Third party contractors

I talked to Bruce Blake from Advanced Hybrid Aircraft about building the envelope for my UL design. He suggested a multi-tube "mattress"-like envelope with a ppg motor. He doesn't think my envelope design can develop enough lift to carry the pilot's weight. 

He offered to do a design drawing of his concept for a fee of $1500. I wanted to see what everyone thinks about that. 

BTW, I am in the process of moving, so that is why I haven't been active for a few days. But I will have internet installed at home soon.

Dude , I'm sorry , If there is  truly  a hell,  It will involve ......moving..... I hated moving With a passion. 
 I'd  give Southern balloon works  a crack at it ,  They  may  be able to  produce a  working   RC scale  for that money  .

   Bruce Blake has been in the picture for a long time, but I would not pay for someone to promote their design. I would love for someone to pay me to promote my design!
   If Bruce can find a source for envelopes, fine. I have not been able to find the site I saw, thought I saved it.
   China is making envelopes and ships, but I refuse to send my business offshore.
   Work obligations have kept me from working on the model. I'm going to have to move the thermoform oven, my shop is too flammable. I have another room next door. I would like to have the model ready for show by September, the deadline for the competition. If everybody else is going as slowly as I am, maybe the deadline can be moved.
  Welcome, erniejunior, help us in finding envelope sources. We are trying to bring down the cost of flying.

I believe Blake makes his own envelopes. That is why I contacted him. I have no problem supporting the development of a design that will fulfill our needs. That is the point of the forum. However, I am not all that confident in his design concept. So I need a little more information before I would be willing to put any money behind his concept. I just want to see what other members think.  

Well, as he is an engineer and you are the customer maybe he should have worked with your design and told you what it could or could not do, and then what size/shape using your design it would need to be.

Plus modelling your own design is funner anyway.  Learn by trial and error, unless you just want to get something built and then just farm it all out...

Ps: I have some Aerotube samples, quite sturdy stuff.

<<<He doesn't think my envelope design can develop enough lift to carry the pilot's weight. >>>

   He could be right. So that leaves you with the option of a] making the wing area bigger and/or b], gulp, more power/speed for more dynamic lift ? 

  I guess that a little of both a and b would be the middle path and the safest way to proceed.  As a potential customer, you can probably get Blake's advice on this course for free or for short bread.

Up is good.

He may be right, but he was just looking at a sketch done in paint. He didn't see any specs, so it was just a guess. I think I will contact him again, maybe he would be interested in basic feasibility study... I think that airship can develop that amount of aero lift. I had calculated it out, as best I can.

I emailed Bruce Blake again tonight to explain more about my design and request more info. Hopefully we will warm to my concept. But even if he isn't a fan of the design, he might be willing to construct an envelope for it. In any case, we will see.

Got a good response from Bruce. He said his rule of thumb for envelope costs is 3 times the cost of the envelope material. I assume this uses the cost of polyurethane coated polyester as the base. He also said his supplier charges about $38 dollars per yard (~ 53 in wide) for material. So that may help others ball-park their envelope costs. He also inquired about my lift and drag numbers. I'll get that data and respond with it soon. 

    I think this one post pretty much tells it all for personal airship. At $38 a yard for uncut, un-sewn/welded material plus three times that for construction, you can see why ships cost so much.
  My plastic is costing about $12 to $15 for a 32 square foot sheet, plus freight. That works to about $4 or so a yard, at 48" wide. The loss and wastage should be about the same. Cost of a thermoform oven is probably less than a commercial sealer we have seen in use. I think a thermoform oven can be home made, it's just like a pizza oven. The vacuumform molds can be home made, too. Labor would probably be about the same, both techniques are labor intensive.
   The big difference between rigid and non-rigid is storage when not in use. A non-rigid can be boxed up and put away, a rigid has to be taken care of for the life of the ship. Either it is tough enough to tolerate being outside, like a lot of airplanes, or it will require a hangar. I'm going for tough.
   The material I am talking about is used for roofing, so there you go.

Mikek;

What is the brand name of the material you're going to use?

