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<h2> Introduction </h2>
<p> This document lists a number of problems with the Inventor Centre and Single Motor Hovercraft Kits. There are a large number of aspects of the kits that Interplay and EDU did wonderfully well, and they are going to go completely unmentioned here. I hope you won't take offense - I'd be very happy to write a glowing letter of well-deserved praise as well. However, the goal is to help you improve the kits.
<p> Of course, any product could always be improved, so the question becomes: why isn't the current state of affairs good enough? Why are the improvements worth it?
<p>The Inventor Centre twin motor hovercraft has a few problems which I believe should be immediately addressed, and I hope that once you see the videos and photos below, we will be in agreement on that.
<p>As for the rest of the problems listed in this document, I don't know what it will cost to follow my advice, but wherever possible, I've tried to offer solutions that would require Interplay to only modify the instruction manual. I assumed that this would be the most inexpensive modification possible.
<p>I think any improvements must be considered alongside the reviews the Single Motor kit has already received. I've found only a few so far, but they've been available online since the 2008 Christmas season.
<p>Have you seen <a href="http://www.youtube.com/watch?v=Hl7rcYHS1hg" target="_blank">this review (click here) by HEXUStv</a>?
<p>(You can also see the same review at the HEXUStv site here: <a href="http://tv.hexus.net/show/2008/11/Gifts_for_Christmas_-_Interplay_Hovercraft/" target="_blank">http://tv.hexus.net/show/2008/11/Gifts_for_Christmas_-_Interplay_Hovercraft/</a>)
<p>Please note this review is the first link that comes up (at least here in the US) when you search google for "interplay hovercraft", and if you put the search terms in quotes, references to the HEXUStv review swamp all other references, including those on interplay's own website.
<p>The ending of the video review particularly bothered me. There was no way to avoid the reviewer's attitude and approach, but I thought the performance of the hovercraft at the end was very disappointing, and the worst thing about the review. And this was bolstered by the comment that the youtube video received: <br> <i> "We built ours and it didn't hover or move at all."</i>
<p>The kit is also reviewed on
<a href="http://www.amazon.co.uk/Interplay-UK-Technokit-Hovercraft/dp/B001CIJIRU/ref=sr_1_20?ie=UTF8&s=kids&qid=1224796741&sr=1-20" target="_blank">its page at Amazon.co.uk</a>
<p>For many months there was only one review at the Amazon page, and it was a tellling one: <br><i>
"It was great building this with my nephew, a bonding experience. We were really tackling the challenge together and were looking forward to seeing the fruits of our labour with a hovering hovercraft. Sadly we were disappointed, it did not hover at all." </i> [Written on Christmas Day, 2008]
<p>Fortunately, a second more positive review has recently shown up on the Amazon page. Also, I suspect the same person left both the negative comment on the Amazon page and the negative one on youtube.
<p>Nevertheless, that person's comments illustrate the obvious: despite all the comic pratfalls by the HEXUStv reviewer, the building process isn't so bad. The problem is when the hovercraft doesn't perform well in the end!
<p>I think the problem in the review was simply that the hovercraft doesn't perform well on carpet. Below, I demonstrate a way to fix the problem, so that the hovercraft can hover well on carpet. I also point out that if Interplay doesn't want to fix the problem, they could avoid further disappointed customers and bad reviews by clearly stating in the instructions that the hovercraft is intended for use on hard surfaces such as flooring and pavement, and not carpeting.
<p>I suppose that the Inventor Centre will receive its first reviews during the Christmas season. My hope is that this document will help lead to better reviews and fewer disappointed customers. I hope this document makes it clear that at least a few things must be fixed, and I thought that once you're contemplating fixes, it would be helpful if I listed every issue I could think of so that you'd have the big picture. I hope this document is helpful!
