FTC21 Seaplane Challenge/Martin XP6M-1 Seamaster

[cyclone3350]

You may not need this, but one of the things I studied at one time. The established way of drafting a hull. It's very interesting....and very educational.

https://www.dixdesign.com/lofting1.htm

I agree. Ordering from China is a big gamble. Take every effort to get stuff from ANYWHERE else.

I had skimmed through that website, and on the surface it does look like some value in knowledge that I can use. I will go over it more in detail tonight. It is not something I probably would have stumbled on, so thanks for sharing.

 

[EAS]

I had skimmed through that website, and on the surface it does look like some value in knowledge that I can use. I will go over it more in detail tonight. It is not something I probably would have stumbled on, so thanks for sharing.

I grew up with "french curves". My dad had a room full of guys putting his aiplane designs on to paper. Even his last prototype jet, the SJ30....he lofted. That was in the "90s. But by 6, I was studying all those drawings. Sailboat hull drafting facinated me...."lofting" as they used to call it. The 747 was the last aircraft Boeing lofted.

 

[cyclone3350]

Or go ahead and get the one from China. Hey a steal's a steal. (I mean you, not the seller!) And "game changer", that's some pretty impactful words.

That is what I thought. Impactful words. I'd figure if that was to be the case, then why not be the first kid on the block with a set. I was looking on reviews on those selling. The problem looks like not so much the seller, but that sometimes items can get stalled @ length in customs and I really want to order now and receive in August.

 

[cyclone3350]

I grew up with "french curves". My dad had a room full of guys putting his aiplane designs on to paper. Even his last prototype jet, the SJ30....he lofted. That was in the "90s. But by 6, I was studying all those drawings. Sailboat hull drafting facinated me...."lofting" as they used to call it. The 747 was the last aircraft Boeing lofted.

That is funny that U mentioned French curves. This is my workbench next to my drafting table. My father was a Civil Engineer so I too started early playing with his stuff. BTW, i won't get into too much detail, but let's just say I have a little bit of experience in Corporate jets. That is why I was interested in that photo U posted. @ first glance, looking @ the wind screen, I first thought it was a Lear. But then I looked @ it again realized that I couldn't identify it. As I am sure U know, most Corporate jets R between .74 and .77 with a few that go above .80. Mach .9+ in that size should make the SJ30 a seller.

 

[EAS]

The prototype did .9 as an anhedral, but it was decided by the big money investors to use a dihedral instead...easier to land. The FAA restricted it to .83....still faster than most, and a 2800 + mile range beats everybody in that size jet, not to mention 12psi cabin....

 

[cyclone3350]

The prototype did .9 as an anhedral, but it was decided by the big money investors to use a dihedral instead...easier to land. The FAA restricted it to .83....still faster than most, and a 2800 + mile range beats everybody in that size jet, not to mention 12psi cabin....

OMG, 2800 is nuts for that size. That was one of the annoying draw backs of private charters. Just because it is a jet, doesn't mean U can go from the east to west with out @ least one fuel stop and most likely two. Unless U R wanting the BE400 because it is cheap. Then make it three. Oh, if U want to bring some friends, then make it four. Don't even get me started on the early Slotations, I mean Citations.

 

[EAS]

There was one other piece of drafting equipment I've never seen anywhere else, they called a drafting "shoe". A metal weight with an "L" shaped screwdriver, embedded in the end pointing downward. It (or several) held down a long piece of plastic indented on each side...maybe 3/8" high and 1/8" thick. They could move it around and make any curve they wanted.

 

[cyclone3350]

That is one I haven't seen. That sound like something I could use. I have this flexible curve, but find it almost useless as it it hard to shape into a smooth flowing curve. I just use it to measure a linear length in a curve.

 

[EAS]

That is one I haven't seen. That sound like something I could use. I have this flexible curve, but find it almost useless as it it hard to shape into a smooth flowing curve. I just use it to measure a linear length in a curve.

Yeah, me too. That's where the technique on that website comes in handy, but a bit easier in my software.....old drawing program made by micrografx for Win95....runs on Win7 too. Corel bought it years ago and made it disappear. I bought it a couple years before Corel got hold of it....haha $50.

... sometimes freehanding can get you there.