Thanks

My model is clear PETG, .020" thick, non-uv resistant. I got it from Midland Plastics in Wisconsin, if my records are correct. It's made by Sheffield Plastics, on the East Coast, I think.
I haven't called them about the roofing plastic, will do so soon. It said UV resistant in the store, so that sounds good. You can almost stand on the corrugated plastic roofing, the corrugations make it real strong. When we install stuff like this, we have to carefully walk on the rafters, or put plywood over it.
I would hope the white plastic is sold flat, ready to thermoform. I'll have to send them an e-mail, they are very helpful.

Products made of PVC coated or urethane-coated nylon lose helium quickly and Hydrogen only  slightly better which increases your costs.  If  damaged ,  cannot be repaired  easy  , and  certainly  not in the field. 
 Your   best option   is to use  urethane Bladders  in a rigid  plastic shell  Like Mikek 's  theory
 Or  In   others   approach , including mine,  It  would be  a  form  fitting or  frame supported shroud of  ripstop nylon,  or in some  cases  tarps as Nav  is  looking at ,  even  Tyvek  house wrap could be used  if properly  sewn with load tapes.
   Tyvek  Has  a very good  chance of  becoming my  envelope shroud . You  can  do  a lot with it  that  I didn't know about    http://www.polymernotes.org/resources/tyvekdupont.htm 
 But however  it goes ,  urethane  bladders  are the  way to go.  or  a more  expensive  nylon  polyester , laminated   urethane bladder ,  This is not the same as a coated nylon.  But  still , this type cannot  be  repaired in the field  ether.  A separate  bladder  and  "skin"  would offer the  best  results, and  can  be repaired in the field.  OR  replaced   keeping  the majority of your  airship intact .  All  the loads  would be  carried  by the "skin"  .The  bladders   are  only  "captured"  in the Skin with no loads placed on it  at  points. The  entire  bladder would  "see" the load.  Not just  certain  areas or points.
  The  Areophile  NG  30  Tourist balloon I  worked on   was  a HUGE 100% urethane  bladder  surrounded by  a nylon  net .  All the  attachment points   were on the netting.  Nothing  was  attached  to the  bladder that was load bearing.  It  required  topping off  about  every  3 months.   We're talking  about  a ton  and a half of  airship here .  

I have calculated the cost of my envelope based on the numbers I got from Blake. Very rough calculations indicate the envelope will cost about 10 grand. So, there it is.

OUCH!   Ok ,  Plan B ?  for  bladders that are commercially  made by the  thousands,   and shroud them ?   Or ?

Well, if the envelope costs 10,000 and the paramotor costs 5,000, put it together and you have a blimp for less than 20,000. IMO, that fulfills the goals of the prototype. I think it can be done cheaper, but not by a whole lot. 

 Well crap , .  I thought the  goal  was 10 G .   Guess that  was my goal  anyway. 

It is. I was just moving the goal posts a little for a prototype in comparison to a production model; assuming that a production run would reduce the cost significantly. The actual dollar figure is a little arbitrary, the point is to make it affordable. Since the nearest competition is like $200,000, I think 20 grand is in the ball park for a prototype.

Also, I'm not sure a shrouded design would save much since 75% of the cost of the envelope is assembly labor. That doesn't leave a whole lot of room for improvement. The place to save money is in the assembly costs. Can a shroud be built that much easier?

Yes,  I would think so. Or one could be bought custom made.  .  I'm looking hard at  foil faced Tyvek thermo wrap .  Its UV proof   and does not  stretch . 9 foot  x 100 foot roll for 95 dollars.  Can be  sewn with  common  household  sewing machine  using conventional  sail making  thread  and construction  methods. 2.35 oz  a sq yard.    

I contacted  Souther  balloon works.  They have  a 40 foot  rip stop shroud  for  8750.oo .
  I think  I could build one   out of   aluminum faced Tyvek  for  500.oo  or less.
 Going  to  Home  depot or Lowes   and  try to get a sample  if that have  any in stock. Do  some  test sewing  and  destruction tests.