<!-- Commented Out
\
Part 1 goes here. Links to reviews goes here. I will highlight solutions that require changing only the instruction manual.
http://tv.hexus.net/show/2008/11/Gifts_for_Christmas_-_Interplay_Hovercraft/
and (????????????????????????????? http://forums.hexus.net/hexus-tv-turn-technology/152282-gifts-christmas-interplay-hovercraft.html)
and
(????????????????? http://www.amazon.co.uk/Interplay-UK-Technokit-Hovercraft/dp/B001CIJIRU/ref=sr_1_20?ie=UTF8&s=kids&qid=1224796741&sr=1-20
http://www.youtube.com/watch?v=Hl7rcYHS1hg
Youtube comment: "We built ours and it didn't hover or move at all :( "
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Amazon commnets: from Dec 25 (Christmas!) 2008:
It was great building this with my nephew, a bonding experience. We were really tackling the challenge together and were looking forward to seeing the fruits of our labour with a hovering hovercraft. Sadly we were disappointed, it did not hover at all.
From April 21, 2009:
My son received the Hovercraft kit for his birthday. He's a bit of a Hovercraft fanatic. He loves anything to do with Hovercrafts, so when he opened this present he was (to say the least) over the moon. I liked it because there is an educational aspect to the kit. He made the Hovercraft all by him self apart from a little help with putting the skirt on, which is probably the trickiest part as you need to get the skirt in exactly the right position for it to hover correctly. It took a couple of attempts but he's got it just right now and it hovers a treat.
Commented out -->
<br><br>
<hr><hr>
<p>Important note: This document uses YouTube as a video server. All YouTube videos herein are locked behind a password. The videos are not available to youtube's general audience. They are only accessible through this webpage, and only Interplay has been given this webpage's URL.
<hr><hr>
<br>
<h2> Twin Motor Hovercraft Performance: Problems & Solutions </h2>
<!-- Commented out
<p> What we want is a hovercraft that can go straight and can take hard knocks without getting damaged. What we've got in the Inventor Centre kit is a twin motor hovercraft that only goes in circles and gets destroyed after only a few bumps.
commented out -->
<h3>Problem: The EDU version of the twin motor craft does not fly straight.</h3>
<p>In the first video the original GH-2 is seen flying mostly straight. You'll note there is a slight tendency to veer right while on the tile, and when the hovercraft crosses over to the carpet, it straightens out.
<p> In the next video, the twin motor craft from the Inventor Centre is seen in the same setting. The tendency to veer to the right is so much more pronounced that the hovercraft is incapable of flying straight at all. <br>
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<!-- Commented out On the left, the original GH-2 is seen flying straight and taking a lot of bumps without getting damaged. On the right, the twin motor craft from the Inventor Centre is seen in exactly the same setting, unable to fly straight, and getting damaged in the process:
commented out -->
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<br>
<h3> Solution #1: Anti-Spin Tape (or Redoing the Anti-Spin Protrusion)</h3>
<p>The video on the left, below, explains the source of the problem and demonstrates an ad-hoc solution using a piece of tape:<br>
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<br>
<p>You might wonder why we are having the problem. Shouldn't we have this fixed by now? You might remember that last summer, I was given a pair of prototype trays to test. I mocked-up a blue twin motor cabin piece (the production version wasn't available yet), and I found that the prototype tray had a strong tendency to spin, despite having an anti-spin protrusion in the same place as on the original GH-2 trays. After experimenting with different placements for the anti-spin protrusion, I recommended a new configuration. The video on the right, above, shows my final mocked-up prototype, which didn't spin. Of course, a mock-up is never exactly the same as the production version. I don't know if the production version of the cabin was ever tested with the production version of the tray, but I wasn't given the chance to do this test. I was given three production versions of the kits (as a very nice Christmas present, by the way) with the understand that the kits were now in production and that it was too late to make changes.
<p> In any case, I recommend returning to the original anti-spin configuration, as illustrated below. I'm hopeful that it will not be a major operation to change the die which cuts out the anti-spin shape once again.
<br>
<img src="tray-regression.jpg" height=100><br>
<pre> Original Current Recommended </pre>
<br>
The solution proposed above worked for the majority of the models I tested, but, maddeningly, not for all for all of them. Sometimes, the solution was overkill, and caused the hovercraft to turn left. More frequently, the solution was insufficient, and the hovercraft continued to turn right. Why? Possibly, some trays are warped (this problem is discussed below). Possibly, the trays become damaged from impacts (this problem is discussed next). In any case, I think the customers should be taught that they can adjust the trim on their hovercraft by bending the rudders.
