Newbie Looking Leaning Towards a Foamie (My Question Thread)

[KCStudly]

Are you thinking about which of the holes you will use? I'm thinking that the two widest ones and one of the lower ones would be more than adequate. My thinking is that the extra holes are provided for nailing, whereas you are screwing, which is much stronger.

[jseyfert3]

Are you thinking about which of the holes you will use? I'm thinking that the two widest ones and one of the lower ones would be more than adequate. My thinking is that the extra holes are provided for nailing, whereas you are screwing, which is much stronger.

I did not think about that. I figured I'd just screw them all up. You make a good point though, they are probably not all required.

Do you have any thoughts on the post I made just about yours (bottom of page 5), where they guy on the other forum pointed out that wood and steel have different thermal expansion rates? Is that likely to be an issue with how I'm planning to build it?

Overthinking again.

[KCStudly]

Do you have any thoughts on the post I made just about yours (bottom of page 5), where they guy on the other forum pointed out that wood and steel have different thermal expansion rates? Is that likely to be an issue with how I'm planning to build it?

Yes. My thoughts are that he was correct. He is not an expert, and does not know enough about the subject.

The expansion rate differences are insignificant for the temperature extremes and lengths of material concerned.

The thermal expansion rate for steel is 0.0000073 in/in / deg F.

For wood with the grain it is 0.0000017.

So if we assume you assemble at 65 deg F, and common temperatures in your region or where you camp can range from 100 to zero deg F, then the biggest excursion from 65 deg F is delta 65 deg.
Over 48 inches and 65 deg, the steel will shrink about .023 inch and the wood about .005, for a relative change of .018 inch. If we assume that the action is symmetrical, the screws at either side of your trailer will only see .009 relative change.

Reference expansion rates: http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html

I think the bigger issue with hay wagons is that there is no box structure on top to hold the deck true, so when they overload something that has an axle at each end with hay bales a mile high and drag it over rutted fields it will tend to twist.

Your relatively light single axle trailer with a nice rigid box attached won't have that problem.

[jseyfert3]

Do you have any thoughts on the post I made just about yours (bottom of page 5), where they guy on the other forum pointed out that wood and steel have different thermal expansion rates? Is that likely to be an issue with how I'm planning to build it?

Yes. My thoughts are that he was correct. He is not an expert, and does not know enough about the subject.

The expansion rate differences are insignificant for the temperature extremes and lengths of material concerned.

The thermal expansion rate for steel is 0.0000073 in/in / deg F.

For wood with the grain it is 0.0000017.

So if we assume you assemble at 65 deg F, and common temperatures in your region or where you camp can range from 100 to zero deg F, then the biggest excursion from 65 deg F is delta 65 deg.
Over 48 inches and 65 deg, the steel will shrink about .023 inch and the wood about .005, for a relative change of .018 inch. If we assume that the action is symmetrical, the screws at either side of your trailer will only see .009 relative change.

Reference expansion rates: http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html

I think the bigger issue with hay wagons is that there is no box structure on top to hold the deck true, so when they overload something that has an axle at each end with hay bales a mile high and drag it over rutted fields it will tend to twist.

Your relatively light single axle trailer with a nice rigid box attached won't have that problem.

Thanks for the answer! I'm not at home, and couldn't sit down and check that myself, I had planned to do that tonight when I got back and had my mechanics of materials textbook (been a little bit since I took that class). I still am curious what the stresses would be, assuming they were locked together, I may calculate that out of curiosity later (and helps me remember this stuff later on once I'm done with college).

I did figure the flex thing did not apply in this case, I have heard of nobody here with that issue. In fact, I was thinking the thermal expansion was not much of an issue, but he stuck that idea in my head so of course I had to know. It it was a major issue, I probably would have run across a post by someone about it, but again, my raised sub-frame and the specific attachment method I'm using is a little different then what most use, so I wanted to make sure.

Speaking of which, has anyone ever attached a raised floor frame with hurricane ties before that you know of? It didn't sound like you had heard of it, as you came up with the idea.

I'll probably start drilling holes tonight, if I can decide on 24" or 18" spacing. I think I may do the 18" spacing, 24" may be pushing it for a floor that will just be a sheet of OSB.

