FTC21 Seaplane Challenge/Martin XP6M-1 Seamaster

[cyclone3350]

Here is my official entry for the FT21 Seaplane Challenge. The Martin XP5M-1 Seamaster. I have the drafting table cleared off and along, with some 3 view drawings and the aid of this plastic model, I hope to have something that looks like one. The initial project will be a 1/22 scale glider that will serve as a test bed for the spoilerons and CG confirmation. The plan is to build it out of foam board and depron using the FT master series type of construction. The final version will be hot wired from foam and fiber glassed @ 1/11th scale and powered by four 90mm EDF's. This is where I am now. A car load of foam and a lot of crazy ideas. I have to go out of town and we will see how far I can get on my next group of days off starting on May 4.

 

[FoamyDM]

Looks like a solid start. I am keep to see your method of enlarging the model?

The initial project will be a 1/22 scale glider that will serve as a test bed ...
...The final version will be hot wired from foam and fiber glassed @ 1/11th scale and powered by four 90mm EDF's.

*picks jaw from the ground*
...
*and again*
...
4 - 90mm EDFs (10kg of thrust+?)... the batteries alone...

 

[cyclone3350]

Looks like a solid start. I am keep to see your method of enlarging the model?

*picks jaw from the ground*
...
*and again*
...
4 - 90mm EDFs (10kg of thrust+?)... the batteries alone...

That has been the real challenge. Finding 4 motors + batts that will give me @ least a 1:1 power to weight ratio and stay within a reasonable wing loading. I kept running the numbers, and bigger the I got , the closer I got to those numbers. It looks like the 4 90's on 8s @ the 1/11th scale. If I can get the airframe down to 17lbs, then 6s (my optimum goal) will work for sure.. This is why I am building two versions. The smaller one should tell me that It could be done. If that doesn't work. then I stop right there. The final version @ 1/11th scale = 112" WS X 146" LNGTH with a calculated AUW of 30-35lbs. !

 

[FoamyDM]

@cyclone3350 I assume you have experience with plane that large/heavy.
Have you considered using just two Motors. and saving weight (if there is enough thrust)

 

[cyclone3350]

My final goal is to enter this into the various warbirds events here in the Midwest. 80" WS is the minimum. Two 90's could do that size, but the nacelles would be much taller than scale. So, why not make it bigger and put on four. The first version to will be of a foam board type design for glide testing and to see if how effective spoilerons will be and where to put the CG. Like I said, If that works, then it will be a Carf fiberglass and plywood frame fuse construction with sheeted form core wings and tail. Of course the fuse will be two sections as well as the wings for transport. I doubt that the big one will be done before the deadline.

 

[leaded50]

fiberglass and plywood..... why not use foamboard, carbonfiber/fiberglass and epoxy....

 

[cyclone3350]

Haven't 100% decided on the exact construction. It will be a hot wire foam fuse to either be used as a mold for the glass and then the glass halves glued over plywood supports or use the foam fuse as it is and just glass over that. It will be big and will need to be of strength.

 

[cyclone3350]

Here is the latest update. Got the 3 views back from the printer enlarge to 1/22 scale. This gave me a very good idea, at least, as to the size and and what I could fit for motors. What U see is 56" WS and a total 73" fuse length. Original plan was to use this scale as glider to test out the aerodynamics and go form there. This structure is pretty complex and too time would be spent doing that, so now the plan is to go @ 1/13th scale and use the Freewing 80mm 6s EDF system. ( I have a 64mm, an 80mm and the 90mm as references on the floor ) That is as big as I can make it and still get it in my SUV. I have been watching a lot of Ramy RC videos and Demon Driver as well on youtube. That is how I intended to do the construction of this thing.

 

[cyclone3350]

Making some progress on the Seamaster. I decided to modify this one a bit to better suit the type of flying that I will be doing with it. This will be more of a what if concept. If this plane had gone into the use the Navy wanted, I am sure it would have became an amphibian. I had to think about how the engineers might have gone about doing this. My guess is, they would have add an airfoil type pod for the mains and put a retract nose in the front hull. This would allow them to add the internal reinforcing needed without interfering with the rotating bomb bay. I have it drawn out with Robarts pneumatic retracts for the mains and a modified tailwheel for the nose. It will have a dual wheel set up for the nose and mains and the pod should only extend out about 8" from either side. this is the front half and still have quite a ways to go just on this section.

 

[EAS]

Are you really going to put it in the water? That would make me real nervous....no pontoons (other than outboard), so the fuselage will have to be perfect. Yes, foam and fiberglass.

 

[cyclone3350]

That is my intensions. I can not say for sure that it will work. That is why I am making it amphibious. It has an anhedral wings with fixed floats on the tips that match the fuse waterline. Back to drawing out some more formers today.

 

[EAS]

That is my intensions. I can not say for sure that it will work. That is why I am making it amphibious. It has an anhedral wings with fixed floats on the tips that match the fuse waterline. Back to drawing out some more formers today.

I'm not absolutely sure, but I think those type aircraft placed the wing-tip pontoons slightly above the main's waterline....if the wing-tip dipped during take-off or landing you cartwheel. Maybe a even a little higher, so they only made contact with the water at low speed. Take a good look at all the WWll photos you can find.

 

[leaded50]

Martin XP6M-1 Seamaster didnt had retracts, but a "dolly" it was moved at land with.
Your use of retracts would be functional... and the dolly-system aint functional as flying arouns anyway

 

[cyclone3350]

I thought about doing a functional non scale dolly with a release and putting a thin metal strip on the hull, like that on a Republic SeaBee, for landing on the grass. And that may be the easier way to go. Right now, I like to go complicated on paper as that gives me an idea as to what is feasible.