<br>
<h3> Solution #2: Bending The Rudders</h3>
For the original GH-2, there was no need to design adjustable rudders which would allow the course to be trimmed, but the rudders can be bent (as pictured below) to provide a trimming effect. Even bending the rudders slightly out of position makes a big difference while the craft is traveling forward. The foam mostly bounces back into position, but the rudders can still be given a new overall orientation.
<br>
<img src="bending2-IMG_2027.JPG" height=150>
<img src="bending3-IMG_2029.JPG" height=150>
<img src="bending1-IMG_2025.JPG" height=150>
<br>
<br>
<h3> Problem: The twin motor hovercraft's foam tray gets damaged too easily. </h3>
<p> In the videos you just saw, the original GH-2 took many hits and was not damaged. It wasn't easy to see on video, but the EDU twin motor hovercraft's hull became quite damaged. <br>
<p> I built a new EDU twin motor hovercraft on a pristine foam tray. In 30 seconds of use, after just one impact similar to those seen in the above video, a serious crack appeared:<br>
<img src="cracked-after-thirty-sec-topIMG_2368.JPG" height=250 >
<img src="cracked-after-30-seconds-bottomIMG_2371.JPG" height=250>
<p> After 10 minutes of use, with multiple impacts, the entire front of the craft was bashed in. I used transparent tape to repair the damage, but the hull continued to fall apart between the pieces of tape. <br>
<img src="cracked-hull-IMG_2365.JPG" height=250>
<img src="cracked-hull-IMG_2036.JPG" height=250>
<p> It is hard to demonstrate this with photos, but once the hull ws this damaged, when you picked it up, it felt flexible, cheap, and weak. The bashed in front flexed like a piece of fabric when I poke it with my finger. Also, all the overlapping creases and cracks ruined the craft's apperance.
<br>
<h3> Double Hull Solution </h3>
Both the problem of the craft not flying straight and the problem of the craft taking too much damage can be solved (or at least, largely alleviated) by putting the two hulls together as shown below.
<br>
<img src="Double-Hull-2421.JPG" height=250>
<img src="Double-Hull-2419.JPG" height=250><br>
<p>The additional hull makes the hovercraft 12 grams heavier, but that's not enough to significantly impact performance, and the advantages are overwhelming.
<p> First and foremost, this is the only solution I could think of that requires only the instruction manual to be changed. There are other, better solutions that are less ad hoc, but they will require re-engineering and retesting the foam hull.
<p> With the two trays locked together, the trays form a tube which gives the hull strength to resist breaking. This does not completely fix the problem, but it makes a significant improvement.
<p> When the craft is picked up, the hull feels rigid and strong.
<p> I personally believe the looks are improved. I think the single foam tray looks incomplete, lacking a top. The arrangement also helps hide any damage that occurs underneath. The damage might still need to be repaired with transparent tape, but at least it won't show.
<p>Interestingly, the craft's tendency to turn can be definitively solved by using the rudders.
The anti-spin protrusion does not give consistent results, perhaps because of the flexible nature of the foam tray. The rudder bending solution described above is imprecise because the foam has a tendency to bounce back. The double hull arrangement allows the user to precisely trim the rudders as they see fit. The top hull rubs slightly against the rudders, and holds the rudders in place regardless of how much they are bent. <br>
<img src="adjustable-rudders-doublehull-IMG_2412.JPG" height=250>
<img src="adjust-rudders-right-IMG_2410.JPG" height=250><br>
<p>Truly adjustable rudders make the hovercraf more fun as a toy. They also can be educational: adjustable rudders can be incorporated into a lesson on how rudders work - which leads to a lesson on Newton's third law of motion, on aerodynamics and the properties of air, etc.
<p> I discuss the specifics of the double hull solution further in the instruction book section of this document.