 

[EAS]

That is one I haven't seen. That sound like something I could use. I have this flexible curve, but find it almost useless as it it hard to shape into a smooth flowing curve. I just use it to measure a linear length in a curve.

How is your hull going?

 

[cyclone3350]

How is your hull going?

I have all the formers done and the outline shape @ the water line as viewed from below. I see what is defined by lofting. If this was going to be built up and planked, then I could have used that method. Instead I am going to hot wire and sand shape this one from pink foam. Working on the tail section and hopefully the wing s tonight. Could not find my cutting bows and power pack that I built a few years ago,( buried some where in my storage room I am sure) so tomorrow I will build another one. I will post that build on the scratch build tonight thread.

 

[EAS]

...Could not find my cutting bows and power pack that I built a few years ago,( buried some where in my storage room....

I hate that. It happens to me fairly regularly. I gave up my sailboat and a cruise to Panama.... mostly because of my tools. I have 4 buildings of tools on the property I built after selling my boat. I have to go looking for one thing or another all the time, haha, but it's all here.

Sounds like you're making good progress. I'll look for the "scratch build" post.

 

[cyclone3350]

All I had was this week to work on this thing and this is as far as I manage to accomplish. The only thing left are the wings. I am going to hot wire this thing using the same technique that was used by the FliteTest team on the JA37 Viggen. This should be enough info to build from. The plan is to use the cross sections as templates and cut each section individually and then glue together. Haven't yet settled on the EDF's size. Right now I am leaning towards four 64mm 6s from the Arrows F-15 Eagle. This will make it an 80" W.S.. As I stated before, this is drawn directly from the 1/72 scale plastic model. The only deviation from scale is that I enlarged the horizontal stab by 10% and increased the width of the nacelles as well as adding a little to the height. I am leaving tomorrow and will not be back for a couple of weeks. So stay tuned.

 

[EAS]

Such neat and clean plans. I always used 10th inch velum, and still had visible eracer marks....too heavy handed with pencils I guess. Even mechanical drafting pencils.

Very neat!

 

[cyclone3350]

Such neat and clean plans. I always used 10th inch velum, and still had visible eracer marks....too heavy handed with pencils I guess. Even mechanical drafting pencils.

Very neat!

Many thanks. It is not as neat as U think. I did a little photo editing before posting. This is the original photo. What is interesting is, how straight forward the hull lines turned out to be. However, those damn nacelles really required lofting to get it correct. Instead of plotting it out and doing it on paper, I will just go straight cross section to cross section with foam and sand carve to a more accurate shape.

 

[EAS]

Many thanks. It is not as neat as U think. I did a little photo editing before posting. This is the original photo. What is interesting is, how straight forward the hull lines turned out to be. However, those damn nacelles really required lofting to get it correct. Instead of plotting it out and doing it on paper, I will just go straight cross section to cross section with foam and sand carve to a more accurate shape.

I really like vellum graph paper (1/10th inch) ...helps with the math, and measurements. 10th inch ruller helps too.

I've decided to use xps foam, front and back only. I used to use lots of the blue xps for the whole fusealge on my free-flight models.

I want this model fully painted, so I'm testing different techniques to use spray paint....there are ways to do it, but I'm going to do my own testing first.

 

[cyclone3350]

I hate this new schedule I volunteered for. Home 12 days a nd gone 18. One more month to go. I got home last week and today is the first day I had to work on this thing. Then I leave on Wednesday. I could not find my cutting bow , so I had to start all over and make another one. This is the A/C power supply I built from Jacobs online. Not sure if A/C is better than using a D/C power supply. I figure, that if it is this complicated , then it has to be better. Any way, the last one I made worked extremely well, so I just stuck to this plan. Will make a 30" and a 18" bow after dinner. The tutorial is here if anyone is interested.

BTW I am using the 12/24 V transformer for the longer lengths.

 

[cyclone3350]

The cutting bow is done. just tested it and it works. I think I will test out my cutting skills on a smaller build before I start cutting out something this big. I only made one plane using the bow and pink foam, and it was quite a while ago. The only thing I hot wired , was the wings and tail. The fuse is just a box and sanded to shape. As U can see, it turned out OK.

 

[leaded50]

a tip..... its easier to set formers correct by making a straight line longitudinal, as eg a "thrustline" through the fuselage plan, and mark on the formers