowl alignment immediately improved.
At this point the only thing not verified yet is the spinner gap which is now faintly uneven - about 1/32" side-to-side. This may well be the result of joining the halves outside of the mold.
This cowl can't provide any more answers, so next on the agenda is a new cowl joined in the cowl.
01-13-2008, 04:39 PM
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RE: Improving the TF GS Mustang Cowl
Hi Tony,
Glad to see that there's progress . Looks great ! Will I be able to get mine without the exhaust cut-outs ? I'll be putting a non-scale turboprop in mine and will have to customize the holes myself.
Marc
Glad to see that there's progress . Looks great ! Will I be able to get mine without the exhaust cut-outs ? I'll be putting a non-scale turboprop in mine and will have to customize the holes myself.
Marc
01-13-2008, 05:19 PM
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RE: Improving the TF GS Mustang Cowl
'747
Yes. The exhaust shroud position is marked on the cowl. but not cut out. That's left to the builder. My exhaust kit is designed to be either surface mounted or recessed, recessed being a bit more work. Also the recessed portion behind the spinner will be left to the builder to remove.
These are the type of comments I need to help refine how the cowl will be configured. For example, is there anyone who would not want the air filter intake covers (747drvr?). From my standpoint I would rather not incorporate them into the mold, but rather have the builder cut the opening in the cowl and then put a backing in place just as I did with the cowl in the pictures. But if thats a big selling feature, then I'll do it.
In some ways the cowl is taking on a life of its own. For example I'm thanking about a laser cut jig that would insure the nose of the cowl lines up with the engine thrust line. Easy to design, but it adds cost to the end product.
Things to think about. Any input will be appreciated.
Yes. The exhaust shroud position is marked on the cowl. but not cut out. That's left to the builder. My exhaust kit is designed to be either surface mounted or recessed, recessed being a bit more work. Also the recessed portion behind the spinner will be left to the builder to remove.
These are the type of comments I need to help refine how the cowl will be configured. For example, is there anyone who would not want the air filter intake covers (747drvr?). From my standpoint I would rather not incorporate them into the mold, but rather have the builder cut the opening in the cowl and then put a backing in place just as I did with the cowl in the pictures. But if thats a big selling feature, then I'll do it.
In some ways the cowl is taking on a life of its own. For example I'm thanking about a laser cut jig that would insure the nose of the cowl lines up with the engine thrust line. Easy to design, but it adds cost to the end product.
Things to think about. Any input will be appreciated.
01-13-2008, 05:31 PM
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RE: Improving the TF GS Mustang Cowl
Tony,
if I want to use your cowl with a scale exhaust stack, like Keleo, I´ll have some problem placing or removing the cowl?
Thank you, and good work!
Cheers,
Andre.
if I want to use your cowl with a scale exhaust stack, like Keleo, I´ll have some problem placing or removing the cowl?
Thank you, and good work!
Cheers,
Andre.