# my part 103 ultralight build -thread

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#### WonderousMountain

##### Well-Known Member
Using what you have handy is a tried & true way to be thrifty,
Using an uncommon specialty item muchless so. Mold & Tool
making is a costly part of home & kit building. You will likely buy
twice what you spend on materials & aviation supply on junk that
sits in drawers 99% of the time. However, you will get better with
your own Machinery to tearup stuff.

~CK LuPii
(One of my favorites is a metal brake)

#### mcrae0104

##### Well-Known Member
HBA Supporter
Log Member
...how do I determine what reynolds number my plane will be going at at cruise?
$$R_e=\frac{\rho VC}{\mu}$$
where:
$$\rho$$ = air density ($$\frac{slugs}{ft^3}$$ or $$\frac{lb \times sec^2}{ft^4}$$; at standard temp & sea level, $$\rho$$=0.00238 slugs)
V = velocity (ft/sec)
C = wing chord (ft)
$$\mu$$ = air viscosity ($$\frac{lb \times sec}{ft^2}$$; at standard temp, $$\mu = 0.3735 \times 10^{-6}$$)

When you multiply the units, you find that they cancel and Re is "dimensionless," which is to say it has no units associated with it--it's just a ratio of forces.

When using foot/pound/second units, the shortcut is $$R_e \approx 6400VC$$.

So, for example, if your speed is 50 mph (73.33 ft/sec) and your chord is 4 ft, then $$R_e = 6400 \times 73.33 \times 4 \approx 1,870,000$$.

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#### TFF

##### Well-Known Member
I think a wheel barrow is a little too strong. There is not a lot of excess weight in a 103 UL. A wheel barrow will use up too much. It might look like a good shortcut but it’s not. Is the plan to build in wood or metal or a mix?

#### Gregory Perkins

##### Well-Known Member
Hey everybody, my name is Daedin and I plan to build a part 103 ultralight. I've been designing the ultralight for the past 11 months, and while that sounds like a long time note that I had school going on at the same time for 9 out of those 11 months, and school takes first priority. But I just finished with finals last week, and I can finally give my ultralight my full attention. So, I've been on HBA for a few months under a different account, I just figured that I ought to start a new account with correct details and everything. I've posted on the website before, and I love the community here! Everyone is so incredibly helpful, and I plan to be on here a lot more often because of that.
This thread is for questions I have about ultralight design, (I have a lot of them) and questions any of you guys might have about anything really.

So for my first question, can someone tell me how to estimate what my horizontal and vertical tail surface areas/volumes should be? I tried to use the vertical/horizontal tail sizing equations on pg 36 of Raymer's Simplified Aircraft Design For Homebuilders, but I couldn't tell what value I was supposed to put in for Swing, the wing area or the tail area? And why would I use the tail area in a problem that is meant to help me find the tail area? I tried the equation (pictured bellow) with the wing area for Swing, but I got a value of 39.16 ft^2, which doesn't sound right. Note that I have the tail 7.125 ft from the MAC, (or 5 ft from the trailing edge of the wing) a wing chord of 4.5 ft and a wing area of 124 ft^2.

Thank you, and I look forward to posting more on HBA!
If you are 13 and interested in designing and building airplanes I cannot think of a better place to start than here Home ("The Beaujon Bible")
This has been my bible for imagination in minimum aircraft for 35 years.
The other plane or two which were popularized by being published on the covers
of Popular Mechanics or Mechanix Illustrated etc was the Whing Ding and the Wood Hopper show that it really doesnt have to be that complicated to create a contraption that flys. In fact, you may decide you really dont need power in the beginning
in which case I would point you to the Volmer Jensen created VJ-11 or the Hang Loose.

Decades ago when high schools use to have wood shop classes, many selected fun projects such as these to work on but they were never flown because of liability.
They were always hung from ceilings in gyms etc. ( no actually I remember one instance where the class instructor flew the VJ-11 down a hill several times and sent me photos.... I supplied the plans )

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#### Daedin Does Stuff

##### Member
I cannot think of a better place to start than here Home
Thank you for the link, this little book has absolutely everything I need in it, I'm sure it will be very helpful!