 

[cyclone3350]

Well, I thought I was making progress. When It came down to drawing out the formers, the 3 View plan I was using did not line very well with known points on the side view and top view. It is hard to explain, but I just need to re do it from another perceptive. So plan B will go into place and this will add some time, but should work out. The lower drawing U see is the outline of the lower deck @ the water line with the first set of formers. It is hard to see because, I first use a light hard graphite before I go to the softer darker one. The plan is to start with the lower deck and from there, the formers will be glued on top, and the triangle shaped portion of the formers on the bottom.

 

[cyclone3350]

Went to plan B and it is going as well as I would have hoped. I have had wondered if a drawing can be reproduced using a plastic model kit and a contour gauge. Now I know that it can be done. As U can see, I am using the halves to do the outlines. I marked lines where I would like some formers to go. I align the fuse half, back on the drawing, and place my contour gauge over that spot. I trace it out on paper and cut out the outline. Use the opening to check for accuracy and then use the cut outs to draw the formers. The drawing is in 1/72 scale and form here I will have it enlarged will make a prototype. This is how far I managed to get from last night to today. BTW , I will probably go with a scale down version from four 90mm EDF to using four 50's for EDF's. QX Motors has released it's latest version, the QF2611. Unfortunately, I have to order directly from China. Has anyone had any experience with ordering form either Ebay, Banggood or Alipress from China to the states?

 

[Monte.C]

Went to plan B and it is going as well as I would have hoped. I have had wondered if a drawing can be reproduced using a plastic model kit and a contour gauge. Now I know that it can be done. As U can see, I am using the halves to do the outlines. I marked lines where I would like some formers to go. I align the fuse half, back on the drawing, and place my contour gauge over that spot. I trace it out on paper and cut out the outline. Use the opening to check for accuracy and then use the cut outs to draw the formers. The drawing is in 1/72 scale and form here I will have it enlarged will make a prototype. This is how far I managed to get from last night to today. BTW , I will probably go with a scale down version from four 90mm EDF to using four 50's for EDF's. QX Motors has released it's latest version, the QF2611. Unfortunately, I have to order directly from China. Has anyone had any experience with ordering form either Ebay, Banggood or Alipress from China to the states?

View attachment 201579

It'll surely be another masterpiece.

Sure I've gotten a couple things from China & Hong Kong, but I don't like to do it. It feels like I'm doing dirty business. You might get your item within a couple weeks or it might take a couple months - from my experience. Some items seem to have a US warehouse. A lot of people have no issues with shipping from China. Some or pretty much all of the stuff is dirt cheap. Here's a vague warning - I've read reports of some simple items are made to two different standards - like some servos, I think Emax (?), some are made for local markets (and Aliexpress and Bangood) where maybe they say metal gear servos and deliver plastic gears, and some are to ship to US - Emax - to be sold in the US. I bought an ultra-cheap pair of bike lights (as we went into the lockdown) that never arrived, and 6 months later I requested a refund. Good news, that particular seller gave me no problem with an immediate refund.

Bangood and Aliexpress - One is like Amazon, they have the product in their own warehouses, and the other is more like Ebay with all individual sellers.

Great savings are to be had. Just be aware that this is a culture where one of their common sayings translates to "If you can cheat and get away with it, then cheat."

 

[EAS]

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.

 

[cyclone3350]

It'll surely be another masterpiece.

Sure I've gotten a couple things from China & Hong Kong, but I don't like to do it. It feels like I'm doing dirty business. You might get your item within a couple weeks or it might take a couple months - from my experience. Some items seem to have a US warehouse. A lot of people have no issues with shipping from China. Some or pretty much all of the stuff is dirt cheap. Here's a vague warning - I've read reports of some simple items are made to two different standards - like some servos, I think Emax (?), some are made for local markets (and Aliexpress and Bangood) where maybe they say metal gear servos and deliver plastic gears, and some are to ship to US - Emax - to be sold in the US. I bought an ultra-cheap pair of bike lights (as we went into the lockdown) that never arrived, and 6 months later I requested a refund. Good news, that particular seller gave me no problem with an immediate refund.

Bangood and Aliexpress - One is like Amazon, they have the product in their own warehouses, and the other is more like Ebay with all individual sellers.

Great savings are to be had. Just be aware that this is a culture where one of their common sayings translates to "If you can cheat and get away with it, then cheat."

Thanks @Monte.C . U pretty much reinforced what I had in mind as far possible issues. The only reason I was considering these, is that QX makes their products under various names sold in the US. I have heard that they have some sort of deal with FMS and I think the make the EDF's for Arrow. Anyway, these 50's R supposed to be a game changer for EDF's of that size. Unfortunately, it hasn't been released to US distributors. There is one, but he has the last versions and only three left. So, I might might just make the nacelles a little larger than scale and put in known 64's.

 

[Monte.C]

Thanks @Monte.C . U pretty much reinforced what I had in mind as far possible issues. The only reason I was considering these, is that QX makes their products under various names sold in the US. I have heard that they have some sort of deal with FMS and I think the make the EDF's for Arrow. Anyway, these 50's R supposed to be a game changer for EDF's of that size. Unfortunately, it hasn't been released to US distributors. There is one, but he has the last versions and only three left. So, I might might just make the nacelles a little larger than scale and put in known 64's.

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.