<h3> Alternatives to the Double Hull Solution </h3>
<p> As for the durability of the hull, another solution would be to have EDU re-engineer the foam tray. I'll comment briefly on that here, but if it is a serious possibility, I'd be happy to elaborate, and to help in any way I can.
<p> At a minimum, perhaps EDU could use denser thicker sturdier polystyrene foam, like the foam trays that I used in the original GH-2. That might be all that is necessary -- if the material was different, the design might be much more sturdy. Alternatively, EPP could be used. I mentioned in the past that EPP (Expanded Polypropelene is often used to make indestructable moddel airplanes. It is lightweight and not particularly more sturdy than polystyrene but it can take much more abuse.
<p> Going beyond that, I originally suggested filling in the voids with foam, and I still think this would be the sturdiest and most durable solution.
<p> More conservatively, the unique shape of the hull could be abandoned in favor of the standard foam tray shape. I had hoped that the slanted sides would improve the craft's performance, and they do in some ways, but if the craft is made from such weak foam, the design makes the craft too vulnerable. I have found that if all of the other EDU parts are positioned atop the original GH-2 tray, as shown below, the resulting model works just as well as the original GH-2.
<br> <center> <img src="EDU-parts-on-GH2-hull.JPG" height=250></center>
<p> The original GH-2 tray's shape is easy to copy. The EDU cabin piece already has extensions to allow it to fit the GH-2 tray (it is just as long as the EDU tray, but the inside cabin in roomier). I don't know if the same dense and strong material could be supplied by EDU. If it could, replicating the original GH-2 tray might be considered. (Ideally the "wavejumper" attachment would also be built by EDU!)
<br><br><br>
<h2> Flying Saucer Performance: Problem & Solutions </h2>
<h3> Problem: the EDU version of the flying saucer doesn't work on carpet</h3>
<p> The Flying Saucer might not strike you as important enough to be worth considering. However, this section teaches a lesson about a issue that also shows up in the other hovercraft models, and it is most easily demonstrated using the flying saucer on carpeting.
<p> On hard flooring, the GH and EDU versions of the flying saucer are similar, but on carpet, they are quite different. Compare the original GH and the EDU versions of the flying saucer in the video below. Both were powered by identical fresh disposable batteries straight out of the box. The white GH model spins rapidly and floats around on its own. The yellow GH model, after moving for the first few seconds, sits motionless for the rest of the time, only moving for a bit when it is shoved. The video goes on a bit too long, but I wanted to show how much more fun the GH model was.<br>
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<br>
<p>Interestingly, there is nothing wrong with any of the EDU components, considered in isolation. In the very short video below, I switch the ducts, so that the EDU duct is riding on top of the white GH picnic plate, and the GH duct is sitting atop the yellow EDU flying saucer hull. You can see that both saucers now work equally well on carpet.<br>
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<br>
<p> In the surprising video below, the EDU duct is back on top of the EDU hull. Once the rear guard is removed from the EDU duct, the flying saucer behaves just like the GH version.<br>
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<br>
<p> So what's going on? The two videos illustrate that sufficient plenum area is required in order to perform well on carpet. The white foam picnic plate is slightly taller than the yellow EDU version. And the EDU duct is slightly longer than the GH duct, due to the rear guard. The extra height from the white picnic plate allows the EDU duct to perform well. Removing the rear guard restores the EDU duct back to the same dimensions as the original GH duct, and this allows the yellow EDU hull to perform well too.