2 ft spans are pretty generous, and that is about what I have in my floor (maybe closer to 18 inches?). I only have 3/16 thick skins (5 mm) but have a piece of scrap 1/2 ply on rosin paper laid down during the build so I can walk on it. Once the roof goes on and the mattress is down there won't be so much point loading (will only be crawling or laying down) so it will be fine. The foam is, however, fully glued to both the upper and lower skins, so there is a great deal of modular strength built in. Just stuffing chunks of foam under your floor won't give the same strength as a torsion box.

If you want to dance on it, I wouldn't go less than the 1/2 inch, and with larger spans and a single top skin only, you might want the 5/8. Just an opinion from what I have read here, really; not hard fact. $.02

Which reminded me of this, I forgot to reply to it. I wasn't planning under the floor to be structural, just insulation. Didn't want to get super complicated in this build (even if I tend that way sometimes). Probably do 18" spacing and 0.5" OSB and call it good. I am far from heavy, that's for sure. (6'5" and 155 lbs)

[jseyfert3]

If you don't mind another question...

I've got some ideas floating around in my head for a deep cycle battery mount, but if anyone had any, that would be appreciated as well. What I'm thinking, is that I can hide the battery in the curved front of my teardrop, and keep away from installing a tongue box. However, such a mount would be putting a 50-70 lb battery or batteries. I'm thinking size wise I'd like 3 nights running a Fan-Tastic fan on medium (2.3 Amps), which for 9 hours a night ends up at 62 Amp-hours. Add in a little bit of lighting draw (LEDs), and the 80% discharge limit for longer life, and I'd probably want say, 100 Amp-hours?

From what I've seen, group 27 deep cycle batteries are between 50-70 lbs, and around 100 Amp-hours or so. But mounting a 60 lb battery about 2 feet up and 1 foot forward of the nearest steel beam on the trailer seems like it could be a little tricky to do in a lightweight and secure fashion. I do have something thought up, and plan on doing a Sketchup drawing for thoughts on it. I'll post up in a little bit once I get that done.

[jseyfert3]

Okay. Bear in mind this is an initial sketch, just to get my general idea down. I was not intending it to specify exact sizes and materials that would be used, just a general idea I have in my head.


Battery Mount Sketch (1) by jseyfert3, on Flickr


Battery Mount Sketch (2) by jseyfert3, on Flickr

I was originally thinking the "main" support would be a wood beam of some sort, which is why it's square. This I figured would take most of the load of supporting the battery. But since the battery is forward of the bottom of the support, it wants to "fall forward" in simple terms, and the only way I could see to help support that was running some angle iron or similar (C channel or square tube would probably be better) to the edges, where a thin strip of steel or aluminum would run forward in a channel in the foam and anchor into of of the wood sub-frame supports.

I was not intending it, but I thought after I got done (3D sketches are very useful, I'm finding!), that the OSB "headboard" could also be used as a vertical support on one side of the battery to carry some of the load, especially if reinforced with some strips of 1x2 framing or similar to help stiffen it.

This would require a small vent of some sort on the front of the trailer, to allow hydrogen gas that could be generated to leave, as a vent on the bottom would not allow that since hydrogen rises. Then a small vent at the bottom of the trailer to let air in.

Certainly, my sketch seems to help me see it's doable, even if what I have is not the best way to mount it, and I'm certain it's not. Thoughts?

[GPW]

May not be the best place to mount it ... especially up so high ...

[KCStudly]

How about under the floor near the axle? Just ahead or just behind it. Check out how Danny does his in traditional builds. I think Zach's X2 had an under slung battery, as well.

[GPW]

Anybody ever salvage an Auto battery box (boneyard), and just bolt/weld it to the trailer.. ?

[Mary C]

Js and KC and you other guys if I didn't know any better I would think you are building a spaceship going to the moon, Keep it simple. I own an oil well that gets a profit and it is .00000000024 and that equals to 16 cents a year. Now that is really a lot and that is at full production and if it is not, they want 6 dollars a year. So you figure it out. It is not worth the paperwork for me but it is fun. So if discussing the .000074 and the perfection of all the ratios just make sure it is worth your time and effort to change it for the better. so......I will be just KISS for me I am not worried about those .00000000things there are bigger fish to fry, speaking of fish I need to go fishing........ winter is making me crazy!!!!!

No, put the battery LOW. I cant tell you exactly why, but I saw a batterys damage on a person once (acid) and I would put it low, protected and away from persons.