#### Daedin Does Stuff

##### Member
I think a wheel barrow is a little too strong. There is not a lot of excess weight in a 103 UL. A wheel barrow will use up too much. It might look like a good shortcut but it’s not. Is the plan to build in wood or metal or a mix?
Yeah, I'm starting to think that maybe using a wheelbarrow will create more problems than it will solve. My UL will be almost entirely wood, the only exception being a rectangle with an X in it made out of aluminum that connects the fuselage and the two wing halves. I circled it in the picture bellow.

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#### Victor Bravo

##### Well-Known Member
HBA Supporter
Daedin, about 6,937.3 of us here on HBA are very glad you allowed your original thinking to evolve past the wheelbarrow. That shows one of the most important skills that the world's greatest engineers possess... realizing that one "solution" eventually created more problems than it solved. You have no idea how many smart people can't get past that trap.

Since you are looking at wood as a construction material, you might get some useful inspiration from the all-wood Cloudster and other ultralights on this page: Cloudster Ultralight – Simplex Aeroplanes Perhaps some of the people here have personal experience or knowledge on these in terms of safety, building difficulty, and cost. Mr. Perkins???

Also, one of our HBA members Little Scrapper has some experience with another popular (and demonstrated safe) wood ultralight, the MiniMax. You might hit him up for some info, he's a great guy and definitely is interested in helping people build stuff. He made a fantastic set of videos about starting to build a MiniMax on the lowest possible budget... absolutely worth watching.

#### Gregory Perkins

##### Well-Known Member
I think what VictorBravo is getting at is hundreds and hundreds have gone before you
and as we all start at the same place, it is always helpful to retrace the design path
that every interesting plane has undergone. Ultimately there are no ideas that have not been thought about and the ideas that survived the analysis, resulted in planes that we can learn from. There are only so many variables in design and hopefully there exists some plans that mimick some of your preferences and then to make it yours .... if you dare.... you make some changes.... always aware that the changes may be for the worse since you are a beginner and an older design is likely to be proven. You may have noticed that a lot of guys here have an embarrassing number of plans (embarrassing only to those who dont understand) that they have used to do their graduate studies as they get to look into the minds and see the decisions made by often times really gifted aircraft designers. I believe 40, 50 and 60 years ago before the technology age, many gifted
designers worked with scale RC craft for prototyping as that was the closest thing
to CAD today. After you closely scrutinize the design of various planes, you will likely
acquire some favorites in terms of material, technique, layout, and style. You have been given enough to keep you busy for a few years but other designs will pop up for analysis and may displace the next one on your list to figure out and you might like it so much that even if it does not have available plans, you may pursue actually creating your own.
The Cloudster is indeed an attractive and tempting wood design with available plans but so also would be .... kinda... some other earlier designs, such as the many variants of the Demoiselle and (one of my all time favorites )the Dormoy Bathtub and the many varieties of power added to
the Primary Gliders in the 1930's and 40's etc. Then the Skypup and for your PHD
in lite wood craft, the ULF-1 glider and the French Souricette and the BiPlum. This all assumes wood as a primary material. ( special honor for the Ritz Std design without available plans ) Oh and cant forget the Birdman TL-1A !
What about the Harlan Dierrere as a tow glider ?

I personally have become a devoted fan of all the "flying lawn chair" types as I think
the evolution and availablity of aluminum tubing to be the the greatest achievement of
mankind. What I like about them mostly is that the architecture is nearly always honest. ie. you can inspect all the joints and nuts and bolts and rivets and gussets etc. for many decades
after the initial build. With wood, you cannot do that even next week if someone
else built it because gluing wood is very process intense. What glue, how old, how long was it on the shelf, at what temperature and under what clamp force and how much used, did the joints fit right, was the wood too wet or too dry etc. Even if you built it yourself, how much confidence do you have ?