<p> We see here a reminder that the parts can't be tested in isolation, and more specifically, we see that the plenum size of a model hovercraft can be critical - something to keep in mind for the RC hovercraft project. <br>
<h3> There are only two possible solutions for the flying saucers </h3>
<p>1) change the instruction manual to indicate that the flying saucer works best on smooth hard surfaces such as flooring, and not carpeting,
<p>or, better yet,
<p> 2) slightly re-engineer the picnic plate hull by increasing the height of the the flying saucer hull to match the original GH white picnic plate version.<br>
<h2> Single Motor Hovercraft Performance: Problem & Solutions </h2>
<p> The single motor hovercraft's foam tray has the same problem as the flying saucer: the plenum is not quite tall enough. Compare the GH-1's performance on carpet compared to the EDU version in the following video. Again, identical disposable batteries were used, directly out of the box, and again, there are large differences in performance:<br>
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<br><br>
<p> The GH-1's performance isn't perfect - it gets hung up on ripples in the carpet - but for the most part, it goes forward until it hits something. (Its performance would be much better with recharageable batteries!) In contrast, the EDU version needs to be pushed multiple times to traverse the same distance that the GH-1 can travel on its own.<br>
<p> Although the single motor hovercraft has many components, it was easy to figure out that the foam tray was the primary reason why the GH-1 worked better than the EDU version.
<pre>Motor/Prop/Duct Airbox Tray Result
EDU EDU EDU goes poorly on carpet
EDU EDU GH goes well on carpet
EDU GH EDU goes poorly on carpet
EDU GH GH goes well on carpet
</pre>
The original GH-1 foam tray is slightly taller than the EDU version, and this creates a larger plenum underneath the hovercraft, and I believe this accounts for the difference in performance.
<br>
<p>Again, as with the flying saucer, there are only two solutions: <br><br>
1) change the instruction manual to make it clear that the single motor hovercraft only operates well on wooden or tiled floors inside, and smooth pavement outside, and won't operate very well or at all on carpeting , grass, or rough pavement. <br><br> 2) Re-engineer the foam tray so that the sides are as tall as the original GH-1 foam tray. <br>
<br>
<h2> Further Problems With The Foam Trays</h2>
<h3> Problem: Foam Tray Warping</h3>
<p> One of the single motor trays did not sit flat at all, right out of the box. It showed severe bending in width and breadth allowing the cushion air to leak out. The warping along the long dimenion is not pictured, but warping along the length of the craft is even worse - it can severely impair the craft's ability to hover. We don't know why the hovercraft reviews listed in the introduction said "it did not hover at all", but maybe this was the problem.<br>
<img src="warped-1-tray-crop.jpg" height=250><br>
<p> Perhaps quality control in China can catch these. Or perhaps the user can be instructed to try to gently bend foam trays until they sit fairly level on a flat table.
<!-- Commented out
<p>Foam Tray Condition: Indentations at the ground contact line of the twin motor tray, directly out of the box.
-->
<br>
<h3> Problem: Foam Tray Material</h3>
<p> The foam tray's material also has odd interactions with the velcro. I've seen the following problem shown on the left several times: the velcro doesn't stick to the foam tray material. It would be easy to blame the velcro adhesive for this problem. But look at the photo on the right: twice now, after an impact, I found that the velcro had stuck to the foam tray quite well, but the tray's material is so weak that the velcro tore a hole straight through the tray. I've been building and selling the GH-2 since the year 2000 in one form or another, and I've never seen or heard of this happening before!
<br>
<img src="velcro-not-sticking-to-hull.JPG" height=250>
<img src="closeup-severe-tray-damage-from-velcro-r-IMG_1948.jpg" height=250>
<br>
<p> Either way, the customer gets disappointed. Both problems might be fixed by changing the tray material.
<br><br>
<p> A related phenomenon I've noticed is that sometimes the foam tray delaminates as it becomes damaged from impacts. Below are photos of a foam tray that only suffered a very few impacts, and yet you can see how where the creases from previous impacts intersected, a triangle shaped piece of the foam tray material separated itself from the rest of the tray. A hole in the tray developed soon after.<br>
<img src="delaminate-IMG_2529-m.jpg" height=250>
<img src="delaminate-IMG_2527-m.jpg" height=250>
<br><br>
<h3> Problem: Skirts For Twin Motor Hovercraft Are Too Short</h3>
<p>All four skirt tubes in each of the Inventor Centre Kits I received were 37 3/8th inches = (approximately 949 mm). That simply isn't long enough to build the skirt according to the directions. If the skirt is attached to the hull according to the current instructions, it will come up short. The following photos illustrate this:
<p> Skirt Images go here
<p>As you know, I believe the current Inventor Centre instructions do not show the best way to attach the skirt to the hull. The skirt should be attached to the outermost perimeter, so that the slanted sides of the bottom will resist the skirt's tendency to tuck under. I offer photos in the next section. For this better way of attaching the skirt, the skirt is much too short.