Mary C.


edited twice to get the spelling just right

[KCStudly]

It's just a little "knowing" and a little math, Mary. Just one of the things that I like to do for fun, and because it exercises my brain. The fact that we were talking decimal points is the exact answer to JS's question; 'nope, it does not matter so don't worry about it, and... here is the scientific proof'.

It's too cold to build here, so I guess I got a little bored.

[jseyfert3]

Indeed Mary, I agree with what KCStudly said, I understand what he posted and enjoy doing stuff like that, or I would not currently have my Associate in Engineering Science Degree and be continuing towards my B.S. in Mechanical Engineering this fall. In fact, I want to (just for fun) calculate the stresses in the wood caused by the said 0.0000017 in/in / ­°F. Especially cause it's bugging me that I didn't remember why the units where in/in (don't tell me KCStudly!).

So yes, I was worried about thermal expansion, but the 0.000017 was just to show that it was nothing to worry about.

Don't worry, I AM pushing ahead with the build, and I'm trying to KISS, but my brain keeps getting in the way.

No, put the battery LOW. I cant tell you exactly why, but I saw a batterys damage on a person once (acid) and I would put it low, protected and away from persons.

Hmm, I didn't think about that. Very good point, thank you Mary!

How about under the floor near the axle? Just ahead or just behind it. Check out how Danny does his in traditional builds. I think Zach's X2 had an under slung battery, as well.

I'll see if I can find that. It didn't occur to me to put it there, as I would have thought a 12" battery could have some ground clearance issues. But on second thought, with the raised floor, it would still have more clearance then my car itself does, as the HF trailer sit somewhat high in the stock configuration.

So, tonight, start drilling holes and mounting hurricane ties! Then, slide the battery in my model up under the trailer, in front of the axle, so I can "see" the ground clearance. And convert the forward area into small cabinets for storage.

Right now, I'm thinking mount the AC up above the bed (why am I putting all these heavy things high? ), above the axle, so if it's not hot I can take it out. Vent the heat out with computer fans and tubes to below the trailer, or add a small hatch in the galley hatch that pops open when the AC is on.

[KCStudly]

On a street going camper (as opposed to an off road rig) ground clearance is like a triangle; greatest near the axle tapering toward the tongue and rear "bumper" (assuming that nothing pokes up higher than the axle). Near the axle is not affected by dips and transitions.

Here is a link to a thread on under slung battery mounts.

[jseyfert3]

On a street going camper (as opposed to an off road rig) ground clearance is like a triangle; greatest near the axle tapering toward the tongue and rear "bumper" (assuming that nothing pokes up higher than the axle). Near the axle is not affected by dips and transitions.

Here is a link to a thread on under slung battery mounts.

Cool! I will plan on that. Also, about the AC, I asked my coworker where I should put it (for ideas), and he said underneath. If it will work for a 12" tall battery that weights 50-60 lbs, it'll work for a 12" tall "window shaker" that weighs only 43 lbs, right?

Cool! Planning will commence on these lines!

[KCStudly]

A/C location is always a compromise. I don't plan on having one, but have read all I can so can pass on what I have read.

Up front can create an issue with weather tightness since driving forces rainwater in thru any chink in the "weather proofing armor". Also, some people don't like the cool air drifting down on their heads.

Galley mounted units need careful attention to sealing the area underneath, "the pan", and a means to control drainage. They take up room in the galley and several have had venting/crosstalk/heat soak issues due to improper venting and duct routing.

Some have made adapters that allow them to remove a side door and install the A/C in place of, but they usually give up the use of the door (no bueno).

GPW's Foamstream has a side hatch that will allow him to pop the unit in when needed, but then his is a larger camper and has room for that.

Divorce d units where the unit sits on the ground next to the camper or on the tongue may have portable or permanent hoses to duct the air to and from, but you will need to hack the thermostat and controls for remote operation, and build the necessary shrouds.

In any case, they have to be mounted high enough that the bedding does not interfere with the ducting.

Oakinteriors is currently working on a rather ingenious install where he made built in ducts between his bulkhead and rear cabinets, and is mounting the unit hanging on a sliding rail under the floor. Travels onboard, but slides into position underneath during camp setup. Don't need it, leave it at home.

Many people don't bother, depending on the climate where they camp.

Look at Aggie79/Tom's Silver Beatle. He uses a Pet Cool unit mounted in the tongue box. Planovet's Little Swiss has his mounted behind the bulkhead. Other build's from Texas seem to have the bugs worked out since A/C is a "must have" for that region.