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#### TFF

##### Well-Known Member
I have always had a thing for Primary Gliders from the 30s. ClaudeL - Dickson 1930
Depending on where you live, that may be an option. Unluckily it does require a crew, but you can start pretty young flying them. Goat is a modern version in aluminum

The MiniMax is probably the best wood UL or one of the versions. It would be good to study. It hasn’t flown but some students are designing a UL and they share some here. You might search for it. It’s not wood though but you might correspond with them.

#### Daedin Does Stuff

##### Member
Alright, I need some help here. Bellow is a side profile of the entire tail section. There is 7 ft between the trailing edge of the tail and the trailing edge of the wing. I have two questions, one, how many sides should the tail have, and two, what should I do to make the tail surfaces more structurally sound? So for the first question, I like the idea of a tapering 4 sided tail the most, but I'm afraid it will add too much weight and end up being overkill. Will a one sided tail do? If the tail were to look exactly like it does in the picture, made with 1x1 wood beams, would it be enough to support the tail surfaces? Then for my second question, whenever I designed the vertical tail surface I felt like I had made a bowl of spaghetti and called it engineering. Anyone have any tips or anything that might improve the structure?

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#### WonderousMountain

##### Well-Known Member
So I chopped the top off your Fin,
Removed the lower back pane &
Reverse engineered the Yaweron.

Hope you like it, no hard feelings
If you do not. ~ CK LuPii

#### WonderousMountain

##### Well-Known Member
Sorry to string post, thinking yesterday in the wilderness,
I came up with a make using one less structural member.
An' then proceded to botch the sketch pad layout. Final
Diagonal triangulates without the upward brace, hinge Line
is raked to improve overall balance. Another aft end option.

~Sincerely CK LuPii

##### Well-Known Member
What about a tail with a triangular cross section like the one Sir Percy flew in Those Magnificent Men and Their Flying Machines? It would be lighter than 4 sided.

#### WonderousMountain

##### Well-Known Member
A triangle section will make an all flying plank out of the yaw stab upper region, but it is easy enough, and might well be light.

#### Victor Bravo

##### Well-Known Member
HBA Supporter
What about a tail with a triangular cross section like the one Sir Percy flew in Those Magnificent Men and Their Flying Machines? It would be lighter than 4 sided.
Not that bounder Sir Percy ?!?!

#### Daedin Does Stuff

##### Member
Ok, so I revised my design (pictured below) and I'm a little happier with it now. I've decided to go with a tapered 4-sided T tail. CK LuPii, I love your design, but my tail will be a T-tail, and I don't think that your design would provide enough support for the horizontal elevator in my case. Thank you for sharing the design though, if it weren't for the T-tail it would be perfect!

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#### WonderousMountain

##### Well-Known Member
You might consider using a wider/larger main rudder post.
Reasons:

A T-tail may tansfer assymetric loads.
Bundle of sticks problem is hard to fix
with the usual Mission requirements.
Weight may actually be better with a
Clean layout.

Small light spaceframe construction
was pioneered by lotus car (racing) One,
enginee of which built an unusual wood
sailplane, with good performance,
yet little of record remains.

Sincerely, ~CK LuPii

#### Daedin Does Stuff

##### Member
Alright, I gave myself a deadline of June 30th to have my design completed right? Well on the 24th I'm going on a trip with family and won't return until early July. What this means it that these few days before June 24th are my last chance to make design changes before I begin building it whenever I get back from the trip. If you guys have anything to say or point out about my design, now is your last chance before I start building (in two weeks)!
Now I have a question. Should I glue all the wood together, or use screws and bolts? Originally I thought that I would just use metal plates and gusset all the wood together like you would with metal tubes, but I think that would add on a lot of weight and might not be as effective as other methods. I think glue would work better but I'm not so sure. As Gregory Perkins mentioned, gluing wood together is apparently a lengthy and complicated process. Using screws and nails seems a lot more straightforward but I don't know if its the best solution. Anyone have any tips or anything? Thank you.