<p>The skirt should be at least ________ long to follow the current instructions.<br>
<p> To follow the outer perimeter as I recommend, the skirt should be at least _______ inches long.<br>
<!--
<p>Twin Motor cabin piece: needed more creases on central flap to fold properly! OR, as is, but instructions should suggest attaching the central flap before attaching the left and right arms.
-->
<br><br><br>
<h2> Suggested Changes To The Instruction Manual </h2>
<p> In this section, I'm going offer suggestions on improving the instruction manual. The first three sections all have the same theme: that users need more help.
<h3> Closing the airbox door </h3>
<p>I think many users will not read the text, and will not understand that they need to close the airbox door when building the twin motor hovercraft. A picture like the one below would explain it. The current illustration on page 17 could be replaced with a drawing in which the perspective is from behind the airbox. The new drawing could show that the airbox should be attached to the foam tray, but could also show that the airbox door is closed. Alternatively, perhaps the perpective could just shift a bit, so that the airbox door could be seen through the duct, and an arrow could highlight which shows the tray from behind, so that the airbox is shown closed.<br>
<img src="GH-trapdoor-closed.jpg" height=250>
<br><br>
<h3> Bumper Tape (and Skirt Tubing) Comes In Different Lengths</h3>
<p>I think many users won't notice that the bumper tape comes in different lengths. The text on page 13 of the Inventor Centre instructions could say "Find the medium length bumper tape..." I'm unclear on whether the skirt is supposed to come in different lengths. I thought you said it was, but the instruction manual makes no mention of it, and the kits I received contained 4 identical-length strips.
<h3> Velcro Polarity </h3>
<p>If the user doesn't think ahead (and read ahead), he or she might end up with mismatched velcro. In my version of the instructions, I arbitrarily tell users to attach loop ("soft") velcro to the battery holders, and this ensures that everything will be interchangeable later.
<h3> Bumper Tape Not Optional </h3>
<p> the text suggests that the bumper tape be left off the foam tray if a separate skirt tray is used, "as it will interfere with stacking the trays" (see page 18 of the Inventor Centre instructions). A skirt tray can be stacked underneath the main tray, even if bumper tape is applied to the main tray. The skirt tray experience some deformation at the perimeter, but it does not impair the skirt's ability to work. Given the vulnerability that the tray has to damage (at least, as it is currently manufactured) I think users should be encouraged to always use the foam bumper tape. (This entry presumes that the double hull method is not used, of course.)
<h3> Carpeting </h3>
<p>If the models aren't redesigned to perform well on carpet, the instructions should repeatedly caution the users that the models work best on wood or tile floors, and smooth pavement, and may not work well on carpet.
<h3> Tricks To Get The Twin Motor Craft To Fly Straight </h3>
<p>If the twin motor tray is not redesigned so that it reliably goes straight, the instructions can teach the user the two tricks shown in the first section of this document. Users can be shown how to apply tape to extend the anti-spin protrusion's length, and users can be shown how to bend the rudders. The instructions could be couched in a conditional clause: "If your hovercraft does not fly straight on its own, you can use these two tricks to fine tune your hovercraft..."
<h3> Skirt Feed </h3>
<p> I think the instructions for the Inventor Centre do not quite show how to properly set up the ends of the skirt tube for the twin motor craft. Look how the brass fastener is set up in the photo below - it pulls the skirt tube around and up. In the current Inventor Centre instructions, the user is instructed to bend the tubes into position, but there is nothing to prevent them from blowing back down again. Also, I use a second fastener to keep the the tubes open and in the correct position. <br>
<br><br>
<img src="GH-skirt-feed2.jpg" height=250>
<img src="GH-skirt-feed3.jpg" height=250>
<br><br>
<h3> Skirt Attachment </h3>
<p> The photos below show a better place to attach the skirt. The photos show the double hull arrangement, but the skirt would be attached in the same place regardless of whether a top hull is used. <br>
<img src="double-hull-skirtIMG_2428.JPG" height=250>
<img src="double-hull-skirt-frontIMG_2440.JPG" height=250>
<br><br>
<img src="double-hull-skirt-sideIMG_2431.JPG" height=250>
<img src="double-hull-skirtIMG_2432.JPG" height=250>
<p>
<h3> Skirt Attachment (Part 2) </h3>
<p>I think the skirt should be attached to the hull with loops of adhesive tape, or double sided tape, or by bending the tape into the shape of a lower-case "n". This works fine - I've done it successfully for years. In the case of the double hull arrangement, there is no access for brass fasteners to be used. In the case of the single tray arrangement, I'm reluctant to further weaken or destroy the foam tray, when it might be needed intact later.
<br><br>
<h3> Double Hull Arrangement </h3>
<p> Two trays are used. Remove the protrusions from one of the trays as shown. Place this tray on top of the other tray, and line them up. There will be a gap at the edges. Pinch the two edges together and secure with transparent tape. Use three or four vertical lengths of tape per side to completely join the two trays together. Now add the blue hovercraft parts as specified in the instructions, pushing the brass fasteners through both trays. Add black bumper tape and you're done!<br>
<img src="double-hulls-side-by-sideIMG_2451.JPG" height=250>
<img src="double-hull-breakoff-protrusionsIMG_2448.JPG" height=250>
<img src="double-hulls-on-top-birdseyeviewIMG_2461.JPG" height=250>
<img src="double-hulls-34view-IMG_2463.JPG" height=250>
<img src="double-hull-gapIMG_2466.JPG" height=250>
<img src="double-hull-pinch-tapeIMG_2484.JPG" height=250>
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<img src="double-hull-stripes-of-tapeIMG_2489.JPG" height=250>
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<img src="double-hull-taped-closedIMG_2500.JPG" height=250>
<img src="Double-Hull-2404.JPG" height=250>
<br><br>
<h3> Fresh Batteries </h3>
<p> For step 11 (page 13 of the inventor centre kit, page 11 of the single motor kit), I suggest inserting the word "new", as in "Install 4 new AAA batteries". I know it sounds obvious to you, but I've learned that many people don't realize that new (disposable) batteries provide much more power than used ones.
<h3> Rechargeable Batteries </h3>
<p> The instructions to not use rechargeable batteries are regrettable. This document has gotten long enough, but if you'd like, I can shoot video showing the big difference between disposable and rechargeable NIMH batteries. I understand you are following EU toy regulations, but I keep wondering if there is some way to follow the law and yet hint that rechargeable batteries won't cause any harm to the toy. How about saying "Due to the risk of swallowing, do not use rechargeable AAA batteries" so that customers will understand that rechargeable batteries will not burn out the motor or something along those lines.
<p> Better yet would be something that somehow hinted that rechargeable batteries are more powerful, even if they are verboten. How about something like this: "For ages up to 13 and for those with young children in the home, rechargeable batteries are not recommended due to a swallowing hazard. Teenage and adult users with no young children at home will find that NiMH rechargeable batteries will provide more power." I don't know the regulations and I'm just grasping at straws, but I do know that using rechargeable batteries is the quickest and easiest way to dramatically improve performance.
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<h2> Recurring Advice</h2>
<h3>Battery Box </h3>
<p>Three irritants:<br>
<p>1) The requirement of a screwdriver to open and close the battery box;
<p>2) The difficulty of removing the batteries makes the box inappropriate for classrooms (where teachers have the students swap the batteries back and forth frequently to control for that variable).
<p>3) The on-off switch is still far too small.
<h3> Airbox Roof </h3>
<p>Airbox roof: There is still too large a gap in the airbox roof for the single motor craft. Testing shows that this problem is has only a minimal impact on performance. Fixing this problem need not be a high priority. On the other hand, every little bit helps.
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<h3> Extra Trays </h3>
<p> Add extra trays. Cite HEXUStv comment.
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